Schweizer 1-26E ~ 1/2.5-scale Kit by Peter Goldsmith (Build thread by JimD)

[JimD]

Link to Peter Goldsmith Designs Web Page:

https://www.petergoldsmithdesigns.com/product-page/schweizer-1-26

On Tuesday, January 9th, we made the 9 hour drive out to Monticello, Illinois to visit with Peter Goldsmith. He had finished drawing the plans for the 40% Schweizer 1-26E and was in the process of cutting the first set of parts for a test build. He has given me the honor of doing the first build of the first kit and to develop the instruction manual.

This build thread will be the draft copy of that manual and you are going to participate by helping me keep these instructions clear and on track!

Peter has already completed his fuselage, fin/rudder, and stab/elevator and made adjustments to parts as needed. My kit is the second run with those revisions made. He has not yet built the wings, so i may be ahead of him on this phase (at least for a day or two) and the parts are the first run.

The wings are ingeniously simple in design which translates into easy to build!

Wings are fully sheeted with 1/32" plywood. The kit includes 8 sheets measuring 24" x 48" in size. Basically, two of these sheets need to be joined to make a 24" x 96" sheet. The spar and ribs can then be positioned over this sheet so that it can be cut to size before gluing things in place.

First step for me was figuring out an easy way to make a scarf joint for these sheets. A trip to the home improvement store provided inspiration and we decided to try the following. Using a piece 1/8" thick aluminum strap and a sanding bar with half a strip of sandpaper, the sanding angle makes a nice 1/4" taper without too much effort.

[JimD]

Proof of concept test was great so we moved on to joining the 24' x 48' sheets.

The aluminum bar was taped to the bench to help stabilize its position and then the plywood was positioned over it and also taped to the bench. Wax paper was placed beside the aluminum bar so the the sanding bar could glide along that instead of the raw bench top.



Sanding bar could be a block of wood with sandpaper attached with double sided carpet tape.





Draw an ink line 1/4" from the edge (BTW 1/4" scarf joint is 8:1 ratio for 1/32" plywood sheet)




Watch the glue lines and the ink line as you sand.



Keep the plywood tight down against the aluminum bar so you don't sand away on high spots. This will be very evident watching the exposed glue layers in the plywood and the ink line drawn on the sheet.




Sand away just to the point that the ink line disappears while keeping the plywood glue lines parallel.

[Swiss1]

Jim,how about clamping a guide to the table where the sanding bar contacts the surface, once you found your correct angle the following sheets will be identical without any guess work! Just my 2cents worth.

[JimD]

As for gluing these sheets together, Speed Bond glue by Deluxe Materials (This product is available through Horizon Hobby) and a hot iron make the process really easy. Note that a strip of masking tape was added 1/4" back from the edge of the plywood wing skin to limit glue from spreading beyond the joint. A thin film of the Speed Bod is applied to both pieces of plywood and allowed to dry (white glue turns clear as it dries)



Overlap the two pieces of plywood and align using the masking tape as a guide.



Since the plywood sheets are not exactly the same size, one edge of each sheet was placed against a 48" straight edge so one side would be even.



Use a covering iron set on its highest setting and glide it along the joint while applying downward pressure. The glue will active and the two sides will bond.



Next step is to make a spar from two pieces of the 3/8" x 1/2" x 48" basswood stock. We made a fixture for the slide on our band saw that allows a 5 degree angle to be cut on the ends of the spars. This produced a 4" overlap (slightly greater than an 8;1 ratio) Could experiment with cutting at maybe 7 degrees to make the scarf closer to 3"

We checked that the 3/8" thickness was consistent from one side of the scarf joint to the other before gluing the parts together with slow set epoxy. Parts were clamped together until glue was fully cured.

[ARUP]

Nice job with the plywood joining. The aliphatic glue and iron really works! I have a model over 20 years old using this method. The glue hasn't failed, yet.

