Please tell us the last time you actually heeled your boat!! We want to learn from your vast experience!

--
"j" ganz @@
www.sailnow.com

"Jim Cate" wrote in message ...


Capt. Scumbalino wrote:

wrote:

Knowing a thang er two bout that fiziks an njineerin stuff (MS
Physics, MSEE), I think that water ballast does nothing until it is
raised above the waterline.

If the centre of rotation as the boat heels is in the centre of gravity of
the mass of the water ballast, then that might be the case. If the centre of
the boat's heeling rotation is above the COG of the ballast, then it has to
pull that enclosed mass around - ergo, the water ballast can have an effect
when it's below the waterline. I think this is the same thing as what I was
saying about bouyancy, but from the perspective of te ballast rather than
the air above it.


I think this is the answer. - The downward forces on the water ballast tank tend to pull the boat down to the lowermost floating position, at point which the boat is in an upright position, absent other forces. For example, ocean liners utilize water ballast below the waterline. From personal experience, the Mac 26M is initially somewhat tender but becomes increasingly stiffer as it heels.

Jim

In article ,
says...

"Dave Doe" wrote in message .

Water weighs the same above or below the waterline, and the
same in or
out of water assuming the same gravitational potential.

No it doesn't!

The *mass* is the same.

Take a plastic bag of water and push if off a bench.

Take the same and do the same off a wee bench in a tub of
water.



Dave, the water in a ballast tank is KNOT IN the water.

Sheesh!!!!

Neither is the water in the plastic bag!

Sheesh!

--
Duncan

I've looked at the Dix boats and a few others. Unfortunately, I am
6'1" so headroom matters. I also think that use of the boat will
decrease exponentially with rigging difficulty so that a boat that has
very low difficulty will get used much more. Thus, I am not in favor
of the marconi rig on a trailer boat and like the Gaff rig of the
cormorant with no shrouds. I cannot ascertain the headroom of the
Cormorant

OK, Duncan. here's a little experiment you can do in your
bathtub.

1. Put an empty Coke bottle in the water. Observe how it floats.
2. Fill the Coke bottle 1/4 with water. Observe how it floats.
3. Fill the bottle 1/2 way. Observe how it floats
4. Fill it 3/4 full. Observe how it floats
5. Is the water in the coke bottle below the tub water surface?
6. Wash your butt last.

Scotty






"Dave Doe" wrote in message
. nz...
In article ,
says...

"Dave Doe" wrote in message .

Water weighs the same above or below the waterline, and
the
same in or
out of water assuming the same gravitational potential.

No it doesn't!

The *mass* is the same.

Take a plastic bag of water and push if off a bench.

Take the same and do the same off a wee bench in a tub of
water.



Dave, the water in a ballast tank is KNOT IN the water.

Sheesh!!!!

Neither is the water in the plastic bag!

Sheesh!

--
Duncan

In article ,
says...
OK, Duncan. here's a little experiment you can do in your
bathtub.

1. Put an empty Coke bottle in the water. Observe how it floats.
2. Fill the Coke bottle 1/4 with water. Observe how it floats.
3. Fill the bottle 1/2 way. Observe how it floats
4. Fill it 3/4 full. Observe how it floats
5. Is the water in the coke bottle below the tub water surface?
6. Wash your butt last.

Scotty

a) What is the *point* of your experiement? - other than to only prove
my argument correct.

b) try this (your experiment pretty much, say 4) ...

So 3/4 full. Hold the bottle at the top and note the weight. Slowly
lower it into the water. Note the weight changing! ??? How can it be
getting lighter all by itself?

Note also the final level in the water. There is almost no difference
in the level of the water in the bottle and the level to which it has
sunk. (The difference being a result of the boyancy of the plastic).

ie, Ans to your Q5. the level of the water in the bottle is very
slightly higher than the water it is in.

PS: experiment not conducted, just using simple physics. Feel free to
do it and get back to me if I'm wrong.

--
Duncan
[Farr 7500 'Hi-Time' http://hitime.no-ip.info]

Whoa Davey
Here's a better idea.... jump in the water and see how much water you
displace. If you displace a lot ...as I suspect... you should still float
well enough to undertake the test due to the residue of hot air.

Now drink a quarter bottle of Lamb's Navy Overproof Rum and see where you
float... continue drinking and take readings at every quarter mark of the
bottle.

Get Back to Us on Water Ballast.... we'll inform the multi national sailing
franchises of your position that they're delusional and water ballast is
ineffective.
I'm certain someone would be willing to write a "definitive book" regarding
your findings.

CM

"Dave Doe" wrote in message
. nz...
In article ,
says...
OK, Duncan. here's a little experiment you can do in your
bathtub.

