Gunwales, bench seat tops & bow deck - Epoxy & paint or primer & paint?

[DayTripper]

The 12 foot jon boat that I'm building (using marine plywood) will have:

1. Douglas fir gunwales with the end grain of the 1/4" plywood sides exposed on the top surface.
2. Two bench seat tops made out of 1/2" plywood. The sides of the 1/2" plywood tops will be exposed plywood end grain.
3. Small 2 feet long x 3.5 feet wide (tapered to 3 feet) bow deck made out of 3/8" plywood.

For the flat items above that's exposed to the sun, would you recommend that:

• Epoxy the surfaces and then paint with topside paint -or-
• Primer the surfaces and then paint with topside paint.

The inside of the boat will be primed and then painted with topside paint. The floor will have anti-skid added to the topside paint. (The topside paint will be Rust-Oleum Marine TopSide paint.)

I'm especially wondering about the bench seat plywood tops wear & tear. Would coating with epoxy first then painting be better than no epoxy and just using primer followed by topside paint?

[JimConlin]

There’s an in-between answer, epoxy primer.
I like Jamestown’s TotalBoat epoxy primers and their TotalProtect primer which is a bit heavier and similar to Interlux Interprotect. They all stick as well as epoxy resin, lay down flatter than epoxy resin and are easier to sand flat.

[DayTripper]

There’s an in-between answer, epoxy primer.
I like Jamestown’s TotalBoat epoxy primers and their TotalProtect primer which is a bit heavier and similar to Interlux Interprotect. They all lay down flatter than epoxy resin.

Thanks Jim.

I expect to have excess epoxy and hardener left over after I fiberglass the outside of the hull. (West Systems 105 resin and 206 hardener) So I would like to use that for the topside flat areas. However I've read that epoxy on the topside without cloth can check so I thought I'd get opinions from the experienced folks on this forum before doing it.

The bench seat tops and the bow deck use marine plywood so I'm "guessing" that they might be stable enough to handle the epoxy. The gunwales are 2-3/8" wide x 7/8" thick douglas fir so I'm not sure whether expansion & contraction will check if coated with epoxy. Two coats of epoxy on the gunwales if it works though, would be good for the wear and tear on them.

[jpatrick]

It's not a lot of extra work to add solid wood edging to the ply edges. This treatment will look better, resist impacts better, and be easier to seal with paint.

Jeff

[Todd Bradshaw]

If you epoxy coat those items, Gougeon Brothers wants you to apply two coats if it won't be sanded smooth and three coats if you do plan to sand it smooth after application. This is to build enough thickness to seal the wood properly. Do be aware though, that epoxy resin is not paint and it doesn't go on like paint. Unsanded epoxy is rather lumpy and looks like crap. Leaving it that way is a great way to make your boat and your craftsmanship look really bad. I think I'd prime and paint those surfaces (no epoxy) and just do a little maintenance from time to time.

This top surface is unsanded WEST Epoxy

mandolin 001.jpg

This is the same piece after sanding and varnish

mandolin 003.jpg

[DayTripper]

It's not a lot of extra work to add solid wood edging to the ply edges. This treatment will look better, resist impacts better, and be easier to seal with paint.
Jeff

Agree and I considered doing that on the side edges of the 1/2" ply bench seat tops. But I did not and the 1/2" ply bench seat tops are already permanently installed, so I'll have to go with that flow. Thanks.

[Woxbox]

Marine fir ply in question here? It can check no matter what you do, so give it the two coats of epoxy, then primer, then paint for best insurance

[DayTripper]

If you epoxy coat those items, Gougeon Brothers wants you to apply two coats if it won't be sanded smooth and three coats if you do plan to sand it smooth after application. This is to build enough thickness to seal the wood properly. Do be aware though, that epoxy resin is not paint and it doesn't go on like paint. Unsanded epoxy is rather lumpy and looks like crap. Leaving it that way is a great way to make your boat and your craftsmanship look really bad. I think I'd prime and paint those surfaces (no epoxy) and just do a little maintenance from time to time.

This top surface is unsanded WEST Epoxy

mandolin 001.jpg

This is the same piece after sanding and varnish

mandolin 003.jpg

Thanks for the info and picture examples. Since the Gougeon Brothers are OK with putting epoxy without cloth on topside surfaces, I think I'll put 3 coats of epoxy on the bench seat tops first (most wear and tear), then continue with the gunwales if I have enough left over epoxy, and finally the bow deck if there's enough left over epoxy. Since the bow deck is a larger area with less wear and tear, there may not be enough left over epoxy for 3 coats in which case I'll just primer and paint it.

Thanks for the info. Helps a lot.

[DayTripper]

Marine fir ply in question here? It can check no matter what you do, so give it the two coats of epoxy, then primer, then paint for best insurance

I'll do that along the lines of my response to Todd's post. Three coats of epoxy on the bench seat tops, primer and 3 coats of topside paint. Thanks for your input.

