THe RV-4 I am working on was shipped from the US to Uk without any bolts to hold the WD-409 tailspring weldment to the F-412 bulkhead. THe result can be seen here:
So if anyone is tempted to transport their pride and joy from home to the hangar without putting these bolts in - DON'T!!
My concern now is how best to effect the repair. AS you can see above, the F-412 is well and truyly knackered and needs to be replaced. Removing it was an interesting procedure because of the numerous rivets that were hidden along the top and bottom longerons - eventually solved witha aa die grinder. The overall finish wasn't too good so I have a bit of filing and polishing to do to get rid of sharp coners, hacksaw arks and so on.
The big problem is that the F-411 is not vertical WRT to the top longeron. If I put in the new F-412 properly, normal to the longeron, it is about 3/16-1/4" out WRT to the aft plate of the weldment. I don't want to have to remove the F-411 as well and anyway, as the skin is already drilled, any attempt to true it up will lead to edge distance issues on the F-411 flanges. Putting the F-412 in at the same angle as the F-411 leads to some interesting problems at the bottom, with insufficient room to get the rivet into the flange. I suspect that the weldment never butted up to the F-412 properly....
My preferred solution would be to mount the F-412 correctly ie normal to the longeron, and put some shims under the weldment mounts - say 1/8' at each end. Here's a couple more pictures.
Here the strip of aluminum is clamped along the line that would be parallel to the back side of F-411
Finally, I have new bulkhead parts from Vans but the fit is not brilliant. I wondered about riveting a flange in place at the correct location and making a new bulkhead that would have a better fit, then to rivet to the flange, then riveting a second bulkhead over the first with another flange, to emulate the original Van's design with a double flange.
I hope all is clear. Any suggestions guys?
Thanks as always for help and comments.
RV-8 - built, flown, sold
RV-4 - in remediation