changing design?

[hermitsing]

I am a novice builder and have come across a sailboat plan that I would like to make bigger. Is it possible to do this by multiplying all data (offsets/lines, etc.) by a given factor, say 1.4?
Thanks for any help/advice.
A

[sorenfdk]

Well, it depends on how much bigger you want to make your boat. If it is less than, say, 5% then maybe you could just multiply all the dimensions by 1,05, though I wouldn't recommend it.
But if it is more than that, you'll end up with quite another beast regarding performance, stability and feel.
I recommend that you get hold of Larsson & Eliasson's excellent book "Principles of Yacht Design", where the scaling of dimensions is discussed. You could also search this site for some postings by Stephen Ditmore, where he discusses scaling.
But there's one thing that you absolutely must not forget: The loads will also scale, so you'll need to calculate all the scantlings all over. Better check with a designer if you have no experience with this!

[SailDesign]

Also bear in mind that if you change the deisgn in any way (and scaling by any amount will do this), then you have absolutely no recourse to the designer if something breaks, goes wrong, doesn't work as intended, or if the boat just plain won't sail, won't achieve the correct speed under power, has no stability to speak of, etc., etc., etc.

The designer, however, may well have the right to sue YOU for stealing his design, even if you have scaled it.

Steve "so what design is it, anyway?"

[PAR]

In a word, NO. You've recommended 40% and this means too fat for her length, too deep, etc.

You clearly are an amateur, by you own admission, why screw with things you don't understand? Making changes is normal, but whole redesign, by nearly half as much is foolish, in fact dangerous.

I spend 6 months to a year on each design. I'm not wasting my time farting around with someone else's money. Nor is any other designer I know.

Slight changes to the accommodations, the sail plan or other is expected. If the design isn't what you're after, then there are thousands of others that may be, closer to the displacement range (or whatever) you're interested in.

Talk to the design staff, they will set you on the path towards your goal(s) . . . (this is why we pay them in the first place)

[hermitsing]

Thanks alot. I guess that's why I was asking. I'll keep looking.

Originally Posted by PAR

In a word, NO. You've recommended 40% and this means too fat for her length, too deep, etc.

You clearly are an amateur, by you own admission, why screw with things you don't understand? Making changes is normal, but whole redesign, by nearly half as much is foolish, in fact dangerous.

I spend 6 months to a year on each design. I'm not wasting my time farting around with someone else's money. Nor is any other designer I know.

Slight changes to the accommodations, the sail plan or other is expected. If the design isn't what you're after, then there are thousands of others that may be, closer to the displacement range (or whatever) you're interested in.

Talk to the design staff, they will set you on the path towards your goal(s) . . . (this is why we pay them in the first place)