Polyester V' Resin V' Gelcoat. Can I use together ?

[Andy12]

I bought Boat Cote resin from the shop that knew I wanted to use a gelcoat finish. When I went back to buy the gelcoat after spending weeks patching with resin, another salesman tells me they are incomparable and I can't gel coat now.

Is there a good solution for me ?

[GordMay]

Bote-Cote is an Australian marine epoxy resin, specially formulated to match the physical properties of timber [wood].
➥ https://boatcraft.com.au/information...tecote-tds.htm
➥ https://boatcraft.com.au/information...structions.htm

Contact BoatCraft Pacific:
➥ https://boatcraft.com.au/information...contact_us.php

[Tupaia]

Not really. Epoxy does not have good UV resistance so your best option is fairing with epoxy and then paint. Having said that polyester (resin) does not bond well to old existing polyester. If the boat is old (or at least not new) epoxy is a much better repair solution than polyester. There are specialist Epoxy gel-coats that you might like to try or even Vinylester gel coat, that is an epoxy/polyester hybrid and will bond to both epoxy and polyester. Colour matching will be you biggest challenge with these options.

[Andy12]

That is great news.

I was actually in the Boat Cote shop, that's who I was dealing with. The guy I spoke to made it seem like I was screwed and had put down a product based on their recommendation that is not suitable.

I'll go to another shop and see what they can offer, I'll sleep better tonight.... Thanks

[Rucksta]

When the epoxy is faired ready for gel coat, paint on a layer of unwaxed vynal ester resin.

It will bond with the epoxy but wont set up hard unless you exclude oxygen from the surface.
This is good because you can reactivate a tacky surface with an acetone wipe up.
Problematic if you need to sand it as it clogs the paper.
Two or three weeks seems to be the limit for reactivation but a couple of days is better.

Now apply your standard poly ester waxed gel coat which will physically & chemically bond with the vynal ester and dry hard ready for polishing.

This avoids using epoxy based flow coats which are expensive and problematic in application and longevity (UV yellowing) or the limited colour range of hard to find vynal ester gel coats.


P.S. Whilst Bote Cote is formulated for wooden boat construction it does have other uses and advantages. Indefinite shelf life, non blushing, easy mixed in small or large batches, various speed hardeners including a UV stabilised non yellowing hardener and viscosity modifiers claiming low toxicity.

The mixed resin is quite viscous which means wetting out a lamination requires good technique.
For filleting and fairing it produces a stiff wet mix offering superior adhesion and sag resistance

The strength numbers stack up close to high performance high strength resin bases whist maintaining laminate adhesion when repeatedly flexed.

The price is good

I have no affiliation with Boat Craft Pacific other than being satisfied with their products.

[Tupaia]

Originally Posted by Rucksta

When the epoxy is faired ready for gel coat, paint on a layer of unwaxed vynal ester resin.

It will bond with the epoxy but wont set up hard unless you exclude oxygen from the surface.

Good bit of lateral thinking hadn't thought of that. Yes, using a Vinylester as an intermediate bonding layer would work.

[FPNC]

They make vinylester gelcoat.

[Giro]

I would not base my decision on what one SALESMAN tells me!
It’s definitely time for you to enlist the advise of a marine engineer and/or architect.

[Tupaia]

Originally Posted by Giro

I would not base my decision on what one SALESMAN tells me!
It’s definitely time for you to enlist the advise of a marine engineer and/or architect.

Sorry if I sound a bit harsh, but that must be the worst piece of advice ever. Even if you found one and agreed a massive fee, I cannot possibly imagine what "marine engineer and or architect" could advise in these circumstances. The OP is repairing a boat, not difficult, just needs some pointers and perhaps a couple of good books on the subject of which there are many.


The Blue Gee Glass Fibre and Epoxy Wood Book

West System Fiberglass Boat Repair & Maintenance

The fiberglass boat repair manual

Fiberglass repair polyester or epoxy

To mention a few.

[Giro]

Originally Posted by Tupaia

Sorry if I sound a bit harsh, but that must be the worst piece of advice ever. Even if you found one and agreed a massive fee, I cannot possibly imagine what "marine engineer and or architect" could advise in these circumstances. The OP is repairing a boat, not difficult, just needs some pointers and perhaps a couple of good books on the subject of which there are many.


The Blue Gee Glass Fibre and Epoxy Wood Book

West System Fiberglass Boat Repair & Maintenance

The fiberglass boat repair manual

Fiberglass repair polyester or epoxy

To mention a few.

Marinas are full of abominations created by water vessel owners too cheap to invest in sound advise before attempting bad projects.

[boatpoker]

Originally Posted by Giro

Marinas are full of abominations created by water vessel owners too cheap to invest in sound advise before attempting bad projects.

I agree however I've yet to meet a marine engineer or naval architect who were also polymer chemists or had any training in that field.

[Giro]

Originally Posted by boatpoker

I agree however I've yet to meet a marine engineer or naval architect who were also polymer chemists or had any training in that field.

I appreciate your intelligent response to my comment. However, I am fairly confident that either of the professionals I referenced would know of such chemists and would be pleased to direct the inquiry accordingly.

[Jim Cate]

Personally I doubt that many "marine engineers" would have knowledge and experience that would lead to good advice about the foibles of specific products from this relatively small Epoxy supplier.

In the OP's place, interacting with the manufacturer of the product seems like a good place to learn how to use it. If that route does not provide the answer, personal contact with a professional shipwright who actually uses the product in the real world would be my next step. If all else fails, personal experimentation with small lots on test samples would be my last step in the learning process.

I have great respect for both marine engineers and naval architects, but their knowledge tends towards the theoretical rather than the real world of DIY repair efforts.

Jim

[Andy12]

Thanks everyone.

I went down Jim Cates path. I spoke to a couple of professionals in the yard and went to the chandlery at the Boatworks, the guy there was a champion and rang his suppliers technical guy on speaker and he directed me to an epoxy flow coat type product. This was the agreed solution by all.

It is a bit thinner than gel coat but it hardens in a linear manner which gives you a chance to apply it on a sloping surface as it goes off..sort of.

We will see how it went tomorrow 🙂

Thanks again
A great relief.

[Jim Cate]

^^^^
Sounds like CF doin' its thing once again! Hope it works out well for you! (And ain't the Boatworks a great yard?)

Jim