Thanks Bart:
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. I'll forego discussion about the diff tween mass and
weight.

wrote in message
oups.com...
Thanks Bart:
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.

Well, you're wrong!

Scotty

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.


--
Capt Scumbalino

Scumbalino. agreed

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

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

If you want to build a boat, have you considered
the Dudley Dix kits built in South Africa? You
could also buy just the plans.

Their Mini design could be built with water ballast
albeit I don't think the kit includes that feature.

http://www.dixdesign.com/didimini.htm

I've thought about building one. I like the mini's but
the wooden designs are not very competitive, albeit
I'm sure they are a blast to sail.

wrote

Thanks Bart:
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. I'll forego discussion about the diff tween mass and
weight.

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