Empathy List Archives

CS

Cortland Steck

Mon, Feb 27, 2006 6:32 PM

True you will have more surface area to weather for a wave to push against,
and more lateral area below the waterline for the boat to trip over.

But length doesn't really come into play beyond that.
Regardless of length, the boat will become unstable when it heels far enough
so that the CG (center of gravity) of the entire vessel (which should be on
centerline
of the vessel) moves over and past the CB (center of bouyancy) of the
leeward hull.
Hense, the higher the CG the sooner it will pass this point and the boat
will capsize.

Making the boat unusually long for its beam (high length to beam ratio) will
have
more negative effects, like increased drag due to wave interference between
hulls.
Therefore you will see that most power cats are in the 2:1 to 3:1 length to
beam ratio range.

While sailing cats are about 2:1 because they need the stability to carry
enough sail.

Cort

True you will have more surface area to weather for a wave to push against, and more lateral area below the waterline for the boat to trip over. But length doesn't really come into play beyond that. Regardless of length, the boat will become unstable when it heels far enough so that the CG (center of gravity) of the entire vessel (which should be on centerline of the vessel) moves over and past the CB (center of bouyancy) of the leeward hull. Hense, the higher the CG the sooner it will pass this point and the boat will capsize. Making the boat unusually long for its beam (high length to beam ratio) will have more negative effects, like increased drag due to wave interference between hulls. Therefore you will see that most power cats are in the 2:1 to 3:1 length to beam ratio range. While sailing cats are about 2:1 because they need the stability to carry enough sail. Cort -----

CS

Cortland Steck

Mon, Feb 27, 2006 6:37 PM

Yes - you can load down one hull more than the other and as you do so you
will
have the effect of moving the center of gravity further to one side. Like
hiking out on a beach cat.
This will make the boat more stable in one direction than the other.

However if you load the boat to much to one side you will effect the motion
of the boat and you
will effect steering by increasing the drag of one hull while reducing the
drag of the other.

Cort

----- Original Message -----
From: "Victor Aspey" sales@motorcats.com
To: "'Power Catamaran List'" power-catamaran@lists.samurai.com
Sent: Monday, February 27, 2006 11:44 AM
Subject: Re: [PCW] Stability and length/beam ratios

Can you not put a lot of weight on 1 hull before you get an unacceptable
list? A hobiecat maybe not - but a cruising cat?

Victor

Yes - you can load down one hull more than the other and as you do so you will have the effect of moving the center of gravity further to one side. Like hiking out on a beach cat. This will make the boat more stable in one direction than the other. However if you load the boat to much to one side you will effect the motion of the boat and you will effect steering by increasing the drag of one hull while reducing the drag of the other. Cort ----- Original Message ----- From: "Victor Aspey" <sales@motorcats.com> To: "'Power Catamaran List'" <power-catamaran@lists.samurai.com> Sent: Monday, February 27, 2006 11:44 AM Subject: Re: [PCW] Stability and length/beam ratios > Can you not put a lot of weight on 1 hull before you get an unacceptable > list? A hobiecat maybe not - but a cruising cat? > > Victor

GK

Georgs Kolesnikovs

Mon, Feb 27, 2006 7:24 PM

Just a quick note to thank Cort Steck for weighing in with his expert
understanding of multihulls, sail and power.

--Listmeister Georgs

Just a quick note to thank Cort Steck for weighing in with his expert understanding of multihulls, sail and power. --Listmeister Georgs

RD

Robert Deering

Tue, Feb 28, 2006 5:20 AM

Thanks All for bearing with my rudimentary questions. I feel a lot more
comfortable with the subject now. The lessons I'm taking from this are
to keep the weight low and keep the hulls (relatively) skinny.

Now, about wing deck height...!

Bob Deering
Juneau Alaska

Thanks All for bearing with my rudimentary questions. I feel a lot more comfortable with the subject now. The lessons I'm taking from this are to keep the weight low and keep the hulls (relatively) skinny. Now, about wing deck height...! Bob Deering Juneau Alaska

power-catamaran@lists.trawlering.com

Stability