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Re: Seeking: Why free plans only?
By:ancient kayaker
Date: 1/11/2014, 11:16 pm
In Response To: Re: Seeking: Why free plans only? (Andy Waddington)

My own canoe is symmetrical and the seat is about 1 foot behind the midpoint, since that centers the CoG of a paddler seated with legs almost straight. If your hull shape is symmetrical you'll get the same result. Study the shape of the stations and the waterline in the bodyplan view to get a feel for how buoyancy is distributed in your design.

A sea kayak is designed to take waves in its stride, the long bow has lots of reserve buoyancy but doesn't displace as much water as it might seem to. It is part of an asymmetrical hull with extra buoyancy aft. If you want to move the center of buoyancy aft you'll obviously need to reduce the immersed volume at the bow and increase it aft of the cockpit location, either by changing the draft at those locations, or increasing beam aft or - more subtly - by changing the shapes of the stations.

Of course, when you get into a boat this all sorts itself out automatically as the waterline settles out to where it needs to be to place the CoB at the CoG: if your software permits you can simply rotate the hull about the Z axis to move the CoB fore or aft.

Asymmetry can be overdone: a lot of commercial kayaks become difficult to keep in a straight line if you raise the rudder, because there is too much lateral area up front. I ran into this problem: it was so bad I had to return the boat.

Messages In This Thread

Seeking: Why free plans only?
Jeff Horton -- 12/20/2013, 7:09 am
Re: Seeking: Why free plans only?
ddaniels -- 12/20/2013, 7:45 am
Re: Seeking: Why free plans only?
Jay Babina -- 12/20/2013, 9:57 am
Re: Seeking: Why free plans only?
Jeff Horton -- 12/20/2013, 11:28 am
Re: Seeking: Why free plans only?
Noel Bennett -- 12/20/2013, 8:48 pm
Re: Seeking: Why free plans only?
John Messinger -- 12/20/2013, 5:38 pm
Re: Seeking: Why free plans only?
george jung -- 12/20/2013, 10:33 pm
Re: Seeking: Why free plans only?
ancient kayaker -- 12/20/2013, 11:19 pm
Re: Seeking: Why free plans only?
Bryan Hansel -- 12/24/2013, 1:26 am
Re: Seeking: Why free plans only?
Bill Hamm -- 12/25/2013, 12:22 am
Re: Seeking: Why free plans only?
Bryan Hansel -- 12/25/2013, 9:42 am
Re: Seeking: Why free plans only?
Andy Waddington -- 1/8/2014, 7:01 pm
Re: Seeking: Why free plans only?
ancient kayaker -- 1/8/2014, 11:26 pm
Re: Seeking: Why free plans only?
Andy Waddington -- 1/9/2014, 4:51 am
Re: Seeking: Why free plans only?
ancient kayaker -- 1/9/2014, 10:48 am
Re: Seeking: Why free plans only?
Andy Waddington -- 1/10/2014, 1:04 pm
Re: Seeking: Why free plans only?
ancient kayaker -- 1/11/2014, 11:16 pm
Re: Seeking: Why free plans only?
Andy Waddington -- 1/12/2014, 3:06 pm
Re: Seeking: Why free plans only?
MattGeerts -- 9/10/2014, 4:55 pm
Re: Seeking: Why free plans only?
JohnAbercrombie -- 9/10/2014, 5:20 pm
Re: Seeking: Why free plans only?
MattGeerts -- 9/10/2014, 6:11 pm
Re: Seeking: Why free plans only?
Mike Bielski -- 9/10/2014, 9:54 pm
Re: Seeking: Why free plans only?
MattGeerts -- 9/11/2014, 12:48 pm
Is "giving" bad or suspicious?
Jay Babina -- 9/11/2014, 10:51 am
Re: Is "giving" bad or suspicious?
Mike Bielski -- 9/11/2014, 11:19 am
Re: Is "giving" bad or suspicious?
Christopher Crowhurst -- 9/11/2014, 1:53 pm
Re: Is "giving" bad or suspicious?
Etienne Muller -- 9/11/2014, 6:37 pm
Re: Is "giving" bad or suspicious?
Mike Bielski -- 9/16/2014, 1:27 pm
Re: Is "giving" bad or suspicious?
scottbaxter -- 9/11/2014, 8:17 pm
Re: Is "giving" bad or suspicious?
JohnAbercrombie -- 9/11/2014, 9:38 pm
Re: Is "giving" bad or suspicious?
scottbaxter -- 9/11/2014, 10:39 pm
Re: Is "giving" bad or suspicious?
JohnAbercrombie -- 9/12/2014, 12:40 am
Re: Is "giving" bad or suspicious?
Christopher Crowhurst -- 9/12/2014, 8:06 am
Re: Is "giving" bad or suspicious?
Kurt Maurer -- 9/13/2014, 10:33 am
Re: Is "giving" bad or suspicious?
Daniel Thaler -- 9/11/2014, 1:06 pm