Schweizer 1-35 Ramblings

 

 

1-35 HOME

 

 

 

Buying a SGS 1-35: (by Tom Rent)

The 1-35 is rated at 38:1 vs 36:1 for the 1-35c. The primary cause is the
fixed vs retract gear, the secondary is the 1-35's fuse and wings are
smoothed with thicker paint and microbaloons. Many 1-35c's have exposed
rivet heads on the fuse aft of the wing, adding to drag. For some reason my
1-35c doesn't. The 1-35c also has an exposed towhook where the 1-35's
towhook retracts. Again my 1-35c towhook is a retract style. I think I
have a 1-35 fuse with fixed gear .... perhaps an "end of the month" factory
decision. I'm not complaining.

The 1-35 has more flap settings but is more complicated too. It is also
heavier when dry, which is a disadvantage generally. The factory also offered

wing fairings which some ships you'll see might have. A plus.

Some ships have a hinged canopy ... a major plus but it cuts down max pilot
weight, possible to about 190 pounds. Check this before you buy.

I would not get too hung up on either model. Look for good condition all
around. Look for one not kept out much if at all.

The trailer is a key factor too .... some prefer a so-so glider with a good
trailer vs a good glider with a so-so trailer.

Prices on good ships with good trailers go from $16K-$20K ... a great
price-performance for a safe and durable sailplane.

The flaps are wonderful and easy to use. I had zero trouble ... they add a
lot to the ship's versatility. Do not hesitate to buy a SGS 1-35 because of flaps … they

are a major advantage over airbrakes in my opinion.

No special tow-out equipment is needed for the SGS 1-35 (tail dolly, ect ). I use a lightweight plastic $20 Folding
sawhorse (Stanley) for assembly. Assembly is a breeze with me and one other person.

 

 

 

From (ex) SSA PRESIDENT Larry Sanderson …..

Tom,

It is nice, once in awhile, to have a chance to talk about something other than
SSA business. I owned 1-35 #98 for a number of years.

I thoroughly enjoyed the 1-35 and found it to be an excellent glider for the
money. Relatively easy to maintain and good handling. I flew mostly in the
desert and enjoyed the performance. The spin will get your attention but it is
recognizable and easily managed provided you don't make foolish mistakes.

The best suggestion is to fly the different gliders you are thinking about.
Sometimes this isn't easy because of logistics but that is really the only way
to find what you are comfortable with. By the way, body size may or may not be
an issue. At 6'5" I just fit in the 1-35 but once in felt fine. Some other
gliders of similar size didn't feel so good.

Larry Sanderson
President, SSA

 

 

 

Ideas on sealing the canopy:

Several times, over the years, the rubber strip and it's adhesive glue
have been scraped out of the groove in the bottom of the canopy
frame....and then replaced with a similar material. We have also tried
various combinations of gasket material....The results have never been
completely satisfactory.

The canopy-to-turtle deck fit at your shoulder is poor. Since there is
very little slope on the turtle deck, the seal gets rubbed vigorously when
the canopy is opened or closed. This wear soon leads to a leak which
leads to a stream of cold air on each side and contributes to the high
noise level.

We are very happy with the foam seat pad we made a couple of years ago.
It is two (one inch) layers of the high energy absorbing material.
Initially it is like sitting on a board, but in a few minutes it conforms
to your body, and several hours later you are still comfortable. [There
was a time when I had to force myself to not think about my butt after
being in the air for about 1.5 hours.]

U4 passed its aileron push rod inspection.....tight, sound joints with no
loose rivets. All else on the annual was O.K. We had the rod end and
bolt at the bottom of the stick renewed. Hopefully this will take care
of the rest of the fore and aft slop in the stick.....The elevator bell
cranks and connection pins were treated last year and got 80% of the slop.
So, hopefully this is it for another 22 years and 1200 hours.

Looking forward to your collective knowledge.

Good soaring,

Dale Thompson

Dale,

I've made several attempts to seal the canopy on 2M, none of which have
ever been of much success. The best seal has been latex tubing. I've never
been successful at getting a complete seal. Since I'm in the process of
replacing the canopy on 2M, I'm very interested in any techniques/secrets
that any of you know of.

Speaking of canopies, I'm patiently waiting for Thermo-Tec (Ray Poquette)
to make a mold and then make a canopy. Ray is also making a canopy for
another 1-35 owner (Gary Phillips, g_phillips@fre.fsu.umd.edu). My old
canopy was not useful for making a mold, so Gary sent his canopy to Ray and
Ray is making a mold from it and then two canopies from the mold. The good
news is that a 1-35 canopy mold will exist in case any 1-35 owners need
canopies. The bad news is that the wait is 4 to 6 weeks. I did locate a new
1-35 canopy elsewhere (Mark Keene in the Dallas area). Mark is a 1-26 pilot
and has a business selling Schweizer parts. I contacted him (after I had
given Ray the go-ahead) and sure enough, Mark had a canopy.

Question - After removing the canopy from the frame, I found several small
pins located in the center of the canopy frame rails in the area where the
frame goes around the turtledeck and the wing. There are not any pins in
the frame rails on the sides or on the front. The pins are small (about
1/16-in. diameter and stick out of the frame about 1/16 in. They look like
they are used for locating devices. Can anyone shed some light on this?

Regards,

Bob

Dale & Gang,
On the turtle deck of my 1-35, I've installed a rubber, adhesive backed
weather strip called EPDM P-Strip. I bought it at a Home Depot, and it's on
it's second year of use now. I think it's intended to seal home doors, and
it's easily identified by viewing from the end. It looks like a P . For
the canopy edge, try using an adhesive backed "Formed Foam Weatherstrip".
It's made of the same type of rubber as the 'P' strip, and looks like an
elongated 'w' when viewed from the end. Don't confuse these strips with
the black lightweight foam rubber sealing strips. Mine are gray, are fairly
durable, and easy to apply. I'm into my second season with them, and they
are doing well.

Since we're exchanging 1-35 notes, does anyone have a suggestion for an
easy way to clean the inside of the front of the canopy? Especially up
near the front vent? Also, what about a good aileron seal? I bought a roll
of 3M Matte Finish Wide V-Seal Weatherstrip (it's flat. you have to fold it
to make a V) on my junket through Home Depot, but I'm afraid to apply it. I
have this vision of the adhesive coming loose while in flight, the strip
trailing behind or wadding up in the joint, and me making a graceful
corkscrew into the ground...

Glenn Holden
N2922H (now sold to Matt Harris)

Hi Glenn,

Thanks for the response and seal ideas.

Canopy.....We use Lemon Pledge (and if you use Pledge, lore has it that
"Lemon" is the only way to go.)

Aileron gap seals.....We have used white 3M electrical tape since the
beginning of time. Hard to find at hardware stores, but a trip to a
wholesale/retail electrical equipment supply house works. It comes in
boxes of 10 rolls.

I believe the 1-35 was delivered with tape on both the ailerons and
flaps. It is my opinion that aileron taping is very important because of
the flow disruption through the gap with a major deflection (as might
occur on a wing drop). I've even wondered if it is part of the type
certificate, since ours was delivered from the factory with tape in place.

Aileron push rod seals.....Our best, and current solution, is a conical
seal made of chamois. Try K-Mart or your local auto parts store. It is
stitched into a conical shape, glued to the root rib with trim cement, and
secured to the push rod with a wire tie.

Does anyone know of a really good seal for the flap drive rod?
Cheers to all,

Dale Thompson

 

 

Aileron-Flap interconnect info and –2 degree incidence mods

These were options available for the 1-35 and 1-35A.  I don't know about the
history of the mods; assume that Ernie and Bill were always interested in
improving the 1-35s performance. I don't know when they first were
available. My ship was field retrofitted.

The standard wing incidence angle was -5 degrees. The mod changes the
incidence angle to -2 degrees. I suppose this was done to lessen profile
drag of the fuselage.

The flap/aileron interconnect couples the flaps and ailerons so that they
move together from -8 to +12 degrees. After +12 degrees, they uncouple and
move independent of each other. My guess is this was done to improve
performance. Michael Pitoniak once wrote me after he had an interesting
conversation with Dave Wells at Schweizer. Dave said that there is a
documented issue with negative flaps that states you must go back to 0
degrees at high speeds to prevent unloading the inboard portion of the
wing, thereby causing all flight loads to be carried by the outboard
section. If this is true, the f/a interconnect would negate this effect.

In the interest of 1-35 trivia -- My ship, (s/n 25) was the testbed for the
demountable tail. All of the test flights to gain FAA approval for the
demountable tail are recorded in the logbook. It's interesting reading.

Regards, Bob Thrasher   3/2001

From: Michael Davis

To: tmrent@goldengate.net

Sent: Saturday, February 24, 2001 4:12 PM

Subject: Disassembly

I'm a new 1-35C owner who is seeking some general advise about easier assembly and disassembly.  Since moving from a club operation (lots of available and willing help) to a commercial operation (lots of available but not-so-willing help) I need to find more efficient ways of doing this with 2 or maybe even 1 person.  Short of buying an expensive one-man assembly apparatus, anyone have some good suggestions?  One thing I'm having a problem with is during disassembly when I use the special "lever" tool to unmate the two wing roots, both wings move out and I'm a bit afraid that the unattended wing will move too far and rotate.  Should I leave the drag pin in?  (Not the best option, I presume, as there is increased likelyhood of damage there). 

So far, outside of an horrific first landing, I really like this glider and its abililty to land in a short field.  Gives the pilot extra confidence on cross-countries.  There's two other 135's here, including the specially-painted 2,000th Schweizer plane (N200D).  

Mike (N135DB)

From: Tom Rent

To: Michael Davis

Sent: Saturday, February 24, 2001 2:04 PM

Subject: Re: Disassembly

Hi Mike, 

All us 1-35ers have a bit of trouble in this area.  The trouble comes when the lever favors the easier wing (with all 4 pins out).  It pops the easy wing loose and the fuselage and remaining weight "settle into each other" (a weight shift) which pinches the bayonet pins of the remaining wing, making it almost impossible to free.  

We have 3 1-35s here and we all pull the 2 spar pins and one drag pin first, leaving the other drag pin in when we use the lever.  We just "pop" the one loose wing out enough for it to clear it's bayonet pins.  This loose wing wont go anywhere as it can rest on the spar and the spar is still aligned in the channel.  

As long as your fuselage is secure in its dolly, you can put down the tool and you and a partner can extract and store the loose wing. 

