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Jul 20, 2021, 03:21 PM
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Build Log

Yellow Jacket GS Tail Construction

I have been flying more than building for a while, but recently I inflicted a mishap on one of my Yellow Jackets, and decided the time was ripe. even though the damage was easily repairable, I ordered yet another YJ-GS. It arrived from Corky yesterday. Before commencing this morning I want it to take to Muncie), I casually reviewd the build thread, and realized something: the new, built-up tails never got a good louk for construction. So, here today (if you are still interested), is how to build the Yellow Jacket GS tail set.

The built-up tail set is a kit in itself: parts, jig and drawing. The jig assembles without glue or tools, and suffices for both surfaces of the V-tail. Any parts without part numbers laser-burned on them, will only fit one way. Any parts with numbers cut on them, are clearly marked, and shown on the accompanying drawing. Eezzy-peezy.

So, here it goes: an entire morning of "effort", with time out for bringing in groceries and even lunch.

The Jig

The parts are shown, and come out of the heavy plastic bag that contains everything for the fixed tail surfaces (which includes the carbon tube spars, leading edge, and what look awfully like ribs. I arranged the cross pieces so that they were in order, root-to-tip, and aligned all the same way. Which way does NOT matter!

I started at the root, and carefully pressed in the cross piece #1. Try to get it all the way, but fully seating it will come later. Continue to the tip, take them in order, and just do your best getting them fully seated, without worry at this point. Once all cross pieces are in, I used a wood block to bear down on each, until it was fully seated. No tools, no glue (except the wood block). Mine finished up perfectly flat, but I pinned it to my build board anyway.

Fixed Tail Surfaces

Again, I sorted the parts and show them in order. They are clearly shown on the drawing, but putting them together like this may help you understand how to proceed. There are eight ribs with part numbers that have an "L" or "R" prefix - those are root ribs for left and right tails, respectively. All other parts are interchangeable, left or right. I used a 2mm drill bit to ream the holes in ribs L1, L2, L3, L4 R1, R2, R3 and R4 for the mounting posts. I used a 3mm drill bit to ream the holes in all ribs to accept the carbon tube spar.

Start by pairing the balsa L1 with plywood L2, and gluing them together. glue them so that either L1 or L2 can still be seen, because this differentiates between left tail and right tail. Do the same for L3 and L4, R1 and R2, and finally R3 and R4. You will have four balsa/ply sandwiches. I used a 2mm and a 3mm drill bit to ensure alignment.

Line the jig with a piece of wax paper. I make sure one edge is straight, and align that edge with the trailing edge. You don't want to glue a rib set into the jig, and that is all too easy with thin CA, which will be the adhesive in choice for this. String a set of ribs (starting with A12, and working back to A5) onto a carbon spar. Set a trailing edge into the jig, and use that to space the ribs. By now, you can work with the laminated ribs, and I selected the L3/L4 pair, and finished with L1/L2. I jiggled and wiggled until each rib could be inserted into its notch in the trailing edge. With weights, it will settle into place, and entirely without glue. Examine it carefully - it is possible to assemble the tail to this point, and not have the trailing edge properly aligned even though each rib is fully in its notch. I pinned mine in place, to the jig.

I used a small, CA applicator, and (holding my breath) I carefully applied a small drop to each joint, whether wood-to-wood, or wood-to-carbon.

I finished the fixed surface by carefully pressing in the thin carbon rod into the notch in the noses of ribs A12 and A11. Once pressed in, I applied a small drop of thin CA to the rod in A12. I moved in order to the root, pressing in the carbon rod into each rib nose, and gluing the previous joint.

You can safely remove the surface from the jig at this point - and do the same job all over again! Same parts, same order, except use R1/R2 instead of L1/L2, and R3/R4 instead of L3/L4.

I call these "Ribs a la brochette"
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Jul 20, 2021, 03:31 PM
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Now, for the elevators.

There is a drawing, but it is only half-scale. But, it is also only for reference - you don't need it.

Once again, I laid out all the parts and pieces. Once again, if they can be confused, they are laser-etched with a letter. All parts are interchangeable, left or right.

I pinned a ruler to my build board, then pinned the leading edges to each side of the ruler. Note I did not pin through the wood, but only trapped the pieces against the ruler.

The outline pieces go next. By the way, I am using only Titebond wood glue for this. If you prefer CA, go for it.

I started at the root of each elevator, and laid in the ribs, A through G. No need to cut anything, the fit is excellent. I added pins to keep all joints in contact. At the end, for rib "G", I finally used a tool: I had to handle part G with tweezers.

Out for a bite to eat, help my wife bring in the groceries from Cosco, and the elevators are ready to come off the board.

Is this easy enough?
Jul 21, 2021, 02:50 PM
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This will be very handy for folk Greg ......
I was wondering If you are doing springs on this, could you post dia, sizes and angles for folk, so that it is all in one easy to find place? I rarely fly any of my other planes now I've got the GS, it is such a sweet efficient flyer off a bungee.
Jul 22, 2021, 08:23 PM
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This is a timely post for me as I just ordered two (2) GS models from Corky. He is a busy guy!

thanks for the pictures and would like to see how the elevators are hooked up to the pushrods.

Jul 22, 2021, 11:25 PM
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Here is how I prepare a tail for pull-spring. I do the same for a push rod installation, but leave out the spring.

The pictures show one of my existing Yellow Jacket tails, made on exactly the same jig depicted in the opening posts. I even used Corky's plywood control horns, but drilled my own hole, and cut the notch to allow the tails to be removed.

The spring itself was chosen because it was what I had. It is 0.010" or .25mm wire. Had I thicker wire, I could have made the shank longer to reduce tension. Much thinner, and it is too flexible.

I make a bend at each end of 90 degrees. I make the bends orthogonal. That is, when one bend is flat on the board, the other sticks up. You can also make the bends opposite to each other - that is, both lie flat on the board. That is a way of increasing tension.

I made the torque shaft on this spring at 3.1", which allows the bend going into the fixed surface to penetrate a rib for greater security when the bend in the moving portion is next to the control horn. If I want more tension, I make the torque shaft shorter, to insert into the next rib down. For less tension, I make the shaft longer, to insert into the next rib up.

I will occasionally use a small drill as a pilot hole for a spring, drilling the hole into the middle of whatever piece has to be penetrated. I will also occasionally reinforce the hole with a SMALL drop of thin CA.
Last edited by glidermang; Jul 23, 2021 at 10:44 AM.
Jul 23, 2021, 10:49 AM
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To install push rods in the Yellow Jacket is easy. Once the tubes are secured at both ends (while being pulled as tight as possible), I insert the wire and do a simple Z-bend at the servo end.

Back at the tail, I mark where the L-bend must go when the servo and elevator are both neutral. I make a simple L-bend, and cut the excess to leave about a quarter inch to go into the control horn. If I insert the L-bend into the control horn from the top, natural wire tension will keep it from ever popping out. No need for a keeper.

For pull-spring, I will search a previous thread where that is illustrated (PuRES or Slite build should have it). It is pretty easy, once the usual qualms of how such a lash-up could work are overcome. Pull/spring is my default solution for RC gliders, especially small ones. There is nothing wrong with push rods - I am just into saving weight at the back end of the airplane.

Yours, Greg
Jul 23, 2021, 11:59 PM
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I was wondering how this spring stuff worked. Now I know.
Many thanks for your pics and explanations.
Last edited by PierreYves; Jul 24, 2021 at 02:07 PM.
Jul 24, 2021, 12:08 PM
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Thanks Greg.

Very timely. We have 4 heading here shortly.

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