What fibreglass with epoxy resin?

[Hornet Rider]

Hi. I've done some patch repairing to my glass transom top & need to reglass a few areas. To increase the strength & provide a better bonding with existing glass I intend to use epoxy resin instead of poly resin. Can any type of fibreglass matt, chopped strand etc be used with epoxy resin, or is there a particular type that must be used?

Also, after the reglassing, I intend to finish the job by flowcoating the repaired areas. Is there any particular type of flowcoat that must be used over epoxy resin repairs, or cany a poly based flowcoat be used? Any advice please?

cheers, HR

[Grand_Marlin]

Howdy,

You are headed for trouble with using epoxy, and there is no need to change from polyester to epoxy.

The chopped strand mat is what gives the strength, not the resin.

The epoxy will stick to the existing glass, but you will end up with adhesion problems trying to put flowcoat over epoxy.
If you go this way, it would end up being a 2 pac painted repair.

My advice - stick with the polyester resin and make sure you prep your surfaces by grinding / sanding and cleaning thoroughly with acetone.

This is what I do when doing repairs on existing glass and have not had a problem.

Cheers

Pete

[Hornet Rider]

Howdy,

You are headed for trouble with using epoxy, and there is no need to change from polyester to epoxy.

The chopped strand mat is what gives the strength, not the resin.

The epoxy will stick to the existing glass, but you will end up with adhesion problems trying to put flowcoat over epoxy.
If you go this way, it would end up being a 2 pac painted repair.

My advice - stick with the polyester resin and make sure you prep your surfaces by grinding / sanding and cleaning thoroughly with acetone.

This is what I do when doing repairs on existing glass and have not had a problem.

Cheers

Pete

Thanks Pete, will stick with the poly & prep surfaces as you've indicated. Much appreciated.

cheers, HR

[Noelm]

always been a bit confused by all this Polyester, Vinylester, epoxy thing (mind you I have never done a big fibre glass job) all I have ever needed to do was repair some holes and a dozen surfboards so those small kits is about my style, might do a bit of research as I may be about to embark on a large "project"

[oldboot]

There should be no problems what ever using epoxy over polyester.
In fact is it used extensivly to repair ozmosis damage on fibreglass hulls.

there are however some very important things to consider.

firstly the glass mats used are exactly the same stuff, woven mat will always be stronger and give a better finish.

when preparing the repair you must be sure to remove all paint, wax and other residues or you will have problems.

there are adhesion problens with epoxy and it is the same going epoxy over epoxy.

Almost all of the brands of epoxy need to be dewaxed if they are allowed to cure, even if overcoating with epoxy.
When epoxy cures any surplus unreacted product and some byproduct remains on the surface....if this is not scrubbed ( scrubbed ) of with strong detergent or similar it will present significant adhesion problems.

After scrubbing you can then either overcoat with the same epoxy or sand and overcoat with just about anything.....the marine epoxies are almots completely innert and inpervious after cure.

failure to dewax can lead to disasterous adhesion problems.

there is plenty of information about this stuff.
West system have booklet specificlay on epoxy over glass repairs.

check out
woodwork forums.....the wooden boat section...there is extensive discussion there.
michael storers ( marine archetect and boat builder) there are several pages there on epoxy.
west systems web site

Boatcraft pacific at loganholme..( inspite of a recent fire) will be able to help. they manufacture a very nice marine epoxy in australia and have a very reasonably priced book on the subject.....they also supply every thing you may need at competitive prices....decent guys ( no connections)

As I said there is no problem with using epoxy BUT there are a couple of things you must do for good sucess.

For those who may not understand... there are several families of resins that are very much chemicaly different....polyester is the most commin used with glass fibre, mostly because it is cheaper.....it does have some other advantages.
it is also softer than epoxy.

Just because something comes in two parts, that does not mean it is an epoxy.
There are many two part resins and there are single pack epoxies.

the biggest differences between epoxy and polyester are.
epoxy is very much harder
epoxy is totaly impervious where polyester is not
Generaly all of the mixed product reacts into the finished resin with epoxy, where with polyester there is solvent which evaporates.
You should not change the mix ratio with marine epoxy ( accurate measurement required) where with polyester you can change the amount of catalist to manipulate drying time.
epoxy is a true 2 part resin, polyester is a resin and catalist product.
polyester typiclay goes off faster and doesn not have a prolonged green stage unlike epoxy.
Epoxy sticks to wood exceedingly well polyester does not.

Once you get a handle on these modern marine epoxies they are a spactacular product.

cheers

[oldboot]

I will correct myself here.

