Water ballast (WAS: Catalina 250)
 

On Mon, 20 Oct 2003 18:02:00 +0000, DSK wrote:

Lloyd Sumpter wrote:


Tell me, is your boat's stability increased by filling a fuel tank
down low in the hull? Fuel is definitely lighter than water. How
about a big cooler full of ice & beer?


Compared to AIR, yes. Compared to lead, no. I'd show you the
mathematics if you feed me beer.

Math, huh? Do you do numbers any better than you do logic?

So... because lead ballast is better, as ballast, does that mean water
cannot function AT ALL as ballast?

No. Of course not.



Yes, it does.

(actually, it's physics, not math, but you owe me a beer anyway)

Draw a diagram if you like. Now, the keel imparts a righting moment on the
boat because it exerts a downward force offset (in the x-dir) from the
center of rotation by the distance from the CofR (ie how deep the keel is)
and the angle of heel. Problem is, a water-filled keel does not sink and
therefore exerts NO downward force in water! (actually it does sink a bit
because the fibreglass the keel is made from sinks. You'd be better off
with a solid fibreglass keel...) Remember the water-filled bottle?

People think that because water is "heavy" in air means that it's also
"heavy" (ie exerts a significant downward force) in water. This is simply
not the case. Imagine this: get a boat with no keel and a mast. Put a rope
on the mast and pull on it, giving the boat heel. Now, put a boom out the
upward side with a bucket filled with water. As long as the bucket is in
air, it exerts a righting moment against the rope. But when it's in the
water, the only righting moment from the bucket is from the bucket itself
- the water exerts no righting moment whatsoever.

Now, having a water-filled keel that exerts virtually no downward force is
still preferable to an air-filled keel, which exerts an UPWARD force.
Also, water in the keel will help the boat's "stability" in that it
increases the overall mass (F=ma) so movement is dampened.

But "ballast"? No.

Lloyd Sumpter
"Far Cove" Catalina 36

Water ballast (WAS: Catalina 250)
 

I'm going to print this out and read it thoroughly, but, overall, I'm
going to disagree.
Filling a fuel tank or beer cooler, down low in the hull, will
DEFINITELY increase stability. It's a question of added weights to the hull.
Water Ballast, is a great way to add draft as well as stability, to a
hull (unless you leave the tank slack, in which case, the "free surface"
can outweigh the additional stability).

otn

Lloyd Sumpter wrote:

On Mon, 20 Oct 2003 18:02:00 +0000, DSK wrote:

Lloyd Sumpter wrote:



Tell me, is your boat's stability increased by filling a fuel tank
down low in the hull? Fuel is definitely lighter than water. How
about a big cooler full of ice & beer?



Compared to AIR, yes. Compared to lead, no. I'd show you the
mathematics if you feed me beer.

Math, huh? Do you do numbers any better than you do logic?

So... because lead ballast is better, as ballast, does that mean water
cannot function AT ALL as ballast?

No. Of course not.




Yes, it does.

(actually, it's physics, not math, but you owe me a beer anyway)

Draw a diagram if you like. Now, the keel imparts a righting moment on the
boat because it exerts a downward force offset (in the x-dir) from the
center of rotation by the distance from the CofR (ie how deep the keel is)
and the angle of heel. Problem is, a water-filled keel does not sink and
therefore exerts NO downward force in water! (actually it does sink a bit
because the fibreglass the keel is made from sinks. You'd be better off
with a solid fibreglass keel...) Remember the water-filled bottle?

People think that because water is "heavy" in air means that it's also
"heavy" (ie exerts a significant downward force) in water. This is simply
not the case. Imagine this: get a boat with no keel and a mast. Put a rope
on the mast and pull on it, giving the boat heel. Now, put a boom out the
upward side with a bucket filled with water. As long as the bucket is in
air, it exerts a righting moment against the rope. But when it's in the
water, the only righting moment from the bucket is from the bucket itself
- the water exerts no righting moment whatsoever.

Now, having a water-filled keel that exerts virtually no downward force is
still preferable to an air-filled keel, which exerts an UPWARD force.
Also, water in the keel will help the boat's "stability" in that it
increases the overall mass (F=ma) so movement is dampened.

But "ballast"? No.

Lloyd Sumpter
"Far Cove" Catalina 36

Catalina 250
 

OK...take your basic Merit/Olsen/Martin/Hotfoot/J and:.

Lloyd if you new anything you would know that the Merit and Olson are nothing
like the Martin and the Hotfoot. By the way the displacement of the Catalina
250 is not far off from the Merit or Olson so there goes the rest of your
argument.
S/V Express 30 "Ringmaster"
Trains are a winter sport

Catalina 250
 

4. Add 6 mos accumulation of marine growth on the hull

So are you saying that the Catalina comes into her own under these conditions?


S/V Express 30 "Ringmaster"
Trains are a winter sport

Catalina 250
 

Loco enjoys bashing boats and anyone who doesn't like what he likes.


