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Rudder question

JohnR

Well Known Member
I am about ready to do the trailing edge of my rudder and remember seeing comments about not needing the dobs of RTV or pro-seal between the stiffeners on the newer models. My plans still mention it. On the newer kits do you still need the RTV/pro-seal between the stiffeners to prevent cracking or do the heavier skins and longer stiffeners take care of it. I'm going to use pro-seal on the trailing edge but just have a tiny 2 oz container from Van's as they said that was all I would need for the rudder. I don't think there is enough to do the dobs, so if needed I will get some RTV. Thought I would check and see what others are doing.

Thanks,
 
Rudder TE

Keep in mind that RTV cannot be painted...proseal can. Although it's a small seam, it may make a difference (to some).

Sam
7A@ABI
 
John,

The riveted trailing edge rudder doesn't need RTV blobbed around the stiffeners. The old style rudder was like the elevators (folded in a brake) and had a propensity for cracking at the stiffeners. The pieced-together assembly doesn't have the same stress problem. It's difficulty is keeping the trailing edge straight during riveting. A bit of tank sealant or RTV is used to glue the wedge and skins together while clamped straight. If you like to watch grass grow, the cure time is bearable. You still need to assure the trailing edge is restrained straight as you rivet. You also need to assure that no glue plugs the rivet holes and dimples; tough to remove.

John Siebold
 
Use the proseal on the AEX wedge and skins for the trailing edge. Use RTV inside where the stiffeners meet near the trailing edge. This is done after the trailing edge is all finished and just before you rivet the rest of the rudder skin to the spar.

I used a 5 foot length of 3/16 X 2" angle steel to hold the rudder all together during riveting. I drilled every other hole into the angle and clecoed the assembly to the angle. The rivets were set on the angle pointing up so I could set them, using the angle as a sub back rivet plate. I then partially set the rivets. Once every other rivet was set near fully, I removed the rudder from the angle and set the remaining rivets. Use as large of a back rivet plate as you can find and move about the rudder setting each rivet just a little at a time. That way you can counter any warp if/as it develops. It's a long slow process, but patience yields a nice straight rudder.

There are other ways, but this worked for me.

Roberta
 
I used a small dab of RTV between the shop heads of the far aft rivets of the stiffeners just to be sure there was no way the shop heads could vibrate against each other. At $3 a tube, I figured it was cheap insurance.
 
Thnks for the replies. I can't finish the rudder unti lTuesday as I don;t have on of the dimple dies I need so will be calling Cleaveland in the AM. Seems like a weekly thing. :eek:
 
Resurrecting this old thread: I've got a 2020 tail, so do I need to use proseal on the stiffeners or not? And where? I've read that some guys put it UNDER the stiffeners (spread it full length between the stiffener and skin) and others are putting dabs on TOP of the stiffeners near the aft end to keep the left and right side stiffeners from touching each other. Plans say nothing.
 
Resurrecting this old thread: I've got a 2020 tail, so do I need to use proseal on the stiffeners or not? And where? I've read that some guys put it UNDER the stiffeners (spread it full length between the stiffener and skin) and others are putting dabs on TOP of the stiffeners near the aft end to keep the left and right side stiffeners from touching each other. Plans say nothing.

The idea is to affix the stiffeners to the opposite side to reduce flexing and crack forming at the end of the stiffener. If the flange is not trimmed enough then it will hit the opposite side.

Taking a straight edge from the spar to the TE one can see how much the height the dab will require to meet the opposite side.
 
I do conditional inspections on RV's and have seen 3 airplanes with the newer rudder develop cracks at the forward end of the stiffeners in the skin. It is recommended that you put a dab of silicon at the forward end of the stiffener just aft of the spar. Also an engineer at work recommended that you make sure the leading edge radius is rolled completely to reduce stress at the same area.
 
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