Boat Building Forum

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

Re: Material: Strongback length after modifying

For locating the cockpit after changing the overall length from the plans:

I just measured the back of the cockpit to the nearest rear form on the 18 footer and used that measurement, the small measurement that I was off did not affect the kayak.

That seems to me to be a pretty good way to do it. As you say, the 'error' would be very small, and probably less than the variability in seat placement from builder to builder.
Some plans specify the cockpit/seat position with a measurement from the stern. In that case you need to change the measurement, proportional to the change in overall boat length.