[Phil]

Hi Everyone,

Last night I managed to stay awake until 2Am working on the tailcone.

I finally had to go to bed when I found this issue. The shape of the bulkhead flanges do not allow the flange to sit correctly against the fuselage skin.

I'm considering knocking off the corners of the flanges and letting it sit against the skins correctly, however I wanted to pick your brain.

1) Did you experience this same gap, or do I have poorly manufactured product (RV-10)?

2) How did you fix it?

Thanks,
Phil

 

[Lionclaw]

Slightly OT - But it looks like Cessna ignored the same problem on their 162 prototype

I think others were recommending liquid shim. A search on the forums might reveal something helpful.

 

[rv7charlie]

Try re-forming the tabs by bending the sides of the tabs so that the tab more closely follows the curve of the skin. You should be able to get the fit a lot better than you might think when you 1st look at the situation.

One thing to watch is the 'corners' formed by bending the flange after the notch in the bulkhead was cut. You can round off that corner with a scotchbrite wheel. Also, do the same on the outer corners of the tabs, or roll them slightly with your seamer. If you don't do this, you'll likely get bumps in the skin when you rivet.

I hope that makes sense.

If you do get the flattened spots in the skin like the pic of the C162, you can sometimes take them out by using a wood or plastic dowel on the shop head of the rivet & bump it outward with a mallet. This will reshape the tab & skin closer to a smooth curve.

Charlie

 

[Rick6a]

My pre match hole -6A kit had similar gaps in various locations, a few of which were considerably more severe that shown in your photographs. This photo does not show the repair of a severe tapering gap very well...the Akzo epoxy primer hides it very well.



The repair is very quick and very easy. You just have to know what to do. I wrote a tip some time ago that addresses that very issue: the infamous bulkhead to skin gap issue. Don't cheap out and end up with pucks like that Cessna or countless RV's I have observed. Shim it! Here's how:

http://www.vansairforce.com/community/showthread.php?t=6750&highlight=liquid+shim

 

[Phil]

To benefit others, I thought I'd provide the feedback that was provided from Vans.......

Phil,

File or hammer down the corners of the flanges so that they don't make the outward dent in the skin, then shim the flange to make the bulkhead fit the skin better.

Bruce

 

[SvingenB]

To me this looks a bit strange, maybe someone could explain the structural stuff a bit more in detail. But wouldn't the "Cessna-rivets" still be allmost 100% structurally sound? It will make the whole structure a bit "softer" (and uglier) but not much weaker? A shim will probably make the structure weaker because shear loads in the rivets are transferred to tension due to gliding and bending of the surfaces on each side of the shim, but very dependant of the thickness of the shim I guess. That epoxy will probably not glide much, and act as a glue, but a epoxy-paste sandwiched between metal, how will such a structure work in relation to the rivet? Wouldn't this be the same as a glued metal to metal bond, but with an extremely large gap for the glue? How will the rivet expand in the epoxy vs in the metal parts?

 

[jsharkey]

Another builder I know took a 1/2 wooden dowel and used it as a soft punch to hammer gently on the tail of the rivet at the offending point from inside the airframe. He was thus able to reduce the "dents" on the outside skin. I haven't been brave enough to try it - but I did use metal shims at a few spots where the gap was too much to squeeze closed during riveting. I guess you could drill out rivets at bad spots and slip in a metal shim or squeeze some liquid shim into the gap before re-riveting if you were particularly concerned.
Jim Sharkey
RV6 - nearly there!