Epoxy with pigment instead of gelcoat

[Cheechako]

Originally Posted by sailortype

slight thread drift but a fellow passing through our marina coated his hatchboards with epoxy as a sealer and then several coats of Helmsman's Varnish... he had just spent five years in Florida and they still looked great. I was thinking od following suit... any experience with this?

It's been done many times. The big issue is keeping it coated with exterior varnish to protect from UV. If you screw up once for too long you are going to have an unimaginable mess.

It begs the question: If you MUST have varnish on it 100% of the time, why epoxy it?

[jmschmidt]

To my knowledge Epoxy (in all its forms, pigmented or not) has little or no UV protection. It needs a paint or gelcoat topcoat to provide this.

I use two coats of epoxy resin thinned as a sanding base for teak but always topcoat it with at least four coats of clear LPU or good spar varnish.

[s/v Jedi]

A filler or pigment that makes epoxy opaque is a good UV blocker, but the outer layer still oxydizes because epoxy is exposed to UV there. Using the UV resisting hardener with West System helps as well, but a top coat is the real solution.

For a clear finish it is much more difficult. Based on my experiences, I would now opt to first sand the wood until it is 100% bare wood, then use a penetrating epoxy (I use Totalboat Penetrating Epoxy and reduce it 40% with denatured alcohol), then wash it with water (eliminates amine blush) and sand it back down to wood fiber again (it has become a very hard surface but you want to get rid of any epoxy floating on top of the wood).
Now on top of this I would use Epifanes gloss varnish. When you prefer non-gloss then still use gloss until the final coat or two (gloss is much more durable).

[sailortype]

for a 'complete seal'. Anywhere that the slightest bit of water gets in, it starts to grey and you have to start over.

Grab rails are the worst... sealing the bottoms where the bolts protrude through the deck is nigh on impossible.

[GordMay]

Originally Posted by jmschmidt

To my knowledge Epoxy (in all its forms, pigmented or not) has little or no UV protection. It needs a paint or gelcoat topcoat to provide this...

INDEED!

Excerpted from pages 37 & 38 of the West System User Manual & Product Guide
➥ https://www.westsystem.com/wp-conten...anual-2016.pdf

“... Final Surface Preparation
Proper finishing techniques will not only add beauty to your efforts, but will also protect your work from ultraviolet light, which will break down epoxy over time. The most common methods of finishing are painting or varnishing. These coating systems protect the epoxy from ultraviolet light and require proper preparation of the surface before application ...
... Finish Coatings
Coating Function
A finish coating—paint or varnish—over an epoxy barrier coat protects the epoxy from sunlight as well as decorating the surface. In doing so, the finish coating extends the life of the epoxy moisture barrier, which in turn, provides a stable base that extends the life of the finish coating. Together, the two form a protective system far more durable than either coating by itself.
Protection from sunlight is a primary consideration in the selection of a finish coating. Long term UV protection of the barrier coat depends on how well the finish coating itself resists UV and keeps its pigments, or its shield of UV filters on the surface of the epoxy barrier coat. A high gloss finish reflects a higher proportion of the light hitting the surface than a dull surface. All other things being equal, a white (especially a glossy white) coating will last the longest ..”

As I said before, "West System additives & pigments do NOT provide UV resistance, they "improve epoxy’s abrasion resistance or moisture resistance".

[zstine]

you should never gelcoat over epoxy, they are not compatible. you paint epoxy

sorry if someone said that before, I didn't read all replies..

[GordMay]

Originally Posted by zstine

you should never gelcoat over epoxy, they are not compatible. you paint epoxy ...

Applying Polyester Gelcoat over Epoxy
“There are some myths out there as to whether you can apply gelcoat over epoxy. ...”
➥ https://www.epoxyworks.com/index.php...at-over-epoxy/

[LakeSuperior]

They do make 2 part epoxy coatings which are commercially available. I would imagine that these coatings are the clear epoxy resins with pigment added.

[zstine]

Originally Posted by GordMay

Applying Polyester Gelcoat over Epoxy
“There are some myths out there as to whether you can apply gelcoat over epoxy. ...”
➥ https://www.epoxyworks.com/index.php...at-over-epoxy/

I'm familiar with the show and his non scientific tests... no temp testing. no moisture testing. no age testing... will it work sometimes? sure. Will it last for a decade in the tropics? not so sure. in general, putting polyester resins over epoxy is a no no. if you have a small patch on your hull and want to match a gellcoat finish, fine use gellcoat. if you just built a hard dodger out of epoxy (expensive) it would be foolish to coat it with gellcoat and risk it cracking or peeling in a few years... IMO.

