How to tell polyester from epoxy?

Is there a way to differentiate a polyester resin built hull from an epoxy resin built hull? I have the transom removed from my hull, and am getting the list of materials together before I start anything else, and after reading a couple of other threads here that talked a little bit about poly vs epoxy and how they won't bond to each other. My boat is a 1967 Larson All American and the fiberglass that's in there now has a green tint to it if that helps.

Thanks,
Terry

 

Tja

The boat is polyester. Keep it simple. Put it back the same way it was made when new.

 

wide Lapels, and shiny spots on the back

 

Well that really bites...

Are you 100% sure it polyester resin? Does the green tint give that away? I have read that vinyl ester is a pain to work with far more than epoxy, and this really throws a monkey wrench square in the middle of everything.

 

The green tint, more so the age. Why the monkey wrench? New polyester sticks to old polyester, new epoxy sticks to old polyester. New polyester won't stick to old OR new epoxy. Sam

 

Well, I guess it really doesn't mess me up other messing my budget up. I've been reading about epoxy resin, how it works, etc and have learned nothing about polyester. I am also under the impression that polyester is weaker than epoxy and that concerns me. I'm basically glassing in an entirely new transom, tabbing the transom in place and allowing the outer skin to flap over onto the existing hull. The motor weighs in at 280 (90HP Evinrude, '82), but I plan on putting a Yamaha 2 stroke 90 on at some point next year. I'm just concerned about the structural integrity of polyester vs epoxy. How much more difficult is it to work with than epoxy? I've also heard that new epoxy will stick to old poly, but only for a short while and that eventually it will delaminate. Eventually being much sooner than an epoxy/epoxy bond or poly/poly bond.

 

The year of the boat pretty much insures it's poly. Even today there are very few epoxy boats.

Polyester is about the same, some say easier, others harder to work with then epoxy. I find they both are about the same, requiring similar rules, precautions and procedures for good results.

Yes, epoxy is stronger then both types of poly. In you boats situation it doesn't matter how much stronger epoxy is. The layup on your hull is over done, excessively strong and more then enough to hold up the outboard, if the repair matches or exceeds the original layup.

I'm assuming your replacing the plywood transom core and addressing any other structural needs? You can see the thickness of the laminate, so matching this shouldn't pose a problem. Insure you have a good laminate, squeegee out excess resin (epoxy or poly, your choice), no floating cloth, air bubbles, puckers, etc. and you'll get her done.

 

I am indeed replacing the plywood core, as well as the rest of the wood that was used in the boat because it was all rotten. The stringers were so waterlogged they felt about 10 times heavier than a comparable piece of dry wood would. The plywood transom core apparently had gas in it as well as water because once I removed the glass that was on it you could smell the gas almost like you were at a pump. I have no glass at the back of the boat where the transom should be now, so I'm really doing the entire transom, laminate and all, and that will have to tie in to the existing structure. I think I can do it, and I'm reading as much as I can and will be playing with the glass/resin before hand to build some test items to get used to it's properties, but I'm still a little nervous. Being in the Chesapeake Bay with a sinking boat is not my idea of fun.

 

Tja

Well from the sounds of it you cut off the back of the transom instead of removing the deck and then removing the old wood from the inside which is the right way to do it. No offence but if your going to ask for advise you should ask before you do anything to the boat and then you won't screw it all up. vynalester resins aren't any harder to work with then polyester. Polyester is cheaper and easier to work with then epoxy. You may also want to check the stringers as I have never seen that model and year that didn't have bad stringers and white foam under the floor that weighed about two or three hundred pounds being full of water. I've restringered more then six boats just like yours. Under the floor you will find two boxes that are about eight to ten inches wide running the length of the boat forming the stringers. I

 

Tja

To finish if the floor sounds sold then take a plastic hammer to the bottom. If it sounds solid thats good. If it sounds dead or like a thud thats bad. Sorry if my coments are a little derect. The guys out there that do this for a living understand why. There's no problem with you tackling this job just always have a good plan before you steat. Good luck.

 

You can reuse the removed 'glass sections of transom (a good idea that saves a bunch of materials and fairing effort) They just need to be prepped properly, ground well back with generous feathered tapers, so they can receive plenty of tabbing to key them back on.

There are several threads on this and related subjects on this site. Use the search thingie in the upper right of the BoatDesign masthead to find more tips and info . . .