Jump to content

Update for 1970s Sterling Schweizer 1-34


Recommended Posts

Time to install aileron servo wiring. I usually make a custom extension wire but this time I decided to just buy them. 24 in. extensions were a little too short so I had to add an additional 3 in.  extension. 

 

The wire is placed into a slot cut into the top of the core but only after most of the bottom sheeting is installed. I was worried that cutting the wire slot may weaken the core too much and cause the airfoil to distort so the bottom skin went on. 

The inline connection is glued to a piece of 1/64 ply so it can’t come apart. The servo end is placed into an indentation cut into the foam and covered with 1/64 ply. Later when I cut a servo hole from the underside, the aileron servo wire will be loose. The ply pieces are inset and made flush with the wing surface. D2B37239-59F7-4298-AF2B-6AE196CF54B5.thumb.jpeg.eb88aa22dbd0edee904b746b889ba99e.jpeg

C0DC69FA-6D7E-4E69-B1A4-2E8AE2E15AFC.jpeg

Link to comment
Share on other sites

Ok getting close to done. 

 

Sheeting is completed for each wing panel. I vacuum bagged some of it after using contact spray. Otherwise I just used weights. If I had to do it again, I’d vacuum bag where possible. The is no LE or final sanding in these DFAE2CBB-8F37-4592-B346-459970CF3DED.thumb.jpeg.f99cf2bb68f3afd83ec1aa0ef064fc5b.jpegphotos. 

 

There is an incidence alignment tube toward the rear of the root ribs. These tubes are being epoxied in place, after matching the incidence for each panel. This is what being done in the photo where both panels are seen. 

 

0E1C9157-BAE7-4339-B3D6-407D4D32C707.jpeg
 

 

51DEC90C-19F4-4D72-9379-993D9B80FFEC.jpeg

Edited by Slope445
Link to comment
Share on other sites

5F1A34EF-BAB3-4F91-8E37-CE71FA114990.thumb.jpeg.95e7e01dbb7dc322cab7f67209df07a9.jpeg
 

Wing mounting

 

You may know that the 70s kit wing attachment method was to hard glue around a 2ft wing center section to the fuselage. Then the long “tip” sections were slid onto wooden dowels and tongues. As happened to my old Schweizer 1-26 which used a similar wing attachment method, when those dowels or tongues break... you’re screwed as fixing the damage is very difficult. So I wanted a more conventional and up to date wing attachment approach. 

 

So since I’m going with a 2 piece, removable wing, I had to come up with a suitable wing mount. I wanted an approach that would allow slight tweaks of incidence, alignment with the tail surfaces and squareness with the fuselage. 

 

I came up with a scheme using 2 vertical wing mount brackets to fit into slots in a wing mount plate. 

 

Slots are cut with this drill press/ mill vice rig. A dremel saw cutter is chucked up. 

 

Once in the slots, the brackets can be moved slightly, up and down and forward and back until the wing is aligned perfectly. Then the brackets are CA glued to lock them in place on the mounting plate. Then the plate is removed and some gussets are epoxied on the back side. EFBD6CE9-748F-4C83-AD1E-FC229279B4CD.thumb.jpeg.31201b6d7c5341452151b543b42fbaca.jpeg

575B8B0D-E40A-4634-8F8D-5CBADF72E66B.jpeg

E97C98E4-4569-4811-ADBC-6957B66D49C8.jpeg

Link to comment
Share on other sites

Ok. The Schweizer is about 90% complete. I made the wing fairing. All that’s left now is to cut out the ailerons and install the aileron servos, cover the wing/stab and do final finish and paint the fuse.  

 

I sure I’ll be flying it before painting because, as usual, I can’t wait to see how it flys!  

 

Weight has come out at slightly less than 43 ozs. It will need a little nose weight but it’s close to proper balance with just the battery installed so I don’t expect much more weight.  We’re looking at a wing loading of less than 12oz/sqft. That’s not bad although I was aiming for around 8. 

 

An interesting coincidence:  I ran across the original Sterling kit, in the vintage stack at the local hobby store ?. There’s a price of $299 on it!!  ??. I guess I came out ahead because I only spent ~$200? on my version ?maybe...

 

I started getting interested in building this around last November. It became my pandemic plane. I worked on it several hours a week. 

 

Hopefully I’ll post some successful test flight results soon!

 

84634B6E-0C54-4845-9867-4D29942AA6E6.thumb.jpeg.45c1ecbe41a2923ebb0c72f0a4af8d2e.jpeg
 

AEFBFED6-2E00-405C-88AB-99D12A3B4F83.thumb.jpeg.c3e5832a1f8f1aad2527f0f72ad5bb6c.jpeg

 

 

74CE563E-13E7-4EEC-9E91-55B82585281F.jpeg

 

 

D1634F17-072C-4311-8077-F6108620947D.jpeg

 

 

455A9BBF-4AE9-4CFB-9EE2-A905CE3CDE43.jpeg

Edited by Slope445
Link to comment
Share on other sites

  • 1 month later...

