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Fuel tank skin fit

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CaptPausert

Well Known Member
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so i have a bit of a fit issue with my tank skins. They have been a bit tight in the nose from the beginning and have a noticeably tighter radius than the outboard wing skins which fit to the ribs perfectly. When i put the tanks on the wing they do not perfectly match up to the outboard skins. Does anyone have a good suggestion on how to deal with this? I tried using some pvc pipe to open it up a bit but couldent get anywhere.

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It has been a long time, but I remember having to work those skins to get a better fit. Being thicker adds challenge to the effort 😎
 
It getting close to 20 years ago when I was at this stage of build, but I had just the opposite issue. on my wing and tank leading edges I really had to message and file the ribs to get them to nest into the skins.

Maybe something to do with how the ribs / skins are made now. I would send those pics back to Vans and ask them what they thoughts.
 
I think it is a good practice to remove all the blue vinyl covering on the tank before working on it. Just another thing to look out for.
Have you cleco all the match holes on the rib/skin of the tank? It looks as though some holes are left open.
 
I took the vinal off the inside. I left it on the outside to minimize scratches. The blue you are seeing is on the reinforcement plates
 
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CaptPausert said:
The fit varies a bit but they all have a gap.
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It's been a while, but I recall most of mine having at least somewhat of a gap. Aside from the outside ribs which will get the extra plate anyway, the nose section of the ribs aren't a leak path, so in that regard a gap doesn't matter all that much.
 
Are you referring to a mismatch between the tank skin and leading edge skin? And yes, the tank ribs are buggers.
 
yes they do not have the same profile. the tank skins are more squished. they have a tighter radius. The outboard ribs fit perfectly they were tight no question, but they fit. The nose ribs do not. When mounted on the spar the tank skins stick out further than the leading edge skins.

If i take the reinforcement plates and put them on the outboard skins there is no gap whatsoever. they fit perfectly but on the tanks they have the gap shown in the picture,

I am currently building a former in the airfoil shape using MDF which i will stack about 12-15 pieces of and then fit it into the skin and see if I can get the radius to change using a rubber mallet.
 
Brian, I'm building the RV-9A also and had the same issue, both with the leading edge of the wing and the tanks. I had to use a lot of force to get them in place. I called Van's and emailed them that they did not fit. I ended up putting the tanks in the jig and starting from the front inserting clecos one row at a time, alternating one side to the other. Some of the holes got stretched, but I didn't see any other way to do it. I do have some...imprinting..on the wing skins from this. :(
I've talked to other RV-9A builders that built prior to 2009 and they say they didn't have a problem and couldn't remember the leading edges being tight.
My theory is that Van's changed vendor for either the skin or the ribs, or something got entered wrong on the CNC or punches or what not.
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JZ
 
I built extended tanks for one of my RV6’s which meant I had to make custom skins. The first skin ended up with a slightly too tight radius bend. I was able to spread it out by ‘unbending’ it a bit.
A buddy held the bottom half of the skin on the floor, 2x4 layed over it to even out the forces & I pulled up on the top half of the skin to open up the radius. Didn’t take much adjustment to match things up.
 
I second Ralph's experience. I didn't use any rocket science. I just unbent the skin a little, applying the unbending force as close to the nose as possible. Like Ralph, I used 2x4s to hold the bottom of the skin down and to help apply force evenly to the upper half. It didn't take much on mine.
Bruce
 
Back when I built my tanks in 2009, the skins were all UNDERbent on just about every kit. Maybe Vans has redone the pre-bending of those skins, and possibly overshot the mark a bit.
 
I had to do a lot of massaging to get the rib tips/cleco holes lined up on both the RV-10, and RV-9A fuel tanks. I found that putting a slight bevel on the edges of the tabs using the de-burring wheel helped a lot. Also, starting the clecoing at the tips first, alternating from top to bottom skins and working your way aft, seemed to help a bit, using metal scribe's to pull the holes into cleco position.
 
CaptPausert said:
so i have a bit of a fit issue with my tank skins. They have been a bit tight in the nose from the beginning and have a noticeably tighter radius than the outboard wing skins which fit to the ribs perfectly. When i put the tanks on the wing they do not perfectly match up to the outboard skins. Does anyone have a good suggestion on how to deal with this? I tried using some pvc pipe to open it up a bit but couldent get anywhere.

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This was a SERIOUS PITA when I build my 9 wings. I couldn't even force them into place. I ended up having the bend the rib flanges to narrow the rib (or at least the nose portion of the rib). I always thought this was something that Vans should have addressed. Mine at least were just the wrong shape. Take your time and bend the flanges 1/16 - 1/8" as I've shown below. Good luck!
 

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