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

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

Hmmmm...has the mast got any visible welded attachments?
If yes, it may have been heat treated post-weld.
Or, you may be lucky and the material is weldable as is.
But probably not.

Perhaps the best approach is properly contoured doublers
RIVETTED to the mast. An A&P (airframe mechanic)
would know how to do this without raising too much stress.

But this is life or death stuff, no doubt. Take care

Brian Whatcott Altus OK

On Wed, 16 Feb 2005 21:34:05 -0500, "Roger Derby"
wrote:

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

U¿ytkownik "Dave Buttle" napisa³ w wiadomo¶ci
...
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

If the square hole is located at very bottom of the mast, near the mast
step, I would consider filling the mast interior completely with composite
mixture (e.g. epoxy mixed with portland cement).
Square hole must be patched beforehand with proper composite prepreg patch
and composite filling apparatus must be constructed (e.g. basing on the
grease gun mechanism). Mast bottom section must be sealed also. Operation
should be performed on mast in vertical position and amount of mixture
calculated to provide filling to the proper level.
This filling will spread vertical forces from the mast on a much bigger
area.
Regards
Tadeusz

Thanks for all the input. Sounds like an artfull welder with maximum
emphasis on cool welding, and then maybe inject the bottom 2 ft with closed
cell foam or something to spread the load. I'll keep a good eye on the
repair, looking for stress cracks, as we shakedown on the way to the east
coast from Lake Ontario. If it shows any stress, I'll cut the mast off at
the bottom and raise the mast base up 10 in..Lowering the rigging would be a
job and a half.
Thanks again.
Dave
www.blueeden.ca
Nice cutter Glenn.

"Tadeusz Jerzy Korsak" wrote in message
...

U¿ytkownik "Dave Buttle" napisa³ w wiadomo¶ci
...
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

If the square hole is located at very bottom of the mast, near the mast
step, I would consider filling the mast interior completely with composite
mixture (e.g. epoxy mixed with portland cement).
Square hole must be patched beforehand with proper composite prepreg patch
and composite filling apparatus must be constructed (e.g. basing on the
grease gun mechanism). Mast bottom section must be sealed also. Operation
should be performed on mast in vertical position and amount of mixture
calculated to provide filling to the proper level.
This filling will spread vertical forces from the mast on a much bigger
area.
Regards
Tadeusz