"Maxprop" wrote in message
nk.net...

"Scotty" wrote in message
. ..

I guess I'm spoiled. 2 minute motor out of the marina,
and
I'm sailing!

I'm so sorry. Such a long motor is the price some have to
pay for being so
far from open water.

Since we've moved to the leeward side of the dock, on
low-traffic days we
shove the boat manually out of the slip, sails raised, and
sail out of the
marina. Sail back into the slip, too. Let the
powerboaters brag all they
want about how 'green' they are using biodiesel.


You win !

"Maxprop" wrote
..... Let the
powerboaters brag all they
want about how 'green' they are using biodiesel.



Scotty wrote:
You win !


I'm trying to remember if I bragged about using biodiesel.

DSK

JimC wrote:
Scotty wrote:

I guess I'm spoiled. 2 minute motor out of the marina, and
I'm sailing!

Scotty



That's a rather unusual situation.

What's unusual about it? I walk to the waterfront outside my yard - 2
minutes - row out to the mooring, and sail off. Maybe 5 minutes, 10
max, from my door to dropping the mooring.

PDW

"DSK" wrote in message
...
... If conventional boats with heavy, weighted keels, particularly those
of heavy construction, had enough positive flotation to keep the boat
afloat, there would be little room left in the cabin.


Bull****.


Maxprop wrote:
You are correct, but I'd be interested to see the volume of flotation
material needed to compensate for that displacement of water. *The
volume of flotation material required to offset a given volume of water
is not necessarily same.*

I'm not sure what you mean, here.

A cube of lead one inch per side will not necessarily float with a cube of
floatation material of the same size attached. Depending upon the type of
flotation material it might require more or less than a 1" cube to float the
lead cube.


... Lear Siegler, the builder of O'Day boats, published a lengthy report
some years ago about why larger boats don't have positive flotation. It
was written from an engineering point of view and made sense to me at the
time, albeit I'm no engineer. Their point was essentially what Jim C was
claiming--loss of interior volume in a marketplace demanding more and
more interior space.

Whoa... "marketplace" and "Engineering" are usually two viewpoints in
conflict.

From an engineering standpoint, there is less than no reason at all why
*any* boat shouldn't have positive flotation. Just fill it all up with
foam.

Engineers, fortunately or not, work for the same companies that also employ
the marketing gurus. While their philosophies may differ radically, the two
disciplines are not mutually exclusive.


From a more practical standpoint of a useful cruising boat, then you (as I
believe you were driving at above) all you need is a flotation volume
equal to the difference between the boat's volume of material and the
immersed volume needed to float that weight. I've worked out such figures
for a couple of production boats and the answer is that the volume of the
seat & berth cushions is pretty close to enough.

If I'm interpreting you correctly, that would allow a capsized vessel to
float with virtually nothing above the water level.

Of course, you need a safety margin, and that volume needs to be both
*secure* and also distributed in such a way that the boat floats in it's
proper attitude (ie not bow pointed down, or leaned over 45 degrees) & has
some stability.

. . . and at least some of the boat out of the water and able to support
the maximum allowable crew complement. Boston Whaler is renowned for this.

... They even explored the concept of flotation that could be inflated in
crisis, but cited cost and space requirements for even this more compact
system.

There have been two such systems on the market, both went out of business.
People won't pay enough for such a system... from a viewpoint of market
analysis, a failure. From a viewpoint of somebody who wants as much safety
as practical, and cares less about costs, it's a total success.

I suspect it has more to do with one's desire to save his boat from sinking.
I'd think a life raft would suffice if safety were the only consideration.
I recall such aftermarket flotation systems, incidentally. Older Snipes
occasionally used air bags.


People buy cheap stuff. Why do think Wal-Mart does so well?

Probably the same reason MacGregor sells lots of boats.

... So I'm not quite sure Jim is wrong.

From a marketing standpoint, sure. MacGregor can only afford to offer
positive floation because it's partially installed anyway by their
building method... and their foam is the cheap stuff.



... Can you provide some documentation to the contrary, beyond just your
opinion?


Umm, show me a boat that doesn't float to start with, and I'll show you
one that probably can't have positive flotation.





Positive flotation probably wouldn't be offered by manufacturers
voluntarily.

It already is, by several. Sadler & Etap spring to mind.

I wasn't aware of that. Do their boats all have pos. flotation? I don't
know much about either mfr.--are they higher-end boats?

... It would most likely be the result of a government requirement
(there's that nanny state again, Doug), and it would have to be applied
to all boats, regardless of design.

Show me where I suggested that it be mandated that all boats be required
to have positive flotation.

Easy there, Doug. I didn't say you did. That nanny comment was mine, and
intended as a gentle elbow to the ribs.

So according to your last paragraph, such a ruling might eliminate a
whole class of boats. Small class racers like the Mumm 30 come to mind.


Heck, the Mumm 30 would be real easy to put positive flotation in. Not
much of a premium on cabin space, anyway.

The last Mumm 30 on which I crewed was owned by a sailor who bitterly
complained about the inability of his boat to carry adequate spares due to
the limited interior volume. Then again he believed that nothing short of a
dozen sails was minimal in order to be prepared for any sort of weather.
When I pointed out that those extra sails add lots of weight, he poo-poo'd
the idea. Of course he never finished all that well, either.

The bottom line is that positive flotation is *definitely* possible... as
I said, all you need is to fill the boat with foam up to the static
waterline, and put your cabin floor over that. Or apply that same volume
of foam to a carefully distributed set of unused voids & crannies.

Or at least part of that flotation foam could be used as hull stiffening,
ala Boston Whaler. My sailboat has an Airex foam core between the hull
laminates. It's not particularly thick, but it does add a substantial
amount of rigidity, and the builder claimed it even provided enough
flotation effect that it wouldn't take a lot of additional flotation
material or air bags to make the boat float in event of capsize. Not that I
exactly care one way or the other.


Is it desirable? Depends. If I were going to do a lot of ocean crossing,
making passages along rough & rocky coasts, etc etc, I would want it.

Why? If making open-water passages, what would you achieve by keeping your
boat afloat. A capsized cruising sailboat a thousand miles from anywhere is
a total loss, floating or not. Unless you can bail the boat out and sail it
subsequently there is little value in keeping at afloat. Near shore may be
another matter entirely, but along the "rocky coast" I'm not sure there
would be any value either. A liferaft makes more sense to me--it will move
along relatively well with the prevailing winds and currents. It will also
be able to stay afloat in rough seas, where the flooded, low floating boat
would simply take monstrous waves over the deck until it breaks up. Here in
the Great Lakes, or on Pamlico Sound, a floating boat could be salvaged.

There are tremendous advantages in a boat that just plain will not ever
sink. It's possible that I would make it a high enough priority to put in
myself. Do I expect anybody else to? Not really, especially the people who
rave about the advantages of Wal-Mart type boats.

I asked Ted Gozzard about positive flotation at Strictly Sail in Chicago a
few years ago. He just laughed at me, as if I were some idiot. I asked him
to elucidate, to which he responded, "See those little cat boats over there?
(18' Marshall) That's what you want if you want positive flotation." I
said I wasn't personally interested in positive flotation, but was asking
the question hypothetically. He just laughed again and turned away. I'm
not quite sure how to interpret that, but it would appear that he regarded
positive flotation as a non-issue. FWIW.

Max

"Goofball_star_dot_etal" wrote in message
...
On Sun, 12 Nov 2006 11:48:01 -0500, DSK wrote:

Positive flotation probably wouldn't be offered by manufacturers
voluntarily.




It already is, by several. Sadler & Etap spring to mind.



http://www.mikelucasyachting.co.uk/story.htm

Interesting reading. It sounds as if the 26 was able to maintain decent
freeboard when flooded, but I'm wondering if the larger boats would do
similarly?

Nice looking boats.

Max

"DSK" wrote in message
.. .
"Maxprop" wrote
..... Let the
powerboaters brag all they
want about how 'green' they are using biodiesel.



Scotty wrote:
You win !


I'm trying to remember if I bragged about using biodiesel.

You can't brag about it if you don't use it.

Around here the main customers for biodiesel are commercial vessels. They
smell like someone is making popcorn when they motor by. Most of the
recreational powerboaters burn petroleum diesel, primarily because it's
readily available, and many are leery of using biodiesel for some unknown
reason. Those who do, however, brag about being 'green.' To a sailor
that's like Richard Simmons boasting to Vin Diesel about being manly.

