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.

Thanks again Matt for your extensive reply to my post. The plan I have
is a plan from the 1940's which I printed from the internet.
The boat which I really like as far as lines and size is (13' by 5').
This plan is also from the 40's from the Eddy Ship Building Co. of Bay
City, Mi. now out of business. The designer was Douglas Van Patten who
also designed the "Canada" unlimited hydroplanes in the early 50's.
This url: http://boatdesign.net/boat-plans-archive/
is a scanned sheet of construction drawings posted on a boat
discussion/forum web site. The problem is that some of the lines are too
faint to make out. Would a blueprint service be able to correct this
problem? Thanks again, Ted.

ps- I do know how to spell _lengthening_!

Thanks for the link!
surfnturf

"Ted W Lee" wrote in message
...
Thanks again Matt for your extensive reply to my post. The plan I have
is a plan from the 1940's which I printed from the internet.
The boat which I really like as far as lines and size is (13' by 5').
This plan is also from the 40's from the Eddy Ship Building Co. of Bay
City, Mi. now out of business. The designer was Douglas Van Patten who
also designed the "Canada" unlimited hydroplanes in the early 50's.
This url: http://boatdesign.net/boat-plans-archive/
is a scanned sheet of construction drawings posted on a boat
discussion/forum web site. The problem is that some of the lines are too
faint to make out. Would a blueprint service be able to correct this
problem? Thanks again, Ted.

ps- I do know how to spell _lengthening_!

Ted,

The construction plans as posted at
http://boatdesign.net/boat-plans-arc...dycat-plan.htm and
http://boatdesign.net/boat-plans-arc...dycat-plan.htm
are incomplete.

The information required to construct the frames is not there. Some of
this could be scaled off the drawing, but the sides above the chine will
be very difficult to get correct on the first try.

If you are not a very experienced boatbuilder, this would not be a good
place to start. (I am a naval architect and marine engineer and have
been building small boats on and off for most of my near sixty years and
I would have a very hard time working from the posted material.)

Yes - Some blue print services could bring out some of the faded lines
somewhat, but blue print services (very rare these days) largely just
print a copy of the drawing you give them. If you are diligent, you
could do as well to get large prints of your files and recreate the
lines with a batten. I did have a local office that I did use, but they
have disappeared with the advent of electronic drawing handling (now a
days offices set up an FTP where you can get to and download the IGES
file you need.)

It does look like a pretty little boat, and if you really want to
attempt this, then the very scaled build would be the only place to
start. Keep complete notes of your measurements and corrections (make a
few small changes and sell the design as your own). If you do add a
couple of feet to the LOA then it is your design.

Good Luck
Matt Colie