Polyester vs Epoxy Resin

[Ashley S.]

I have several repairs to make to my 65 (firewall, spine repair, transmission tunnel, etc) and I'm curious about the different types of resins available.

In the past, I have used a polyester resin and so far the results have been ok. I've been reading about the epoxy resins and wanted to get opinions from the board.

Is there a reason I wouldn't want to use the epoxy resin? If I am reading it correctly, it has better performance than the polyester resins. What would be the down side of using epoxy?

This a link where I was looking at it.

http://www.shopmaninc.com/epoxy.html

Any comments would be appreciated.

Thanks,

Ashley

[Michael M.]

Re: Polyester vs Epoxy Resin

I am in the marine industry and sell both epoxies and poly resins. The cars were made of polyester so I guess it is natural to use the polyester on them. General rule of thumb. Epoxies will stick to polyesters but polyesters don`t stick to epoxies very well. Everything on my car has been done in epoxy but most won`t agree with this I don`t think. Known fact is that the strength of the epoxy is much greater and it is more flexable than the poly. If the epoxy sets hard it is very hard to sand and it is also harder than the existing polyester and can be a bear not to sand into the polyester trying to get the epoxy blended in. I use no fillers (polyester, bondo etc) other than an epoxy fairing or filling compound. It can be a pain to work with. Costs are about 3 times greater with the epoxy. I would recommend using West System or System Three epoxy if you decide to go that way. All the Custom boats I deal with are built with epoxy so I had a lot more experence with that than I do with the polyesters. I have seen people do great things with the polyesters but I am not that good. Usually you have a 24 hour wait on the epoxy curing to sand while the polyesters are much faster. I am sure others will chime in with their views . Good Luck, Mike

[Richard M.]

Re: Polyester vs Epoxy Resin

Ashley,

Mike has some great info. I also restored some wooden boats and can attest to the West Epoxy product. Example here.

I myself have some basic knowledge and have some good friends in the marine industry who helped me choose resins etc with this '59 project.

If you choose polyester resin, I would recommend the vinyl-ester product. I used it to splice the front end and do some major repairs and panel splicing on the '59. The left rear quarter had pounds of bondo with sheetmetal backing plates and screws. I dug it all out and used layers of heavy mat and resin to rebuild and strengthen. It's a very strong resin. From your link, see the #700 product description. http://www.shopmaninc.com/polyesters.html

I then used the polyester Duratec surfacing primer on the entire body, blocked sanded out to 180 grit, then off to the paint shop for final sealer, epoxy prime, block and paint. Just got it back last week. Before & after pics below.

Rich

[Joe R.]

Re: Polyester vs Epoxy Resin

Really impressive work on that C-1. Beautiful results. Thanks for the mini seminar!

JR

[Domenic T.]

Re: Polyester vs Epoxy Resin

I have a very close friend that worked in the lab at a resin manufacturer.

They were in CA till the regulations went nuts. He said basically what Michael said about the strength of each and which one is better over the other.

What I use on small cracks that can't be reached from the back side to strengthen is a epoxy that has kept the cracks from coming back for over 40 years.

It is JB weld, Yes, it sounds like buba work but it is a very strong epoxy and it has held up for over 40 years.

Look at the millions of lane devider bumps glued to the road with epoxy. I have never seen one come off. Polyester resin would not last on a road like the epoxy does.

I told my friend who specialized in vette repair since the 50's about JB weld and he was amazed at how good it holds up. He said he wished he would have found out about how good it worked when he took over his body shop in IL back in the 60's.

DOM

[Roger W.]

Re: Polyester vs Epoxy Resin

Nice Work. Did you design the body dolly yourself or are there plans avaiable some place?

[Richard M.]

Re: Polyester vs Epoxy Resin

Nice Work. Did you design the body dolly yourself or are there plans avaiable some place?

Thanks..........

Actually, I bought from someone after he had his 62 on it for many years while restoring. He built it from scratch. I have no build plans, sorry.

Rich

[Joe R.]

Re: Polyester vs Epoxy Resin

Nice Work. Did you design the body dolly yourself or are there plans avaiable some place?

Roger,

There is an article in "The Corvette Restorer" Vol 38 Number 2 Fall 2011 about building a C-2 Dolly. It could be very easily converted to a C-1 with just a few modifications to the dimensions.

I'm in the process of building that Dolly now for a 63 project. The points or height of #1, #3 are the same but #2 is different on a 63 because of a stamped portion in the side rail.

JR

[Dick W.]

Re: Polyester vs Epoxy Resin

Roger,

There is an article in "The Corvette Restorer" Vol 38 Number 2 Fall 2011 about building a C-2 Dolly. It could be very easily converted to a C-1 with just a few modifications to the dimensions.

I'm in the process of building that Dolly now for a 63 project.

JR

Oh No! Johnny Cash is alive and well...... One piece at a time

[Roger W.]

Re: Polyester vs Epoxy Resin

Thanks for the info. Iwill take a look at it.

[Tom B.]

Re: Polyester vs Epoxy Resin

There is some great information here. Thanks for the links. I haven't done any glassing in many years but the '59 is calling me to get it finished. Frankly, I have been confused with all of the products available today. It used to be that you just went to the marina and got what they had. This info will help me choose what to buy.

Tom

[Ashley S.]

Re: Polyester vs Epoxy Resin

Thanks to all who replied. I'm still on the fence on which way to go, but I have a lot more info to make my decision with.