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Re: cold molding and skin on frame
By:Paul G. Jacobson
Date: 8/18/1999, 6:17 am
In Response To: cold molding and skin on frame (Tom Kurth)

> Question No. 1: the subject of cold molding has showed up here recently.
> sounds interesting--anybody have any sources to recommend?

> No. 2: What kind of cost range should one expectfor a skin on frame boat?

> Thanks, Tom

I found about 1 page on this technique in a book by the Gougeon Brothers on Wood Boat Building and West System epoxy. The copy I saw was on the shelf at an E&B Marine store, so I browsed through it. Lots of nice stuff in the book, but if you are really only interested in this one building technique you can read all they have to say about it in about 2 minutes -- which would not make the book a good buy for you.

By the way, the section after it is on strip building boats. They mention canoes, prams, and dinghys -- but mostly canoes. Not a word on building kayaks from strips.

On one page they give a chart showing the difference in strength between various combinations. They bend a sample until it breaks. I'm doing this from memory, so I may be rounding these numbers a bit. If anyone has the book they can correct me. For 3/16 cedar strips covered with a layer of 6 ounce cloth on each side it took 211 pounds, for 1/4 inch cedar strips covered with 6 ounce cloth on each side it was 225 and for 4 mm okoume (not glassed) it was 215 pounds. The okoume weighed 10.5 ounces per square foot, the 1/4 inch cedar was 9.8 ounces per square foot,and the 3/16 cedar was 8 ounces per square foot.

They had specs on thicker strips, but this was what jumped out at me: There was no significant difference in strength on the cedar strips between 3/16 and 1/4 inch, though the 3/16 flexed a lot more before it broke. Sonds to me like the thinner material would give a bit more, rather than puncture -- something like the way a fabric skin does on skin-on-frame design -- should you hit an obsruction.

A while ago the engineers in this crowd (amateur and pro) hashed out a long debate on the methods of testing, the validity of some tests, and a bunch of othre technical stuff on the relative "strength" of the materials we use. I don't want ot restart that battle. As I saw it, the real outcome is that you shouldn't rely on any single given indicator, as the results seem to be contradicted by later tests. So, don't read anything into this data from the book. I probably don't have it quoted accurately anyhow.

Hope this helps

Paul G. Jacobson

Messages In This Thread

cold molding and skin on frame
Tom Kurth -- 8/15/1999, 4:04 pm
Re: cold molding and skin on frame
Paul G. Jacobson -- 8/18/1999, 6:17 am
Re: cold molding and skin on frame
Paul G. Jacobson -- 8/15/1999, 8:31 pm
Re: cold molding and skin on frame
Tom Kurth -- 8/15/1999, 10:56 pm
Re: - boat building habit
Hank -- 8/16/1999, 12:23 pm
Re: cold molding and skin on frame
garland reese -- 8/16/1999, 10:33 am
Re: cold molding and skin on frame
Mike Hanks -- 8/15/1999, 8:46 pm