RV-7 rudder

My son has started building his RV-7A. He has the vertical stab done, and is working on the rudder. The instructions strongly suggest you use a "sealant" on the rudder trailing edge to help it stay straight while riveting. He has ordered a tube of the reccommended firewall sealant for this. My question is: Is this necessary, what other types of sealant does/did everyone else use? For those that didn't seal the trailing edge, did you have any trouble keeping the trailing edge straight?

Thanks,
Mike

Lots of information and alternatives in the RV-6/7/8/10 forums on www.vansairforce.com

Use the forum search feature.

I used fuel tank sealant, commonly called by one of the brands, ProSeal. PR1440 and PR1428 are the spec numbers. I used PR1440 on mine-what I had on hand. Don't use anything silicon-based (is firewall sealant???) because any sealant that strays on to the surface will affect paint results down the road. Silicon wreaks havoc on surfaces to be painted. If it's going to be polished, no worries on silicon...

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Originally Posted by Marty Santic

Lots of information and alternatives in the RV-6/7/8/10 forums on www.vansairforce.com

Use the forum search feature.

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It's great to have the info here too...;)

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Originally Posted by Mike B

My son has started building his RV-7A. He has the vertical stab done, and is working on the rudder. The instructions strongly suggest you use a "sealant" on the rudder trailing edge to help it stay straight while riveting. He has ordered a tube of the reccommended firewall sealant for this. My question is: Is this necessary, what other types of sealant does/did everyone else use? For those that didn't seal the trailing edge, did you have any trouble keeping the trailing edge straight?

Thanks,
Mike

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I consider it necesssary because of the double-flush riveting techinque (essentially back-rvieting both sides) used on the trailing edges. I used a marine sealant I picked up at Lowes on my rudder and Proseal on my alierons and flaps--got the same results. It really doesn't matter what you use (other than a silicone based product as Chad mentions) because what you are really doing is simply substituting the sealant/glue for clecos to hold the edges together while you rivet.

I failed to mention that there is a technique that works without using any Proseal or similar "glue" to keep the trailing edge together while riveting. What you do is bolt a long piece of angle iron to the edge of the workbench. Then using the skin as a drill guide, match drill the trailing edge rivet holes into the angle. You can then cleco the trailing edge to the angle which becomes a back-riveting plate and double-flush rivet per the plans using the techinque as described in Chapter 5.

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Originally Posted by Auburntsts

I consider it necesssary because of the double-flush riveting techinque (essentially back-rvieting both sides) used on the trailing edges. I used a marine sealant I picked up at Lowes on my rudder and Proseal on my alierons and flaps--got the same results. It really doesn't matter what you use (other than a silicone based product as Chad mentions) because what you are really doing is simply substituting the sealant/glue for clecos to hold the edges together while you rivet.

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I have no experience with RV construction, but why can't you use clecos in this operation? Anybody have a pic of how this looks? I'm curious!

I used the steel angle on the edge of a bench, but you still want to use sealant to keep it straight...

http://www.chadandbrittne.com/images...25-05-002w.jpg

http://www.chadandbrittne.com/images...25-05-004w.jpg

I built mine with a series of numbers on the rivets, 1-5, and started with the 1's at each end, then the two's, and so on. You can see, just barely in this pic (my site was very limited in space back in 2005) the numbers...

http://www.chadandbrittne.com/images...27-05-005w.jpg

Came out nice and straight!

http://www.chadandbrittne.com/images...27-05-004w.jpg

Chad,
IMO using sealant and clecos is a belt and suspenders approach. Nothing wrong with it, but I think either will keep it straight as long as you follow Van's advice as to the riveting technique. I went the tradional sealant only route and had no issues whatsoever. I believe the key to a straight trailing edge when using the angle and no sealant is to set some of the rviets from the opposite side by flipping the assembly over. YMMV...

MrMorden,
The reason that you can't use clecos without the angle is the back riveting technique. When you back-rivet you're reversing the normal rivet bucking techinque that places the rivet set against the factory head and the bucking bar against the shank to form the shop head. With back-riveting, you place the rivets in the holes and rivet tape is placed over the rivet to hold them in-place. The reason this is you place typically place the assembly on a back-rivet plate (just a big, flat piece of polished steel) so that the factory head of the rivet (these are AN426 flush rivets by the way) is flush aganist the plate. The plate will now become the bucking bar. You then use a special back-rivet set to form the shop head. If you had clecos in-place, the tips would not allow the rivet to sit flush on the plate. With double-flush riveting you partially set the rivet and then flip it over so that both sides of the assembly end up "flush" after you completely set the rivet.

Attachment 1031Attachment 1030

I also used an angle clamped to the trailing edge to keep it straight during construction, but I used a set of rivet squeezer dies that were ground down at the angle of the trailing edge. That allowed both dies to line up exactly flat to both surfaces. Do a search on the VAF site for pictures of the dies.

Jim Cone
Tech counselor (Gold)

Thanks for the replies and advice :thumbsup: