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Re: Weight & Balance
By:Dave Houser
Date: 12/31/2007, 8:43 pm
In Response To: Re: Weight & Balance (Tom Yost)

Tom,

You certainly have more experience than I do. I have built only three S&G’s and fussed with skegs and seat location to trim for wind. I can only agree that it is easier to move the paddler (and seat) if there is room in the cockpit opening and clearance forward is usually more available than back. In S&G’s bulkheads limit how far the coaming can be moved.

One can make a good attempt to design a wind neutral kayak by balancing the lateral areas above and below the waterline. The wind force acts through the centroid of the area above the water. And the lateral force of the water acts the centroid of the area under the waterline. So the trick is line the two centroids up vertically. If the wind centroid is behind the water centroid the kayak will weathercock. So you go to the trouble to design a kayak with the length, width, rocker, chine height, center of buoyancy location, deck height, bow height, stern height, etc. you want. Then you check the lateral areas and centroid locations and then adjust the bow height and stern height to align the area centroids. You should have a kayak that is close to being balanced. But when a kayak moves through the water its center of lateral resistance moves back. So all of this lateral area calculation is approximate. So in the end you move the heaviest weight (the paddler and seat) to trim the kayak. And if you do a test paddle during construction you can move the coaming while moving the seat location. Moving the paddler back increases the bow height, lowers the stern height, raises the forward keel (increases forward rocker) and lowers the aft keel (decreases aft rocker) all reduce weathercocking. It also moves the lateral area above the waterline forward, moves the lateral area below the waterline back, and moves the center of buoyancy back. All this number crunching (engineering) is supposed to reduce the number of prototypes necessary to create the final design. In building a touring kayak, it probably is quicker to just build the prototypes.

Have a great year,
Dave

Messages In This Thread

S&G: Back band to center of buoyancy distance
HenkA -- 12/28/2007, 2:32 pm
Re: S&G: Back band to center of buoyancy distance
Tom Yost -- 12/29/2007, 10:17 am
Weight & Balance
Dave Houser -- 12/31/2007, 12:41 pm
Re: Weight & Balance
HenkA -- 12/31/2007, 8:00 pm
Re: Weight & Balance
Tom Yost -- 12/31/2007, 7:08 pm
Re: Weight & Balance
Dave Houser -- 12/31/2007, 8:43 pm
Re: Weight & Balance
Bill Hamm -- 1/2/2008, 2:11 am
Re: S&G: Back band to center of buoyancy distance
JohnK -- 12/29/2007, 9:02 pm
Re: S&G: Back band to center of buoyancy distance
Tom Yost -- 12/29/2007, 10:05 pm
Re: S&G: Back band to center of buoyancy distance
JohnK -- 12/30/2007, 1:59 am
Re: S&G: Back band to center of buoyancy distance
Bryan Hansel -- 12/28/2007, 10:25 pm
Re: S&G: Back band to center of buoyancy distance
Duane Strosaker -- 12/28/2007, 4:39 pm
Re: S&G: Back band to center of buoyancy distance
Kurt Maurer -- 12/28/2007, 6:42 pm
Re: S&G: Back band to center of buoyancy distance
Duane Strosaker -- 12/28/2007, 11:24 pm
Re: S&G: Back band to center of buoyancy distance
Bryan Hansel -- 12/28/2007, 10:27 pm
Re: S&G: Back band to center of buoyancy distance
Glen Smith -- 12/28/2007, 2:52 pm