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Delamination again
By:Lennart Berlin
Date: 10/16/1998, 7:09 pm

I want to build a strip kayak. For the moment I lack two things: place to work and time to do it. Sometime in the future... In the meantime I read this bulletin board with great interest.

Recently there was a discussion about how to avoid delamination between wood and epoxy. I found suggestions about two methods: priming with hydroxymethylated resorcinol or using CPES. The first method will make the wood reddish. I don't like that because I will use Swedish spruce (Picea Abies) which is a pale wood. CPES has a lot of nasty solvents. I prefer not to use such matters. Besides I wonder if I could get it in Sweden.

Could there be another way? I decided to do a little armchair research and visited the websites of some Swedish universities, Technical Institutes and Wood Laboratories. There is a lot interesting research going on. Now I have phoned a few professors and graduated students. Most of their research is yet very theoretical, but some findings are of practical value. A lot I already knew but at least a couple of things were new to me.

1. Use dry wood

2. Use right kind of epoxy

3. Get rid of all dust on the surface of the wood

The surface of wood is a weak boundary layer (WBL). The reason is both chemical and mechanical. Wood is selfcontaminating. A new wood surface can be glued very well. After a while resin and other things migrate to the surface and make the joint much weaker. Most of the researchers recommended to seal the surface with glue within a couple of hours (one said within a couple of days). This leads me to following conclusion:

4. Seal a new wood surface with epoxy within a couple of hours.

A wood surface which is sawn, sanded or planed has a lot of tattered, crashed and compressed grain. A layer with a thickness of 0.1 to 0.2 mm is very weak. Most of the researcher think that it doesn't matter how you make the surface. One person think that a planed surface could be less disturbed. In one project they study if it is possible to get rid of the weak layer with an UV-Laser. As I don't own an UV-Laser I don't see what conclusion I can make of this.

5. ???

As I said in the beginning I have no experience in building a strip kayak. It could be interesting to see if you can make any practical use of these theoretical findings.


Messages In This Thread

Delamination again
Lennart Berlin -- 10/16/1998, 7:09 pm
Re: Delamination, my ideas
Gary Gilbert -- 10/23/1998, 1:06 pm
Re: Delamination again
Nick Schade -- 10/19/1998, 10:22 am
Re: Delamination again
Lennart Berlin -- 10/19/1998, 6:29 pm
Re: Delamination again
Jay Babina -- 10/19/1998, 10:00 am
Re: Delamination again
Capt Patrick McCrary -- 10/16/1998, 9:36 pm
Re: Delamination again
Lennart Berlin -- 10/17/1998, 3:52 am