Max

"Peter" wrote in message
ups.com...

JimC wrote:
Scotty wrote:

I guess I'm spoiled. 2 minute motor out of the marina, and
I'm sailing!

Scotty



That's a rather unusual situation.

What's unusual about it? I walk to the waterfront outside my yard - 2
minutes - row out to the mooring, and sail off. Maybe 5 minutes, 10
max, from my door to dropping the mooring.

You should have a Carey 50 for getting to and from your mooring, Pete.

Max

Maxprop wrote:
"Peter" wrote in message
ups.com...

JimC wrote:
Scotty wrote:

I guess I'm spoiled. 2 minute motor out of the marina, and
I'm sailing!

Scotty



That's a rather unusual situation.

What's unusual about it? I walk to the waterfront outside my yard - 2
minutes - row out to the mooring, and sail off. Maybe 5 minutes, 10
max, from my door to dropping the mooring.

You should have a Carey 50 for getting to and from your mooring, Pete.

Nah. I'm waiting for the sea level to rise so I can tie up at my back
door. Or at least at the bottom of the yard. 2 or 3 metres rise would
be good.

PDW

Maxprop wrote:
A cube of lead one inch per side will not necessarily float with a cube of
floatation material of the same size attached. Depending upon the type of
flotation material it might require more or less than a 1" cube to float the
lead cube.


Of course. The flotation has to be of sufficient volume &
density to bring the average specific gravity below 1.0

A point that is occasionally overlooked is that the
flotation also has to be structurally sound. I learned this
lesson in practice, trying to install positive flotation on
the cheap for an old racing class boat.



... "marketplace" and "Engineering" are usually two viewpoints in
conflict.



Engineers, fortunately or not, work for the same companies that also employ
the marketing gurus. While their philosophies may differ radically, the two
disciplines are not mutually exclusive.


Sure. Occasionally you see both talents combined in the same
guy. But just because a product won't sell profitably, that
doesn't mean it isn't possible or even practical.



From a more practical standpoint of a useful cruising boat, then you (as I
believe you were driving at above) all you need is a flotation volume
equal to the difference between the boat's volume of material and the
immersed volume needed to float that weight. I've worked out such figures
for a couple of production boats and the answer is that the volume of the
seat & berth cushions is pretty close to enough.


If I'm interpreting you correctly, that would allow a capsized vessel to
float with virtually nothing above the water level.


At minimum, yes. But that wouldn't serve much purpose other
than to make the recoverable after an accident, at which
point it would be worthless... no value to the crew, who
would still need a survival craft, and no value in the
marketplace. So that is not a good enough answer, which is
why I then said:



Of course, you need a safety margin, and that volume needs to be both
*secure* and also distributed in such a way that the boat floats in it's
proper attitude (ie not bow pointed down, or leaned over 45 degrees) & has
some stability.


. . . and at least some of the boat out of the water and able to support
the maximum allowable crew complement. Boston Whaler is renowned for this.


Definitely agreed.


I'd think a life raft would suffice if safety were the only consideration.

Depends. The whole boat is more desirable than a life raft.
Otherwise why have the boat, why not just cruise in the life
raft in the first place?

It's a bit more of a challenge to build a boat that would be
liveable and operable (even sailable) after severe flooding,
but it's certainly possible. And I think, for some types of
sailing, it's highly desirable.

I can't believe that there are still some centerboard racing
classes that are not self-rescuing; some don't even have
positive flotation. WTF are they thinking?



Show me where I suggested that it be mandated that all boats be required
to have positive flotation.


Easy there, Doug. I didn't say you did. That nanny comment was mine, and
intended as a gentle elbow to the ribs.


Ah so, got it now.


Heck, the Mumm 30 would be real easy to put positive flotation in. Not
much of a premium on cabin space, anyway.


The last Mumm 30 on which I crewed was owned by a sailor who bitterly
complained about the inability of his boat to carry adequate spares due to
the limited interior volume. Then again he believed that nothing short of a
dozen sails was minimal in order to be prepared for any sort of weather.
When I pointed out that those extra sails add lots of weight, he poo-poo'd
the idea. Of course he never finished all that well, either.


