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

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?


About the only foam you would ever consider placing inside a mast would
be blocks of soft furniture foam for the purpose of quieting any wires
inside the mast that might be slapping the mast.

IMHO, the result is almost the biggest PITA on the planet.

Been there, done that.

A good messenger cable makes the problem go away.

Lew

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.

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.

Bingo...

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...

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...

I would not recommend filling the complete void in the mast, but
sealing of the mast might be considered. As this was a suggestion by
someone making their boat 'bluewater' ready as just one of the things
they would do.

Also if the mast is buoyant then it could help the righting momentum.

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

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

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

On Thu, 27 Oct 2005 16:22:26 -0700, Robert or Karen Swarts wrote:

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

[snip]

This all seems very doubtful. I am not sure if you understand how dynamic
the sea-state is in conditions likely to cause a knockdown in the first
place.

Maybe you should ask a real naval architect (marine engineer) about
this. I think it is a very bad idea which you will regret if you do it,
but I am not an expert.

--Mac

This is not an original idea with me. I have seen it recommended in a couple
of articles/books on deep water sailing/boats. There is no disputing the
math, although other factors do come into it.

BS

"Mac" wrote in message
news
On Thu, 27 Oct 2005 16:22:26 -0700, Robert or Karen Swarts wrote:

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

[snip]

This all seems very doubtful. I am not sure if you understand how dynamic
the sea-state is in conditions likely to cause a knockdown in the first
place.

Maybe you should ask a real naval architect (marine engineer) about
this. I think it is a very bad idea which you will regret if you do it,
but I am not an expert.

--Mac

Mac wrote:
On Thu, 27 Oct 2005 16:22:26 -0700, Robert or Karen Swarts wrote:


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


[snip]

This all seems very doubtful. I am not sure if you understand how dynamic
the sea-state is in conditions likely to cause a knockdown in the first
place.

Maybe you should ask a real naval architect (marine engineer) about
this. I think it is a very bad idea which you will regret if you do it,
but I am not an expert.

--Mac


It seems, if you are worried, that if the mast is reasonably tight,
it would not flood immediately after being whipped into the water.
It's speed of descent would provide a great deal of drag through
water to decellerate the rolling momentum, and would provide some
righting bouyancy until it filled.

Sealing a mast may be impossible, but slowing its flooding, possibly
with external halyards and a wad of foam or some pop bottles and
even pumping it once horizontal with a small hose to the mast head,
might be a better plan, strange as it sounds.

Once on it's side, a keel boat will want to right itself, until it
fills with water. Keep the properly designed companionway bottom
board in place. On a trampoline / catamaran, you will want righting
accessories like possibly a self inflating "Mae West" at the
masthead. 200 lbs bouyancy might to, and that is about 1.5 cubic
feet of balloon, 10 pounds of tennis balls?

Many catamarans have servicable rope loops rigged, to enable
overboard capsized crew to pull the boat upright once it has landed
on it's side. They take a moment or three to turtle after resting on
their sides, with the mast flooding and because of their geometry,
wanting to continue rolling inverted. The floating mast is their
only hope, however faint.

The dynamics of weather tending to capsize the boat will be greatly
diminished, once you come to a stop and the sails are horizontal on
the water. The sail itself would prevent rapid sinking of the mast,
if it did not simply tear, sheeted in. The mast may well break open.

Dare I suggest floating line shrouds as an adjunct, or even a
floating, sealed at the ends hollow wooden mast?

Once turtled, a long enough halyard or spare detached from the sail
head and "lowered" from it's submerged cleat now only a foot or so
submerged, brought to the surface athwartships, can haul the boat
back upright, if enough bouyancy and counterweight can be found
amongst swimming crew with lifejackets, coolers, floating cushions,
gas tanks, rescue assist vessels, and whatever.

Flooding one completely upside down cat hull to make it sink so the
boat is suspended by one floating hull also helps. Once it is a
little more downwind than the floating hull, raising it is easier,
since all you need do is counterbalance the submerged, reduced
weight and especially, the mast, once horizontal at the waters
surface, and which, we hope, is still trying to float, at least a
little. Pumping the submerged hull will right the boat. Crossed hull
pumping lines and a pump tied on to avoid it's loss, able to inflate
the hull with air or extract water complete the scheme. Such serious
righting arrangements are able and can be seen on serious cats if
you ask their skippers.

Flooding the hull may seem difficult, but an "air syphon" hose will
do it easily and dependably, if a hatch can be opened aside from
this air vent / pumping hose.

One would hope the design permits a loaded cruising cat to still
float, even with one hull full of water, purposely flooded. Small
cats are a natural, larger ones will want bouyancy compartments
sufficient to minimally float the boat even when capsized and
flooding if the companionway hatches are not watertight. Just one
more reason to keep those through hulls closed, eh?

Terry K

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