Thread: scaling plans

Shhhhhhhhh !!!!
Don't let MIK or PAR hear you say that!!!!

Have a squiz at Duckworks - Rules of Thumb
or at MIK's website for the original article at FAQ - Boat Building and Repair Methods - Plywood Epoxy Fibreglass Cedar Strip - Michael Storer Wooden Boat Plans
(scroll down the page to Q&A - Shrink or expand or extend a boat in a plan - Michael Storer Wooden Boat Plans)

In summary - talk to the designer - sometimes it is possible. However, if you
deviate from the plans without the designer's blessing, whatever happens is
100% your fault - you have no recourse at all...

cheers
AJ

As a rule, scaling doesn't work well. If you want a boat 20% longer, then look for a design that is 20% longer. If you attempt to proportional scale things up and down, all sorts of weird and seemingly unpredictable things happen (actually quite predictable if you understand the math). This is simply based on the physical laws of mechanical similitude and relativity and is true of anything you attempt to scale up or down in size.

What 20' boat do you want to make 22'?

looking through the fence at a slipway several months back and was talking to a guy who was adding about 2ft to the back of his cat so he could have walk up steps. he commented it could be done easily. i know nothing about this stuff so thought i'd ask someone who does. Par the 20 / 22 ft was just to make maths easy in my tiny brain. i do appreciate the time people go to on this forum to try and educate the rest of us.
thanks.

Probably adding or extending transom scoops.
Since they are largely out of the water except at speed, that is probably fairly
harmless. Provided they were done right.
One of Murray Isles' clients did so & got away with it, although Murray didn't
sound too impressed when he first heard it.. Islesdesign Goings On

Once you start mucking around with things like width, you start changing
critical things like stability, waterline, overall weight vs sail-plan, etc, etc.
Bad karma unless you have the knowledge & maths to calculate it out.