How Do I Make the Trailing Edge Straight?

So I'm ready to rivet the aileron trailing edge and am concerned about how wavy it is. It is much wavier than the elevators and rudder were before they were riveted. Will this straighten out when I rivet the trailing edge? Is there a special technique that I should follow?

I don't know if you can see the waviness in this picture but here it is.

Interesting problem. I had the same thing happen to me, my aileron trailing edges came out looking like a drunk snake when I assembled them as per Vans directions. I pulled them back apart, found the problem, and modified the plans assembly method slightly.

The problem (as I found it, anyway) was that the forward skin of the aileron is slightly underbent, and is stiff enough to have enough spring force to pull the main spar flanges outward (up and down, respectively) which results in an aft bow (on the ends) of the main spar. This has the effect of drawing the skin inward at the mid-span of the aileron, trying to shorten the aileron, but the structure resists where it is riveted to the counterweight tube, which puts the trailing edge in compression and results in the horrendous waviness. My solution was to massage the aileron main spar flanges as much as possible to get them more correct, but in the end this was not enough and I decided there needed to be more support between the main spar and the counterweight tube to keep them at the proper distance from each other. I solved this problem by ordering 4 more counterweight tube ribs, 2 left and 2 right, one pair for each aileron, and installing them at the 1/3 and 2/3 position in the aileron, locking the distance between the counterweight tube and the spar for the entire aileron length. With these in place, the main spar cannot bend forward in the middle, and the trailing edge won't be in compression. This immediately cured my wavy trailing edge as it took the trailing edge out of compression, and I built on. You will find it difficult to install the pop rivets in all the ribs holes to the counterweight tube due to tool clearances - I only installed one pop rivet in each center rib to the counterweight tube, since those points will always be in compression anyway and I only needed to make sure the ribs didn't shift left/right on the tube. In fact, I didn't even rivet the extra ribs to the skin of the aileron - their only purpose is to keep the main spar where it should be with respect to the counterweight tube.

See my build log for more - http://websites.expercraft.com/airguy/index.php?q=log_entry&log_id=33903

I'm guessing because I don't have a RV-9 plans set but if you proseal the trailing edge (like the -10 trailing edges), then what you do is put the TE on a flat surface with the clecos just overhanging. Weight the TE down and let the proseal cure a few days, then clean out the dimples (a hand deburring tool will get the proseal out of the dimples), and finally do the riveting. The weights will keep the TE straight while the proseal cures and then the cured proseal will keep it straight while you rivet.

I agree with Patrick. I let my trailing edges sit for several days, weighted and clecoed to the table top, allowing the proseal to dry totally. Then layed the trailing edge on a long piece of angle iron to rivet it.

http://www.smittysrv.com/more_stuff.asp?ID=466

For what it's worth, on my QB alierons and flaps I can see and feel the remains of proseal on them. So that seems to be how they are done at the factory. It's hard to tell it's there, but I'm pretty sure I've come across a few rolled up bits. They are as straight as my rudder which I did with proseal as well.

I didn't use proseal on the elevators, but they came out straight without issue.

Thanks for the help...

I'll get back on it today and let you know how it comes out.

Mine were the same...

Both my ailerons looked wavy like yours when clecoed together. After riveting they are both perfectly straight. I did not use pro-seal or make any other adjustments from the plans or instructions.

I'm not suggesting you take my approach. Just telling you my experience.

Attach to table

If your table top is nice and flat, consider drilling into it and clecoing the trailing edge right to the table top when you do the proseal. Make sure the leading edge is straight and there are no twists, but fixing it directly to the table will insure a good result in most cases.

I hope Mike doesnt mind me posting this But i was browsing through his build log the other day and I saw he used 2 pieces of 4' Alumunim Channel To sandwhich the rudder skins inbetween. Each channel was back drilled to get the same holes and then all 4 pieces were clecod together. Seems to have worked out great. heres a link
http://www.nippaero.com/log/20070811.php

hope that helps.

It worked for me

I did not use proseal on the aileron and flap trailing edges. I did construct the ailerons and flaps on the special flat-to-itself work surface mentioned in the plans. I recommend using the 2x gun.
I weighed down the top surface of the ailerons and flaps with double Hefty Freezer bags of potting soil (other builders use bags of shot or weights) placed on a long shelf board. It ended up being 10 bags each weighing 5lbs.
Then back-rivet the TE together. Work from the middle toward the ends partially setting the rivets, then flip it over and finish setting the rivets with a small diameter flush set. I used a long narrow polished steel back rivet plate available at HoDe.

Success!

Even though the trailing edge was ugly as sin before riveting, I guess I didn't need to worry so much. I did it without proseal and it came out perfectly straight! For my back rivet plate, I mounted a piece of 1/8" angle (actually a "T") iron garage door opener track that I happened to have, to the edge of my flat table top and laid a 4'x2' piece of 1/8" masonite under the aileron. Then I riveted the TE using the standard trailing edge riveting technique. The hardest part was keeping the rivets in the holes and laying down the rivet tape since the 2 skins formed large gaps at the TE. The weights are 4 - 15# sand bags from Home Depot.

Thanks for the help from everyone. It gave me the confidence to press forward. Here is a picture after I finished it.

Looks great Allen, keep banging away. I wish I read more before buying the QB kit, I would have done the wings myself. Though my bucking bar holder (aka wife) wants the plane done sooner than later, which works well for me when I ask to spend money.

Good Advise from all

Skybolt Al said:

So I'm ready to rivet the aileron trailing edge and am concerned about how wavy it is. It is much wavier than the elevators and rudder were before they were riveted. Will this straighten out when I rivet the trailing edge? Is there a special technique that I should follow?

I don't know if you can see the waviness in this picture but here it is.

Click to expand...

I have found to keep things streight I use a combination of some of these suggestions. I do use proseal, I do lay it flat on a flat table, I do use weighted bags to hold it flat, I clamp a length of Al angle to the table side flush with the top along it's length and cleco the trailing edge to the angle. Then go do something else for 2-3 days. Hope this helps.