Re: [bolger] Re: Recent News from PCB, Cartoon 40 - Now "Smart Water"
The clue is in the "let the outside shape of the hull remain the same." Then it doesn't matter if the filling is lead, pudding, or water. Only its density matters.
(unless you have significant free surface, then the dynamics get nasty)
Roger
derbyrm@...
http://home.insightbb.com/~derbyrm
(unless you have significant free surface, then the dynamics get nasty)
Roger
derbyrm@...
http://home.insightbb.com/~derbyrm
----- Original Message -----
From: Gene T
To:bolger@yahoogroups.com
Sent: Tuesday, November 28, 2006 10:50 AM
Subject: Re: [bolger] Re: Recent News from PCB, Cartoon 40 - Now "Smart Water"
Let the Alchemy begin (or however that is spelled). If I hadn't taken all those physics classes this wouldn't make me suffer so!
Sincerely,
Gene T.
"A house ashore is but a boat, so poorly
built it will not float ---- "
----- Original Message ----
From: adventures_in_astrophotography <jon@...>
To:bolger@yahoogroups.com
Sent: Tuesday, November 28, 2006 9:32:28 AM
Subject: [bolger] Re: Recent News from PCB, Cartoon 40
Hi Peter,
> No.
> Water ballast is a tricky and misunderstood thing, and I don't mean to
> start a long, fruitless discussion, but the above sentence is not true
> in this case, even if PCB did write something to that effect. The
> comparison is between the hull with water ballast and the hull with
> the "ballast tank" removed (in the sense of being taken off the
> outside of the boat). In this case, the "tank removed" hull would have
> the deepest part of the v-bottome removed - a completely different
> hull shape.
>
> If you keep the v-shape and fill the bottom part with water ballast,
> you lower the center of gravity (or, equivalently raise the center of
> buoyancy) which improves stability.
Such a discussion may not be frutiless, so I'll bite - politely I hope.
I agree with your statement that filling the bottom part of the v-shape
with water improves stability, but not because it acts as ballast all
the time. It is simply neutral bouyancy, not the positive bouyancy
that the empty space would have, and not the negative bouyancy that
lead or another heavy ballast material would have. For stability,
neutral bouyancy is better than positive bouyancy in that part of the
hull. However, it won't help the boat when heeled as much as negative
bouyancy in that location unless it gets above the waterline where it
then acts against the heeling motion of the boat. Any empty volume
submerged by heeling will resist the heeling force, but the water will
do nothing to counter this force as long as it remains below the
surface as neutral bouyancy. The v-shape of this hull concentrates the
flooded volume near the centerline, thus requiring more heel to get
much of it above the surface, which I claim makes it less effective as
ballast than denser materials.
Because of this, I maintain that my original statement is valid, but is
perhaps better if restated: Replacing the lead/steel/concrete called
for on the plans with neutral bouyancy in the same location will not be
effective *as ballast* unless the boat heels enough to get some of that
volume above the water line.
I'm not saying it won't work at all in this boat, I just think it won't
be as effective as it might seem at first.
Jon Kolb
www.kolbsadventures.com/boatbuilding_index.htm
Bolger rules!!!
- NO "GO AWAY SPAMMER!" posts!!! Please!
- no cursing, flaming, trolling, spamming, respamming, or flogging dead horses
- stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
- Pls add your comments at the TOP, SIGN your posts, and snip away
- Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax: (978) 282-1349
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- Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
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[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
Let the Alchemy begin (or however that is spelled). If I hadn't taken all those physics classes this wouldn't make me suffer so!
Sincerely,
Gene T.
