: Are you aware of "Kayak Foundry", the kayak designing
: program available free from the blueheron site?

: http://www.blueheronkayaks.com/kayak/index.html

: I just used it to confirm what I suspected would be the effect of
: what you are describing. If you simply lower the sheerline at
: the bow and stern, but keep the plan view the same shape, then
: apart from the loss of volume, there is a tiny change in the
: waterline shape. There is less height for the bit just behind
: the bow to reach out to the width at the sheerline, so it flares
: out a bit more and the waterline shape changes very slightly.

: The effect on the drag and stability and the trim are almost
: imperceptible if the bow and stern are dropped about an inch. On
: the design I was playing with, the drag increased at 4.5 knots
: by about half of one percent. That is probably because the
: waterline has a very slightly less fine angle of entry. You
: would not notice a change as small as that.

: Changing just the bow moves the centre of buoyancy, but only by
: 1/10th inch, so you wouldn't notice that either. Changing the
: stern as well brings it back more or less to where it started.

: You could compensate for that by reshaping the first form, but I
: think the difference would be less than the amount you would
: sand off the strips to get the hull smooth.

: My impression, which playing with a design confirms, is that if you
: are only thinking of dropping the bow by an inch, then you would
: not notice any difference in the behavior of the kayak and it
: probably would not create an uneven curve. Any more than an inch
: and you might need to check as you fit the strips that you still
: have a smooth curve.

: So my instinct and my experiment with "Kayak Foundry"
: suggests that the effect of the change you are describing would
: probably be significantly less than the effect of your leaning
: slightly forward or back as you paddle.

Thanks Allan, yeah, I've been playing with it a bit because somebody in a previous post suggested it. What Bill H said or was it Mike? about getting as much volume in the bow as possible to aleviate submarining makes sense and that may not show up in the program, I think this is where the experience takes over because my original thoughts were that it was only changing the sheerline a bit.

I was trying quite a few different tactics when I was in the surf yesterday, leaning forward or backwards was one of them. I even went to shore to adjust my seat position forward a bit to see what difference it made, I think my kayak is a bit nose heavy because the centre of gravity seems to be a bit further forward than it is supposed to be.
I'm happy to go with experienced advice from people who've already made plenty of mistakes & know the result, that's why I'm more than happy to buy plans rather than design my own.
I'm good at my day job not so much because of what I know will work, but I know what won't work, too many years of makin' stoopid mistakes! oops, that didn't work, don't do that again!.... if that makes sense :-)

Anyway, I'm getting off topic, back to the upswept bow & stern of the Petrel.

Glen G
Learn by the mistakes of others, you won't live long enough to make them all yourself.