[sailortype]

totally agree. Lots of hocus pocus... but why take the chance on a horrible mess if it fails

[GordMay]

OK, you guys win. No polyester over epoxy.


From another manufacturer, System Three Resins:
“Can I put polyester gelcoat over cured epoxy?
In general, polyester resins won't cure properly or bond well to epoxy resin products without a "tie-coat" barrier resin in between. System Three SB-112 resin system can be used as a tie coat in between epoxy laminating or coating resins, and polyester laminating or gelcoat resins. Using this resin allows you to gelcoat an epoxy-built or epoxy-repaired boat.”
➥ https://www.systemthree.com/pages/faqs
SB-112 ➥ https://www.systemthree.com/collecti...urfboard-epoxy

FWIW: We’ve discussed this before (lots of opinions):

See especially, minaret’s expert advice ➥ https://www.cruisersforum.com/forums...xy-123711.html

I even started one ➥ https://www.cruisersforum.com/forums...poxy-5794.html

➥ https://www.cruisersforum.com/forums...oxy-34619.html

➥ https://www.cruisersforum.com/forums...on-186341.html

➥ https://www.cruisersforum.com/forums...rs-161137.html

[markcoulter]

Originally Posted by zstine

you should never gelcoat over epoxy, they are not compatible. you paint epoxy

sorry if someone said that before, I didn't read all replies..

https://www.systemthree.com/products/sb-112-surfboard-epoxy
System Three makes a blush-free UV resistant resin system that's designed to be compatible with polyester resins, including gel-coat, if coated soon after it's cured. For brightwork, they recommend a few coats of epoxy followed by a couple of coats of their water-based LPU paint.
I've used both West System and System Three epoxies, and I prefer System Three for the following reasons:
The 2-1 mix ratio makes small amounts easier to measure
If you re-coat within 72 hours, you don't have to sand between coats. With West System, you only get a mechanical rather than chemical bond between layers, hence the need to sand between coats. this results in more work, lots of dust you shouldn't breath, and a waste of epoxy. With System Three, as soon as it's tack-free, you can put on another coat without sanding as it bonds to itself chemically.

[Thumbs Up]

Years ago there was some good threads with expert advice on here but don't know if they can be accessed anymore. A member named Minaret was the expert. There is no hard and fast rules for recoat times because cure rate depends on temperature. Markcoulter, Looks like you bought Hotsauce. We looked at that boat around ten years ago! Minaret said that you can gelcoat over Awlgrip 545 primer.

[markcoulter]

Originally Posted by Thumbs Up

Years ago there was some good threads with expert advice on here but don't know if they can be accessed anymore. A member named Minaret was the expert. There is no hard and fast rules for recoat times because cure rate depends on temperature. Markcoulter, Looks like you bought Hotsauce. We looked at that boat around ten years ago! Minaret said that you can gelcoat over Awlgrip 545 primer.

Actually, there were two Banks 44 trimarans built. I own the other one, originally launched in Esquimalt BC as RAJ I in 1986. I found her on Lummi Island, WA registered in Tempe Arizona as Desert Wind. She’s now back in Canadian registry as Albatross I. The hulls are from the same moulds, though modified with sponsons above the waterline in the center section of the main hull for added seating space in the salon. The rear beam is mounted aft of the cockpit, allowing easier access to the cabin. The amas are mounted lower, so both are always touching the surface, eliminating flopping back and forth. Trevor Banks, the designer told me that when he and his wife lived aboard Hot Sauce, they stuffed a block of styrofoam under one AMA when anchored to stop that. I further modified the boat by raising the salon roof a foot to gain standing headroom.(I’m 6’6”) The added windows give much better light and all-round visibility in the cabin.

[GordMay]

Originally Posted by Thumbs Up

Years ago there was some good threads with expert advice on here but don't know if they can be accessed anymore. A member named Minaret was the expert...

Well, we agree on something.

Originally Posted by GordMay

...
FWIW: We’ve discussed this before (lots of opinions):

See especially, minaret’s expert advice ➥ https://www.cruisersforum.com/forums...xy-123711.html

I even started one ➥ https://www.cruisersforum.com/forums...poxy-5794.html

➥ https://www.cruisersforum.com/forums...oxy-34619.html

➥ https://www.cruisersforum.com/forums...on-186341.html

➥ https://www.cruisersforum.com/forums...rs-161137.html