Proseal on stiffeners

Hi,

I see some builders putting ProSeal on the stiffeners where both sides meet. Nothing seems to be mentioned in the plans about it.

What is the advantage or reason to add this extra Proseal? Should it then be done on all stiffeners (both elevators & rudder)?

Thank you!

On the older RVs there were instructions to put RTV where the stiffeners met at the trailing edges of the flight controls, but I think this was only applicable on the flight controls that had the radius trailing edge.

Yes, there is a potential advantage. Connecting the ends of the stiffeners will add a bit of stiffness to the skin. This has two effects, one if there is any oil canning, it will lessen the likelihood of cracking at the rivet nearest the TE. Apparently this was found on the early RV6, but none widely reported on the riveted TE style rudder. Second, it will add some torsional stiffness and help add some margin to Vne. No quantification on either.

So, it is a good idea. Just don't add a huge glob on each rib, just enough to contact both sides. Be sure to balance your elevators separately, before flight, and after paint.

Have replaced cracked skins on both bent & wedge type surfaces, and both .016 & .020 skins, old and even current kits. All have the potential to crack if not treated with dabs of pro seal to minimize oil canning type movement. Have seen cracks form at both rear rivet AND front rivet on stiffeners. A dab forward & aft is good insurance.

Proseal stiffeners

Some proseal the stiffeners to the skin as well. Rudder and elevators. I did.
Just a thin application to both sides.

This thread is very timely for me since I am about to rivet rudder stiffeners and have riveted elevator stiffeners but not yet bent the trailing edges. I have a couple of questions:

1) In section 5.7, the manual says "place a dab of RTV or tank sealant about the size of a wad of chewing gum at the inside of the skin where the two stiffeners overlap near the trailing edge." In England "a wad of chewing gum" isn't a frequently used unit of measurement! Can someone offer a translation please?

2) What is the thinking behind using RTV or Proseal? Wouldn't something rigid like JB Weld or Araldite 420 be better?

Thanks for any help - it's always enlightening to hear the collective wisdom!

Many thanks for the clarification on this. I think I am going to do it too as it is not much extra work and if it helps, great. If it don't, nothing harmfull done. But I think of using some other sealant because I don't have a lot of Proseal on stock.

Proseal

A wad of gum is about a teaspoon. Or you can chew a piece of gum, take it out of your mouth and look at the size for comparison.

Vans sells small quantity of proseal.