[BryanB]

Maybe use double sided tape to hold the plywood down evenly and securely on the aluminum bar for sanding?

This exciting! I’ve been wanting a large 1-26 for some time. Used to fly these and a few others when I was going to school in Seattle back in the 80’s. I really have a soft spot for the 1-23 though.

[JimD]

Yes, you could do that...but then you need to get the tape off...and it really likes to stick!

I found that using a shorter sanding block and simply pressing down on the plywood where you are sanding worked best.

[BryanB]

Didn't think of that. Guess just holding it down would be best. Maybe even using an additional flat bar for even pressure.

[JimD]

That is an idea...once you try it, however, you will find that it goes pretty quick and easy. Neat watching the glue stripes appear!

[ErichS]

Will be watching Jim.

[MarnochS]

Excellent
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[Gliderhead]

Beautiful work. Jim. I've been following Peter's build thread with great interest. I'm sure you'll have the build done come Spring fly time. Would love to take a 'family' picture of yours along with my 1/4 and 1/5 scale 1-26. Happy building !!!

[DennisB]

Jim, keep it coming, this is great info for any wooden build. I am putting together an ASK-14 and am not far from having to scarf the wing sheeting just as you have here. I’ll try the Speed Bond glue for the scarf joint. And Pete’s build is incredible, maybe it has something to do with it being 2 degrees there and not 70 degrees as it is here, forces you into the basement for some long hours.

[BStaley]

Nice work! The glue/iron step is a neat trick. I used it before and it works great. I wonder who came up with this idea-furniture makers maybe?

[JimD]

Once you have the bottom sheeting and spar joined, time to move ahead. Locate all of the ribs and shear webs and dry fit to parts on top of the bottom sheeting. To assist with organization and ease of packing, the parts are supplied in the sheets from which they are cut. Use a sharp blade to cut through the tabs that hold them in place.



Use a sanding block to level off any nubs of wood.



Dry fit the parts in order to locate where the spar will need to be attached to the wing sheeting.

[JimD]

All of the ribs (including W1) are perpendicular to the spar. When positioning the spar and W1 on the 24" x 96" plywood wood skin, note that W1 cannot simply align with the edge of the plywood. The wing root follows the flat side of the fuselage straight back from the wing tube until reaching former F6. At that point the fuselage begins a straight taper toward the tail. This "break" in W1 is 10-1/8" back from the rear edge of the wing tube hole.





The aft end of W1 is offset by 1/2"





W1 will need to be placed parallel with the edge of the wing sheeting but with a 1/2" setback.




The trailing edge of the wing between W1 and W3 will extend back more than the 24" width of the wing skin sheeting so a small section will need to be add.



W1 needs to be cut along a vertical line 10-1/8" behind the edge of the wing tube hole.

[JimD]

Another thing to note is that W1 is not vertically perpendicular to the bottom wing sheeting and spar. It is vertically perpendicular to the wing tube/rod. Two "Root Rib Template" parts are provided to set the correct angle for W1, The shear webs between W1 and W2 also have this angle on the root end. All of the other ribs are placed vertically perpendicular to the spar/bottom sheeting.

[JimD]

Adding the 1/32" plywood wing skin extension, it is best to have the larger panel overlap the smaller piece on the outside surface going from front to back.

The 1/2" set back for W1 was marked and a 1/4" line was drawn along the trailing edge as a sanding reference.



The inside of the larger wing skin was sanded to a taper along the trailing edge.



A smaller piece was then added using the Speed Bond/hot iron technique

[JimD]

Measure 7" back from the front edge of the wind sheeting and draw a straight line down the 96" length. At the root end, measure 1/2" back from the end and draw a line that is perpendicular to the spar line. These reference lines will be used for placement of the spar and W1.



Glue the spar in place using the ink line as a reference for the front edge of the 1/2" x 3/8" x 96" spar (actually shorter by 4" because of the scarf joint overlap). Use weights to hold the spar in place and to keep it tight against the sheeting.