Ted,
The parallel mid-section is more than just flat bottom, typically it is
a portion where the bottom, deck and both sides are straight for some
distance. This is not an effective hydrodynamic form, but if you have
limits on draft and beam then you do what you have to do to carry cargo.

Back to your situation.
Assuming that what you have are plans for a straight frame "plywood and
tape" design (meaning that the stations and frames are made of straight
lines and the skin is wrapped or twisted plywood), you should be able to
loft (layout) an intermediate station that will be fair.

As you are not currently a boat builder or a loftsman, I stongly suggest
that you build a very accurate scale model in balsa or foam core. This
will give you the opportunity to both loft your additional station and
get a preview of the result.

Will this effect the almost every aspect of the boat's characteristics?
Yes - for better or worse? I can't tell you without studying the
plans and the changes. The boat's load and trim lines will change as
well as the stability characteristics. The sailplan will change some
because the relative locations of the centerboard, mast and rudder will
change.

What do you hope or expect to get for the extra 2 feet?

Does the designer of this boat you like have a set of plans for the
larger sister? (This is very often the case, and if they are a
purchased set of plans, the plans and included rights can be sold.) If
these plans were purchased from the designer, he may be able to point
you to a good alternative.

Short answers -
Can you do this? - Yes
Will the result have lines you so appreciate? - Maybe.
Will you get what you want from it? - I can't tell you.

Matt Colie


Ted W Lee wrote:
Thanks for your response Matt. Does "parallel mid-section" refer to the
flat mid-section of the bottom of a ship?
I have plans for a v-bottom boat (I like the lines of this particular
boat) which I would like to lengthen. It would be fibre glassed plywood.
Thanks, Ted.