[nedL]

I can’t contribute to the good advice here. However, I can suggest there is no such thing as a “bow deck”. I don’t believe you will find that term in any legitimate printed reference. It is a “foredeck”. (Sorry, just one of those “fingers down the chalkboard” things to me.)

[Garret]

Just to add a bit of probably unnecessary advice:

Make sure the epoxy is well scrubbed with lots of water & a scotchbrite pad to get rid of blush. Water, not solvent.

Also make sure there is no epoxy left exposed to sunlight. Even epoxy mixed with the UV resistant hardener deteriorates very quickly: yellowing, bubbles, lifting & all sorts of fun stuff.

[DayTripper]

I can’t contribute to the good advice here. However, I can suggest there is no such thing as a “bow deck”. I don’t believe you will find that term in any legitimate printed reference. It is a “foredeck”. (Sorry, just one of those “fingers down the chalkboard” things to me.)

As a novice boat builder, I didn't know the correct term. Thanks for the education as I do want to use correct terms when discussing boat issues.
Foredeck it is from now on. Thanks.

[Todd Bradshaw]

I don’t believe you will find that term in any legitimate printed reference.

Bow and stern decks are common and perfectly acceptable standard terms when it comes to talking about wooden canoes, so I wouldn't get too hung up on it. Nobody I know talks about a "foredeck" on a canoe, but then canoeists don't generally tend to be as stuffy as a lot of sailors are.

[DayTripper]

Just to add a bit of probably unnecessary advice:

Make sure the epoxy is well scrubbed with lots of water & a scotchbrite pad to get rid of blush. Water, not solvent.

If I apply coats of epoxy when the previous coat is tacky, will blush be a problem? Or does amine blush only occur when the epoxy fully cures?
What's your recommendation for the number of days to let the epoxy cure before scrubbing?

Also make sure there is no epoxy left exposed to sunlight. Even epoxy mixed with the UV resistant hardener deteriorates very quickly: yellowing, bubbles, lifting & all sorts of fun stuff.

Yes, the topside will be completely primed and painted with no exposed epoxy.

Thanks for the help!

[stromborg]

From West:
Liquid—Open Time
Open time (also working time or wet lay-up time) is the portion of the cure time, after mixing,
that the resin/hardener mixture remains a liquid and is workable and suitable for application. All
assembly and clamping should take place during the open time to ensure a dependablebond.
Gel—Initial Cure Phase
The mixture passes into an initial cure phase (also called the green stage) when it begins to
gel, or “kick-off.” The epoxy is no longer workable and will progress from a tacky, gel consis-
tency to the firmness of hard rubber, which you will be able to dent with yourthumbnail.
The mixture will become tack free about midway through the initial cure phase. While
it is still tacky (about like masking tape), a new application of epoxy will still chemically
bond with it, so you may still bond to or recoat the surface without special preparation.
However, this ability diminishes as the mixture approaches the final curephase.
Solid—Final Cure Phase
The epoxy mixture has cured to a solid state and can be dry sanded. You will no longer be
able to dent it with your thumbnail. At this point the epoxy has reached most of its ultimate
strength, so clamps can be removed. A new application of epoxy will no longer chemically
bond to it, so the surface of the epoxy must be properly prepared and sanded before
re-coating to achieve a good mechanical, secondary bond. SeeSurfacePreparation.
The mixture will continue to cure for the next several days to two weeks at room
temperature, becoming an inert plasticsolid.

More here: https://www.westsystem.com/instructi...product-guide/

I have found allowing a minimum of a week (seven days) between final application and paint usually works. Two weeks is better but as they say it is somewhat temperature dependent. If the epoxy isn't cured to an inert state the paint will stay sticky and all you can do is wipe if off and wait. You also ought to wait for a full cure before sanding because it is still a sensitizer until it is done. This adds a lot of time to the finishing phase of operations, one more argument against slathering on epoxy where you don't need it. A good quality enamel paint wears really well in my experience. Just touch it up if the primer starts showing through. A layer of epoxy in and of itself doesn't add any strength to the wood underneath.

[Garret]

If I apply coats of epoxy when the previous coat is tacky, will blush be a problem? Or does amine blush only occur when the epoxy fully cures?
What's your recommendation for the number of days to let the epoxy cure before scrubbing?



Yes, the topside will be completely primed and painted with no exposed epoxy.

Thanks for the help!

Hot coats shouldn't be a problem & epoxy can be added after it's cured just with sanding AFAIK. It's paint/varnish that's the issue. I wait at least 3 days - but more would be better.

