Polyester VS Epoxy

[mogfisher]

Hello. I'm getting ready to do the floor and transom of my 89 Bass Tracker. I spent some time on the phone with the engineer from the composites place that we get our resin from and he said that I should use polyester. He said that although epoxy is better, there may be adhesion problems with the original hull if it was built with poly, which it most likely was. He said that if the boat is poly, that I should return it to the way it was with poly. He recommended many layers of 1.5 oz matt and perhaps some woven too. Does it sound like good advice? I see a lot of folks using epoxy resin on here and just wanted to see what you folks think of his advice. Thanks!

Adam

 

[ezmobee]

Re: Polyester VS Epoxy

Epoxy sticks to poly, poly sticks to poly, poly doesn't stick well to epoxy. I think you'd be ok with whatever you care to use.

 

[drewpster]

Re: Polyester VS Epoxy

I remember reading a comparison of polyester and epoxy resins in one of my fiberglassing books. (which one?) The jist of it was that epoxy has a much higher bond strength on any compatible surface than polyester. And epoxy will not fracture like polyester does over time. Thats why you can build stronger and lighter using epoxy using less cloth or mat. Some folks swear by it, and that is just fine because epoxy has many qualities that are better for restoration work. (especially for novices like me)
The down side to using epoxy is cost.
In my opinion epoxy is overkill in major restoration work. The benefits of using epoxy do not outweigh the cost of the product. Epoxy is generally double the cost of polyester. It is true that you can offset some of the extra cost by bulding lighter. But a novice (like me) has to ask how light? I am no engineer so a tend to overbuild everything. Epoxy would just cost too much.
Boat repairs have been made using polyester resin for years with no ill effects. As with any resin, preparing the part you are fixing is key to doing a good repair. In fact most of the examples of major repairs I have researched have been done using polyester resin up to and including full recores and restorations of fiberglass boats. So in my opinion polyester is the best base resin to use. I do however use epoxy resins and products, (fillers and such) for fairing and finishing work on surfaces that are going to be painted. I also like to use epoxy for non-structural gluing where bonding is the most important thing. Each one has its place but you could do a complete restoration using only polyester resin and do a good job.

 

[erikgreen]

Re: Polyester VS Epoxy

Hello. I'm getting ready to do the floor and transom of my 89 Bass Tracker. I spent some time on the phone with the engineer from the composites place that we get our resin from and he said that I should use polyester. He said that although epoxy is better, there may be adhesion problems with the original hull if it was built with poly, which it most likely was. He said that if the boat is poly, that I should return it to the way it was with poly. He recommended many layers of 1.5 oz matt and perhaps some woven too. Does it sound like good advice? I see a lot of folks using epoxy resin on here and just wanted to see what you folks think of his advice. Thanks!

Adam

It sounds like you should find a new "engineer" and potentially a new composites place.

He's got that almost exactly backwards... epoxy will stick to almost anything, and do so far better than poly will. Poly will stick to poly adequately if prepped right, but epoxy is still a stronger bond for repair and refit work.

Since your original boat is likely poly (almost all are) then you can go with either one. Poly is substantially cheaper than epoxy, or you can split the difference with vinylester resin.

"returning the boat back the way it was" is a ridiculous idea.. unless you take care to tell people, no one will know what resin you used, and if he's implying that the boat will be safer or more valuable if rebuilt with poly so it's an "all poly boat" or something, then he's just flat wrong.

Either he's clueless about the stuff he's supposed to know forward and backward, or else he's one of those old guys who's "used poly for XX years" and doesn't trust this new fangled epoxy stuff since "poly was good enough to make the boat with, it's good enough to repair it with".

Anyway, ranting aside, use what you want, because unless you've already done repairs with epoxy the poly will do fine. If you want the strongest repair and don't care about the extra $$, epoxy is the way to go.

Erik

 

[oops!]

Re: Polyester VS Epoxy

im betting 10 more posts before this one hits the toilet !

the best advise is to read these forums.....read ...read......read...

the lay up schedule the guy suggested was way off ....(dont know what a layup schedule is???......you need to read more here )

take lots of pictures of your boat and we can assist you with the type of the repairs to do !....you are among friends here,


B.T.W.,,,,,,,EPOXY IS FOR PEOPLE THAT HAVE NEVER USED POLY BEFORE !
.....

