Boat Building Forum

Find advice on all aspects of building your own kayak, canoe or any lightweight boats

don't confuse stability with ability
By:Paul G. Jacobson
Date: 10/24/2009, 5:18 pm
In Response To: Re: Stability in two different words--core strengt (Craig Robinson)

: One suggestion regarding stability which has popped up in previous threads is
: to get some time up in a kayak that actually is tippy, i.e if you have
: access to one. a K1 might be a bit of a stretch but a tk1 or similar might
: do the trick. Its not much fun going back to a barge once you have stepped
: up to a more challenging & livelier boat. . .

Stability is an actual number which can be measured.

Imagine this. Stick a board out 5 feet from the right side of your boat. Put a weight on the outside end of that board and see how much the deck tilts. Put a heavier weight on the board and the deck will tilt some more. If the weight is heavy enough the deck will go under water, and maybe the boat will roll over on its side. You can measure the weight, the length of the board, and the amount of tilt. Do this with a canoe and you'll get more tilting (less stability) than if you do this with the same board and weight with a wide rowboat.

With practice and agility you can teach small children to ride bicycles--an item which is extremely unstable when at rest. eventually they can ride with no hands, or ride while juggling packages. Same goes with learning to paddle a kayak. With practice a person can master a "tippy" boat, and even retrieve fish or rescue other boaters.

But that is Ability, not Stability.

Adding an heavy outrigger to a narrow boat increases the bouyancy on the side where the outrigger is in the water. Try to rotate the boat in the direction of the outrigger and you push it under the water, making it displace additional water in proportion to the forces involved. Try to rotate the boat in the other direction and you have to lift that heavy outrigger out of the water. Either way you rotate you have a lot of resistance to making that move.

That is one reason why you don't need an outrigger on both sides of the boat. If you space the outrigger far enough from the main hull, and put your paddle in the gap between the two, then you will be shifting your weight in the direction of the outrigger, and have a nice stable platform.

When you use a long paddle, such as a GP, it has a great deal of resistance moving through the water. It is roughly the same as using a draw stroke, Try that with a regular paddle and you can feel the resistance. With a longer paddle that resistance is even greater. Add a light-weight float to that paddle and you also get some added bouyancy and the outrigger effect. At least on that one side. With that light float on one side of the boat you get no help if you rotate in the other direction.

Put a small amount of weight to one side of the center of bouyancy and the boat will rotate in that direction. With a paddle in the water the resistance slows down the speed of that rotation so the paddler can compensate. With an outrigger you tilt to the point where the forces balance and that's it.

PGJ

Messages In This Thread

S&G: Stability
Gord Clarke -- 10/20/2009, 8:16 pm
Re: S&G: Stability
Gord Clarke -- 10/22/2009, 9:51 am
Re: S&G: Stability
Bill Hamm -- 10/22/2009, 4:53 pm
Re: S&G: Stability
vk1nf -- 10/21/2009, 1:50 pm
Re: S&G: Stability
Andy Waddington -- 10/21/2009, 11:46 am
Re: S&G: Stability
Bill Hamm -- 10/21/2009, 12:12 am
Re: S&G: Stability------WebKitFormBoundaryOHu1V+g5
Robert N Pruden------WebKitFormBoundaryOHu1V+g5wLS -- 10/21/2009, 9:51 am
Re: S&G: Stability------WebKitFormBoundaryOHu1V+g5
Bill Hamm -- 10/22/2009, 2:57 am
Yep, Nick's S&G Night Heron *NM*
Robert N Pruden -- 10/20/2009, 10:03 pm
Stability in two words--paddle float
Paul G. Jacobson -- 10/20/2009, 9:01 pm
Re: Stability in two words--Greenland paddle
Ogata, eric -- 10/21/2009, 3:29 pm
Re: Stability in two words--paddle float
etienne Muller -- 10/21/2009, 9:26 am
Re: Stability in two words--paddle float *LINK*
Barry -- 10/26/2009, 11:49 am
Re: Stability in two words--paddle float
Etienne Muller -- 10/28/2009, 12:10 pm
Re: Stability in two different words--core strengt
Craig Robinson -- 10/21/2009, 4:14 am
don't confuse stability with ability
Paul G. Jacobson -- 10/24/2009, 5:18 pm
Re: don't confuse stability with ability
Craig Robinson -- 10/27/2009, 1:22 am
Re: S&G: Stability
Charlie -- 10/20/2009, 8:40 pm