Most mast extrusions are 6061-T6 or at least in the 6000 series. The more
corrosion resistant "marine" 5000 series does not extrude well enough for
masts. The real problem is the T6 part. That is the temper or hardness.
Any extra heat from welding is going to reduce the temper. and make the
whole base weaker. It will age harden on its own given enough time but
not in time to make an Atlantic transit this season.

He needs an artist with an AC TIG outfit to weld it closed. TIG welding
aluminum requires a high frequency AC current. A skilled operator can do it
without heating the surounding metal excessively and a generous application
of head dam clay around the weld area will keep the heat from spreading
around the mast.

To stop the cracks a small hole should be drilled right at the end of the
crack. This will spread out the stress point and stop it from progressing
any further.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Roger Derby" wrote in message
...
Check around at your local small airports and ask the maintenance
department
of the FBO if they have expertise in welding aluminum. (It's an art.)
See
if you can find out in advance what the alloy is.

I would guess that taking it to the shop would be a challenge.

Roger

http://derbyrm.mystarband.net/default.htm

"Dave Buttle" wrote in message
...
Someone cut a nasty hole at the bottom of the mast (with square
corners). I have attached photos of the mast needing repair. Two of the
lower corners of the square hole have started to crack slightly. The
hole
is not needed, so it could be closed up. The mast is 72' tall, stepped
on
deck. I would be grateful if anyone could advise me of how, and with
which
material, this repair could be welded up for maximum strength. The
concern
is that this is an offshore boat. We are preparing for an North Atlantic
circumnavigation.
More on our trip preparations. www.blueeden.ca
Dave