Finally getting back to the Schweitzer. Cutting out the ailerons is the next step. I cut them somewhat longer than scale since I’m more interested in flying performance than in keeping it strictly to scale.  They’re 22 inches long as opposed to the 14.6 inches shown on the plans. After they’re cut, the underside skin in cutback another 1/4 inch on each side to make room for a 3/32 balsa aileron spars. 

 

0986DEAD-05B5-421E-AF6D-6087659AA918.thumb.jpeg.a9686b36207d451ebc114793b0b007af.jpeg

 

EDB26DDE-D808-433D-A711-2E5DDE2D402E.thumb.jpeg.63d25ad8aa714c8fe9cf8c2df142a667.jpeg

Link to comment
Share on other sites

So a balsa spar is glued to both the aileron an the wing. The raw spar material has the top edge sanded at a angle and glued to the underside of the top skin. It’s also glued to the foam and the bottom skin (see photo). 

75EFBC39-BD7A-4222-B705-FE952183EA29.jpeg

 

The spars are trimmed and sanded after installation.  

 

B71810EE-26C0-4950-93FF-5E8CD0183FA4.jpeg

 

The hinges will be installed from below as shown below, after the spars are notched.  I discovered that these Dubro hinges will not fold flat against themselves and that may limit down travel. That’s one reason to try this out first. If everything is good, the hinges will be trimmed down, more gluing holes added, then epoxied in place. Everything is only tack glued currently. 

 

 

1C1867EE-D03B-4F5F-BD9B-6CE3AB081237.jpeg

Edited by Slope445
Link to comment
Share on other sites

 

Aileron hinging

 

I wanted to hinge the ailerons at the top edge as I usually do but I didn’t think slotting them in just below the 1/32 balsa skin was going to work too well. So I decided to mount them on the underside by bonding them to the spars. I also decided to install one aileron with simple tack gluing first to see how it was going to work out. 

 

 

DB3F8682-EEE2-443F-B60A-E204C843F9B9.jpeg

Link to comment
Share on other sites

I like the result. Plenty of up and down throw and the installation produces a nice tight hinge line. I need to install the servos next and get the linkage setup. I decided it’s easier to cover the wing and ailerons separately, before permanently installing the ailerons. So, I’ll get the servos installed and setup using the temporary aileron installation for now. 

D4D4155D-95B4-47E1-8C55-B895A40F7530.jpeg

8DD808E9-4D49-4523-BF97-65D94DC5683A.jpeg

Link to comment
Share on other sites

I’m cutting servo openings in the bottom of the wing. I like to keep them as small as possible. Sometimes I just epoxy the servo directly into the wing but that can be problematic. Gluing with RTV can work but I’ve had that approach loosen after a few years. But a broken servo can be pried out if necessary. However, it’s best to mechanically install the servo so it can be taken out if necessary. I made a small servo bracket from 1/32 ply. It holds the servo and prohibits movement in all 3 directions but the servo can still slip out by removing the screw. The servo bracket is glued in using Gorilla glue. That type of glue is kind of like an expanding foam so it fills in any void between the ply and the 1/32 balsa wing skin. If you’re not careful, you may cause a dent to be visible on the upper surface right where the servo cutout is so this glue avoids that problem.  The connector for the previously installed servo extension lead is just under the curved portion of the cutout. 

 

Even these tiny servos stick out of this thin glider wind so I’ll make some fairings after fabrication the linkage. 

 

AF2DFB87-4DC1-4C40-8C39-5529C8FDF8E9.jpeg

 

66209A73-7954-4A19-9E43-40A454F8EE0B.jpeg

 

 

753AB085-62DE-4F0E-AAA1-830C153CFE01.jpeg

 

 

 

68DC71F1-E7C8-462B-9A2A-08F747B6C205.jpeg

Edited by Slope445
Link to comment
Share on other sites

I usually mock up control linkages for ailerons, as I did here, before making the final assembly. I like the ball link approach and have used ball links for ailerons before. Mocking up let’s me get the ball the right distance above the surface and get the push rod length correct and bent properly if needed.  The dowel the ball is threaded into is just tack glued in so I can pop it out and sand it down if I need to. The mock-up push rod here is simply made from a large paper clip. The threaded rod end is CA’d to the mock-up push rod. When I’m done playing with things, I’ll have the details needed for the final fabrication and installation. 

 

I’m setting up the model with spoilerons.  Gotta have a way to get down if I happened to get into a killer thermal!  You can see me playing with that in the video. 

 

I think it’s all good to go. 

8CCB0B2D-0C76-476B-8FEB-E87E5454582E.jpeg

Edited by Slope445
Link to comment
Share on other sites

  • 3 weeks later...

I had to come up with a 2 piece aileron servo fairing. I can’t move the servo forward since I’d be cutting into the carbon spar so a part of the fairing has to be on the aileron. I didn’t want a big gap so I made the aileron part fold into the forward fairing piece. The gap stays closed for aileron movement during general flying maneuvers.

