I have used epoxy construction but what about using polyester resins? Do they stick to the wood well? Do they handle sunlight damage better?
Yes
And they do a nice job.
Resins
Then why use epoxy?
Be careful
with polyester resin and some woods. Oily woods can prevent the polyester from curing. I had major trouble with a boat using polyester with redwood strips.
Hate to disagree but no
– Last Updated: Oct-13-09 8:21 AM EST –
Epoxy is light years ahead of polyester as a bonding agent for many reasons. Epoxy is flexible and that's what makes into a glue. You cannot glue things together with polyester. I was once working with polyester and had a tiny puddle drop on the floor of hardened poly and it shattered. Poly is good for making castings with fiberglass cloth like boats. Years back some people did strip work with it but for the most part it will fail. As the wood expands or shrinks or flexes it will break away. The reason boats are not made of epoxy is the increased cost and the slower hardening time. This is all hard cold fact. If you're going to put your hard time and passion into a wood kayak, use the right stuff. No kit builder or anyone who knows anything will sell you polyester for a wood strip kayak. If you have a mold and want to lay up layers of fiberglass cloth to make a seat, polyester will be perfect but not better than epoxy.
Is
Is polyester any problem with cedar that you know of?
Just be aware
That Epoxies degrade when exposed to UV radiation.
Which is why you last coat is Spar
varnish or paint.
Exactly.
Epoxy is better, polyester is less money
Polyester resin does work, and with care you will make a boat that will last a long time. As Jay says epoxy is a better adhesive than polyester. This means that it bonds to the wood better.
Polyester is also permeable to water. This means that if you leave water in the boat, it will soak through the polyester into the wood. This can happen with thin coat of epoxy as well, but is less likely.
All things being equal epoxy will generally hold up better on average than polyester. While epoxy is significantly more expensive than polyester, given the amount of time and effort you put into making the boat, going cheap on the resin may not be worth it. However, if you are on a tight budget polyester may be a cost effective money saver.
Shelf Life?
I have had some epoxy sitting around for about 2 years. Is it still usable?
LF
yes
– Last Updated: Oct-13-09 11:41 AM EST –
but if the resin was stored in cold temps it might have crystalized and need to be reheated to melt them.
Cedar could be oily
If I was doing it today instead of 1978 I would use Epoxy.
After I ripped off the uncured outer layer of glass I had to wash the boat in acetone to remove the sticky uncured resin. In some places the resin cured and bonded to the wood and some of that pulled off with the cloth. After a lot of cleaning, re-sanding and some plastic wood filler, I washed the boat with acetone to wash off the surface oils (or drive them deeper into the wood) and then painted the redwood hull with a very light coat of resin thinned with acetone. That did cure, so then I sanded the hardened surface and laid out a new layer of cloth. Everything went well the second time and the boat is still doing fine today.
There are a lot more readily available resin choices today. I would use epoxy. Choosing which product would be the challenge!
Best,
~wetzool
It’s Cheaper
The woods I was using were spruce and fir, all dry.
There are some woods that don’t like and delaminate Plyester and Epoxy.
Cedar may be worth looking into I may be WAY off base with other woods.
Epoxy is a better product.
For the amount of time it takes to
build a stripper the last thing you want to do is get cheap with resin.
You got that right!
“Old” Epoxy
I recently built a kayak with 7 year old epoxy and had no issues at all. It was never opened and stored in a heated space.
Why would you spend the time…
… effort and cost to construct a cedar strip boat, then cheap out on the resin used to glass it? Do you really want to put 200 hours (or more) and a few hundred dollars into building a boat, then risk ruining it with a cheapo glassing job?
Polyester resin is laminating resin that’s meant to be used to create composites with fiberglass and other reinforcing materials. It IS NOT an adhesive for bonding wood or bonding materials to wood. Epoxy, on the other hand, works as both an adhesive AND a laminating resin. It is much stronger and creates a much stronger bond with wood. It’s really the only decent product for constructing wood/glass boats.
If you try to skimp and save a few buck with polyester resin, you may regret it. Epoxy is a safe bet.
darkened hardener is no problem
After a few years West hardener will darken to a molasses color. I called them once to see if that’s a problem, and they said it’s normal and doesn’t affect the performance at all.