Hi Jack
Glen has it right but centre of balance while sitting is probably the best. I guess you could find this by each of you sitting on a board with dowel
roller underneath on a smooth floor and moving back and forth till the board tilts. Mark on the floor where the dowel is and using a square to align with your back measure the distance between the square and the mark. Use this distance in the calulation to position the rear of each cockpit. If you need to increase the distance between cockpits will youll need to be half the additional length required added to the distance of each body COG from the COG of the kayak.
Cheers
Niven
Niven
: Hi All-

: I’m currently building a double skin baidarka based on a pdf survey of an
: “Aleut two-hole kayak” from the National Museum in Washington DC, USNM
: 160336. The plans are a pdf made from lines taken by David Zimmerly in
: 1975. http://www.arctickayaks.com/plans.htm

: The boat was drawn for 2 paddlers, each 150 lbs, placed at a specific
: location. My problem is that Maggie and I are both very different weights,
: so the front paddler will be 115 lbs and the rear 200. The boat is 20ft
: 7in long and around 22.5in in beam.

: So my problem is this... If we keep the front paddler (115 lbs) at the same
: place where the original 150 lb paddler was, how far would we have to move
: the heavier rear paddler to maintain trim of the boat?

: I would assume if we kept the cockpit placements as they were in the
: original, it would trim stern down.

: We came up with moving the rear cockpit forward about 12 to 18 inches.
: This was done sorta unscientifically, so we wanted to run this by the more
: sophisticated designers out there.

: I also figure the extra 15lbs would not make a significant difference in the
: displacement of the boat.

: Lots of assumptions here, based on gut feelings more than real engineering.

: Are we close? Anyone got a clue how to maintain trim by moving the cockpits?

: Thanks so much for any help!

: Jack Gilman

: ps: the boat is being made with a combination of Tom Yost's frame-and
: -stringer type of construction with a few strategically placed ribs. We're
: looking to build a fast, light double to race this year's Run of the
: Charles up in Boston.