[DayTripper]

From West:
Liquid—Open Time
Open time (also working time or wet lay-up time) is the portion of the cure time, after mixing,
that the resin/hardener mixture remains a liquid and is workable and suitable for application. All
assembly and clamping should take place during the open time to ensure a dependablebond.
Gel—Initial Cure Phase
The mixture passes into an initial cure phase (also called the green stage) when it begins to
gel, or “kick-off.” The epoxy is no longer workable and will progress from a tacky, gel consis-
tency to the firmness of hard rubber, which you will be able to dent with yourthumbnail.
The mixture will become tack free about midway through the initial cure phase. While
it is still tacky (about like masking tape), a new application of epoxy will still chemically
bond with it, so you may still bond to or recoat the surface without special preparation.
However, this ability diminishes as the mixture approaches the final curephase.
Solid—Final Cure Phase
The epoxy mixture has cured to a solid state and can be dry sanded. You will no longer be
able to dent it with your thumbnail. At this point the epoxy has reached most of its ultimate
strength, so clamps can be removed. A new application of epoxy will no longer chemically
bond to it, so the surface of the epoxy must be properly prepared and sanded before
re-coating to achieve a good mechanical, secondary bond. SeeSurfacePreparation.
The mixture will continue to cure for the next several days to two weeks at room
temperature, becoming an inert plasticsolid.

More here: https://www.westsystem.com/instructi...product-guide/

I have found allowing a minimum of a week (seven days) between final application and paint usually works. Two weeks is better but as they say it is somewhat temperature dependent. If the epoxy isn't cured to an inert state the paint will stay sticky and all you can do is wipe if off and wait. You also ought to wait for a full cure before sanding because it is still a sensitizer until it is done. This adds a lot of time to the finishing phase of operations, one more argument against slathering on epoxy where you don't need it. A good quality enamel paint wears really well in my experience. Just touch it up if the primer starts showing through. A layer of epoxy in and of itself doesn't add any strength to the wood underneath.

Thanks for taking the time to post the West narrative. OK, what you said in bold above and along with what Todd said, I'll skip epoxying stuff on the topside and just go with primer and paint. Will be easier to just prime and paint anyway. Thanks.

[DayTripper]

Hot coats shouldn't be a problem & epoxy can be added after it's cured just with sanding AFAIK. It's paint/varnish that's the issue. I wait at least 3 days - but more would be better.

I've decided to skip epoxy on the topside and just go with primer and paint. Thanks for the help.

[Garret]

I've decided to skip epoxy on the topside and just go with primer and paint. Thanks for the help.

I think that's a good move. I might still consider a couple of coats of epoxy on any exposed plywood ends under the primer & paint though.

[ahp]

My Ohio sharpie will finally hit the water for the first time in a week or so. The plywood is BS 1088, System Three epoxy, and silicon bronze screws, lots of them. OK, I used the best stuff. Now for things like bench seats, I used cypress, which is plentiful down in Georgia where I built it. I doubt there is much cypress in Hawaii. What is available, cheap and reasonably durable where you are? Use it. I know, nothing is cheap in Hawaii.

For finishing the seats I used Behr water based porch and deck paint, no primer, no epoxy. We shall see. I avoid stuff that has the word "yacht" when possible.

[DayTripper]

I think that's a good move. I might still consider a couple of coats of epoxy on any exposed plywood ends under the primer & paint though.

Cure time delay will negate that move for me. Thanks.

[DayTripper]

My Ohio sharpie will finally hit the water for the first time in a week or so. The plywood is BS 1088, System Three epoxy, and silicon bronze screws, lots of them. OK, I used the best stuff. Now for things like bench seats, I used cypress, which is plentiful down in Georgia where I built it. I doubt there is much cypress in Hawaii. What is available, cheap and reasonably durable where you are? Use it. I know, nothing is cheap in Hawaii.

I bought sande marine ply for my boat so the bench seat tops are 1/2" ply. Will carefully apply primer and paint to the end grain and see what happens. Will probably be fine since the boat will stored in the shade at home, except when we are out boating.

For finishing the seats I used Behr water based porch and deck paint, no primer, no epoxy. We shall see. I avoid stuff that has the word "yacht" when possible.

Do post your results after a year. I will do the same. Thanks.

[Rigadog]

Thanks for the info and picture examples. Since the Gougeon Brothers are OK with putting epoxy without cloth on topside surfaces, I think I'll put 3 coats of epoxy on the bench seat tops first (most wear and tear), then continue with the gunwales if I have enough left over epoxy, and finally the bow deck if there's enough left over epoxy. Since the bow deck is a larger area with less wear and tear, there may not be enough left over epoxy for 3 coats in which case I'll just primer and paint it.

Thanks for the info. Helps a lot.

Nice Tele! beautiful
I like the lipstick pickup.

[nedL]

Bow and stern decks are common and perfectly acceptable standard terms when it comes to talking about wooden canoes, so I wouldn't get too hung up on it. Nobody I know talks about a "foredeck" on a canoe, but then canoeists don't generally tend to be as stuffy as a lot of sailors are.

Ahh,… good point and well taken about canoes Todd.

ok,….so, outside the world of canoes it’s eek!