Boat Building Forum

Find advice on all aspects of building your own kayak, canoe or any lightweight boats

George Roberts' Challenge
By:Ian Johnston
Date: 8/27/1999, 4:15 am

George As you may have noticed I have just recently began posting on this B.B.

I was quite intrigued with your challenge of building a lighter and yet stronger kayak than any other builder. Several other people here feel you are just so much hot air, but I felt that you had no reason to lie to me so your claim must be true. From here the challenge was to figure out how you could do this or, barring that, to figure out how I could make a kayak similar to your specs. Now this may not be of much interest to you as you have already developed a process that works but I would be interested in your or anyone elses opinion.

From my figuring (thinking mostly) I feel that the weakness in a cedar strip kayak is the cedar strips. The strength in a laminate is in the fact that all the structural components (cloth and strips) are locked together by the binding component ( epoxy resin), so that nothing can move without moving everything else. The trouble with the strips is that they are not saturated with resin so their fibers are not locked in with the rest of the laminate except for some penetration on the surface. For this reason I would use 1/8 inch strips, this would give me two obvious benefits: 1-it would eliminate 50% of my wood weight, (about 10# as George already confirmed) 2- it would give me a higher percentage of resin saturation and wouldn't eliminate strength but would actually eliminate a weakness (unsaturated cedar). A third and maybe not so obvious benefit of 1/8 inch strips is that the distance between the inside and outside epoxy layups would be reduced and in a laminate this is important to keep everything tightly interlocked and this will become important when glueing the strips together.

If carpenters glue is used to hold our strips together we end up with a sandwich effect with our lamination. We have a epoxy layer adhered to a cedar strip center adhered to another epoxy layer. The cedar epoxy adhesion is quite good but cedar strips are weak and can split, causing seperation. The epoxy/ carpenter glue joint is very poor. For these reasons I would use epoxy to glue my strips, this would give higher resin saturation on the cedar (4 sides instead of 2) and would also bind with the inner and outer epoxy layups and form part of the laminate. The result of this is a laminate that is locked together nearly equally in three dimensions, giving a honeycomb type structure instead of a sandwich.(This would be even stronger because the two epoxy layers are only seperated by 1/8 inch strips.)

The last thing that I would do is a double or triple layup of a very light fiberglass cloth. As I stated in previous posts, I think that this would be much lighter and stronger than a single heavier cloth layup.

I know this is a simplified explanation of the process and I would have included numbers to back up some things I have said but it seems that with every figure you include in a post you lose 50% of your readers through boredom. As for your challenge, I won't take you up on it, but when I build a kayak and try some of these ideas your challenge will have been the motivation behind it.

As for anyone else who has made it this far, I would also be interested in your opinions. Thanks in advance.

P.S.- I have avoided asking you any questions because I am from Canada and with the difference in the dollar, $20 US is like $500 Can. and I can't afford that.

Messages In This Thread

George Roberts' Challenge
Ian Johnston -- 8/27/1999, 4:15 am
Re: George Roberts' Challenge
Rick S. -- 9/3/1999, 12:42 am
Re: "ultimate layups"
lee -- 8/31/1999, 11:11 am
Re: "ultimate layups"
Mike Hanks -- 9/1/1999, 4:17 pm
Re: "ultimate layups"
lee -- 9/14/1999, 10:18 am
Re: "ultimate layups"
Paul G. Jacobson -- 9/15/1999, 1:44 am
Re: "ultimate layups"
Mike Hanks -- 9/14/1999, 9:05 pm
Re: "ultimate layups"
lee -- 9/16/1999, 2:46 am
Re: "ultimate layups"
Mike Hanks -- 9/16/1999, 10:51 am
The Challenge: Don't forget this!
Jan Gunnar Moe -- 8/30/1999, 3:57 am
Re: George Roberts' Challenge
Jamin -- 8/29/1999, 9:05 pm
Re: George Roberts' Challenge
Dale Frolander -- 8/28/1999, 2:26 am
Re: George Roberts' Challenge
Ian Johnston -- 8/28/1999, 9:34 pm
Re: George Roberts' Challenge
Dale Frolander -- 8/28/1999, 10:27 pm
Re: George Roberts' Challenge
Jeff DeJongh -- 8/29/1999, 3:18 pm
Re: George Roberts' Challenge
Ian Johnston -- 8/29/1999, 5:46 pm
Re: George Roberts' Challenge
Dan Lindberg -- 8/29/1999, 8:43 pm
Re: George Roberts' Challenge
Jeff DeJongh -- 8/29/1999, 7:36 pm
Re: George Roberts' Challenge
Ian Johnston -- 8/28/1999, 11:06 pm
Re: George Roberts' Challenge
Don Lueder -- 8/27/1999, 8:03 pm
Re: George Roberts' Challenge
jay roberts -- 8/27/1999, 5:10 pm
Re: George Roberts' Challenge
Edgar Kleindinst -- 8/27/1999, 10:49 am
Re: George Roberts' Challenge
J . P. Scheib -- 8/27/1999, 5:24 am