Please, please use epoxy!!
Please don't try to save a few bucks using polyester resin for boat repairs. You will very likely be sorry later! This is penny wise and pound foolish.
Polyester may be fine for new construction, but for repairs to existing construction you need the "secondary bonding" capability of epoxy. Like Ebb said, epoxy is an adhesive resin, while polyester is not.
Polyester works well only with primary bonds--that is, the chemical bond that forms when layers are added within the "green" working time. Once this brief window of opportunity has passed, the bonds will not be particularly strong. The same goes (especially) for bonding wooden pieces with polyester--wood and polyester do NOT like to stick together for any length of time.
No one ever said boat repairs were cheap. You still have to use the right product for the job. For most boat repairs, the right resin is epoxy. It doesn't have to be West System--many of the other epoxies are also excellent. Each system has its own unique qualities, strengths and weaknesses, however, and each is slightly different to work with. West System is an excellent epoxy, but my no means the only one out there. Amine blush is, to my way of thinking, an extremely minor thing to worry about--it's very simple to scrub with water and Scotchbrite pad, and once it's a habit you don't even think twice about it.
Unless you are laminating on green resin of any kind, you are getting only a secondary bond. Once the green stage is passed, you need to choose the product that will give you the strongest mechanical, or secondary (adhesive) bond.
Don't mess with this. There is a difference between poly and epoxy, and it's a very important one for this application.
Personally, I didn't like MAS epoxies when I tried them--I had trouble with incomplete curing, among other things. I have never experienced a single problem with West System--it always works exactly as intended. Also try System 3 or Raka. Buying the small cannisters of West System filler products will break your budget in a hurry--you can buy any filler in bulk from Raka or System 3. They are the same thing, and also work with polyester (not that you should be using poly!)
Tim
Danger! Danger! Danger! Will Robinson!
While working on my dingy Sunday, I came upon a particularly difficult substance to remove. I was coating a piece of ply in epoxy and mounting it to the transom for the motor, and there was a 'goo' that acetone would not remove.
I went to MEK, that I found in a rusty can in the flam locker, and it worked.
I remember years ago, that I had decided MEK was a substance I would no longer use, (something about being absorbed through the skin and there being no means for the body to excrete it) so I went online this morning to refresh my memory.
Came upon an unrelated piece of information about MEKP
Methyl Ethyl Ketone Peroxide that is used to cure polyester.
Apparently, if it is exposed to acetone, the results can be drastic. Kinda scary considering the two chemicals are regularly used, and stored together.
:eek: :eek: :eek:
Note to self. Don't store poly catalyst and acetone together.
Here is where I found this, fwiw
Link to discussion of hazzards of MEKP
Any thoughts Ebb?....