1. Put an empty Coke bottle in the water. Observe how it floats.
2. Fill the Coke bottle 1/4 with water. Observe how it floats.
3. Fill the bottle 1/2 way. Observe how it floats
4. Fill it 3/4 full. Observe how it floats
5. Is the water in the coke bottle below the tub water surface?
6. Wash your butt last.

Scotty

a) What is the *point* of your experiement? - other than to only prove
my argument correct.

b) try this (your experiment pretty much, say 4) ...

So 3/4 full. Hold the bottle at the top and note the weight. Slowly
lower it into the water. Note the weight changing! ??? How can it be
getting lighter all by itself?

Note also the final level in the water. There is almost no difference
in the level of the water in the bottle and the level to which it has
sunk. (The difference being a result of the boyancy of the plastic).

ie, Ans to your Q5. the level of the water in the bottle is very
slightly higher than the water it is in.

PS: experiment not conducted, just using simple physics. Feel free to
do it and get back to me if I'm wrong.

--
Duncan
[Farr 7500 'Hi-Time' http://hitime.no-ip.info]

In article %2Gwf.47038$km.7540@edtnps89,
says...
Whoa Davey
Here's a better idea.... jump in the water and see how much water you
displace. If you displace a lot ...as I suspect... you should still float
well enough to undertake the test due to the residue of hot air.

Now drink a quarter bottle of Lamb's Navy Overproof Rum and see where you
float... continue drinking and take readings at every quarter mark of the
bottle.

Get Back to Us on Water Ballast.... we'll inform the multi national sailing
franchises of your position that they're delusional and water ballast is
ineffective.
I'm certain someone would be willing to write a "definitive book" regarding
your findings.

LOL - I *love* the idea - mind if I make that a nice single malt scotch
though?

PS: the book was written many years ago now, some dude called Archimedes
IIRC - shame he's not still alive for Scotty to prove him wrong.


--
Duncan

"Dave Doe" wrote in message

LOL - I *love* the idea - mind if I make that a nice single malt scotch
though?

Single Malt is a worthy choice

PS: the book was written many years ago now, some dude called Archimedes
IIRC - shame he's not still alive for Scotty to prove him wrong.

Yeah... I believe something about the buoyant force on the solid object is
equal to the weight of the fluid displaced . So... are you saying that 50
gallons of water in your bilge won't lower your waterline??? Good Grief
that means I can store unlimited supplies of rum onboard.

CM

"Dave Doe" wrote in message
. nz...
In article ,
says...
OK, Duncan. here's a little experiment you can do in your
bathtub.

1. Put an empty Coke bottle in the water. Observe how it
floats.
2. Fill the Coke bottle 1/4 with water. Observe how it
floats.
3. Fill the bottle 1/2 way. Observe how it floats
4. Fill it 3/4 full. Observe how it floats
5. Is the water in the coke bottle below the tub water
surface?
6. Wash your butt last.

Scotty

a) What is the *point* of your experiement? - other than to
only prove
my argument correct.


To prove to you that water BELOW the water line can still act as
ballast.
Also , to wash some of the stink off of you.



Scotty

Dave Doe wrote:
a) What is the *point* of your experiement? - other than to only prove
my argument correct.


Dave, since your argument is not correct, it would be pretty
hard to prove.

Are you saying that the water ballast inside a boat hull
does not affect it's stability? That the water ballast
"weighs nothing" until it is above the waterline?

If that were true, the boat's waterline would be the same
when the ballast tank was empty as when it is full.

Does the boat's displacement increase when the ballast tank
is filled? If so, then the the water ballast "weighs"
something, regardless of where it is relative to the waterline.

If the unit conter of gravity is below what the boat's
Center of Gravity would be without the ballast, then it
increases the boat's stability, regardless of whether the
tank is above or below the waterline.

b) try this (your experiment pretty much, say 4) ...

So 3/4 full. Hold the bottle at the top and note the weight. Slowly
lower it into the water. Note the weight changing! ??? How can it be
getting lighter all by itself?


Try this experiment.

Float an empty bottle. Mark where the waterline is.

Now fill it however full you want, 1/4 or 3/4 or whatever.

Does the bottle sink any deeper into the water?

No?

Then it "weighs" more, the water inside the bottle must be
weighing it down.



PS: experiment not conducted, just using simple physics. Feel free to
do it and get back to me if I'm wrong.


Yep, it's just simple physics. But a number of people have
tried to proclaim that water ballast can't possibly work
because "water doesn't weigh anything in water." But it
obviously *does* work, and the physics (when considered
correctly) show why.

Fresh Breezes- Doug King