Trammeling- How to adjust drag wires to make spar straight

[Daveembry]

Trammeling the first wing and have a question.

My problem is on keeping the rear spar straight. I did all the steps in the book. I squared tube #2 with both the front and the rear spars perfectly and have the tension on the small wire at that bay around 14 lbs, all good.


Next, per manual, i moved outboard to all the bays and tightened all the wires so all the small wires (only the 1 small wire in bay 2 and all 4 small wires in the next 2 bays going outboard) so they are also around 14 lbs.


I have a stringline on both the front and rear spar outboard edge and it's "pretty good" except right in around the area between tubes 3 & 4 (from inboard end of wing), the rear spar is pulled more towards the front spar by maybe 3/16th inch. Not much but noticeable. Same thing in the front spar. In that same area, the front spar bulges outboard by the same, small amount....so it all needs to move aft by around 3/16"


I just can't' figure out how in the world to get that rear spar to move back? Which wires would you move, etc. Seems like any wire I move would keep it equal??

[c130jake]

Did you loosen all the wires before you start? Finger tight was too tight on the down line wires once you start to tighten the first few. Spent a day on the first wing til I figured that out. Second wing took about an hour.

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[Daveembry]

Did you loosen all the wires before you start? Finger tight was too tight on the down line wires once you start to tighten the first few. Spent a day on the first wing til I figured that out. Second wing took about an hour.

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Hi Jake. Yeah, all loosened first. Tubes are perfectly square as well. Just have that one little bulge. Manual just says to "be sure the spar is straight" but doesn't say how to do it. If you loose the drag wires at that spot, then they won't be 13-15 lbs. if they are all 13-15 lbs, then it pulls that rear spar in. Strange.

[TroyBranch]

You need look at how the bulge in the spar is getting pulled. It may mean you need to loosen/tighten the wire in the other bay. It is hard to explain but imagine how the load in the wire is pulling the spar and correct accordingly to get it close to straight. It doesn't have to be perfect, but as long as it is perfect enough to make you happy.

[Daveembry]

You need look at how the bulge in the spar is getting pulled. It may mean you need to loosen/tighten the wire in the other bay. It is hard to explain but imagine how the load in the wire is pulling the spar and correct accordingly to get it close to straight. It doesn't have to be perfect, but as long as it is perfect enough to make you happy.

Yes, it's very small, only being maybe 3/16" but I would rather it be 0" if possible of course. Not sure what is acceptable as far as the fit as it's almost dead center of aeiloron bay. In the picture you can see it's right where the wires cross in bay 3 so you would think that I would simply loosen the drag wires to the right and left of this position and let that rears bar come back, but if you do that then you don't don't have your 13–15 pounds image.jpg
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[lbell]

Did you loosen all the wires before you start? Finger tight was too tight on the down line wires once you start to tighten the first few. Spent a day on the first wing til I figured that out. Second wing took about an hour.

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same here. day on the first one 1 hr on the second.. I would go back and loosen all wires, start over, get the spar straight then tighten wires. sooner or later you will see what makes the spar move. like he said hard to explain

[Daveembry]

same here. day on the first one 1 hr on the second.. I would go back and loosen all wires, start over, get the spar straight then tighten wires. sooner or later you will see what makes the spar move. like he said hard to explain

yeah, guess that's what I will do. Just leave bay 1 wires as they are as that bay is good and #2 tube is square, then just start over with bay 2-3. I guess then that there really isn't any adjustment to move the spar in or out overall. I did that in bay 1 to be sure the #2 tube was square with both the front and rear spar when the small wire was at 13-15 lbs at the center (adjust 1 wire more than another until the tube was square) but with the other bays, you just tighten the nuts up evenly until you get the right pull. So there really is no adjustment to it it doesn't appear.

[TroyBranch]

You want the aileron bay as exact as possible. The hinges will not line up that well otherwise. Can you point to the high point of the spar on a larger over all picture and say which direction it is going. I can then give you some help on what to try.

[Daveembry]

You want the aileron bay as exact as possible. The hinges will not line up that well otherwise. Can you point to the high point of the spar on a larger over all picture and say which direction it is going. I can then give you some help on what to try.

Troy. It's right where I have the tip of the pen I'm holding. That is the rear spar and it's going inboard about 3/32" at that point only. All wires around 14 lbs. thanks for looking!
image.jpg
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[TroyBranch]

OK loosen that x until you get half of the bow out. Then take up tension in the X beside it. When you loosen it, the others will loosen slightly too. Only tighten the ones that got looser in the other bay. Loosen as required as you tighten the ones on the bay beside until you have it straighter and all tensions the same. See how that works. That X is pulling the spar on you. As you loosen and tighten watch how the spar moves. Keep the string line on it. The tightness of all wires effect every other wire. Hope that makes sense? I might be wrong, but it is easier than starting from scratch