"A house ashore is but a boat, so poorly
built it will not float ---- "
----- Original Message ----
From: adventures_in_astrophotography <jon@...>
To:bolger@yahoogroups.com
Sent: Tuesday, November 28, 2006 9:32:28 AM
Subject: [bolger] Re: Recent News from PCB, Cartoon 40
Hi Peter,
I agree with your statement that filling the bottom part of the v-shape
with water improves stability, but not because it acts as ballast all
the time. It is simply neutral bouyancy, not the positive bouyancy
that the empty space would have, and not the negative bouyancy that
lead or another heavy ballast material would have. For stability,
neutral bouyancy is better than positive bouyancy in that part of the
hull. However, it won't help the boat when heeled as much as negative
bouyancy in that location unless it gets above the waterline where it
then acts against the heeling motion of the boat. Any empty volume
submerged by heeling will resist the heeling force, but the water will
do nothing to counter this force as long as it remains below the
surface as neutral bouyancy. The v-shape of this hull concentrates the
flooded volume near the centerline, thus requiring more heel to get
much of it above the surface, which I claim makes it less effective as
ballast than denser materials.
Because of this, I maintain that my original statement is valid, but is
perhaps better if restated: Replacing the lead/steel/concrete called
for on the plans with neutral bouyancy in the same location will not be
effective *as ballast* unless the boat heels enough to get some of that
volume above the water line.
I'm not saying it won't work at all in this boat, I just think it won't
be as effective as it might seem at first.
Jon Kolb
www.kolbsadventures.com/boatbuilding_index.htm
Bolger rules!!!
- NO "GO AWAY SPAMMER!" posts!!! Please!
- no cursing, flaming, trolling, spamming, respamming, or flogging dead horses
- stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
- Pls add your comments at the TOP, SIGN your posts, and snip away
- Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax: (978) 282-1349
- Unsubscribe:bolger-unsubscribe@yahoogroups.com
- Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
Yahoo! Groups Links
[Non-text portions of this message have been removed]
Sincerely,
Gene T.
"A house ashore is but a boat, so poorly
built it will not float ---- "
----- Original Message ----
From: adventures_in_astrophotography <jon@...>
To:bolger@yahoogroups.com
Sent: Tuesday, November 28, 2006 9:32:28 AM
Subject: [bolger] Re: Recent News from PCB, Cartoon 40
Hi Peter,
> No.Such a discussion may not be frutiless, so I'll bite - politely I hope.
> Water ballast is a tricky and misunderstood thing, and I don't mean to
> start a long, fruitless discussion, but the above sentence is not true
> in this case, even if PCB did write something to that effect. The
> comparison is between the hull with water ballast and the hull with
> the "ballast tank" removed (in the sense of being taken off the
> outside of the boat). In this case, the "tank removed" hull would have
> the deepest part of the v-bottome removed - a completely different
> hull shape.
>
> If you keep the v-shape and fill the bottom part with water ballast,
> you lower the center of gravity (or, equivalently raise the center of
> buoyancy) which improves stability.
I agree with your statement that filling the bottom part of the v-shape
with water improves stability, but not because it acts as ballast all
the time. It is simply neutral bouyancy, not the positive bouyancy
that the empty space would have, and not the negative bouyancy that
lead or another heavy ballast material would have. For stability,
neutral bouyancy is better than positive bouyancy in that part of the
hull. However, it won't help the boat when heeled as much as negative
bouyancy in that location unless it gets above the waterline where it
then acts against the heeling motion of the boat. Any empty volume
submerged by heeling will resist the heeling force, but the water will
do nothing to counter this force as long as it remains below the
surface as neutral bouyancy. The v-shape of this hull concentrates the
flooded volume near the centerline, thus requiring more heel to get
much of it above the surface, which I claim makes it less effective as
ballast than denser materials.
Because of this, I maintain that my original statement is valid, but is
perhaps better if restated: Replacing the lead/steel/concrete called
for on the plans with neutral bouyancy in the same location will not be
effective *as ballast* unless the boat heels enough to get some of that
volume above the water line.
I'm not saying it won't work at all in this boat, I just think it won't
be as effective as it might seem at first.
Jon Kolb
www.kolbsadventures.com/boatbuilding_index.htm
Bolger rules!!!
- NO "GO AWAY SPAMMER!" posts!!! Please!
- no cursing, flaming, trolling, spamming, respamming, or flogging dead horses
- stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
- Pls add your comments at the TOP, SIGN your posts, and snip away
- Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax: (978) 282-1349
- Unsubscribe:bolger-unsubscribe@yahoogroups.com
- Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
Yahoo! Groups Links
[Non-text portions of this message have been removed]