Sounds like he didn't have his priorities quite in order.
Well, it's his boat, his priviledge.

I think J-24s should have positive flotation. AFAIK the
Soling class now requires it (sinkings were fairly common
back in the day); not sure if the Etchells does. The 1D-35
and the new Farr 36 both have positive flotation. A Mumm 30?
A bit harder to sink but still possible...




The bottom line is that positive flotation is *definitely* possible... as
I said, all you need is to fill the boat with foam up to the static
waterline, and put your cabin floor over that. Or apply that same volume
of foam to a carefully distributed set of unused voids & crannies.


Or at least part of that flotation foam could be used as hull stiffening,
ala Boston Whaler. My sailboat has an Airex foam core between the hull
laminates. It's not particularly thick, but it does add a substantial
amount of rigidity, and the builder claimed it even provided enough
flotation effect that it wouldn't take a lot of additional flotation
material or air bags to make the boat float in event of capsize. Not that I
exactly care one way or the other.


True.
Some people hate foam core, though.



Is it desirable? Depends. If I were going to do a lot of ocean crossing,
making passages along rough & rocky coasts, etc etc, I would want it.


Why? If making open-water passages, what would you achieve by keeping your
boat afloat. A capsized cruising sailboat a thousand miles from anywhere is
a total loss, floating or not.

Because if I went to the effort, the boat would not only
remain afloat but have a good positive range of stability &
reserve bouyancy... ie be operable and liveable after severe
flooding...


... Near shore may be
another matter entirely, but along the "rocky coast" I'm not sure there
would be any value either.

Not much sense in making sure theboat remains afloat if it's
going to be smashed to pieces, sure. But if all the pieces
still float, the people have a better chance IMHO.


... Here in
the Great Lakes, or on Pamlico Sound, a floating boat could be salvaged.


Shucks, in Pamlico Sound... or many places along the
Chesapeake... you could just wade ashore. The boat wouldn't
sink very far.





I asked Ted Gozzard about positive flotation at Strictly Sail in Chicago a
few years ago. He just laughed at me, as if I were some idiot. I asked him
to elucidate, to which he responded, "See those little cat boats over there?
(18' Marshall) That's what you want if you want positive flotation." I
said I wasn't personally interested in positive flotation, but was asking
the question hypothetically. He just laughed again and turned away. I'm
not quite sure how to interpret that, but it would appear that he regarded
positive flotation as a non-issue. FWIW.


For him, it almost certainly is. I'm not surprised he's a
bit of a reactionary (I mean, look at his boat designs) but
I'd be surprised if he didn't have a pretty good grip on the
practical issues involved. But then, talking to boat
designers at boat shows is often a futile endeavor...
they're there to sell boats.

DSK

A few points to toss in he

Boats with significant amounts water ballast (i.e. Mac) need much less
flotation because the specific gravity is so close to one. In other
words, a tank of water only needs flotation for the tank material, not
the contents. A number of the smaller water ballast boats have
flotation, Catalina chose not to on the ground that it have taken too
much space.

An other way to look at it is that you only need significant amounts
of flotation for the heavy parts of the boat, like the keel and
engine. This is why my catamaran can have positive flotation, in the
form of six watertight compartments. I'm told that the hull by itself
(which has foam core above the waterline) has a SG of under one.

Its easy to do a "napkin calculation" of how much foam is needed: Say
a 36 foot boat displaces 12000 pounds. That's 333 pounds per foot,
we'll make that 500 pounds because of the pointy ends. Since water is
about 62 pounds per cubic foot, that's 8 cubic feet worth. If we then
consider the circumference, assuming a 12 foot beam, is about 36 feet,
what we're left with is an average coating of under 2.5 inches. In
other words, if the hull were constructed with a sandwich containing 3
inches of foam, it would be enough to provide positive flotation. It
would also give a huge amount of stiffness, collision protection and
insulation.

We can also roughly figure the size of airbag flotation - 12000 pounds
is about 200 cubic feet of water, which is a cube about 6 feet on a
side, or probably better as two spheres of about a bit under 6 feet in
diameter. This should be quite doable.

One problem with these calculations is that they assume a typical
racer/cruiser, not a heavy displacement offshore passage maker.