When you return to the glider, stand in the space where the old wing was and lift up on the spar.  This will also lift the fuse slightly but usually will relax any pinching that might have occurred to the bayonet pins.  Pull the last drag pin and with your partner at the tip, you should be able to guide this wing out it's channel.  Difficulties come in having pinched bayonet pins.  You might also find this channel is tight.  We ask the tip-man to twist the wing slightly (lifting the trailing edge or leading edge) enough to free the tightness in the channel.  One the wing is free of it's bayonet pins, walk around to the other side and lift the root by the spar and you're in the clear. 

When I first got my 1-35c I thought I'd always have trouble derigging, but with practice it is no longer a problem. 

Tom

From: pauley
To: tmrent@goldengate.net
Sent: Monday, March 12, 2001 7:50 AM
Subject: Replacement 1-35 Canopy

Tom,         I recently acquired s/n 47 from Paul Schweizer as a project/restoration. I have had difficulty finding a source for a  replacement canopy. I would also like to know if you have advice on whether to order it w/ tinting and or venting with slide rails. I understand it may be possible to get either gray or green tint.  This s/n came w/ a hinged canopy , so I don't know if  the side vent was also necessary or advisable.  Thanks,  Jess Pauley   pauley@lr.net

Jess et al,

Mark Keene (Keene Soaring,MKEENE221@aol.com) in the Dallas TX area has a good supply of Schweizer parts. I have ordered several items from Mark for my 1-35. Mark's prices are more than fair. Juan Batch in Odessa TX also has Schweizer parts I think. Tim Mara at Wings and Wheels may also be able to help with Schweizer parts.

I replaced the canopy on my 1-35 several years ago. I found two sources for the canopy when I was looking. Mark Keene had a canopy and Ray Poquette could make the canopy. Ray advertises in the Soaring magazine classifieds. I got the canopy from Ray Poquette. (I ordered the canopy before I found out that Mark had a canopy. Mark's price was several hundred dollars less than Ray's.) Ray has a mold for 1-35 canopies and makes them to order. I ordered my canopy clear with a UV blocker. The UV block added $100 to the price but I felt it was worth it because I have a history of skin cancer on my face and arms. The canopy came with the side window hole already cut. The canopy was slightly thicker than the original and is a work of art optically.

My 2 cents worth -- get a clear canopy and opt for the side window. Instead of using the original Schweizer one-piece side window, I ordered a Mecaplex window with the pop-out vent from Knauff and Grove and use it as my primary source of ventilation. I do most of my flying in south Texas (hot) and like all of the ventilation that I can get. The side window also allows you to reach through the canopy to lock it down; something you may want to do while trailering or if the ship is tied down outside.

Regards, Bob Thrasher

===

I have a "raw" canopy that has not had the frame attached (it's just the plexiglas). It came with the directions on how to make the frame when I purchased my plane. Apparently the previous owners (Long Island Soaring) bought a pair at one time and replaced the original leaving a spare. I'd be open to a reasonable offer. My canopy is hinged and my plane is S/N-49. Hinge or no hinge, I think you'll want a side rail and window (it's necessary for locking the canopy from the outside).


David Pilati

Tom,

 Attached are photos of the 2000th Schweizer Sailplane, a 1-35C (SN 84).  The N number on it is N2000D which registered on the aircraft when it was manufactured by Schweizer.  It was made in 1978 and I purchased it directly from Schweizer in 1979 after they had paraded it around the country in various shows.  The lettering on the fuselage denoting the aircraft as "The 2000th Schweizer Sailplane" was placed on the aircraft when it was new by the Schweizer factory.

 When I purchased the aircraft, Paul Schweizer requested that, when I've finished flying the plane, it be donated back to the Soaring Museum.  I intend to honor his request.

 It is quite special.  It is completely filled and no rivets show anywhere.  It has wing fillets and a retractable tow hook.  It has Imron paint (original) and also has the pointed nose cone.  All of these are quite unusual for the "C" model.

 If you have any questions, please email me at N2000D@home.com

 Regards,

 Sam McAllister

=======

Tom:
 
I used Microsoft Paint to see what our planes would look like with winglets. 
It makes for a great computer display background for the terminal dreamer.

Also, George Applebay is putting on a new canopy for me.  Also, he is installing a
Zuni hinged canopy system for only $400.  He designed and built the Zuni so
that makes me believe that he knows what he is doing.

Raul D. Boerner

Tom, I just stumbled onto the 1-35 site while checking some webring sites.  Congratulations!  I don't know how long this site has been active, but it's really nice.

 

I took some liberties . . . . like

    1. Added a link to your page on the list of Classic Sailplane "type-sites" at the Vintage Sailplane Association's Classic Division website (see http://classicsailplane.org/default.htm)

    2. Added a link to your page on the Classic Sailplane page of the Schempp-Hirth Cirrus website (see http://classicsailplane.org/Cirrus/default.htm)

 You might want to consider adding some link(s) to your page to refer people to related Classic sites.  As you can tell (if you didn't already know), we in the VSA have been actively encouraging volunteers to take up building and maintaining sites exactly like yours for the rapidly growing fleet of Classic Sailplanes (machines defined by the VSA as over 25 years old). 

 And I might also suggest considering a plug to join - if you're not already a member- the VSA and/or add a "plug" for them on your website!

 Please keep in touch!

 Jim Kellett – VSA Chair

Subject: Replacement 1-35 Canopy

I contacted Mecaplex in Switzerland, and Tim Mara in NY.  They have
canopies but the price is very high.  On top of that, shipping would be
about $500.  Also, I have been e-mailing L.P. Aero who is currently
experimenting with a new material.  They plan on making 1-35 canopies,
again.  However, they may not be ready in time for me.

But just this week I spoke with George Applebay from Moriarty, NM.  He has
been making gliders and repairing them for about 50 years.  There are
numerous stories about him in SOARING Magazine.  One goes back to 1975 when
he designed and built the Mescalero.  I don't know him, but he has a good
and long reputation.  Anyway, he told me that he makes canopies, too.  So
this week, I will be driving down to see his work.

Hinged canopy?  I have the factory plans but they look complicated.  The
factory only has some of the easy parts in stock.  The others will require
fabrication.  What are your plans for the hinge?  I just drove to Moriarty,
NM and visited with a Arthur Krelle.  He installed a hinge kit but with a
slight difference.  The factory plan has the spring assembly (strut)
attached to the two pins via a hinge assembly.  Art took out the hinge
assembly and just let the strut go from the floor mount to the bayonets.
His strut has 80 pounds of pressure.  He said that the 60 pounder that he
first tried was too weak for windy days.

For Christmas, I hope to get a digital camera.  With this, I can document
some of the work being done on my plane and then put the pictures on Tom's
web page.  That page has been a tremendous source of information for me and
has contributed greatly to my enjoyment and appreciation of the 1-35.

Incidentally, the February '75 issue of SOARING magazine (Volume 39) has a
story called "The 1-35: An Interim Opinion by Ed Byars."  Numerous issues
around that time frame have back cover advertisements of the 1-35 that are
great pictures.

Thank you for responding.  I am very interested to hear more about your
hinge plans.  I made one that was a side hinge that lifted the canopy 8
inches before allowing it to rotate open.  The hinge failed (bent), so I
gave up.

Respectfully,
Raul D. Boerner

 

CONOPY LINKS

http://www.airsuppliers.com/aircraftparts/aviation-catalog/WINDSHIELD-SCHWEIZER-1-35-CANOPY-FOR_AIRCRAFT.asp

http://www.aeroperform.com/aircraftparts/aircraft-parts-catalog/--WINDSHIELD-SCHWEIZER-1-35-CANOPY--aircraft-parts.asp

http://www.texair.com/aircraftparts/aircraft-parts-catalog/SCHWEIZER-1-35-CANOPY-WINDSHIELD-aircraft-parts.asp

1-35 restoration project

Tom,    I am soliciting more advice for my 1-35 restoration project.  - Wing tip wheels, skids or fairings? H2O Ballast and Wing Filling and Contouring......The wings in question are from SN 47, a std 1-35 w/ H20 ballast.  Removal of several layers of paint and  some filler revealed a number of different hole patterns from previous installations on the lower wing tips. No tip wheels or protective skids are currently installed.  What solutions are currently available that you would recommend for low drag or possibly even performance enhancing protection? I will primarily be operating out of our local grass field of however,  I may occasionally land  out on asphalt. Next,  I recently bench tested the H2O ballast system which functioned normally w/ only slight weeping around the dump port on the lower wing.  Does anyone have any advice  on  sealing of  the dump port? It is possible the slight leak will be eliminated when the wing is refinished. Does anyone regularly fly w/ ballast to enhance performance to keep up w/ buddies flying glass?  How does the glider handle when ballasted? How important is it to get every last drop of water out after ballast has been used? Is there any history of internal wing  corrosion associated w/ moisture in the tanks?  Finally,  wing refinishing. I have spoken w/ several people who have stated that they have gone to great lengths to contour the wings to perfection, only to have pretty wings but no noticeable improvement to performance. I had therefore intended to just do a general redressing of the wings and a nice coat of paint. However, after reading Dick Johnson's  "Flight Test of the Schweizer 1-35" on the website,  I see a need to find a method to ensure the proper filling and contouring of the outer wing panels for the best possible stalling characteristics.  What type of filler is recommended? Does anyone have templates or recommended methods for contouring the outer panels?  Any opinions on Dick Johnson's assessment on the tip stall qualities of the 1-35?  Is it possible the Schweizer factory had intentionally "tweaked" the tips, by removing some twist, on an early model in an attempt to improve performance? Answers to any or all of the above would be greatly appreciated.  Jess Pauley,    pauley@lr.net

 

HI, Jess;

We have Schweizer tip skids.  One tore off.  The replacement was overpriced and poorly designed.  Whereas the originals were solid plastic, possibly fiber reinforced, the replacement has a metal insert.  After one or two landings on pavement, the plastic wore down to the metal and the plastic is separating from the metal.

I plan to design metal or plastic wear sections on both tips this winter.  I'm glad we operate on grass.  A past owner operated on pavement and I note the "training wheels" came with the glider.  We've never installed them, but certainly would if operating on pavement.

By the way, the tail wheel was badly worn when we bought the glider, possibly from its early operation on pavement.  The nose skid was also worn through and we replaced it.

For filler, look for glass balloon filled epoxy for good adhesion, light weight, and easy sanding.  There may be other materials with similar or better qualities.

