: It was about scaling a design. You have to be careful doing this,
: just chaning all the numbers by a percentage usually won't work
: except for a very small percentage change, usually well under 5%
: will work.

You can scale all dimensions linearly. Just have to remember the volume change will be cubic.

Example:
Take a sea kayak that is 18' long x 21" wide with a design displacement of 250 pounds.
Now scale it down 20% (80% of full-size).
The new dimensions are 14.4' long x 16.8" wide.
The design displacement is about 1/2 though. It drops to128 lbs (250 lb*80%*0.80%*0.8).
Could be a boat for an advanced child paddler.

=D