If you are working on an polyester substrate it is very likely you will be better if with a polyester resin.
fresh polyester resin will chemicaly key into existing cured resin ( at least to some extent), polyester will not chemicaly key into epoxy, so you need to rely on providing a coarse mechanical key.

So if you are intending to repair an all ( polyester ) fibreglass hull and you intend to overcoat with polyester resin flow coat you will almost rertainly be better off with a polyester resin.

If howevert there are other materials such as wood, steel or aluminium involved you need to do your homework and think about epoxy.

cheers

[Noelm]

OK then, so lets say I can get my hands on a good Glass Boat (quite a few years old) and the floor has been cut out to do a home repair but the guy lost interest, it has been left unprotected for a couple of years in the weather (no flowcoat of course) what resin do I use to repair and fit new stringers and so on??? and will the old existing glass be OK??

[Noelm]

hang on a minute, I have just hijacked this thread, sorry about that Hornet!

[oldboot]

The choice of resin is the least of your problems.

you need to consider your whole process.

You are asking a big question.

cheers

[Grand_Marlin]

I will correct myself here.

If you are working on an polyester substrate it is very likely you will be better if with a polyester resin.
fresh polyester resin will chemicaly key into existing cured resin ( at least to some extent), polyester will not chemicaly key into epoxy, so you need to rely on providing a coarse mechanical key.

So if you are intending to repair an all ( polyester ) fibreglass hull and you intend to overcoat with polyester resin flow coat you will almost rertainly be better off with a polyester resin.

If howevert there are other materials such as wood, steel or aluminium involved you need to do your homework and think about epoxy.

cheers


I am pleased you added that OldBoot ... now I don't have to kick you in the nuts ;D

Cheers

Pete

[Noelm]

so Pete, will the old glass still be OK?? still looks sort of sound, but has a few "hairs" sticking up all over the place! as well as the added bonus that it may be twisted from sitting on the trailer for years with no stringers or floor!

[oldboot]

I am pleased you added that OldBoot ... now I don't have to kick you in the nuts ;D

Cheers

Pete

I have to keep reminding myself that we are talking about plastic boats and when people say poly here they mean 'ester not 'eurathane.

so many people in the woden / composite boat area are going away from polyester.....and those guys tend to paint over with polyeurathane which sticks to justabout anything

These modern epoxies are so good it is easy to get carried away

cheers

[jimbo59]

Just give the areas where you intend on laying glass a good grind with 36 grid i use a 4 inch grinder then brush on acetone then you can start to lay up the glass.
Just watch when grinding old glass you wont be sleeping on silk sheets for a few days:'( :'( .

[Grand_Marlin]

G'day Noel,

The old glass should be fine, as long as it isn't highly stressed (as in major cracks / delamination)

Jimbo might know better than me, but I have never seen properly laid glass loose its structural strength.
I have seen it all hairy (a tank) where it never had flowcoat / gelcoat on it and was left out in the weather for years. It was as strong as anything - it just looked terrible.
I have also seen a few fibreglass aerials like this - hairy, strong and looked terrible.
I have also seen a few women like this ;D

The key thing to look for will be distortion in the hull.
Take the spirit level, use it as a straight edge and look for dips.

Cheers

Pete

[Noelm]

I have thought about this for a while now, the Boat in question is an old 18' like I had a long time ago, it used to have a stern drive, that went to god and the floor was soft, so the guy pulled it all to bits, cut the floor out and then lost interest, it has been in his front yard ever since, so I thought of a new floor, a pod and a second hand Motor and it's done, because it had a stern drive, the transom is just straight across, no Motor well, might be able to make a few bucks on the deal (well that's the idea) don't like the thought of ever going back to a mono for my own Boat!!

[Hornet Rider]

hang on a minute, I have just hijacked this thread, sorry about that Hornet!

No probs Noelm, good bit of useful banter. Thanks for the info. I've got enough to go on now between you & GM. For info, I've read the spots off the West data on the web, as well as Epiglass data for a comparrision.

Jimbo, thanks for that, go it. I'll wear something protective. ;D

cheers, HR

[Blackened]

I'll wear something protective. ;D



G'day

Go and get yourself a sperm suit, and make sure it's all closed up

Dave

[Hornet Rider]

G'day

Go and get yourself a sperm suit, and make sure it's all closed up

Dave

Thanks Dave, but are they any good if you've had a vasectomy?::)

[Blackened]

G'day

Best ask your doctor on that one :P

Dave

[Hornet Rider]

G'day

Best ask your doctor on that one :P

Dave

lmao, I might suit up in the bedroom & see what the reaction is......

[Blackened]

lmao, I might suit up in the bedroom & see what the reaction is......
G'day

Hahaha when you do, post up the results... would be good for a laugh

Dave