The ailerons are very weak and make launch and landing difficult.  One must raise the flaps immediately upon landing (to a negative setting) to maintain some control, and we always launch and tow with the  flaps at negative setting.  Any improvement of airflow over the ailerons should help.

Our glider spins readily, but gives ample aerodynamic warning of stall and I don't consider spinning to be a threat.  Pilot weight may be a factor.  At my weight of 165-170, it stalls well.  Lighter pilots will experience deeper stall, while heavier pilots may experience milder or no stall.  Chris, any comment on this?

Good luck!  It's a fine glider.

Regards, Red

Jess,

Wheels, skids or fairings

I have SGS 1-35 s/n 25. It has the wing incidence and flap/aileron interconnect option. I fly it with the CG 25% forward of the aft permissible CG. I almost always operate it off of asphalt runways. It has polyurethane skids mounted to the bottom of the wings. (See photo 7 on Tom's 1-35 website.) I have not seen another 1-35 with skids like these so I tend to think they were installed by a previous owner. I have a set of tip wheels for the glider but have never used them. The skids have never worn out. Rarely do I ever drop a wing during the last of the landing roll; only when there is no headwind.

Performance enhancement

My 1-35 has fairly benign stall characteristics. I've never experienced the type of stall that DJ did in his flight test of one of the early-model 1-35s. The wings on my glider have been filled and profiled by a previous owner. He did a lousy job. I have oscillated between getting templates made and going through the process of profiling the wings versus sanding and filling where necessary and then repainting. With the Wortman wing section, I think that somewhere in the middle is probably in order.

I have also thought about winglets. HP18s use the same airfoil that the 1-35 does and they seem to better with winglets. I have contacted a winglet maker and may buy a set of winglets from him this winter. Don't know if it's worth it.

I have some articles on wing profiling. I can copy these and send them to you if you like.

Water ballast


Most of my soaring is done in southwest Texas (Uvalde) where the conditions are usually strong in the summer, so ballasting up is part of the preflight. I too had problems getting the valves to seal. I tried all kinds of greases and potions. Finally, I found that wax from a toilet bowl ring will seal the dump valves. (The wax ring is used to seal a toilet bowl to the fitting in the floor.) You can find these at Home Depot Aeromotive, Lowe's Aeromotive, etc. Be sure to clean the sealing surfaces of the valve and seat before the first application of wax.

I don't know of any cases of internal corrosion because of residual water left in the tanks but have also wondered. During the annual inspection, I use a mirror and flashlight to inspect the interior of the tanks as best I can and have never seen any corrosion. My biggest concern is water leaking into other parts of the wing that have no corrosion protection. In between flying, I remove the filler caps and leave the dump valves open to allow air to circulate. My glider stays in a trailer.

As expected, a wet 1-35 does not climb as well as a dry 1-35 but in strong conditions the cruise performance is dramatically enhanced. The ride is also much better. Wet, the roll rate is a little slower. I can't cruise with most of the glass fiber guys either dry or wet and keep up with them during a long glide. I can usually outclimb them. Outclimbing them doesn't count for much flying cross country in strong conditions. In weaker conditions, older glass gliders and the 1-35 are more closely matched, but not much.

The 1-35 is a good cross-country glider. Mine has flown several 500Ks.

Regards, Bob Thrasher


WEAR and TEAR

Tom,

   We know of each other only through our love of flying and the plane we
both sought to fly. I am Paul Rehm, and I am the current owner of 1-35c
N2774H. She just went through annual and @ 2000 hrs. is beginning to show a
bit of wear. I purchased her out of Texas almost exactly 2 years ago and have
proceeded to log 120 - 150 hrs per year. I got in touch with Mr. Welles the
apps person who fields all the questions for the company and as an owner
pilot knows the ship and it's quirks very well. My ship is needing attention
to some play in the elevator bayonet bushings and he informs me that there is
a fix which is not too bad to perform.

    But the real reason for my note is that I caught the following write up
accident report and thought I would pass it along to you for inclusion in
your web page if you deem it noteworthy (see NTSB PAGE). I, like you had no trouble with
learning to fly and land this ship, but I have cautioned others who wish to
try one that they do not have the same sight picture/pitch attitude in
landing as do spoilered ships. The manual and adherence to it's
recommendations for procedure with a view to first landings is all that is
needed for safety. The pilot of the plane that is the subject matter here in
my view most likely had not done due diligence with regard to understanding
the plane. But I will leave individual dissemination to the reader.

    There are two 1-35's at our club, Mid Atlantic Soaring, Myself and
Tinwings are usually found in the skies somewhere over Md., Pa., W. Va. or
Va. We both love our ships and have a blast as two of three who will be the
"last to land' at our club on any given day.

                                        Paul Rehm    "KW"

 

FLAPS and SAFETY

Tom, 

It may be that the pilot failed to understand the difference between
thermaling mode flap settings and the landing mode.  The 1-35 has a dual acting
flap handle.  For thermaling the flap is simply pulled back operating only the
upper extension of the flap handle.  I'm not sure what the max attainable flap
setting this allows but it is something like 30 degrees.  To land it is
necessary to place the upper extension of the handle into the -8 position and
then to move the flap handle outward and then back using the entire flap handle,
moving this fully to the rear allows the max flap settings for landing.  I think
but am not sure that all 1-35 models have this dual mode flap handle and the
1-35c uses a more straightforward flap handle.

The nice thing about the dual mode is that the gear warning can be triggered as
soon as the landing mode flap handle is moved.  With a single mode flap handle a
gear warning can not be triggered until the flap setting exceeds all flap
positions used in thermaling. (like 16 or 20 degrees).

Dale Fletcher

Tom,

May I add just one suggestion for new owners or pilots in either model of 1-35 (we have both, & the 1-35C for sale).

Encourage them to go get some flap training in something like a Lark or Blanik L-13 (30 degree flaps), then rent a local C-150 CFI and tell him to focus on flap procedures only. The steep, steep nose down configuration standing on the pedals on final is just something you have to experience alone for the first time.

Michael
Northwest Soaring
N35AC, N76WR
mhende6388@aol.com
509 674 0621

Tom:

I greatly appreciate the recent message about the landing accident.
Fortunately, the pilot was not hurt.  We all get to learn something from
this report.

Here are two items that may interest you: 1) a message to me from LP Aero,
and 2) my USTALL checklist.

(November 1, 2001)
Mr. Boerner,

CANOPIES
We are working on a new process to manufacture these canopies.  I should
have some positive progress over the next few months.  Although we can form
a window to fit at present, the quality is not up to our standards.

Please check back with us in December or January.

Thanks,

George Mesiarik
Vice Pres. & General Manager


A local company has offered to either install the factory canopy hinge
system or STC their own design.  I have come up with a side hinge plan that
they will look at closely before we decide on which route to take.
Frankly, my system is simple and should be inexpensive.

As for the USTALL checklist, it is in an attached file.  I have been using
this to help with approach speeds.  Naturally, when there is wind, I add
about half of the headwind component to these speeds (in knots) or adjust
accordingly depending on altitude. 

Early on, I discovered that the 1-35C will float a long way with the
slightest bit of unnecessary extra approach speed.  Through tips from
people like you and so many others, I have found my comfort level.
Flap-use is a big topic with this plane.  These flaps are so helpful in
small and rough thermals.  They are also very helpful should the approach
pattern be too high.  And of course, when used properly, you sure can land
in small areas.

BUTTTTTT, as you and others have pointed out, they are not to be used as
spoilers.  If I am too high on final approach, and require full flaps, I
either leave them on until touchdown, or I milk them off ever so slowly if
above about 200 feet AGL and if the indicated airspeed is correct for the
lowered flap setting.  Then, whatever flap is still extended (beyond 25) I
leave on to touchdown.  Once, I experimented with controlling touchdown by
reducing flaps slowly in the flair; it worked out but the landing distance
was almost doubled due to excessive airspeed: not good.

So, through communications from you and others, and through the misfortunes
of some, I move forward with more knowledge.  Thank you for keeping me in
the loop!

Respectfully,
Raul D. Boerner

Checklist - WORD FILE  ß-click TO ACCESS

SGSknots.doc  ß-click TO ACCESS

FLAPS and SAFETY

Hello to all:

I suggest that all who fly or will fly the 1-35 need to understand the
aerodynamics of camber changing flaps (as on the 1-35).  They modify the
polar, the stall, min sink, and max L/D speeds and, especially when
extended beyond the performance settings, increase the drag.  The
changing camber changes the angle of incidence relative to the fuselage,
which combined with the increased drag at large flap deflections, makes
necessary the large pitch down to maintain airspeed.  I agree with the
suggestion to get some dual training in other aircraft with flaps, and
recommend those with simple camber changing flaps, not the Fowler flaps
of Cessnas (and, as I recall, the L-13).  However, if Fowler flaps are
all that are available, training with them is much better than no
experience with flaps.

The pilot new to the 1-35 needs to tow high, more than 3000', and
practice maintaining correct approach speed and trimming the pitch
attitude at several flap settings covering the range from 0 to full
flaps.

Extending the flaps decreases stall speed, whereas extending dive brakes
increases stall speed.  Hence, approach speed with flaps must be
slightly less than speed without flaps to avoid excessive float.

I find it advantageous to reduce approach speed on short final.  Keep up
the speed for as long as there is possibility of encountering sink,
turbulence, etc, but reduce it before flaring.  The best way to do this
is by controlling the approach to fly the final segment with less than
full flaps, then extend more flap without pitching down in time to
reduce the approach speed.  I don't look at the instruments at that time
and cannot cite numbers, but this technique gives me consistent smooth
landings with short landing rolls.  Prior to that last speed reduction,
I maintain 55 mph or more in the approach; I don't practice low energy
approaches for all the reasons that apply to all gliders.  Only reduce
speed or energy when there is no danger of landing short or encountering
negative wind shear, and when you don't need the additional control
provided by a LITTLE extra speed to cope with turbulence.

Don't try to land the 1-35 hot.  It will use a lot of runway and you may
experience pilot induced oscillations and multiple touchdowns, possibly
some hard ones.  Just land it level, not hot and not stalled.  If it is
a bit hot, don't raise the flaps until it is landed; that will permit it
to float much farther, in ground effect with excess speed and no flaps
for drag.

Raise the flaps to the highest limit after landing to improve the
aileron effectiveness, and be prepared to apply the wheel brake if the
glider begins to swerve.

