On Aug 21, 6:32*am, mhorowit wrote:
I have to replace the trailing edge end of a stamped aluminum rib from
a '47 Tcraft. I've cut away the corroded portion, bent metal to
replace that part and would like to use Cherry "N" rivets to hold it
in place.

Well, I think you can get the strength you need from a reasonable
pattern of Cherry commercial rivets as you propose, but I also think
that A&Ps and IAs are going to look askance at it, and you run the
risk of having them make you redo it. That's one good reason to follow
the guidelines of AC43.13, it gives folks that warm fuzzy feeling they
need in order to sign stuff off as being something like airworthy.

I have some questions regarding what spec to look for when ordering.
*A. *Rivet Material: 5052 Aluminum or 5056 - does it make any
difference for this old a rib?

If you're set on using the Cherry commercial rivets, I'd suggest
either MSP monel rivets or the BSPQ high-shear aluminum rivets. The
MSPs have about the same shear strength as MS20470ADs of equivalent
size, and the monel is galvanically about as neutral as you can get
outside of aluminum. The Cherry aluminum BSPQs have similar shear
properties and a nice stem retension feature, and look enough like
CherryMax to the casual eye that they might pass for such under a coat
of primer, and you can honestly say "Yup, I used Cherry rivets here."

B. Mandrel Material: Aluminum or steel - am I correct that
dissimilar metals could cause a problem and I should stick with
aluminum? In that case why make a steel mandrel?

One reason to avoid aluminum stems is that they are so much weaker
than the steel stems that they have to make the rivet itself out of
very soft material in order to be so malleable that it can be pulled
into shape by the weaker stem. So aluminum stem rivets are generally
much weaker than steel stem rivets. I never use aluminum stem pops on
aircraft parts.

All told, if you're so set against hard rivets I'd suggest that you
just bite the bullet and use CherryMax or whatever at a dollar a pop
or so. They'll look AC43.13 official and that will make signoff more
likely painless.

However, if you're going to make a habit of doing riveted repairs, it
really pays to get a few simple tools to drive solid rivets. I've done
plenty of MS20470AD and MS20426AD rivets with a hammer and a drift,
and maybe a set clamped in the jaws of a vise.

Thanks, Bob K.
www.hpaircraft.com/hp-24