LettersFromFlyoverCountry

LettersFromFlyoverCountry

Well Known Member
While my RV-7A is almost done, I'm not going to bother trying to fly it until next year (I haven't been flying for almost a year and my wife found out on vacation last week that her job is being eliminated, so I'm on the austerity plan for awhile), which probably gives me more time to spend over the winter getting it in ship shape and fixing parts of the 10-year construction that need attention.

One of the problems I'd like to fix is this:
2011-07-27_19-02-06_434.jpg


This comes from doing a poor job of drilling the 1/4" hole in the hinge ears a few years ago. It also creates a bigger gap on the side. The other side is OK.

It's compounded by the fact that when I riveted the reinforcing kit to the canopy skin, I forgot to put a shim along the flange to help the canopy skin get "above" the forward skin.

My building pal, Brad Benson, has suggested removing it and welding the present hole shut, refitting and redrilling. And also drilling out the canopy skin and inserting the shim. This is a little problematic because the rivets are presently buried under the beautiful fiberglass fairing I spent months on a few years ago; I guess that would have to be sanded off.

So a couple of questions: (a) is this a good way to go? (b) is this the best way to go and (c) is there anyone who knows welding who can make a house call since I don't want to take the canopy to somebody's shop who I don't know (and I don't know any welders).
 
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Bob,

Most tippers have this air scoop issue at 10 & 2 o'clock. Several people have different ideas on what the root cause is.

It looks like the center of the front of your canopy skin is fitting nice to the aft side of the front fuse skin. If that is the case, you can't fix the scoops by moving the pivot points because you can't go any lower with the whole thing without screwing up that area in the center.

To keep the front of the canopy skin from catching on the aft side of the fuse skin, you need a pretty good gap in there. Don't try to make this gap too narrow or it will catch and bend the canopy skin!

The scoops can be delt with by using glass and filler to fair the top fuse skin in to match the canopy skin. Start way up fwd and slowly build it up till it meets the canopy skin. If this is done properly, it will mask the problem and will look fine. Don't try to do this all with just filler or it will crack down the road.

It is my personal opinion that the canopy ribs are not formed correctly from Vans to match the curve of the top fuse skin that is formed by the subpanel. They tell you in the directions to somehow flute these very thick ribs to match the curve. Yeah right! Those things are thick and have flanges on both sides. How the heck are you suppose to flute them and change the radius of that curve in them? Not gonna happen unless you use a 10 ton press or something major to bend them more or less.
 
Bob,

I found some pics of how I fixed mine...

Here is before showing that I also had scoops. I sanded the poo out of the skin before adding the filler.

DSCN8323.JPG


Here is the first layer of filler that was a resin and Flocked Cotton or Flox. Another layer of resin and micro balloons was added to the top of this for fairing it out and filling the voids.

DSCN8339.JPG


My painter final finished this and made it look nice. Here is the end result. No more scoops!

DPP_1139.JPG
 
Brantel said:
Bob,

To keep the front of the canopy skin from catching on the aft side of the fuse skin, you need a pretty good gap in there. Don't try to make this gap too narrow or it will catch and bend the canopy skin!
Click to expand...

Thanks. You know, it's funny. I think the instructions say a gap of 3/32" there will work. It sure didn't work with mine. I think the gap there is about the size of Delaware. :confused:

I have no problem building up the forward skin. I guess, though, I'd have to fill all the way across (I only have the problem on the pilot's side) in order to hide all of the rivet heads, rather than just have the ones on one side hidden.
 
Same problem with canopy on mine

FWIW Bob, I had the same problem with mine. Its the one part of the plane where I wish I new enough to know how good a fit was good enough (mine wasn't). That said, it's been flying for 5 years. I don't get much flying in the rain in Las Vegas, but it certainly caused some wet feet when I went to Oshkosh in 2007.
For the gap in the sides, I ordered some seals from McMaster-Carr (got the link from Checkoway's site). It did a fantastic job of sealing the sides. For the 10 and 2 o clock positions, I put some clear silicone there and it's worked all right.
I guess since you have the time now, you can work on it. The building up in front seems like the easiest, but the welding and redrilling of the hinge holes is probably the most elegant if the overall curvature is all right. I think I thought about redoing the holes in the ribs by moving the delrin blocks down a bit and ovaling the holes in the ribs. Just another idea, but untested here...

Good luck, and glad to know you're still building.


Seb Trost
RV-7A
Boulder City, NV
 
There is another option and it worked for me.

I simply cut a bunch of stripes of aluminum that tapered out to the full depth of the gap and riveted them under the foreskin to shim it up. No fiberglass needed to build up that area.

For details, go to this page and scroll all the way to the very last entry.

Keep going Bob, you are almost there!
 
I tried the shims...was no way they would work with the amount of thickness I needed without buying a new non prepunched top skin. Looks like he needs even more thickness.
 
Mine looks just like Bob's. Sounds like I'll need a combination of shims and filler. Some shims to minimize the amount of filler. Been racking my head trying to think of a solution.

Steve
 
Something to consider... On my -6, the "ears" at the front of the tip-up do lift up a bit in flight, making this gap worse. I haven't found a gap seal that can accommodate the variation in gap from the back of the canopy where the latch is all the way up to the front when in flight. The gap varies from about 1/16" at the back to about 3/8" at the front.
 
Shims affect hole spacing?

I am working on this area now. I have slight scoops - not very bad, but then the c-702 canopy skin is not riveted on yet so they could very well be worse once that is done.

I am considering shimming the forward top skin but I am worried that it won't fit over the shims and the holes will be slightly off. After all, the aft edge of this is of a fixed length and is captured on each side by the holes through the longerons. All we can do is re-distribute the upwards curve between these two points and the sub-panel curve limits our freedom to do that. If the skin edge is raised at some points, surely it must be lower at other points to compensate. How would that be possible when it rests on the sub-panel top flange? Otherwise the skin has to stretch or the edges have to be pulled up from their position on the longerons. In both cases, the holes will be slightly off.

Bottom line is that we are asking a fixed length piece of material to cover a greater distance

For those of you who used shims, did you have problems with fit and/or hole matching when the shims were installed?
 
This is the problem I ran into. I needed more shim than I could get out of that skin. I almost ordered a non pre-punched skin and back drilled that with the shims in place but decided not to.

Loman said:
I am working on this area now. I have slight scoops - not very bad, but then the c-702 canopy skin is not riveted on yet so they could very well be worse once that is done.

I am considering shimming the forward top skin but I am worried that it won't fit over the shims and the holes will be slightly off. After all, the aft edge of this is of a fixed length and is captured on each side by the holes through the longerons. All we can do is re-distribute the upwards curve between these two points and the sub-panel curve limits our freedom to do that. If the skin edge is raised at some points, surely it must be lower at other points to compensate. How would that be possible when it rests on the sub-panel top flange? Otherwise the skin has to stretch or the edges have to be pulled up from their position on the longerons. In both cases, the holes will be slightly off.

Bottom line is that we are asking a fixed length piece of material to cover a greater distance

For those of you who used shims, did you have problems with fit and/or hole matching when the shims were installed?
Click to expand...
 
N941WR said:
I simply cut a bunch of stripes of aluminum that tapered out to the full depth of the gap and riveted them under the foreskin to shim it up. No fiberglass needed to build up that area.
Click to expand...

I thought about doing that but as you do it, aren't the already-drilled holes going to be pulled out of present alignment in increasing amounts as you work your way down?
 
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