The 1-35 often blows over in a cross win, puts the downwind wing tip on
the surface and swerves downwind.  The wheel brake puts the nose skid
down hard and helps prevent the swerve.

Stopping quickly reduces the chance of colliding with something, as can
happen if it swerves.  I've watched a pilot experiment by not trying to
stop the swerve, when there were no obstacles to hit, and his 1-35
turned a full 270 degrees on grass in the swerve!

Regards, Red

SGS 1-35 drivers out there,

I'd like to thank Red for his comprehensive recap of experience flying the 1-35 and recommendations which I endorse. (Such notes should be inserted in the factory manual) I also submit the following below in response to the often-heard comment by the uninitiated, "The 1-35 is dangerous because the over-designed flaps are all you have and that causes the much higher than normal number of 1-35 accidents."

I know plenty of glass owners who after gaggle flying with a 1-35, envy both the thermaling versatility and the added landing options provided by the serious flaps even though they often have a higher L/D.

Despite the fact that there were less than (100) 1-35's built, there have not been an unusual number of accidents and the majority have not been flap/landing related.  (Check the stats) The recaps of the eleven NTSB 1-35 incident reports from 1983-2001 [http://www.ntsb.gov/NTSB/query.asp] below show there are they typical other pilot errors as well. (But still only 11 reported incidents in 18 years)

I can think of two landing accidents apparently not reported which call direct attention to the handling characteristics sited by Red. (I could not find the records for the 1970s to the 1983 in any of you know other 1-35 stories to share)

In the first a 1-35A retractable was landed hot into a short field by an experienced CFI. He mistakenly put the flaps up on final and corrected the situation too late, ran out of runway and had to groundloop in a pond. In the second accident an experienced cross-country pilot made a normal landing on to a narrow foreign airfield and could not correct the inherent "swerve" before hitting two 18" tall runway lights at about 40 kts.

Thank you all for sharing any of your experiences as well.

Michael Henderson
Northwest Soaring

Tom,  

CANOPIES

       I recently acquired s/n 47 from Paul Schweizer as a project/restoration. I have had difficulty finding a source for a  replacement canopy. I would also like to know if you have advice on whether to order it w/ tinting and or venting with slide rails. I understand it may be possible to get either gray or green tint.  This s/n came w/ a hinged canopy , so I don't know if  the side vent was also necessary or advisable.  Thanks,  Jess Pauley   pauley@lr.net

 

The canopy frame would be tough. If you just need the plexiglas, any of the outfits that advertise in Soaring should be able to make one if they can get a hold of another from which to make a mold. For the frame, I have heard of an outfit that sells Schweizer salvage-- you might luck out. I think they are in Phoenix (or Texas?). The previous owner of my ship has ordered parts from them, so I'm forwarding this to him-- Dale, what was the name of that outfit?

As far as options, my opinion would be to get the side vent but skip the tinting-- it will be inconvenient in the late day. Good luck with the restoration.

Dave Prather
S/N 54 "U4"

David...and others,

There used to be an ad in soaring offering to buy and sell Schweizer parts. I got a set of tie-down rings from them 5 or 6 years ago. Located in Texas. I don't see the ad in recent issues.

New canopy. The club I belong to (Nevada Soaring Assn.) has had excellent service from Ray Poquette, dba Thermo-Tec. He is located in northern California. See ad in Soaring or website: http://home.inreach.com/thermotc/

Dale Thompson
near San Francisco

Dave Prather wrote:

> As far as options, my opinion would be to get the side vent but skip
> the tinting-- it will be inconvenient in the late day. Good luck with
> the restoration.

I can echo that. Inconvenient is too mild in my opinion. Tinting is of
minimal value, and only really worth considering in the open west and
questionable there. I learned to fly in SoCal, and one of my early
instructors told me to take off my vaunted RayBans on take off and
landing when there was a low sun or shadows. He pointed out that eyes
accomodated more quickly to light than dark.

This was pointed out when a year later I had an engine failure in a
customer Ercoupe that had a tinted screen. Had to slip it into a small
space short of the airport (fortunately it was a split control Forney)
and I missed seeing some crop poles that created some airfoil changes.
The owner was appreciative that it was in one piece but guilt had me
replacing three wing skins and recovering several panels.

I won't forget that.

Cheers, Bob

PS - unless you have a well trained bladder, some well placed vent is
wise. I like on the left since I am right handed.

Jess et al,

Mark Keene (Keene Soaring,MKEENE221@aol.com) in the Dallas TX area has a good supply of Schweizer parts. I have ordered several items from Mark for my 1-35. Mark's prices are more than fair. Juan Batch in Odessa TX also has Schweizer parts I think. Tim Mara at Wings and Wheels may also be able to help with Schweizer parts.

I replaced the canopy on my 1-35 several years ago. I found two sources for the canopy when I was looking. Mark Keene had a canopy and Ray Poquette could make the canopy. Ray advertises in the Soaring magazine classifieds. I got the canopy from Ray Poquette. (I ordered the canopy before I found out that Mark had a canopy. Mark's price was several hundred dollars less than Ray's.) Ray has a mold for 1-35 canopies and makes them to order. I ordered my canopy clear with a UV blocker. The UV block added $100 to the price but I felt it was worth it because I have a history of skin cancer on my face and arms. The canopy came with the side window hole already cut. The canopy was slightly thicker than the original and is a work of art optically.

My 2 cents worth -- get a clear canopy and opt for the side window. Instead of using the original Schweizer one-piece side window, I ordered a Mecaplex window with the pop-out vent from Knauff and Grove and use it as my primary source of ventilation. I do most of my flying in south Texas (hot) and like all of the ventilation that I can get. The side window also allows you to reach through the canopy to lock it down; something you may want to do while trailering or if the ship is tied down outside.

Regards, Bob Thrasher

I have a "raw" canopy that has not had the frame attached (it's just the plexiglas). It came with the directions on how to make the frame when I purchased my plane. Apparently the previous owners (Long Island Soaring) bought a pair at one time and replaced the original leaving a spare. I'd be open to a reasonable offer. My canopy is hinged and my plane is S/N-49. Hinge or no hinge, I think you'll want a side rail and window (it's necessary for locking the canopy from the outside).
David Pilati

8/01

PERSONAL VIEWS

Good Morning Tom,

I am in the process of purchasing a 1-35 and wondered if I might gain some
thoughts from you.  I have done quite a bit of research concerning the
aircraft, even spent a bit of time talking to the folks at Schweizer.  Your
web site has provided good information, but I'm curious now from a more
personal note. 

Any particular joys or problems worth noting?  The aircraft I am looking at
is in impecable shape.  Very well maintained.  Yes, they are older birds,
but considering the condition and care this airframe has received, I will
take great joy in becoming its new owner. 

I have been flying gliders for a few years now, have a commercial license
and am looking to delve more strongly into the cross-country arena.  My
experience with gliders has predominantly been with Schweizer and Blanik
airframes.  I like glass, but am not too excited about some of the
maintenance issues associated with a glass bird. 

If possible, any thoughts you would care to share would be appreciated.  I'm
curious about long-term maintenance issues, peculiarities in flight,
information sources, etc.  

Thanks for your help.

Dan Thirkill

Dan,

I went for the 1-35 for many of the same reasons as you have.  It is an easy
to fly and almost zer0-cost to maintain glider.

The flaps are a joy and they improve thermalling and landing.  I can thermal
it at 40 mph which will allow it to outclimb just about anything.  I can
land it in really short fields which makes it perfect for XC.  It can come
in steep and can land slowly.  The brake and skid get you stopped in 50 feet
if needed.  So cool !

I don't think it has any weird characteristics, like a bad stall/spin
tendency, but it does spin.

The one trade-off is the performance at speeds above 80mph is not good, so
if you plan to share XC flights with glass ships who like to skate around at
these speeds, the 1-35 will suffer.  If not, no problem.  I rarely fly above
80mph.

If you have specific questions, please ask them.

Good lift,

Tom

4/02

Hi Tom!

 My name is Jim Owens and I wanted to drop you a line on how helpful your website for the 1-35 has been. 

 Living here in Phoenix soaring has been a very BIG part of my life and I am planning on buying my very first glider soon.  I have decided on three to choose from: 1) Grod 102 Club, 2) AC-4 Russia, 3) 1-35.

 I recently aquired my Commercial Glider add-on and now have 100 flights, most in the Grob 103 and the 1-36.  Some of my goals in looking for my first sailplane are:

 A) Basic badge flying,

B) Some racing....but just for fun,

C) Local cross country flying,

D) To find a sailplane that will carry me at 240 pounds (but rapidly working for 230 and hopefully 220!!), radio and maybe a transponder along with the required electrical system.

 I have a ton of questions on buying a sailplane in general not to mention about the 1-35. Some that come to mind are:  How easy (or hard) is she to fly? Does she penetrate well?  While I work for my pay check driving airliners flaps are nothing new to me  :)  but I have never flown a flapped glider...how is the transition?

 It could be summed up this way, "Would you be so kind as to give me your best sales pitch for the 1-35"?

 Thanks for you time and thoughts!

 Jim Owens

Hey Jim,

 1.  1-35 is very easy to fly and the flaps add a lot of stability for thermalling and in the pattern.

2.  She penetrates well but if you examine her polar, above about 80 mph the sink rate is not as good as glass.  Someone did fly side-to-side with an ASW-19 and the glide was identical up to about 100 mph.  So if you stick to the 40-80 mph regime, which non-racers tend to anyway, the 1-35 does very well.  Another plus is the 400 pound dry weight .. it allows faster climbs compared to the best glass, and allows slow landing speeds ... as low as 35 mph with full flaps, which is key to having safe outlandings into small fields.

3.  I never flew a flapped glider till I flew the 1-35.  First flight I took it up to 5000 agl and rode around for 10 minutes at each flap setting.  You quickly learn that flying with flaps is easy, and landings are more precise.  Rule number one is to watch the airspeed as you change flap settings.  Some 1-35 accidents have been by pilots on final at 40-45 mph with full flaps that then go to no-flap as they notice they are falling short of the runway.  Classic stall/spin.  I use 55 mph in the pattern with 25 degree flap then 50 on final at full flap once I know I can make the runway.  I rarely even use up 500 feet of runway. 

 For the sport flyer who wants a reliable, fun, good performance ship, the 1-35 is hard to top.  It has none of the concerns of glass.  It also can be easily repaired, which is less possible with glass. 

