Epoxy vs vinylester
 

Can anyone tell me the difference in epoxy and the other resins available on the market. I've heard some are better for certain applications. I've always used west system on our wooden race boats but I've never messed with the others that much. I am replacing a transom and some other work on the boat so I'm ready to get Rollin. Any input would be greatly appreciated.

If you're taking on a big project like transom replacement, do yourself a favor and buy this book:

http://www.amazon.com/The-Elements-B.../dp/0070231591

Read the chapters on fiberglass construction before you mix any resin.

Dave

Ditto, saved me a ton of work, $, and worry.

Thanks Dave for the recc.

Info
 

Thanks for the book suggestion Dave. I guess i was asking about compatibility to a seacraft. I was always u wanted to match what the boat was built out of.

Vinylester is sort of epoxy. It has styrene in it, it uses cobalt and peroxide, but also has bisphenol-A epoxy in it. So it has good compatibility, better elongation than polyester, and no amine hardener which causes allergy problems. It isn't the BEST of both worlds, but in my opinion is a nice trade off.

http://www.mertons.com/Epoxy/polyest...inylester.html

Edit: dropped the napthenate- some use cobalt octoate

Resins are like boats. They're all a compromise. Dave Gerr explains it better than I, but some things to consider:

• Secondary bond strength (do it stick to the substrate?)
• Physical properties (tensile strength/elongation, compressive strength, etc)
• Ease of use (learning curve for correct mixing/catalyzing)
• Cure time
• Cost $$

I've used polyester and epoxy, but not vinylester. I buy my resins from US Composites, and their vinylester isn't much cheaper than their epoxy. My rule of thumb is to use epoxy where strength or secondary bond is the primary concern, and polyester for fabricated parts. If I were doing a transom, I'd use epoxy. Some would say it's overkill. They may be right, but to me, it's worth the extra $15/gal for the superior bond strength.

Dave

Im not scared of the extra money... Just want a product that lasts... Best quote ive seen" a bitterness of poor quality remains long after the sweetnesss of a low price is forgotten."

so true

U guys are alright!!

Just one word of caution about epoxy (I agree with Dave and would use it anywhere bond strength, or absolute strength and ductility are important, like on a transom) . . . epoxy hardener has some nasty chemicals in it, and even though it doesn't smell like poly or vinylester, the fumes are MUCH more toxic. It's real important to always use a good respirator and nitrile gloves to keep it off your skin. My neighbor, who is a yacht builder that grew up on Thunderboat Row in Miami in the 60's, has had so much exposure to epoxy that he's become highly allergic and can't get anywhere near it! I think Fish Stretcher has also mentioned that he's become somewhat allergic to it also.

When you open the bottle of "hardener" and it makes smoke from the humidity, then that's real epoxy. I used some under a fume hood at one job. I made prototypes for racing bicycles in pressurized molds.

Looking at name brand vinylesters and name brand consumer boat epoxies, the vinylester(epoxies) have equal or better elongation and tensile strength. It depends on what you buy, but I wonder if consumer versus OEM epoxies are different enough that VE and consumer epoxies are about equal? Some VEs are good for higher temp (engine room), too.

Don't forget to compare exotherm values.

That isn't something I think about lots, honestly.

I am interested to hear what you think about it. I can see tuning the process, and worrying about shrinkage- both of which seem like you can control (or lose control of) more with VE/PE over epoxy.