[bolger] Re: Michalak articles on water ballast
Hi Peter,
Quite right. I was only trying to make half a point. The whole point is
whereas multihulls capsize and leadkeelers sink, WB types in theory have no
such ultimate point of sail. If we hang on, the boat will make it home.
But a question. Say I add a little lead, say up to 200#. Why do I have to
add foam? A wooden boat that weighs, say, 2000# has about 1000# of reserve
buoyancy, not so? As long as you don't get near that, why worry? I think a
little lead is a good idea in the long run so that the boat will still have
negative ballast swamped. Bolger warns that WB boats are in danger of
turning turtle if they swamp in deep water.
Ed Haile
Martha Jane "Terrapin"
Quite right. I was only trying to make half a point. The whole point is
whereas multihulls capsize and leadkeelers sink, WB types in theory have no
such ultimate point of sail. If we hang on, the boat will make it home.
But a question. Say I add a little lead, say up to 200#. Why do I have to
add foam? A wooden boat that weighs, say, 2000# has about 1000# of reserve
buoyancy, not so? As long as you don't get near that, why worry? I think a
little lead is a good idea in the long run so that the boat will still have
negative ballast swamped. Bolger warns that WB boats are in danger of
turning turtle if they swamp in deep water.
Ed Haile
Martha Jane "Terrapin"
>______________________________________________________
>Hi Ed, Water ballast does not make or keep a boat unsinkable unless a
>comletely flooded boat is unsinkable without the ballast. Ballast of
>greater specific gravity
>like lead would add mass with less volume than an equal mass of water
>thereby reducing buoyancy and making the boat less unsinkable.
>
>
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Hi John,
Sorry. I addressed a reply to you as "Hi Peter."
______________________________________________________
Sorry. I addressed a reply to you as "Hi Peter."
>Hi Ed, Water ballast does not make or keep a boat unsinkable unlessfrom Ed Haile
______________________________________________________
Hi Ed, Water ballast does not make or keep a boat unsinkable unless a
comletely flooded boat is unsinkable without the ballast, in which case
adding water ballast just displaces the same volume (and mass) of water
and does not change the buoyancy. Ballast of greater specific gravity
like lead would add mass with less volume than an equal mass of water
thereby reducing buoyancy and making the boat less unsinkable. In
sealed ballast tanks a la MJ, X pounds of lead, sand or whatever would
have no more or less effect than X pounds of water assuming the tank
volume remained the same of course, and unsinkability would not
increase or decrease. Just be sure not to hole the tanks when you swamp
the boat. Seems to me the main advantage of water ballast remains its
ease of dumping when not needed and ready availability in a marine
environment. Or am I all wet? Ciao - John
comletely flooded boat is unsinkable without the ballast, in which case
adding water ballast just displaces the same volume (and mass) of water
and does not change the buoyancy. Ballast of greater specific gravity
like lead would add mass with less volume than an equal mass of water
thereby reducing buoyancy and making the boat less unsinkable. In
sealed ballast tanks a la MJ, X pounds of lead, sand or whatever would
have no more or less effect than X pounds of water assuming the tank
volume remained the same of course, and unsinkability would not
increase or decrease. Just be sure not to hole the tanks when you swamp
the boat. Seems to me the main advantage of water ballast remains its
ease of dumping when not needed and ready availability in a marine
environment. Or am I all wet? Ciao - John
> > His brief remarks on the Martha Jane in BWAOM simply state thatThe main advantage of water ballast is that the boat is unsinkable. Both
> > the function of the water ballast is to increase the range of
>stability,
> > without further elaboration. The
>only advantage for water ballast is that you can easily get rid of it
>when you don't need it anymore.
Bolger and Bernie Wolfard maintain that the MJ is a self-righting boat.
ED HAILE
Martha Jane "Terrapin" (not at present self-righting)
>______________________________________________________
>
>
>
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>GET A NEXTCARD VISA, in 30 seconds! Get rates as low as 2.9%
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Hi Bill
wmrpag-@...wrote:
It's in the old issues archive. There are two actually. Here are the
URLs:
http://marina.fortunecity.com/breakwater/274/1998/0228/index.htm#Water
Ballast
http://marina.fortunecity.com/breakwater/274/1998/0315/index.htm#Water
Ballast Details
only advantage for water ballast is that you can easily get rid of it
when you don't need it anymore. Things are different when the water
ballast system is a fairly complex one, such as those used in the 60
footers which took part in the last Around Alone. However, I understand
that it's for trimming or fine tuning, since those monsters have a 5
meter deep bulb keel.
Best, Pippo
wmrpag-@...wrote:
> Pippo: Can you provide a citation for Michalak's article on waterballast?
It's in the old issues archive. There are two actually. Here are the
URLs:
http://marina.fortunecity.com/breakwater/274/1998/0228/index.htm#Water
Ballast
http://marina.fortunecity.com/breakwater/274/1998/0315/index.htm#Water
Ballast Details
> His brief remarks on the Martha Jane in BWAOM simply state thatstability,
> the function of the water ballast is to increase the range of
> without further elaboration. I would be most interested in readingthe
> Michalak article you refer to. Thanks.The range of stability increases by lowering the center of mass. The
only advantage for water ballast is that you can easily get rid of it
when you don't need it anymore. Things are different when the water
ballast system is a fairly complex one, such as those used in the 60
footers which took part in the last Around Alone. However, I understand
that it's for trimming or fine tuning, since those monsters have a 5
meter deep bulb keel.
Best, Pippo
Pippo: Can you provide a citation for Michalak's article on water ballast?
I checked his web-site, but didn't find it there, which doesn't mean that it
is not, given my limited computer skills. I believe that I once read a few
remarks by Bolger on the subject some years ago - my recollection of the gist
of his remarks was that 1) water ballast was no panacea (a disappointment to
me at the time I read the article, but I've forgotten, if I ever really
understood, what he emphasised as its limitations) and 2) he included it in
the design in question more to give the boat greater inertia than to enhance
stability. His brief remarks on the Martha Jane in BWAOM simply state that
the function of the water ballast is to increase the range of stability,
without further elaboration. I would be most interested in reading the
Michalak article you refer to. Thanks.
Bill in MN
I checked his web-site, but didn't find it there, which doesn't mean that it
is not, given my limited computer skills. I believe that I once read a few
remarks by Bolger on the subject some years ago - my recollection of the gist
of his remarks was that 1) water ballast was no panacea (a disappointment to
me at the time I read the article, but I've forgotten, if I ever really
understood, what he emphasised as its limitations) and 2) he included it in
the design in question more to give the boat greater inertia than to enhance
stability. His brief remarks on the Martha Jane in BWAOM simply state that
the function of the water ballast is to increase the range of stability,
without further elaboration. I would be most interested in reading the
Michalak article you refer to. Thanks.
Bill in MN