 In 98 I was looking to buy new, so I compared the L-33, 1-34, Russia, PW-5, and Junior and share the results here:  http://www.goldengate.net/~tmrent/soar/docs/compare.htm

 An immaculate local 1-35c became available and it exceeded all the ones above on almost all measures so I bought it at a premium ..($20K with a good trailer).  Expect to pay $15K-$18K with trailer now, which is a good value for 38:1. 

 At 220#  you will fit fine in the 1-35 as long as your shoulders are not excessively wide.  Try before you buy.  Also, up to 6'4" tall pilots fit. 

 We have  (2) L-33s, (2) PW-5s, and (1) Junior in our club and they all are good ships with good owner satisfaction. 

 Hope this info helps and I'm sure you will be happy with whatever you buy.

 Good lift,

 Tom Rent

SGS 1-35c

sn 87

4/02

I was just directed to your great site.  Thanks for all the 1-35
information.
I am on your list with 34181, which I have owned for 10 years or so.  Most
of my flying in Wyoming is by myself, and towing can be a problem.  I
started in Hobbs in the late 1970's.
Question:  Until I saw your detail about the 1-35, I was not aware that a
hinged canopy reduced pilot weight. I don't recall anything in the book.  My
former partner was in the 220 lb range and I go about 200.  We have had no
difficulty and the ship trims out easily and with its range.
Why the reduction in weight?  Since I have seen few other 1-35's, I was
surprised that there was anything other than the hinged canopy (front
mounted, forked device that swings up and down with the canopy impaled on
it).

Steve Maier

SKIDS

Tom

- I've owned a 1-35 for over 10 years and have
always flown on grass. Six months ago I relocated to
an airport that has asphalt and gravel. I checked my
skid and see that the skid shoe is well worn and even
missing some metal at the contact area. I'd like to
know what others have done to repair the shoe.
(Schweizer has no parts and Mary said the price for
them to manufacture a shoe was very high...so high she
wouldn't even mention the price).
Short of sending each individual on the 1-35 list an
e-mail, is there anyway to broadcast this question?
Thank you for your help.
David Pilati
49DG

Dave,

Suggest you contact Benz Aviation, Ionia, MI.  I think they've done skid replacement on 2-33s which should be somewhat similar.

Dick McEwen

David,

We just replaced skid plates on both the 1-35 and the 1-35C 1/4" Stainless steel (heat treated). Hardly scratches it on the worst asphalt and gravel runway you have ever seen here in the Cascade Mtns. Be sure to replace the screws with high shear type as they will snap.

Michael

p.s. Anyone have a friend who likes your ship and wants to buy a beautiful 1-35C? We have one too many and a Pawnee to pay for.


J. Michael Henderson
NORTHWEST SOARING, INC.
Email: michael@northwestsoaring.com
Tel: (509) 674 0621, (206) 729 5358
Internet: www.northwestsoaring.com

 

David,

I replaced my skid plate with 1/4" hard rolled steel.   It was quite
simple in using the worn skid plate as a template.

Interestingly, an individual at our club has the 1-36 sprite tested by
D. Johnson in '82.  His has the original plate, which has essentially no
visible wear.  This plate is 1/8" SS (grade unknown) with 1/4" hardwood
backing, presumably for standoff distance.  I think I will go that route
next time around, in the interest of weight and durability   (Mike
Henderson, maybe you can comment on this at the end of this season? )

Paul Westerfield

Dave,

Which part is worn? The skid plate or the part the plate attaches to?

If it's the skid plate, they can be easily made from 0.090-in thick 4130
steel. This is what I do and they typically last about a season. The plate
wears more on one end then the other so I turn the plate around to get more
life. My 1-35 is flown on and  off of pavement.

Regards, Bob Thrasher

7/02 FLAPS

Dear Tom, Bob, Jess, Richard, and Mark:

Question: When do you use your negative flaps?

My 1-35C manual limits the airspeed for negative flaps to the same speed as
for positive flaps. This appears to render them useless for high-speed
penetration. Your thoughts are enthusiastically invited.

Raul D. Boerner
N2780H

Raul,

Supplement 1, Page 4, of the 1-35 Operating Manual list the Cruising Speeds for 0,-4 and -8 degree flap settings.

I usually go to -4 degrees when I hit 55kts.  I don't get up to 75kts very often, but when I do, I go to -8 degrees as the manual suggests.

I use -4 degrees for take off and climb to release.

I use -8 degrees after touchdown and during rollout.

I would think that these settings apply to both the 1-35 and the 1-35C.

Dick McEwen

 

Raul,

Takeoff 0 degrees
Thermal 4 degrees
Landing variable

I never use negative flaps, even at higher airspeeds. The only time they go
negative is when the flap handle is briefly moved forward to disengage the
flap mechanism for landing.

My 1-35 is equipped with the wing incidence modification and the
aileron/flap modification.

Regards, Bob Thrasher

8/02 – RADIO ANTENNAs

Tom,

     I wonder if it is possible to ask a question of 1-35 owners via this website?  I would like to find out if someone has determined a good position for mounting a radio antenna.  In the original design it sticks out horizontally to the rear at the top of the rudder.  This means there is no ground plane and the polarization is horizontal compared to all other gliders and ground stations that have vertically polarized antennas.  I find my radio does not work well and I was thinking it may be due to this antenna mounting position.

    An obvious place to mount it that would overcome the ground plane and polarization issues is vertically behind the removable turtle deck on top of the metal fuselage, i.e., as it is done on the 1-26.  But this would be an eyesore and make the ship look like a 1-26.  I imagine that most modern fiberglass ships use an antenna buried in the vertical fin, probably a center fed dipole that would be excellent in sending energy out in the horizontal where it does the most good.  But this can't be done with the metal fin on the 1-35.  I thought that maybe an antenna in the cockpit or in the fiberglass turtle deck structure might work.  I wondered if you had any ideas about this problem or if the homepage could be used to get information?

 Thanks,

Ralph Markson

N135RM

Ralph,

 We have 3 1-35s at our Gliderport and they all have the antennae protrude vertically just aft of the turtledeck.  2 have a "kink" in the antennae that has it angle rearwards at about the 1/3 length point.  It has worked well for me.  Check out photo #3 on my ship (sn87), it gives a good view.

 By the way ... I got a 4 hour flight in yesterday at our gliderport.  Sweet ride.

 Good lift,

 Tom

Ralph, Tom

I would suggest that you check the original installation for a poor
connection.  My antenna has remained in the original position (pointed
to the rear from under the small cover at the top of the fin) and it
works well...  30-50 mile range for talking to someone on the ground and
  one or two hundred mile range to other aircraft.  And once I conversed
with an aircraft at 30,0000 at a range of 500 miles.

One thing to remember about the original position, for best range, do
not fly directly toward or away from the direction of the other radio.
However, in all the years I have flown I have never worried about this.
 
Dale Fletcher

Dale,

    Thanks for the advice.  Knowing it can work well is useful since I had
assumed it could not in that position and now I will try to get measurements
and check the connections.  One of my radio amateur friends says a
horizontal antenna will have about 25% of the sensitivity that it would have
if it were vertical.  Perhaps bending it upward a little might help.  It
sure would save a lot of trouble if it would work well from its current
position.

Ralph

Ralph,

It is certainly true that the nearly horizontal antenna is much less
efficient but it is a good, low drag, installation in a metal sailplane.
Besides a sailplane is a good platform with little interference.  The
original installation had the antenna at about a 12 or 15 degree
inclination.

I assume the radios of today must have two or three times the transmit
power of my old radio.

Another thought, does your sailplane still have the original antenna?
If not, the length of the antenna may be a problem.  It is very
important to have the correct antenna length for the aircraft frequencies.

Also, check to see if the antenna is broken or cracked internally.

Dale Fletcher

Dale,

    It is the original antenna.  This is a special antenna with a coil wound
around it that effectively makes it appear longer, presumably the proper
length for a 1/4 wave antenna.  The radio is a 25 year old Mentor 360
channel that draws a lot of power compared to modern radios but puts out 5
watts.  I will do some testing and let you know how things work out.  Thanks
for your help.

Ralph

ALL,

Today we did some tests of antenna positions and related stuff and I wanted to pass on what we found to those of you who have offered advice.  Steve had a Standing Wave Ratio measuring device which we used.  The original Schweizer antenna in its factory mount position had an SWR of 2 which I gather is acceptable.  I had not realized that the antenna was really about 15 inches long and not just the visible part which is half that long as half is within the fiberglass housing on top of the rudder.  It is wound with a coil to increase the effective length to the nominal 23 inches.  Also with the tailwheel on the ground it sticks up perhaps 15 degrees so since the ship flies with the nose way down it may be sticking up 30 degrees above horizontal in flight.

    We next removed the antenna from the housing and in doing so found that the co-ax cable easily pulled out of the bnc connector at the base of the antenna.  So there may have been a poor connection there which would have been fixed when we put the connector back on the co-ax.  But the SRW of 2 was made before this so maybe the connection was o.k.  Then we mounted the antenna vertically at the top of the semicircular front bulkhead behind the turtle deck where there is metal fuselage all the way back, but no ground plane forward in the turtle deck and cockpit area.  Here the SWR was 3, maybe not so good because the ground plane near the base of the antenna was only toward the rear.

    Then we made some comparisons with a good ground station that I brought along and with the antenna in the vertical position on the bulkhead, the ground station picked up weaker transmissions that the ship's radio did not detect.  So we put the antenna back in its original tail position and here the ship's radio was able to pick up Worcester tower, which is 12 miles away and 500 feet higher, whereas the ground station with its vertical antenna could not pick this up.  So it seems as Dale suggests that despite the relatively horizontal position of the factory installed antenna and no ideal ground plane, the factory position may be satisfactory.  Perhaps my poor reception was due to a bad connection as he suggested although the SRW was 2 before the connector was reassembled.

    No tests of transmission were made.  I will fly it this way and let you know if anything new and interesting becomes evident.  As to the idea of a motor driven antenna mounted on the belly, on second thought this is not a good idea because aside from the complexity and need to provide power, it would not work with the glider on the ground.  Gary's idea of two rubber duckie antennas mounted back to back is intriguing if I could find a place to put them, perhaps within the turtle deck volume, since a centerfed dipole should have better performance.

 Regards,

Ralph

Interesting.

The first question is, is the SWR meter rated for VHF? My one experiment
with an SWR meter rated for only up to 30 MHz indicated they're useless
by about 50 MHz. This is apparently a matter of physical construction of
the meter; the internal L & C begin to dominate the circuit being checked.