 

i glued a hard fiber board disk to the wing skin to give the hold down screw something to bite into.  I’ll put tape over the curved opening the fairing doesn’t cover 

E5FF7A8A-0122-4AF4-B3E7-0E4B57EEA850.jpeg

 

 

 

 

42F9EDC8-566B-4C95-B8D3-94CEE35F4A28.jpeg

 

 

F254AD21-0371-45A9-BB72-CD1F15EDF0E4.png

 

 

E6793F63-C07C-4559-952A-56637EF1EAA7.png

Edited by Slope445
Link to comment
Share on other sites

  • 3 weeks later...

The next step is to permanently install the ailerons.  The temporary aileron installation, used to setup the servo mounting, ball link height and push rod length, is undone. Then the hinges are trimmed and drilled for final installation. After preparing the hinges, they are epoxied to the aileron using a two step process where after the initial gluing, holes are drilled through the existing hinge holes and into the aileron. More epoxy added and allowed to soak through the holes and down into the spar. 1 hour epoxy is used. This makes a sort of epoxy “nail” for some extra bonding strength. 

 

The wing is partially covered now. Seemed easier to cover the hinge line before the aileron is attached. After covering the wing is placed in the upper core bed, the aileron lined up and then CA’d in place with just a small drop of CA on each hinge. The the wing is removed and checked for good aileron alignment. If the alignment is not acceptable, the glue joints can be snapped and tried again. If things are good, 1 hour epoxy is applied and allowed to soak through the holes on the wing side. 

 

I flubbed up with the CA on one hinge (glued it together!) and I didn’t realize it until after I had epoxied it!  Had to redo that hinge. I had to slice it with a Dremel tool and do some surgery. It wasn’t easy and showed me that the epoxy “nail” thing worked pretty well!

 

534E552B-51BC-48C6-84D4-CA7794A76E35.thumb.jpeg.fdf24a74bf716391a88fea23c66ffaaa.jpeg

 

3C9192B4-FFA2-4CAE-AE26-C5C4158D1A70.thumb.jpeg.bae79e859b8674956738bdc9e592b28d.jpeg

Link to comment
Share on other sites

  • 1 month later...

Well I’ve had a small case of 95%itus. A project gets 95% complete and your enthusiasm to finish it drops to 5%!  But I finally got back on this. 

 

Final installation of the aileron servos requires that the servo leads be shortened. So that’s what you see here. The wire splices are staggered so insulating over the individual splices isn’t necessary. This saves a little volume when storing the excess wire. There’s enough slack such that the servos can still be removed, worked on, etc. The service loop of wire is stored in a small volume just next to the servo. 

 

Still need need to finish covering the wing, paint the fuse and firings and a few other things. Then it’s time to test glide!!!!  I can’t wait!

C943D075-33AE-43AB-A5A2-B7EE49183A1E.jpeg

 

 

B66B2014-ABAA-41DB-B631-782D4C947BA9.jpeg

 

 

274DE33C-D614-498F-992C-E889B3EF0BB6.jpeg

 

 

36BD24CE-7B1B-4EE7-851C-CA4656E754D2.jpeg

Edited by Slope445
Link to comment
Share on other sites

  • 1 month later...
  • 2 weeks later...

Fuse painted! Radio installed. Decided to tweak the linkage a bit to better tie down the putter sleeves.  Didn’t like the way the elevator “tape” hinge came out so I’m changing it to standard piano hinges installed the same way I did the aileron hinges. 

 

 

F1B19F52-39C0-42F3-B4A9-1E07CA7AFE21.jpeg

Edited by Slope445
Link to comment
Share on other sites

  • 1 month later...

670BF4DD-EBBC-4E0A-8DBF-85922C9876E1.thumb.jpeg.748973eb4586f35aa1aa9790a849d606.jpegOk. Finally maiden flight ready!  Here’s a photo of the finished aileron servo faring and a shot of the whole airframe. The pup got in the way so he’s a bonus! I added hinge tape to the underside of all hinge lines (except the rudder) to stop air from bleeding through.  Final weight is 56 oz. Wing loading is 14.8. That’s higher than I wanted but should be OK for slope flying. The wing is an RG 15, 11% thickness and is set to an incidence of 3.75 degrees when the stab is at 0.0 degrees. 

 

Ill try try to get some video of it flying but that may be a while since winds this time of year are typically not good. 

 

Here’ hoping for an event free maiden flight!

 

 

09ED7996-1FE3-48F8-94C9-46FF37A56A85.jpeg

Link to comment
Share on other sites

Well I’ve decided to just go for broke and slope launch it. I’ll have one of my flying buddy’s launch it so I can be ready for any serious trim problems. Ive done maiden flights like this before and I’ve only had 1 incident and I threw it myself that time!  ???

  • Like 1
Link to comment
Share on other sites

  • 3 weeks later...

Nope.  Not yet. The 1-34 is aging like a fine wine. Waiting for the perfect day to pop the cork!  I have noticed that the Ultra coat covering I used needs reshrinking AGAIN and is so thin you can see the balsa grain, etc right through it.   ?  But, couldn’t find monokote. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...