> I don't know if we have any Experimental Aircraft Association members on
the
> list but I hope so . . I think there were requirements that "homebuilts"
had to
> use OA rather that any electrical weld mode. Can anyone verify?
> Tony
Traditionally, that's close - EAA has recommended gas welding to the
exclusion of most other methods because of the simplicity and relative
fool-proof nature of gas welding on chrome-moly tubing, the most common
airframe welding done.
However, EAA doesn't make the rules - the FAA does. The FAA generally
regards OA as the method of choice for repairs - in fact they don't address
much else in CAM 18 - but they don't require it. As I mentioned, some
airplane manufacturers indeed use MIG, TIG, and even stick welding. And so
do some homebuilders. And as I also mentioned, Piper used some arc welders
in the 1940's - Lincoln went to the Ponca City, OK Piper plant (a wartime
supplement to the Lock Haven, PA plant) and convinced them to try arc
welding on Cub fuselages, and they liked it some. It was very fast, of
course, and it saw some limited use. I don't remember much else about that,
as it was related by a now-long-gone Piper employee at a Cub Club fly-in
about 20 years ago.
At any rate, lots of EAA'ers are building homebuilts with MIG and TIG, and
for some years now the guys in the EAA welding tents at Oshkosh have been
teaching beginners how to use gas, TIG, and even MIG on airframe parts.
Bottom line - it's up to the builder to do the work and convince his
inspector that it's done properly and safe.
That said, personally I can't see any attraction to going any way but OA for
most airframe work. Thick parts of a landing gear, etc., maybe I'd use TIG
if I had it (it's a real pain sometimes to get enough heat with OA), but
otherwise gas is so easy and forgiving that it's all I use on airplane
parts. Sure it's slow, but you see the penetration of every drop of weld.
And with any welding method, normalization is always a good idea for
non-heat-treated structures. Heat-treated parts require re-heat-treatment
after welding if welding is indeed even permissible - depends on the
specific part.
YMMV
Karl
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