[Also, you said you didn't do any "transmission" tests, but you need a
signal source to measure SWR...?]

Assuming the meter is good to at least 150 MHZ, did you do the SWR tests
with the SWR meter between the transceiver and the feedline?  This is the
right way to do it, but remember that the meter was displaying the SWR of
the whole feedline//antenna system; the reading is reduced by any losses
introduced by the feedline.

The key thing with respect to SWR is the feedline quality; with good
feedline, the SWR is not too important, but with lossy feedline it's
critical - and not directly measurable!  For example, you may find that
disconnecting the feedline at the bottom of the antenna and re-measuring
the SWR, it's still 2:1!  In that case, you're basically measuring the
standing waves on the feedline with no load, ie. measuring how much of
the RF the feedline is eating.  The reflected power, when it gets back
to the SWR meter, may only be sufficient to show a 2:1 SWR.

After a storm, I found that my 200' RG-58 feedline to my ham 10 meter
band antenna was showing a 2:1 SWR instead of the usual 1:1. I thought
a connection somewhere must have been damaged. Sure enough, when I
climbed my tower I found the power feed to my remote switch on top of
the tower had come unplugged. In this state there was no antenna
connection at all, yet the SWR was only 2:1!  Later I replaced the RG-58
with Belden 9913 super-low-loss feedline. With the remote switch powered
off, it showed a nearly infinite SWR.

You should also be able to observe some frequency dependence; ie. the
SWR should vary slowly but smoothly with test frequency. A perfect
system has a 1:1 SWR at the antenna resonance point. Any impedence
mis-matches between transmitter, feedline, and antenna will raise the
minimum SWR. A half-wave resonant feedline will moot the feedline
impedence, but make the entire system more frequency dependent (ie.
the SWR will rise more steeply as frequency is varied away from the
minimum SWR point).

Beware of testing using a receiver; disconnected cheap feedlines DO act
as antennas, due to poor shielding quality. Your connection may have in
fact been broken or only half the circuit. My disconnected RG-58 appeared
to be "working" on receive, though not connected to an antenna; the 9913
was just about silent in the same situation.

The loss in 200' of RG-58 is about 6 db per 100 feet at 125 MHZ; for 9913
it's under 1 db. The connectors are important, too; you should use gold-
plated BNC connectors. Also, it's extremely important that the coax never
has gotten any moisture inside it. Believe it or not you should not build
VHF coax in a humid environment; build cables in a dry environment (AC at
least in the summer, but a house with no humidification in winter is
best), and seal the ends with silicone, then weatherproof the entire
system with good electrical tape when you install it.

I'll bring my antenna reference book when I bring over the thermometer.

Regards,
Gary

I have a citizen band VSWR that I purchased at Radio Shack 20 years ago.  It
works perfectly well at VHF.  I checked it out in my lab when I was working. 
It is pretty dam accurate at VHF.
Bob

Ralph,

  The retractable antenna idea is interesting, but what happens if you
lose sufficient battery power ?  I have a very thin whip antenna on top, angled
in the manner that Tom mentioned.  In reality, it is not
even noticeable, esp from 1/2 wingspan.  Maybe you could consider a 'trailing
wire' configuration as used during the 2nd WW.  As far ad drag is concerned, I
think the fin/rudder gap is horrific and think that alone is of much greater
concern.  I have not found any mylar strip that is wide enough to cover the
lower section of that gap.  Any suggestions?

 

NEW PICS

Tom,

Don't know when you plan on updating the 1-35 web site, but I plan on sending
some new pics of N135V SN22 in the next couple of weeks for an update.  Spent
the winter refurbishing the craft, inside/out and flew it for the first time a
couple of weeks ago (25 hrs. flt time since).  Great fun blasting around on
short 60 mi. X-C with abandone.  Will try H2O this weekend as we are expecting
rather strong conditions here in Austin TX.  This time of the year flt time
seems to be limited by the amount of drinking water you carry....

Additionally, I have a couple of 8-1/2 X 11 scanned photos, apparently supplied
by schweizer to a prior dealer, of a 1-35C and a 1-35A.  These are similar to
the ads. on the web site.  Will send later today.

I have scanned the flt manual for SN 22 in addition to the aileron/flap
interconnect supplement.  If interested, I can burn to CD and mail, as the files
are rather large (JPEG pasted into Word) and I do not know how to reduce the
size, possibly Adobe?

Question,  what is the soaring season in the St. Paul area?  I am considering a
job proposal in that region, and fear I will miss TX soaring condition, to be sure.

Regards,

Paul Westerfield

Paul,

    Thanks for your comment and picture.  Since writing about the
retractable antenna in the belly, I realized this is a pretty dumb idea, not
only because of the complexity and power requirements but because one wants
to be able to use the radio on the ground.  Your installation on the top is
no doubt the way to go.  We have done some testing with the factory antenna
and the radio on my ship does not work well.  It may have something to do
with the original 30 year old cable and associated connections degenerating.
When there is a little time we will investigate further and I will let the
1-35 people know if we come up with any conclusive findings.

    I wonder if you or others in the network have some reliable data on the
1-35 polar, perhaps as a function of wingloading?  As I mentioned to Tom
previously, the ship Dick Johnson flew was one of the first, if not the
first, one built and it had the thin skins with rippling (as he mentioned in
the article).  This was corrected with thicker skins after S/N 46.  The
article and polar by Johnson should not be considered representative of the
1-35 performance and I would imagine that some other 1-35 operators would
have done some rate of sink testing.  Maybe Tom could ask about this on the
1-35 web.

Ralph

8/02 SPARE WINGS

Tom,

I have four 1-35C wings and some control surfaces. All four wings came off
of wrecked gliders (s/n 68 and ?? I think).

I believe that one could come pretty close to making two good left and
right wings out of them; however, it would be a fair amount of work.

I will probably never do anything with them and would like to get them out
of my hanger and to a good home. The asking price is $500 and they are
located in northeast Oklahoma.

Know of anyone that may be interested?

Thanks, Bob Thrasher

GAP SEALS –

Paul,

    I happened to be talking to Tim at Wings and Wheels and mentioned the sealing of the rudder vertical fin gap that you were concerned about.  He seems to know a lot about 1-35s and said that the factory fabric seal keeps the cross flow of air from happening better than a mylar seal that will not seal well when coming against a fabric surface.  So you should stay with the fabric gap seal if you have one.  If not I think he may have some as he has scrapped about 5 1-35s.

 

Ralph

RED BIRD

ALL,

As the webmaster for SHA http://www.sailplanehomebuilders.com, I attended
the Sailplane Homebuilders Association workshop at Tehachapi, CA.  At the
end of the first session, I turned to talk to the fellow next to me to
discover Paul MacCready taking notes in his engineering log book.

While loading my plate at the Sunday banquet, I discovered Cam Martin
standing next to me.  After indicating that his broken web-link to the
Duster BJ-1b website was due to a server problem, Cam asked if my 1-35c is
the red one. The next fellow next in line asked is that the 1-35c with the
black canopy?  I know which one that is."  Amazing!  Cam knew Paul Remde
also.

While preparing for an insurance check ride in an ASK-21 at Tehachapi, my
log book was getting a very rigorous inspection until the instructor, John
Chapman, saw the entries for the SGS 1-35c.  "If you can fly that, I guess
you're OK with the -21."  The logbook inspection was over. During the
checkride, a seagull joined us in a thermal.  Running a ridge was fun too.
The 8 mile stretch of shear lift from Mt. Tehachapi wasn't working that day.
We were able to fly over the "Tehachapi Loop".  The next day, rotor
turbulance was the worst ever and I had to cancel giving Judy a ride.

Being a new 1-35c owner is fun!  Nice to be back where it is green and cool.

Steve Adkins  sn 72

 

NOISY VARIO

Tom,

My two variometer indications were always "nervous." So, I E-mailed Mike
Borgelt (he makes variometers) and this is what he wrote back:

"You need an Irving type [TE probe] with 2 holes and the bend is only 70, not
90, degrees. These don't cause turbulence and provide excellent compensation.
I can sell you one if you want."

The TE probe that came with the plane is 1970s technology and apparently has
a tendency to create its own internal turbulence; this leads to nervous vario
indications.
After installing the new TE probe, my varios are now easier to read as their
indicators respond more smoothly to changing lift. The improvement is
dramatic.

Raul D. Boerner

 

Raul,

Any trouble mounting the new probe?

Tom

Tom:

No trouble at all. Mike Borgelt told me that, should I need the TE probe in a different position, it is OK to bend it a little bit. Well, I did not have to do this, but it is nice to know that the TE probe is not a mystery rod that is highly delicate.

He told me to be sure that my tubing's T-fitting from the TE probe to the two varios is as far from the varios as possible. Mine was just behind the instrument panel. Mike feels that this can cause problems in that one vario can affect the other vario (not the case with varios that don't require capacity bottles). Per his advice, I moved the T-fitting to behind the seat.

Funny thing is that all along I thought that the nervous varios were normal. Well, it is not normal. Mike wrote to me that the TE probe design we have in the 1-35 is a 1970 vintage design. It is known to have internal turbulence problems. His solution: buy a new-generation probe. So, I bought his.

Good lift right back at ya,
Raul D. Boerner

 

NEW FANCY CANOPY

Tom:

Attached please find two photos. Both show my new canopy hinge. One shows the
tail dolly I made; it was my first fiberglass project. [see them under pics for SN 80 – TOM]

Raul D. Boerner

11/02

 

FLUTTER

Tom,
I'm half owner in a 1-35 with Dave Prather.
I'm doing some finish work on it & wonder what i can do about the flutter
problem we have.  U4 has flutter - aileron, i believe.  The advisory service
bulletin about the aileron pushrods has been complied with.
Specifially - how are ailerons balanced?  by weight?
and would mylar gap seals work?
Thanks,
Bob Spielman

First I have heard of flutter on a 1-35.

Check for "play" in the whole system.  I had to add a washer or 2 last year on the aileron bell cranks to tighten up my system.
I also have my gaps sealed with a run of plastic packaging tape on top.  Apply when ailerons are fully down.  This has lasted
for years and gives me good control.

At what airspeed does it do it?

