Thanks for the tips, John!
I'll certainly take a look at that mil-spec

I'd like to offer one point of feedback. The tone of your comment, "Your
photo really sucks, by the way," is outside of what I would consider
productive.

The photo was offered merely to show the relationship of the damaged area
relative to axis of the part. To clarify, I'm looking for help interpreting
the AC 4313 guidelines for patch size, rivet count, and rivet spacing. That
said, if a qualified aerospace engineer steps forward to offer assistance
with a deep analysis of this tailboom component and its repair options, and
he or she would find it helpful, I can certainly provide numerous high
resolution images from my self-hosted IIS box.

- Russ

"John Kimmel" wrote in message
...
RPM the A&P wrote:
Hi,



I'm looking for input on the best way to layout a repair of some "hangar
rash" on the tail boom of my Taylor Coot amphibian project.



The damaged area is on a 10in diameter .065in 6061 T6 tube that serves as
the tail boom on this aircraft. The part was dropped and sustained a
crease roughly perpendicular (but not quite) to the length of the tube.



I have removed the displaced material and now have an opening 4.1in long
and 1.1in wide.



Since I'll be joining two sheets of .065, I've selected -6 rivets. I
also realize that I'll need to slip roll the patch.



I'm now trying to apply the guidance for stressed skin repairs found in
AC 4313-1B around paragraph 4-58 figure 4-16 and tables 4-9 through 4-11
(note that there is apparently no table for 6061 T6).



Here is a link to an image showing the current state of the repair:



http://rilinterface.com/Cootnest/Ima...e/DSCN0997.jpg



I'd love to get folks' input on how best to lay out the repair for this.



Thanks!



Russ

http://rilinterface.com/cootnest


I recommend using 2024-T3 for the repair doubler, putting it inside, and
putting a filler on the outside. This is not because the 2024 is
stronger, but because it will be much easier to buck large, hard rivets
against a harder material than 6061. The heads go against the 6061 outer
skin, you'll need a 5x rivet gun and a really heavy bucking bar. You can
also use fresh icebox rivets (-D, -DD) or heat treat AD rivets, (if you're
daring enough). The most important thing is to thoroughly prime and seal
the skin and repair doublers before riveting them together. Rivet spacing
in 43-13 seems really close to me, compared with actual rivet spacing in
aircraft or in aircraft structural manuals. I'm too lazy myself, but
MIL-HDBK-5 will give you FAA acceptable numbers for calculating the number
and size of rivets needed for the repair.

Your photo really sucks, by the way. Without knowing the location of the
damage on the aircraft, there's no way to determine the load path. With
digital cameras and unlimited web space, there's no reason not to upload a
couple hundred photos of the aircraft to a Google photo album.

--
John Kimmel


I think it will be quiet around here now. So long.