Rudder Ripples and Skin not tight to wedge

sglynn · #1 07-03-2008, 12:44 AM

Any suggestions on what to do about this rudder issue are appreciated. Rudder build was going great. I used fuel tank sealer to glue trailing edge and angle aluminum to hold it straight. I waited two days and riveted it per the plan. It is straight, BUT it has ripples on the shop head side, and the skins are not tight up against the wedge because the black stuff (fuel tank sealer) is in there. ANd I really scraped off the access and tried to use only a little. From arms length everything looks okay, but on closer look there are wavy humps on the rivets and the skins pull away from the wedge in some places. My options seem to be: 1) buy and build a whole new rudder 2) pour solvent on it and wire brush it and smash it more with the flush rivet set or 3) drill out some spots, clean out the black stuff and re-rivet 4) drill out the whole skin and re do and/or with a new skin or 5) get over it, live with it, and use lots of paint.

Your opinions are appreciated. thanks

kiwipete · #2 07-03-2008, 02:33 AM

Hi

A photo of the trailing edge would help to see to what extent the ripples are and how much gap you have would be helpful.
I've just finished a replacement rudder and both this and the first I built didn't pull that tight on the wedge. The problem I found is that the wedge isn't that thick and when it's countersunk from both sides you can't go too deep as you will open the holes up too much.
So it's a catch 22, with only just enough countersink and then the added thickness of the sealant, it does'nt sit as flush as I would have liked. But if I countersunk any more the wedge would have 1/8 holes. With the sealant and a little filler the edge looked fine and with the rivets well squeezed it's plenty strong enough. (The first one held up ok after being hit by an excavator!!)

Peter

sglynn · #3 07-04-2008, 09:23 PM

Here is the photo.

Thanks for your reply and interesting story. Since posting, Van's told me to "live with it."

kiwipete · #4 07-05-2008, 02:15 AM

Steve

It looks no worse that most I've seen! As for the ripples it maybe that you've put a bit of pressure on the skins above the wedge and this has rippled it a little.
The rivets look like they are well formed and given that you've glued it with tank sealant it should be fine.

Keep building

Peter

MikeJ 7A · #5 07-05-2008, 09:03 AM

Hi Steve,

I'm doing the rudder now also (after a year of no progress because of proseal fear and other things keeping me "too busy"). I'm finally back to work and about to do the trailing edge. Thanks for you timely post, I may have to reconsider proseal (vs epoxy vs nothing at all...).

I saw your photo (see below) and it looks like your counterweight skin is primered and riveted under the rudder skin? Is that correct? I might have screwed mine up but I overlapped my counterweight skin on top of the rudder skin.

Does it matter? Is it ok to have the counter weight skin overtop the rudder skin? Anyone?

Best!
MikeJ

mcencula · #6 07-05-2008, 10:59 AM

Mike,

I believe the counterweight skin is supposed to go under the main rudder skin. Aesthetics are the only thing that may be impacted and that only slightly. From a strength standpoint, they should be equal.

Steve,

Regarding skin bulges, my rudder has a slight bulge at every rivet. I didn't notice this until after it was all together, but I'm pretty sure it's caused by the dimples from the skin on one side hitting the dimples from the skin on the other side. The wedge is basically not thick enough for both dimples to sit down in the countersinks.

I told another builder about this and he decided to file down his dimples a little so they wouldn't touch. His rudder came out perfect.

Based on the photos, I'd say your rudder is probably above average. Any little dings can be filled with some microballoons and epoxy or other filler prior to painting and no one will ever be the wiser.

Tom Martin · #7 07-05-2008, 11:18 AM

A lot of imperfections can be cured with the use of a small hammer! You will need a solid flat surface that you can rest the trailing edge of the rudder on. I have a piece of steel angle bolted to the edge of my bench. The top surface is polished. With the trailing edge resting on this angle you can gently tap the areas that are high so that they come into line. The object is to slightly bend then the trailing edge of the skin. If you hit it too hard you will stretch the metal and make it worse. I have used this method on a number of trailing edges to take them to a higher level of finish.

MikeJ 7A · #8 07-05-2008, 12:48 PM

Quote:

Originally Posted by mcencula

I believe the counterweight skin is supposed to go under the main rudder skin. Aesthetics are the only thing that may be impacted and that only slightly. From a strength standpoint, they should be equal.

So the "step up" on the rudder skin where it transitions from contacting the spar to resting on top of the counterweight skin doesn't bother anyone? Seemed like an odd thing to do...

Mike

morlino · #9 07-05-2008, 05:19 PM

Quote:

Originally Posted by MikeJ 7A

So the "step up" on the rudder skin where it transitions from contacting the spar to resting on top of the counterweight skin doesn't bother anyone? Seemed like an odd thing to do...

Mike

Mike,

Check out this thread : http://www.vansairforce.com/communit...ad.php?t=23039

I'm not sure why the instructions are so vague about this. But, get used to it. Unfortunately, the instructions become more and more worthless as you get further into the airplane. If you look on drawing 7, the R-913 counterbalance skin is dashed on the left side view indicating that it is underneath the R-901-L skin.

I feathered the edge of the counterbalance skin to ease the transition. I just used a vixen file to taper about 1" of the R-913 skin so there is a more gentle step. What I did is similar to the "scarf joint" for overlapping wing skins described on Dan C's website - http://www.rvproject.com/20020626.html - scroll down to the bottom of the page.

As is suggested in the other thread, your airplane should still fly. I don't see how it could make a big difference. If anything the way you built it will have less drag.

Jeff R · #10 07-05-2008, 06:12 PM

Quote:

Originally Posted by MikeJ 7A

Thanks for you timely post, I may have to reconsider proseal (vs epoxy vs nothing at all...).

I tried T-88 epoxy and it didn't work all that well for me, so I went back to proseal. I think one key is to make sure the layer of proseal you smear on is thin and consistant.