polyester resin vs epoxy resin

polyester resin vs epoxy resin

Post by Robert L. Whit » Wed, 12 Feb 1997 04:00:00


I need to make a small repair to my fiberglass boat.
However, I am confused about something.

It is my understanding that a majority of boats made in the
last ten years use polyester resin.  Is this true?

If it is true why is it recommended to use epoxy for repairs?

Also I though that there are problems using epoxy resin on
polyester resin or is that the other way around?  i.e.
the two dont mix?

I have found may fiberglass repair products.
The majority of them are polyester i.e. fiberglass bondo,
gelcoat repair kits, putty's, etc etc.

What should I use?

I have a gouge in the hull that is all the way through the gelcoat
and maybe into one layer of glass.  It would seem the easiest
to use one of those putty type repair kits and just fill in the
gouge, but I want to do it right.  

Also I am worried about this compatability problem and here is why.
I am going to have my bottom painted for the first time.  
The hull will be primed with an epoxy primer before the
antifouling paint is put on.  If I use a polyester putty, will
there be a curing problem with the epoxy primer?

Thanks,
Bob

--
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I'd rather be........
        Sailing...... Skiing......... or computing......



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polyester resin vs epoxy resin

Post by William W. Den » Wed, 12 Feb 1997 04:00:00


Quote:
>I need to make a small repair to my fiberglass boat.
>However, I am confused about something.
>It is my understanding that a majority of boats made in the
>last ten years use polyester resin.  Is this true?
>If it is true why is it recommended to use epoxy for repairs?
>Also I though that there are problems using epoxy resin on
>polyester resin or is that the other way around?  i.e.
>the two dont mix?
>I have found may fiberglass repair products.
>The majority of them are polyester i.e. fiberglass bondo,
>gelcoat repair kits, putty's, etc etc.
>What should I use?
>I have a gouge in the hull that is all the way through the gelcoat
>and maybe into one layer of glass.  It would seem the easiest
>to use one of those putty type repair kits and just fill in the
>gouge, but I want to do it right.  
>Also I am worried about this compatability problem and here is why.
>I am going to have my bottom painted for the first time.  
>The hull will be primed with an epoxy primer before the
>antifouling paint is put on.  If I use a polyester putty, will
>there be a curing problem with the epoxy primer?
>Thanks,
>Bob

You should have no problem bonding epoxy to polyester.  Polyester to
fiberglass is not as good.  Contact Gougeon Brothers, Inc. (WEST
system) phone 517-684-7286.  They have excellent literature on all
types of boat repairs and new construction.  I've used them for 20
years.  Look up the Web page.

Bill Denes in Atlanta

- Show quoted text -

Quote:
>--
>____________________________________________________________________________
>I'd rather be........
>    Sailing...... Skiing......... or computing......


>____________________________________________________________________________


 
 
 

polyester resin vs epoxy resin

Post by robert haspe » Thu, 13 Feb 1997 04:00:00

why not read the information from the epoxy makers.......they will tell you
what you need to know. Also the paint manufacturers have technical support
to answer your questions. I am amazed at these sorts of questions......well
maybe not amazed....concidering some of the conversations I hear around
boat yards.

Quote:
> --

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polyester resin vs epoxy resin

Post by Paul and Cindy Kru » Sun, 16 Feb 1997 04:00:00


Quote:
>I need to make a small repair to my fiberglass boat.
>However, I am confused about something.
>It is my understanding that a majority of boats made in the
>last ten years use polyester resin.  Is this true?

You may safely assume that all production fiberglass boats ever made
are polyester.  If someone knows of an exception, then I'm sure that
he will post a correction.  If such an exception exists, then it would
be a very rare boat.

Quote:
>If it is true why is it recommended to use epoxy for repairs?

It is stronger, and it sticks better to old resin, regardless if the
old stuff is epoxy or polyester.

Quote:
>Also I though that there are problems using epoxy resin on
>polyester resin or is that the other way around?  i.e.
>the two dont mix?

No, it is the other way around.

Quote:
>I have found may fiberglass repair products.
>The majority of them are polyester i.e. fiberglass bondo,
>gelcoat repair kits, putty's, etc etc.

That is because it is cheaper.  If you are careful to prepare your
surfaces properly, then you have a good chance that the polyester will
stick for some time, maybe even a long time.  If you use epoxy, and
prepare your surfaces properly, then you can count on it to be a
permenant bond.

Quote:
>What should I use?

Whichever you want.  It depends upon what your objectives are.  If you
are going to keep this boat for a long time, and if you want to be
sure that your repair is the best it can be, then pay the extra money
for epoxy.  Otherwise, buy polyester at a third the cost.  (Which is
the only reason that polyester is more popular than expoxy.)

Quote:
>I have a gouge in the hull that is all the way through the gelcoat
>and maybe into one layer of glass.  It would seem the easiest
>to use one of those putty type repair kits and just fill in the
>gouge, but I want to do it right.  

I have an instruction sheet on my hard drive for repairing blisters.
This procedure would be very similar, and would use the same
materials.  Let me know if you want me to find it and send it to you.

Quote:
>Also I am worried about this compatability problem and here is why.
>I am going to have my bottom painted for the first time.  
>The hull will be primed with an epoxy primer before the
>antifouling paint is put on.  If I use a polyester putty, will
>there be a curing problem with the epoxy primer?

No.


 
 
 

polyester resin vs epoxy resin

Post by John F » Mon, 17 Feb 1997 04:00:00

Paul and Cindy,

Quote:
>You may safely assume that all production fiberglass boats ever made
>are polyester.  If someone knows of an exception, then I'm sure that
>he will post a correction.  If such an exception exists, then it would
>be a very rare boat.

When you assume..... <grin>
Exceptions that I know of:

Boats in the UK by Ovington,
In New Zealand by Cookson and McDell
In the US by Carroll Marine,  Mark Lindsey, Gold Coast, Holby Marine,
and a few by TPI.

While most of the boats are intended for racing, there is a lot more
interest in better performance for cruising boats as well. I think
that you will see a lot more epoxy in production boats.

I agree with everything else that you said.

John

John Fox
FCS Designs

 
 
 

polyester resin vs epoxy resin

Post by Terry Sche » Thu, 20 Feb 1997 04:00:00


<snip>

Quote:
>You may safely assume that all production fiberglass boats ever made
>are polyester.  If someone knows of an exception, then I'm sure that
>he will post a correction.  If such an exception exists, then it would
>be a very rare boat.

I think you will find a lot of boats that use some non-poly resins now.
Particularly for increased blister resistance in the outer-layers and
increased adhesion for the attachment of bulkheads to hull.

Both Epoxies and Vinylesters are in common usage since the early-90's.
Although they rarely make up the bulk of the hull.

Sincerely,
Terry "at-least-that-is-what-the-builder-claims" Schell