Good lift,

Tom

Tom,
Thanks for the info.
If i go above 60 mph with flaps zero, i get pretty significant flutter
unless i go to -4 or -8 flaps.  So i stay out of the flutter range by using
the flaps. I know flutter is dangerous so i'm concerned about it.
The 1-35 had it's stick aileron bell carnk tightened previously, some years
ago, so i'll check i out.

Bob S.

That sounds very bad.  Real Flutter usually occurs up near Vne, not 60 mph!

This ship needs a good going over by a good inspector.  Have him/her go over it both unassembled and assembled.

Let me know what you find out.

Good lift,

Tom

12/02 

NEW PICS

Hello Tom,

Hope all is well and you are staying warm.  Too wet to fly in central TX as of late.

I am sending some recent pics of N135V, SN 22.  It spent last winter undergoing
a refurbish.  Flys great.  Put about 60 hrs on it in the first couple months.
The others at the local club here, Faultline Flyers, seem to be quite impressed,
including Ron Tabery.  One instructor took it on its first flight this year and
commented "It flys like glass" and virtually everyone that sees it for the
first, or second time state they didn't know Schweizer made glass ships.  Enough
for a chuckle.

At your convenience, please delete my street address on the listing.  I have
moved, but still in Austin, TX.

As a note, the 1-35 pics labeled "Water Dump" and "Flaps" are of SN 22, before
the new microballoon fill and paint.

I will send 8 pics, two per email. [see them under pics for SN 22 – TOM]

Regards,

Paul
Westerfield

PAUL – LOOKS GREAT – TOM

Hello Tom,

Yes, the ship has been refinished.  It was completely stripped, new fabric on
the tail feathers, paint stripped/sanded, all delamination of the 'fill'
material removed and a polyester/microballoon material applied to wings and fuse
and sanded to contour.   All tubing (pneumatics) and wiring replaced, etc.
Paint is a PPG Poly with 3 clear coats.  Wings sanded and polished, but the rest
left as is.  Maybe I mentioned before, and maybe not.  The plane was cabled to
the upper rafters of a maintenance hanger for 20 yrs.  I expect that the
temperatures there were somewhat high (TX in the summer at the top of a metal
hanger) and likely caused some differential expansion in the materials (Aluminum
and fillers).

Instruments cleaned up/calibrated, but original, including the dilute/demand O2
regulator....(Navy).  New O2 bottle, though.  I will likely need to replace the
canopy, at some point, and do not look forward to that.  There has been a crack
forming from a corner of the vent window, but has been arrested at this point.
Spent 7 days refinishing the canopy, alone, and it is quite optically clean.  I
had no problem in getting a good canopy seal and the plane is incredibly quite,
even at 110 mph (with the vent closed).  Open the vent...and well, you know.

To give you an idea, attached are a couple of 'pre finish' photos.

Paul

WOW - I remember which one this is now!

You did a great job.  It will make a good story for the website.

Love to hear more about the refinishing process.  What is the trick for sealing the canopy, wing root pushrods, turtledeck,
hook, .....

Mine is still a bit of a whistler!

Tom

 

STIFF CONTROLS

Hello Tom,

Give me a week or so.  I will put a story together and detail some of the things
that were done to quieten the air noise.  I had never flown a 1-35 prior and
after reading the letters on the web site, expected a bit of wind noise.  Was
not the case (vent excluded).  Not sure, but I may re-route the vent to exit
below the "dash", behind the instrument panel as a test.  Otherwise, it flys as
a whisper.

I do have a question for you, as time permits.  My aileron pushrods do make a
racket, noticeably on landing.....on somewhat rough ground.... and when pushing
the plane to launch.....also on rough ground.  Is this normal, or should I be
concerned.  The Aileron force required at the stick is in my opinion, somewhat
heavy, as compared to say an ASW27, but maybe normal for the 1-35.  The
'heaviness' is definately within the wing, as when the wings are off, the stick
friction is less than nill.

Thanks,

Paul

Hi Paul,

My vent is not plumbed to the panel.  It "exhausts" out a port on the same surface as the compass is mounted in the canopy.

As for aileron noise, the pushrod is one long metal tube run straight out to a 90 degree bellcrank located just forward of the
aileron control horn.  The clanking noise is normal (but irritating as hell!) and is this tube flexing under the vibration of
ground motion.  The flexing pushrod hits the metal through-holes cutouts in each rib that are roughly 4" diameter.  Schweizer
opted for this rather than suffer the drag of a more pushrod supports (rollers) along the length which usually involve bearings
which need lubrication/inspection/can cause trouble).

There is an old A.D. to inspect the aileron pushrods which involves taking them out of the wing.  Easy to do.

As for aileron system tightness - you definitely have a problem.  Mine, and others I've worked on, have very light controls.
The wing pushrod, especially when not connected within the fuse, offers almost no resistance in-out.  The only sources of
friction in the wing is one roller, one bellcrank, and the aileron hinges.  The likely culprit is the aileron hinges.  Inspect
and lubricate each will clean up this problem.  let me know what you find out.  The aileron system in the fuse is also light and
an equal inspection should be made of it's friction points.  I suspect years of dryness and dust has crept into the old bird.

Thanks again for the pictures.

Good lift,

Tom

FLUTTER

Tom,

We had a brief exchange of e-mail letters a few months ago which led me
to believe that you might be able to point me into the right direction
to solve a current problem with my treasured sailplane.

My 1-35, C-GJJS, serial number 008, with 700 flying hours and 350
flights, has lately developed a vibration which sets in when I fly into
turbulence (for example, when crossing the wake from the tow plane). 
This happens when the flap is within the "flying" range, i.e. between
negative and +18 degrees.  The shaking can be quite unnerving.  No
vibration is felt on the controls, however.  When I move the flap into
the "landing" range, i.e. +30 to +80 degrees the shaking stops.

When I bought the glider in 1980, the previous owner informed me that he
had received a notice to the effect that the free play at the trailing
edge of the flap should be no more than a specified amount (3/8" ??). 
If greater, some remedial steps had to be taken.  At the time, the
"slop" was less than this, I did not notice any problems in flight, and
therefore there was no need to be concerned.  I proceeded to happily fly
the glider for the next 20+ years.

However, the vibration has now started to occur whenever I fly into
turbulence.  The free play of the flaps also seems to have increased
somewhat over the years.  This leads me to suspect that the vibration is
caused by flutter of the flaps, made possible by the increased free
play.  At large positive flap settings, the aerodynamic load on the
flaps is higher, holding them against their travel limits, and (what
appears to be) flutter does not occur.  To test the free play theory, I
shimmed the gaps between the flap control plugs (in the fuselage) and
the slots at the ends of the flap control rods (in the wings), removing
all slack in those locations.  This reduced the free play of the flaps
by some 15%, indicating that other parts of the flap linkage, within the
wings, account for 85% of the "slop".  On the subsequent flight the
vibration appeared to be noticeably reduced, although not altogether
gone.

What I am now looking for is advice on how to further reduce the free
play on the flaps.  In other words, what advice did Schweizer send out
to owners on this subject, between 1975 and 1980?  Tom, since you are
obviously in close touch with the 1-35 community, would any of your
contacts remember that far back?  Alternatively, has this problem
happened to anyone else?  If so, what was the fix?  I am sending the
same questions to Schweizer, but since they have been out of the
sailplane business for so long now, there may not be anyone left there
who can provide answers.

I would appreciate any suggestions you can give me on this subject.

Best regards,

Ulo Okapuu
Montreal, Canada
(514) 426-3358

ULO,

I have forwarded your email to an original owner (Dale Fletcher) who likely can provide you any info Schweizer sent out. 

I'd appreciate any further resolution you may discover.  You have already done all the things I would have tried.

Does your have the flap/aileron linkage? - that too might have some wear.  How many hours do you have on the ship?

Good lift,

Tom

Tom,

Thank you for this.  I have also e-mailed my questions to Schweizer, but
not yet received a reply.  Will certainly keep you posted.

The first owner of C-GJJS,  John Southworth from Vancouver, had the
flap/aileron linkage installed and then subsequently removed because (he
claims) it made little difference in perfomance and added weight and
cost.      {An interesting historical note:  when John took delivery of
008 it had a beautiful rainbow colour scheme (it was Schweizer's display
ship at the 1975 or 1976 SAC convention).  However, all his club mates
had white fibreglass ships and made cracks about his "gay" colours, so
he had it painted white by the time I took it over in June of 1980.  How
we can be affected by peer pressure, even in our 50's!}

The ship has now some 700 hours and 350 flights, but only a few hours of
this have been on turbulent ridge flying.

I am looking forward to hearing from Dale Fletcher.  All the best to
you, Tom, and good lift to you, too!  By the way, where are you based?

Ulo

Tom,  I do not remember hearing of this issue before.  I assume that
serial number 4 has not been modified in the field to install the
flap/aileron interconnect.  You might ask Fred Hewitt, he and Lloyd did
install the interconnect on thier 1-35.

Dale

DALE/ULO – I have confirmed that this was permitted to be done in the field.

7/03

Tom,

Thank you for asking around, within the 1-35 community. The picture has cleared somewhat at my end. Here is an update.

I contacted Schweizer Aircraft shortly after I wrote to you, and they replied promptly (my hat is off to them!) by sending me a copy of their Service Letter No. SL-102-10 dated July 9, 1975 (Subject: Flutter of Flaps at approx. 60-70 mph. Models affected: SGS 1-35, Serial No.'s 2 thru 35). Attached to this Service Letter was a copy of Schweizer's Engineering Change Order 35-264 dated 7-7-75, titled "Flap Torque Tube - Fuse.", which recommends that the bearing blocks which support the fuselage portion of the flap torque tube be adjusted to produce a friction torque of 5 to 8 in.lbs., if necessary by filing them lightly to achieve this. No mention was made of the flap/aileron interconnect version of the 1-35, so I assume that the basic, non-interconnected version is of concern here.

The hard copies (of these documents) which I received are of such quality that I fear they will not reproduce well in the electronic form. If anyone within the 1-35 community wants to see them, I will be happy to make copies and mail them out, on request. Meanwhile, here is a thumbnail summary of the Service Letter and my own observations on S/N 008:

SL-102-10 says that two cases of flap buzz or flutter have been observed, at speeds of about 60 - 70 mph. This among (at least) the first 35 units produced. In both cases, the buzz was stopped by applying a small amount of flap, positive or negative. Schweizer speculates that at this speed range the flap is not subject to any damping airload at 0 deg. flap position.
[My own observation, on S/N 008, has been that flutter occurred at any flap setting within the "flying range" of full negative to +18 degrees, provided that heavy turbulence was present to start the process. It was successfully stopped by moving the flap into the "landing range", where even the minimum of +30 degrees was sufficient. These events also took place in the 50-70 mph speed range, I did not test at higher speeds.]

