Support for bottom of fuselage

I have seen numerous photos of RV 7s and 8s with "coke can" issues on the bottoms of their fuselages. I read somewhere that there is a fix to reinforce the bottom of the fuselage area. Now that I'm at the point in my project where I would reinforce this area, I can't find the builders log where I originally saw the info re the fix. Can anyone provide some guidance?

Denver Gore

My buddy Mike has done this with his 7A. His build page is here:
http://www.our7a.com/20090328.html

Pic here:

I didn't like the thin unsupported nature of the belly skin in the tail cone either. I noticed it when adding an ADF antenna behind the elevator bellcrank.
O.K., so I'm weird for ADF.. But that fuse bay is stiffer due to the antenna doubler. The farther aft you go, the smaller the unsupported area.
You could rivet in some light angle such as the skin stiffeners in the elevator?
I messed up one elevator skin, so I had some spare stiffeners around. They turned out to be useful for all manner of small things.
Keep the weight down.

panhandler1956 said:

My buddy Mike has done this with his 7A. His build page is here:
http://www.our7a.com/20090328.html

Pic here:

Click to expand...

I did something very similar to this, I used excess J-stringers that I had left over from the fuse. Except I cut my J-stringers at each bulkhead instead of running them through. The way this gentleman did it is superior to mine...there is some feedback in the archives that if you stop your supports short of the bulkhead you can get cracking on the end rivets. Either run them through as one piece or tie them into the bulkhead. In any event, I think this is a great mod...really stiffens up the bottom fuse for little weight penalty or cost, and its easy to do. There are pics on my site if you want to check it out.

Fuselage Support Specific to QBs

I reviewed the responses to my post and was wondering if anyone has figured out how you get the support material through the bulkhead(s) on a QB (how to cut bulkhead so near the skin of the fuselage).
Also, which bulkheads do you go through and where? Lastly, if you go through the bulkheads, do you need to fabricate any extra support specifically at the bulkhead or just drill out the bulkhead rivet, lay the "J" or "L" aluminum and put a little longer rivet in?

On my 8

I looked at this reported problem. I noticed a possibility of oil canning in the bay just aft of the bellcrank assembly bay. The solution I came up with is not as intricate as those previously stated. I installed a 3/4 angle left over from build, in between the bulkheads, but resting on the aft bulkhead flange and an angle riveted to the fwd bulkhead and the stiffener angle. By resting this angle onto the flange of the aft bulkhead, it eliminates the cracking at that location from concentrated stress. Also, I did not rivet this stiffener to anything but the fwd. bulkhead. The angle is in the center of the bay and prosealed to the skin and the bulkheads. I think this is sufficient to stop the oilcanning. The next bay aft is quite a bit smaller and I don't feel a need to stiffen this bay. Time will tell.

bird