I can think of two reason not to fill your aluminum mast with foam.

1. Strange things can happen to uncoated aluminum it is prevented from
oxidizing naturally. (never been a need to paint the inside of a mast in all
these years)

2. In open water, rough seas, I don't think I would want a floating mast
along side. I would prefer that it fill with water and hang below the boat
until the rigging wires can be cut away. It is bad enough when the sails
trap air and keep the mast and boom at or near the surface. Like a battering
ram. I have experienced two de-masting in 45 years of sailing and the most
damage I have noted (aside from the mast) has been to the hull at the water
line due to the floating mast. (once with a solid wooden mast and once with
an aluminum).


--
My experience and opinion, FWIW
--
Steve
s/v Good Intentions


"Robert or Karen Swarts" wrote in message
...
Primary reason is that it increases righting moment in the event of a
capsize. I suppose it might also keep the mast from sinking in case of a
demasting.

Might make the mast marginally stronger if completely filled.

I also misspoke in this area in that what I was envisioning was plugging
the mast with foam rather than completely filling it.

BS

"Bowgus" wrote in message
...
I give up ... why would anyone fill a mast with "foam"?

"Robert or Karen Swarts" wrote in message
...
Assuming one makes provision to access and mechanical or electrical
components within the mast, are there any compelling reasons NOT to foam
fill the mast?

Bob Swarts

On Sun, 16 Oct 2005 15:39:19 -0700, Robert or Karen Swarts wrote:

Primary reason is that it increases righting moment in the event of a
capsize. I suppose it might also keep the mast from sinking in case of a
demasting.

Assuming the boat is designed well, the keel will give it all the righting
moment it needs. And as far as I know, if the mast comes off of the boat,
you don't want it hanging around.

If this is a catamaran, then putting a float at the very top of the mast
might be a good idea. Or at least I have seen some smaller catamarans with
such things on them.


Might make the mast marginally stronger if completely filled.

Maybe. Maybe not. It certainly won't increase the compression strength.
Anyway, this doesn't seem to be a compelling reason.

I also misspoke in this area in that what I was envisioning was plugging the
mast with foam rather than completely filling it.

BS

In my opinion, you want the bottom and top of the mast to be as wide open
as reasonably possible. That way, after a capsize, as the boat starts to
right itself, the mast will drain readily (assuming it is still attached
to the deck).

I don't think there is any way you can seal a mast with internal halyards
sufficiently so that it won't fill up with water when the boat is upside
down. If you attempt to do this, and the mast does fill with water, it
will be even harder for the boat to right itself, because the water will
drain out of the mast more slowly. If anything, you would want to put
extra holes or slots in the mast all along its length so that the water
can drain out fast.

--Mac



"Bowgus" wrote in message
...
I give up ... why would anyone fill a mast with "foam"?

"Robert or Karen Swarts" wrote in message
...
Assuming one makes provision to access and mechanical or electrical
components within the mast, are there any compelling reasons NOT to foam
fill the mast?

Bob Swarts

On Sun, 16 Oct 2005 08:01:04 -0700, "Robert or Karen Swarts"
wrote:

Assuming one makes provision to access and mechanical or electrical
components within the mast, are there any compelling reasons NOT to foam
fill the mast?

Bob Swarts


Hmmm...why foam fill?

If wood, it might preserve from water damage....
If metal, might dampen halliard slapping noise....

Or is there some other purpose - not strength, I don't think

Brian

In article ,
says...
Assuming one makes provision to access and mechanical or electrical
components within the mast, are there any compelling reasons NOT to foam
fill the mast?

Bob Swarts

My 69 oday mariner has a foam filled mast. I assume it was done that way
from the factory. It seems to me that with the foam in place it can't
fill with water and so is less likely to sink if it should go over. It
may also help to keep out some condensate formation.

OK, with my28' S2 with 48' mast, the max righting torque I calculate is
about 4500 ft-lbs. For comparison, the torque produced by the 3300 lb
keel is about 9900 ft-lbs.

Now, for using expanding foam to silence internal halyard slap:

With mast down drill holes at 3' intervals, make the holes about 1/4"
to avoid stress cracking around smaller holes. Inject enough expanding
foam. While it sets over a few hours, work the halyards back and
forth.

With mast UP. go up[ bosuns chair, drill 1/4" holes. Put a small
balloon through the holes and inflate. Push the nozzle of the
expanding foam in beside the balloon and above it. Inject foam. The
balloon is there to keep the foam from just dropping down to the
bottom.

There are various versions of expanding foam, some exerts a lot of
force/area and can push things out of alignment (not an issue here) and
a less strong version intended for insulating around windows that would
also work in this app.

Sounds scary to me. That stuff BONDS! Working the halyards may mean they
aren't anchored to the mast, but if the line is adorned with blobs, it
probably won't pass thru the sheaves freely.

When I spoke of the continued, forcible expansion, I was referring to the
cans labeled "minimal expansion."

Roger

http://home.earthlink.net/~derbyrm

wrote in message
oups.com...

snip
Now, for using expanding foam to silence internal halyard slap:

With mast down drill holes at 3' intervals, make the holes about 1/4"
to avoid stress cracking around smaller holes. Inject enough expanding
foam. While it sets over a few hours, work the halyards back and
forth.