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.

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

An inversion may cause the mast to fill with water, and depending on
the diameter and lenght of mast, the the leverage weight at or near
the masthead would be significant. I think 1square foot of water is
about 64 lbs. Or about 1 gallon of water is about 8lbs...

Cubic foot. One square foot of water has a weight of zero.

Anyone know what the leverage force would be needed to lift 64lbs at
30ft of leverage from the folcrum point? That may not be exactly the
right question...

Approx. 3000Nm, but that's irrelevant:
Assume inversion. The mast will first be underwater. Then the water in
the mast has neutral buoyancy. To get out of the inversion, the
boat uses hull shape and keel weight, if not a racer designed to
remain stable in an upside down position. But these have escape
hatches on the bottom.

Once the mast is parallel to the water surface, the keel has the best
angle of attack to righten it. Much more than during strongly heeled
sailing, i.e. a few gallons of water at the mast top won't do anything.

Not even a few hundred pounds. If you want easier proof: You can hoist
a person up the mast of even small keeboats witout inverting them.

Chris

On 26 Oct 2005 23:23:21 -0700, "Chris" wrote:
///
Not even a few hundred pounds. If you want easier proof: You can hoist
a person up the mast of even small keeboats witout inverting them.

Chris


Can you hoist a person up a mast at 60 degrees to the vertical,
without a capsize?

Brian Whatcott

Several years ago, at the first Atlantic City Sailboat Show I think, there
was a 'solution' to this problem. The Geougeon Brothers {the WEST System
people - forgive the spelling} were manufacturing a 'large' catamaran {I
don't know if they still are} at the time.

Anyway, as I was walking about the hall I noticed what looked like a
miniature 'blimp' {about 3-4 feet long} above the field of masts. It had
their name on it and that's what I thought it was - an airborne
advertisement. As I got closer, I saw that it was actually attached to the
top of the mast of their catamaran . . . but still thought of it as an
advert.

I soon found out that it was really a piece of 'Safety Gear'. The shape was
for aerodynamic reasons. A catamaran has 'Ultimate Stability' at TWO points
.. . . completely upright AND completely upside down!! Having a sufficient
quantity of extremely buoyant, and light weight, material at the end of a
long attached moment arm reduces this to ONE. While you may experience a
'knock-down', you shouldn't be able to 'turtle'.

OBVIOUSLY, it takes a great deal more material {or even air} then can be
contained in the volume of the mast itself.

Regards & Good Luck,
Ron Magen
Backyard Boatshop

"Chris" wrote in message
oups.com...
An inversion may cause the mast to fill with water, and depending on
the diameter and lenght of mast, the the leverage weight at or near
the masthead would be significant. I think 1square foot of water is
about 64 lbs. Or about 1 gallon of water is about 8lbs...

Cubic foot. One square foot of water has a weight of zero.

Anyone know what the leverage force would be needed to lift 64lbs at
30ft of leverage from the folcrum point? That may not be exactly the
right question...

Approx. 3000Nm, but that's irrelevant:
Assume inversion. The mast will first be underwater. Then the water in
the mast has neutral buoyancy. To get out of the inversion, the
boat uses hull shape and keel weight, if not a racer designed to
remain stable in an upside down position. But these have escape
hatches on the bottom.

Once the mast is parallel to the water surface, the keel has the best
angle of attack to righten it. Much more than during strongly heeled
sailing, i.e. a few gallons of water at the mast top won't do anything.

Not even a few hundred pounds. If you want easier proof: You can hoist
a person up the mast of even small keeboats witout inverting them.

Chris

Let us suppose the mast is 4" in diameter and 25 ft long, stepped 4 ft above
waterline. The weight of water it displaces is 138 lb. Let us suppose half
if that is the weight of the mast. That leaves 69 lb positive buoyancy. The
center of buoyancy of the mast is about 16 ft above waterline. That will
create a righting moment of about 1100 ft lb when the boat is flat on the
water. That is not inconsequential, and could be a large help in preventing
a total capsize.

BS

"Brian Whatcott" wrote in message
...
On 26 Oct 2005 23:23:21 -0700, "Chris" wrote:
///
Not even a few hundred pounds. If you want easier proof: You can hoist
a person up the mast of even small keeboats witout inverting them.

Chris


Can you hoist a person up a mast at 60 degrees to the vertical,
without a capsize?

Brian Whatcott

Can you hoist a person up a mast at 60 degrees to the vertical,
without a capsize?

Well, with our imaginary boat w/ a 10m mast, 1.8m keel of
3000 lbs heeled so that the mast is flat on the water:
(roughly a 27-footer, pivot boint between mast and keel
in the center of the cabin, me on top of the mast.)

Mast side: 200 lbs person * 10m = 1000N * 10m = 10,000 Nm
Keel side: 3000 lbs Keel * 0.9m = 15,000N * 0.9m = 13,500 Nm

Give and take a bit with the approximations, I'd say you can
on a 27-footer if you are light and daring and for sure in
anything larger than that.

But then, in waves that tilt the boat 60 deg from vertical, I wouldn't
want to be hoisted to the mast. And I'm afraid that in the waves that
generate the ten housand ++ Nm to get the mast under water, the
1100 ft lb (is that approx. 1500 Nm?) mentioned in the next post
are rather inconsequential. Not that I've ever tried it.

Chris