LOL.................. Your the main boat basher. I just offered an opinion
on some better alternatives in 25' boats.
S/V Express 30 "Ringmaster"
Trains are a winter sport

Water ballast (WAS: Catalina 250)
 

PS Add weight to the hull and you change stability. Add it high, you
lessen stability, add it low, and you increase stability. The
type/composition of the weight, is immaterial.

otn

otnmbrd wrote:
I'm going to print this out and read it thoroughly, but, overall, I'm
going to disagree.
Filling a fuel tank or beer cooler, down low in the hull, will
DEFINITELY increase stability. It's a question of added weights to the
hull.
Water Ballast, is a great way to add draft as well as stability, to a
hull (unless you leave the tank slack, in which case, the "free surface"
can outweigh the additional stability).

otn

Lloyd Sumpter wrote:

On Mon, 20 Oct 2003 18:02:00 +0000, DSK wrote:

Lloyd Sumpter wrote:



Tell me, is your boat's stability increased by filling a fuel tank
down low in the hull? Fuel is definitely lighter than water. How
about a big cooler full of ice & beer?



Compared to AIR, yes. Compared to lead, no. I'd show you the
mathematics if you feed me beer.


Math, huh? Do you do numbers any better than you do logic?

So... because lead ballast is better, as ballast, does that mean water
cannot function AT ALL as ballast?

No. Of course not.




Yes, it does.

(actually, it's physics, not math, but you owe me a beer anyway)

Draw a diagram if you like. Now, the keel imparts a righting moment on
the
boat because it exerts a downward force offset (in the x-dir) from the
center of rotation by the distance from the CofR (ie how deep the keel
is)
and the angle of heel. Problem is, a water-filled keel does not sink and
therefore exerts NO downward force in water! (actually it does sink a bit
because the fibreglass the keel is made from sinks. You'd be better off
with a solid fibreglass keel...) Remember the water-filled bottle?

People think that because water is "heavy" in air means that it's also
"heavy" (ie exerts a significant downward force) in water. This is simply
not the case. Imagine this: get a boat with no keel and a mast. Put a
rope
on the mast and pull on it, giving the boat heel. Now, put a boom out the
upward side with a bucket filled with water. As long as the bucket is in
air, it exerts a righting moment against the rope. But when it's in the
water, the only righting moment from the bucket is from the bucket itself
- the water exerts no righting moment whatsoever.

Now, having a water-filled keel that exerts virtually no downward
force is
still preferable to an air-filled keel, which exerts an UPWARD force.
Also, water in the keel will help the boat's "stability" in that it
increases the overall mass (F=ma) so movement is dampened.

But "ballast"? No.

Lloyd Sumpter
"Far Cove" Catalina 36

Water ballast (WAS: Catalina 250)
 

Lloyd Sumpter wrote:


People think that because water is "heavy" in air means that it's also
"heavy" (ie exerts a significant downward force) in water. This is simply
not the case.

True enough, but totally irrelevant. Which weighs more, a ton of feathers or a
ton of lead?

You are totally off base and your physics is wrong. Sorry to be so blunt. You
have no concept of what produces rightning moment; I suggest reading a good
simplified text on naval architecture, such as Robert Perry's book or Skene's
Elements of Yacht Design. Read the section on "metacentric height' two or
three times.

You point out that lead sinks and water does not. It seems to me that the
point is to increase stability of the boat, not to sink it. Wouldn't water
ballast be better, then?

If you like to paint imaginary scenarios illustrating how water functions as
ballast, then picture the following: a big ice chest full of cold beer. Take
it aboard your boat. The boat sinks a little deeper as the weight of the
cooler comes aboard, it's displacement has increased. In other words, the boat
is supporting the weight of that cooler & it's contents, wether those contents
are feathers or depleted uranium.

Now hoist that cooler to the top of the mast and try heeling the boat. Of
course, stability has been reduced, it will take less force to heel the boat
to any given angle. Now lower the cooler and place it as low as possible
against the bottom of the hull. Try heeling the boat again, of course you'll
find that stability has been improved. It will take more force to heel the
boat to any given angle.

Taa Daa!

A cooler full of ice & beer, which is absolutely lighter than water and does
not sink, has become ballast.

You're welcome.

Doug King

Water ballast (WAS: Catalina 250)
 

anony,

Everyone knows they are anti-flotation devices.

Regards, Ron

Catalina 250
 

Your the main boat basher. I just offered an opinion
on some better alternatives in 25' boats.

No, you didn't. Your post is below. It's bashing a boat you've never sailed.

Great for camping. If you want to sail buy a Merit 25 or an Olson 25.

The Catailina 250 is a fine boat for someone who's seeking greater comfort and
a more forgiving platform for a family. You must also think Doug's boat was
dumb as well. Why not challenge his comments about the 250? Problem is, Loco,
you're a coward and a fool.
Calling the Catalina a "camping" boat that can't sail only proves it. You're
probably just upset that like me, the fellow will have a modern boat while you
sail a dead design dinosaur.

truth

RB

Catalina 250
 

the fellow will have a modern boat while you sail a dead design
dinosaur.

I guess that's why we are first to cross the finish line so often.


S/V Express 30 "Ringmaster"
Trains are a winter sport