 

[oops!]

Re: Polyester VS Epoxy

tee hee.,,,,EZ's gonna kill me over that one......have fun everyone,,,,lol

 

[jonesg]

Re: Polyester VS Epoxy

tee hee.,,,,EZ's gonna kill me over that one......have fun everyone,,,,lol

Anyone who had a quart of overmixed poly start bubbling and spitting in the mixin can knows what you mean.
Epoxy is forgiving, but for the experienced poly is pleasantly fast.

Look at some aftermkt auto moldings such as fiberglass fenders and hoods, they are made with just poly resin and matting but they don't bear any loads, they just kinda sit there.

Critcal load bearing glass work on a boat needs woven cloth for best result, a layer of mat first makes it easier to match up non perfect surfaces such as wood, then follow up with cloth, weight matched to requirement. I do most of my glassing with 2 oz mat followed with 10 oz cloth.
Gunnel molding and center console moldings are fine with mat but stringers and transoms need more strength.

As for strength, I ask myself if I'm fixing a runabout fishing boat or an offshore unlimited racer. But I think the over-riding reasoning behind resin choice is familiarity, if you start learning with poly you will probably stay with it. If someone starts with epoxy they will be surprised by the faster pace of polyester and might not like it. With poly theres no relaxing until the tools are in the acetone can.

If i was going to "scream and fly" I'd use epoxy.
If I was redoing a wooden sailboat I'd use epoxy.

 

[jonesg]

Re: Polyester VS Epoxy

Just remembered a newspaper story in Boston back in the 1980's.
2 guys bought a new 30' fishing boat for commercial lobstering, they hit a wave and the hull split open, the boat quickly sank and one of them died.

It was from a new boat mfger and supposedly almost unsinkable but went down in less than 2 minutes. A small 3 guy boat building operation trying to offer a cheaper alternative to other boats on the mkt.

The CG raised it and on examination the hull split because it was poly with mat, no cloth. It couldn't take an impact.
The boat sank because the foam used was improper , it was not urethane and the fuel dissolved it.
The boat maker closed up shop and slunk off into the night within a week of the accident.

It makes a good case for not using mat by itself.

 

[ondarvr]

Re: Polyester VS Epoxy

Like has already been said, either one works. Neither will fail when used correctly, but shoddy workmanship will create a failure with either one also.

 

[Downwindtracker2]

Re: Polyester VS Epoxy

Polyester is quick curing,a good fiberglasser can do a job in an evening,where as using epoxy it's few days,because of cure time.

 

[sprintst]

Re: Polyester VS Epoxy

I like the time epoxy gives me to work with it. Polyester resin is less forgiving. Just my 2 bits.

 

[mogfisher]

Re: Polyester VS Epoxy

Thanks for all the responses. I did some reading of old posts on this subject and came to the consensus that there is no consensus! I thought the idea of the epoxy not bonding well to the poly sounded strange too so I thought I'd ask. I think I feel more comfortable with poly since i've been using it at work for over 10 years. Though what I do is not as critical as a boat hull. I do custom car audio systems. Plus, at 130 bucks for a 5 gal pail of poly as opposed to 100 per gal of epoxy it just makes sense to me since I also have a whole floor to do. I have a huge roll of woven roving laying around that I've been dying to use for something, plus a ton of 1.5oz mat. Though I wonder if the roving might be too heavy duty. Seems like its heavier than what most of you use. Once I get to that point, if I even decide to do the transom, I'll definetly post some pics with questions. First I need to cut it up and drill some test spots in the transom to see if I even need to go in there. Thanks again, fellas. Appreciate the feedback.

 

[bigredinohio]

Re: Polyester VS Epoxy

Use what you feel comfortable with. I'm personally an epoxy person but there are also health concerns with it that can cause some serious health concerns.

I was told if you are using woven roven to be sure to sandwich it between csm when doing layups.

 

[erikgreen]

Re: Polyester VS Epoxy

I actually use both myself. Epoxy for bonding to existing surfaces, poly for casting and forming new parts.

Erik

 

[tschmidty]

Re: Polyester VS Epoxy

The last reply was right on. Epoxy will bond better to existing surfaces. Poly makes for a plenty strong bond when bonding to itself while curing, ie. building new things.