On Sun, 16 Apr 2006 10:30:08 -0400, zatatime wrote:

On 10 Apr 2006 05:25:14 -0700, "Mike" wrote:

I have 43.13 and CAA 18 and the EAA book on welding. (I'm using
OxyAcy).

They talk about how to do various splices and patches. However, they
seem to be missing some of the practical aspects.

I"m taking apart a tailfeather for a taildragger that has considerable
rust. Some members are so rusted that they are no longer connected. In
some cases, I can see how a finger patch or a gusset might address the
problem, but there are other cases where I"m not sure.

Is there a reference somewhere that shows fixes for common rust
problems (were talking 4130); when to patch, how to patch, when to
replace the member? - Mike


Mike,

When to replace something is largely dependant on the wall thickness
of the metal you are analyzing. There are minimum wall thicknesses
for each type of tubing. If your wall thickness is less than the
minimum it needs to be replaced. How do you tell if you have the
minimum thickness without cutting the tube? There isn't a real good
answer for this, however what an old timer taught me when I was

Actually there is, but finding the equipment is another matter. (and
I've forgotten the name of the device)

A google search turned up lots of coating thickness measurement
devices, but several germane to this discussion also turned up.

In industry we used a device that measured wall thickness for tubes
and tanks. It was easy to use and it was very accurate. We used this
in some critical areas where a rupture ... I'll just say it would have
undesirable consequences.

http://flexbar.com/Merchant2/merchan...o ry_Code=UTG
should meet accuracy requirements. There is also a version for about
1/3 that cost.

Something like that might be a good investment for an active EAA
Chapter, club, or FBO. It worked on virtually all alloys of Steel,
SS, and Aluminum.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com
cutting up the tail of my Cub was to take a very sharp awl and try to
puncture the metal in various places. Places of concern check spots
closer together. If it goes through it's bad. I "punch tested" the
whole fuselage in about 6 inch increments (top, bottom, and sides in
each place). One area where there was water damage I learned that I
needed a much larger patch to the area than just where the hole was.

Any areas that you do cut open, use a micrometer to measure the wall
thickness.

Hope this helps.

z