How much can I shrink a set of Kayak plans?

External Since: Jun 02, 2004 Posts: 2

I am after some simple plans for a stitch and glue kayak for kids in
the 7-10yr range. I have come across loads of plans on the web in the
15' - 17' range and wondered if they could simply be shrunk in length
(only) without compromising the handling too much. Stability is of
more concern than speed so could I just take the 12" offsets and use
them at 10" spacing? (ie a 15' kayak becomes 12'6") - it might still
be a little large but at least said kids can say they've a kayak just
like daddys.

thanks.

ken

External Since: Jun 25, 2003 Posts: 835

Ken (kenhunt@btinternet.com) writes:
> I am after some simple plans for a stitch and glue kayak for kids in
> the 7-10yr range. I have come across loads of plans on the web in the
> 15' - 17' range and wondered if they could simply be shrunk in length
> (only) without compromising the handling too much. Stability is of
> more concern than speed so could I just take the 12" offsets and use
> them at 10" spacing? (ie a 15' kayak becomes 12'6") - it might still
> be a little large but at least said kids can say they've a kayak just
> like daddys.

yes and no

yes, if the weight is also being reduced. don't forget that bouyancy is
volume, not length, and that volumne is basically length times width times
depth. if you multiply the new dimensions and the old dimensions and
compare you'll get a pretty good idea of the reduction in bouyancy as,
say, a percentage. I'd compare that with the percentage difference in the
weight of the occupants. If you want more accuracy you can download a free
hull design program, type in the station (mold) dimensions (offsets), and
compute the numbers for the stations set 10" and 12" apart. I've done it
when investigating a design although I have not built the boat. maybe some
day. TF Jones wrote about a canoe he sucessfully built from plans by
increasing the station distances.

no, shaped plywood panels cannot be reduced in length only and still fit
together. they have to be reduced in both length and width. this will not
only make the boat shorter but also narrower. it may still be wide enough
to sit in comfortably. the bouancy will be reduced more than if the hull
were only shortened. so you have to reduce the length and width and depth
by the same percentage and compare the reduction in volume with the
difference in weight of the occupants.

you can download the free plywood hull desing program from
<a style='text-decoration: underline;' href="http://www.carlsondesign.com" target="_blank">www.carlsondesign.com</a> and scale down the hull any way you want. the
program prints out cutting coordinates for teh resulting plywood panels.
test the results by making a cardboard model before building the scaled
down boat. It took me quite some time to figur out how to plot the panels.
Other people reported at rec.boats.buildign that they use teh program to
plot panels with good fits and no problems. They didn't mention the length
of the learning curve, but it can be done. You can see images of my
limited experince with a model on my webiste under Boats, Designs, Solo 15,
or directly at <a style='text-decoration: underline;' href="http://www.ncf.ca/~ag384/Solo15.htm" target="_blank">www.ncf.ca/~ag384/Solo15.htm</a>

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