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Leading edge skin to top skin gap - normal size

llavalle

llavalle

Well Known Member
I just finished wrestling with the leading edge ribs & skin.

After attaching the leading edge to the spar, I noticed that there is a small gap between the top skin and the leading edge skin. On the top of the wing, the gap is about 1/32". On the bottom, it's less than 1/64" - it fits just fine. (why isn't it the opposite :eek: ?).

The row of cleco that attach the leading edge skin to the spar were very tight and from the look of it, I think it's actually pulling the spar flange outward...

List of questions :
1-Is this a normal occurrence?
2-Is the gap too big?
3-If it is too big, do you have a simple solution?

And because a picture is worth a thousand words :
Top Gap :
DSC03930.JPG


Bottom Gap :
DSC03932.JPG


Thanks for any input.
 
Phillippe,
It is too early to measure real gap. The skins are not prepped, blue film is still on, temperature regime and so on and so forth. Then you dimple etc. I had something like that but somehow mysteriously I was able to minimize the gap while riveting pretty easy. I believe you will be able to correct +/- 1/64 here. Do not sweat it. Move on.
 
We managed to get the two skins essentially butted up against one another on both sides by using 3 or 4 straps to cinch the leading edge down just a smoodge prior to match-drilling, and when doing final fitting and such. Just put the straps around the whole thing, and use some 2x4s on the rear spar so you don't bend the skin, and tighten it up a touch. (We used the nylon webbing cargo straps with the come-alongs on them). Worked beautifully.

Just be sure to put the straps over the ribs, not on a section of skin between the ribs.

I have some pics somewhere that I'll try to find and post.
 
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Flying Scotsman said:
Just be sure to put the straps over the ribs, not on a section of skin between the ribs.

I have some pics somewhere that I'll try to find and post.
Click to expand...

A pic would be nice. Doing this implies that you need to remove the cleclos from the ribs you're "compressing". Did the rib move when you did that?
 
I had the same problem with the tank skins on my -7. Make sure you've rounded the noses of the ribs good. To close the gap a bit on my tanks, I used the cargo strap method Steve descibed. Note: the straps run between the ribs, but this on the thicker tank skins. As Steve said, there are 2x4s stacked under the rear spar so as not to bend the aft edges of top skins.

060114_006.jpg
 
Just like Brad's picture. Be cautious with the hooks and ratcheting devices on these straps, so they don't bang into your skin or scratch/damage it, too.

I don't remember is we removed the cleco's from the rib or just put the strap right up against it (the pics are on another computer at the moment).

I also worked very hard to get the noses on the ribs properly shaped - filed a little in places, opened some bend relief holes here and there, sanded some places - so that the skin has very little visible "deformation" on the outside due to the noses of the ribs pushing against the skin (couldn't get rid of it all, but most of it is gone). That might have helped with the tightness of the butt joints, too, I dunno.
 
Alright, thanks. I'm having some skin deformation on the outside due to the nose of the ribs pushing against the skin. It's ugly... They were really a pita to get clecoed. They were really square and no more fluting was required. The hole lined up perfectly bu they were "out" by a small amount...

I think I'll just uncleco everything and rework the nose of the ribs. We'll see how it goes.
 
Mine looked just like yours!

Mine was that way too. I did nothing about it and as others said it will close up after riveting. Here is a pic of the gap before. I don't have one of
the after, however I can tell you there is virtually no gap at all! I personally wouldn't lose any sleep over it and keep banging away!

gap.jpg
 
Don : that's your tank right? (1/8" clecos...)

Alright, my bigest concern was enlarging the holes in the spar while drilling... I just don't want to do that. I think I'll use a regular drill instead of a reamer...
 
Leading edge gap the same

llavalle said:
Don : that's your tank right? (1/8" clecos...)

Alright, my bigest concern was enlarging the holes in the spar while drilling... I just don't want to do that. I think I'll use a regular drill instead of a reamer...
Click to expand...

Yes, that picture is the tank gap, the leading edge gap was almost identical. I even had the smaller gap on the bottom side of the leading edge just like you do. They all closed up nicely after riveting.

My secret trick to not elongate the holes...... I didn't match drill the leading edge skins to the spars:eek: I figured since you can't match drill the holes for the tank screws, why would it matter to do the same for the leading edges and the strapping it down option seemed way too over the top so to speak. Seriously, it came out beautiful.
Guess I won't be getting my invitation to the master airplane builder club though;)
 
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Don Jones said:
...My secret trick to not elongate the holes...... I didn't match drill the leading edge skins to the spars:eek: ...
Click to expand...

I was thinking about doing the exact same thing...

I'll first dissasemble the leading edge and "tweak" the nose of the ribs a bit. It's way too tight.
 
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