Schweizer further states that experience with their prototype 1-35 along with owner's reports suggest that this flutter could occur if the flap free play is 0.250 inches or more. The free play is measured at the trailing edge of the flap by using only light pressure, about 2-3 lbs. They speculate that the free play is caused by a combination of dimensional tolerances and wear.
[In the case of my S/N 008, with 700 flying hours, the free play is somewhat greater than 0.250". I began to observe flutter about two years ago, low enough not to worry about it at first, but becoming unnerving by this Spring. In 1980, when I took possession of 008, there certainly existed a noticeable amount of free play but the amount was unfortunately not recorded. I can only assume that the original free play was caused by unfavourable tolerance stack-up, and that wear has caused the free play to increase to the point where it is now excessive.]

SL-102-10 advises owners not to fly the sailplane if free play approaches 3/16". If free play exceeds this, try to determine in what area it exists, and carry out rework as per Schweizer's instructions, if necessary.
[The 3/16" maximum suggested by Schweizer seems conservative: I am quite sure I had at least 1/4" free play for years without flutter.
On 008, I found no free play at all in the fuselage flap control, from the handle to the "plug" (for lack of a better term) which mates with the torque tube drive at wing root. All of the free play was due to the 0.012" (total) clearance at the plug (between its two lugs and the slots in the torque tube in the wing) and other flap linkage points within the wing.]

It might be helpful to briefly reflect on the nature of vibrations in general, perhaps this can throw more light on our specific problem:
As I understand it, three factors need to be present for potentially destructive vibrations to occur:

1. a (fluctuating) exciting force must be present, to put energy into the vibration
2. the vibrating part must have its natural frequencies within the frequency range of the exciting force
3. the damping forces (which could absorb the energy provided by the exciting force) must be low

In the present case of flap flutter, the fluctuating exciting force (1) is provided by the aerodynamics of the wing: turbulence in the airmass causes the flow over the flap to momentarily separate from one of its surfaces, producing a difference in pressure which pushes the flap in the direction of lower pressure. The new position of the flap now causes a separation on its other side, which pushes the flap back again. Airspeed influences the frequency of excitation, which explains the speed range of 60 to 70 mph mentioned by Schweizer.

The combination of the flap's inertia and its (amount of) free play controls its natural frequency (2). If this falls within the range of excitation frequencies which correspond to the normal flying speeds, then we can expect flutter.

At large positive flap settings, the flap is prevented from fluttering by air pressure which holds the flap against one of its stops. However, at flap settings within the normal flying range, steady air pressure in either direction is too low to prevent movement caused by the momentary reversal of pressure. The damping force (3) which could absorb the energy supplied by (1) could be supplied by friction in the linkages of the flap control mechanism. I believe this explains Schweizer's Engineering Change Order 35-264: increasing the friction between the bearing block and the fuselage portion of the flap torque tube will provide the increased damping required to absorb the vibration energy PROVIDED THE FREE PLAY IS CAUSED BY THE LINKAGES BETWEEN THE TORQUE TUBE AND THE HANDLE, i.e. provided there is movement between the torque tube and its bearing blocks. This is in effect implied in Schweizer's Service Letter, which recommends that the location of the excessive free play should be first determined, before any rework is undertaken.

In the case of my 008, however, there is no free play within the fuselage portion of the flap control mechanism. All of the free play takes place at the plug/torque tube interface and the flap control linkages within the wings. I have therefore concluded that rework of the bearing block according to ECO 35-264 will most likely not be effective. Means to increase damping forces (3) are therefore not available. Avoiding the air speed range which causes excitation (1) is impracticable - it is too wide and is centered on the most desirable flying speeds. The only remaining fix is to change the natural frequency of the flaps (2).

Of the factors controlling natural frequency, the inertia of the flap cannot be changed without a major redesign of the sailplane. By the process of elimination, the only remaining fix to the problem is to reduce the free play in the linkages. The only point of easy access for this is the plug/torque tube interface, which in the case of 008 has a clearance of 0.012" (between lug and slot, when turned fully in one direction, measured with a feeler gauge). This clearance accounts for (very approximately) one quarter to one third of the total free play. I have chosen to eliminate this by inserting a 0.012" brass shim into the clearance, held in place by a self-adhesive aluminum tape. Reducing the remaining free play would require the removal of wing panels, a major, expensive tear-up which may prove unnecessary.

One test flight in 008 to date, with the shims installed, has shown that this modification has indeed caused a substantial reduction, possibly even the elimination, of the flutter problem. It seems that the 1-35 tolerates quite a bit of flap free play, but there comes a point where enough is enough and flutter sets in.

I have rambled on in more detail than would seem necessary, but I felt that the subject needs to be discussed in depth once and for all. I am not an aircraft mechanic. Some of the more knowledgeable readers of this note could well conclude that I have arrived at an incorrect interpretation of the problem and its solution. If so, please contact me and let's discuss. Meanwhile,

IN SUMMARY:

Only a very few Schweizer 1-35's have encountered flap flutter.
Flap flutter is recognized by violent shaking when flying into turbulence (e.g. wake of tow plane).
If you encounter flap flutter, set the flap into the landing range (+30 degrees or greater).
Flap flutter is most likely caused by excessive amounts of free play in the flap's control linkage.
To eliminate future incidents of flutter, refer to Schweizer's SL-102-10 and ECO 35-264. Begin by determining the major contributor to excessive free play, then take steps to reduce free play and/or provide the recommended damping as recommended by Schweizer.


I will keep you informed of the results of future flights, Tom. Meanwhile, happy soaring!

Ulo

NEW OWNER – YES!

Tom:

Thanks for your informative website on the 1-35.  I'm thinking of buying a 1-35c.  I'm a low time pilot--I learned in a Blanik L-13 and 2-33, I've flown a 1-26, 1-23 and a 1-34 with no trouble.  I've read everything on the website related to landing a 1-35.  Should I be concerned about the flap landings of the 1-35?  Two owners of 1-35 I've spoken to had similar experience to me when they bought their '35s, and although one landed hard, they didn't find transitioning too difficult.

 

Any insights or experiences would be greatly appreciated.

 Thanks,

Peter Wakamatsu

Lancaster, California

Hello Peter -

 The flaps are really wonderful on the 1-35, and is a good reason to BUY a 1-35 rather than to not buy one.  I can outclimb everything in out club with my 1-35 due to the flaps, my landings are short and slow (= SAFE) and the speed performance is acceptable.  The big plus for me is the 1-35 is a great XC ship, able to get into the smallest of fields if needed, and it is strong.  The value is exceptional on a 1-35.  What serial number are you looking at getting?

 If you do buy,  I recommend that the first tow be up to 5000 AGL and then spend much of the time flying several minutes at each positive flap setting, concentrating on maintaining a constant speed (ie:60mph) as you move through the settings.  The 1-35 gets incredibly stable as more flap is added and it is a comfortable feeling.  Also spend some time near stall at each setting to calibrate where the buffet point is for your glider and your weight.  My 1-35c has a distinct buffet which will keep you from going over or dropping a wing. 

 The key with flaps is to not to retract them too abruptly like you can do with spoilers.  You will find that you might be on final at full flap and find you may want to retract the flaps a bit to shallow out the glide.  Just do this non-abruptly and keep on eye on the speed as you do this, so that you stay well above stall.  The practice at altitude will make your first landing pretty easy.  I also retract the flaps once the wheel is on the ground to avoid coming off the ground, but you do not need to worry about this on the first few flights. 

 Another landing tip is to take as much of the runway up to let it ease down to the ground.  You don't want to adjust the flaps while flaring like you can with spoilers - you just easy back on the stick and let the glider settle on the wheel.

 Good luck!

 Tom

Tom:

I just bought 1-35 #21 from Steve Maier in Wyoming.  It only has 200 hours
on it and is in great shape.  I have a question:  There was a small ding in
the nose right where the canopy starts and there is almost an 1/8" on filler
there.  The previous owner did note in the logbook that they had repaired
some small dings in the nose with filler and there isn't any sign of dents
in the aluminum from below.  How much filler did Schweizer use on the 1-35's
fuselage when they built them and what kind of filler did they use (eg epoxy
or polyester)? 

I've used Stits Superfil on both my 1-26 and 1-23 and it's great stuff.  It
almost weighs nothing and is super flexible and sticks great.  I intend to
fill the small dent with Superfil.

The rest of the plane seems original and it has a Schweizer open trailer in
very good condition.  On my way to pick the plane up I was rear-ended on I15
outside of L.A. and this totalled my new pickup truck.  I had to fly up
there and rent a u-haul to bring the plane back but I'm still not well
enough to fly it yet.  I hope to be soon, though!

I'll give you a report when I fly it.

Thanks,
Peter Wakamatsu
Lancaster CA

HELP NEEDED

Hello,

I am trying to get a 1-35C (SN: 81) flying again, after a long storage
period.  We have completed an annual inspection, and have re-weighed the
airplane.  We have a POH, and a Maintenance Manual, but do not have the
information required to finish a new weight and balance.

Does anyone have a copy of the Schweitzer Weight and Balance form for this
airplane?  If you can fax me a copy, or perhaps scan, the form and e-mail it
to me.

Any help will be greatly appreciated.

Thanks - Doug Workings

------------------------------------
Southwest Soaring, Inc.
Doug Workings
Chief Flight Instructor
workings@sticknrudder.com
2336 Greencrest Blvd.
Suite 312
Office: 903-527-3124
fax: 866-860-1575
mobile: 972-921-4170

DOUG – I WILL EMAIL YOU A COPY AND POST IT AS WELL – TOM R.  [ALL- ALSO POSTED ON THE PICS PAGE]

==========

Hello;
I purchased Serial number 64, N55PS, with another individual this fall. We
are keeping it based in Fredrick MD. I wanted to thank you and all the other
people who have added to this exceptional website. It has re-affirmed that
we made an excellent decision in a first ship, and this site assisted in
transition and in understanding our glider at the end of last season. I look
forward to the years in it, and watching this site grow. I intend to utilize
the wonderful advice found on this site. This aircraft, #64 is a standard
fixed gear C model, but has the double pivot flap handle. I was wondering if
any other C owners have this flap mechanism?
Thanks to all
Garv