Protecting Plywood Hull

[Plantman]

After my recent experience with Incompatible paint below the waterline I have now started stripping the Hull back to bare wood & need to know whats best to repaint it with.
Someone suggested chlorinated rubber paint but I would need to remove all traces of the original(pink metalic) primer. This is proving difficult as some of it is ingrained in the ply & I'm a bit reluctant to sand away at it too much.
Epoxy coating is another option but again the problem of a perfectly clean hull.
The boat will stay on the water for about 8 months of the year, fresh water, & I'd don't want to leave it there just to rot!!
At the moment the ply is in very good condition for a 20+yr old boat & I want to keep it that way.

Graeme

[Stiletto]

If the boat stays in the water epoxy is a good way to go. If there is only a very small amount of your primer in the grain of the wood I think it would be ok to use the epoxy. When I repaired my boat with lots of epoxy I found that adhesion was ok on the small amounts of primer I couldnt remove completely.

[sdowney717]

why not use a liquid polyurethane sealer
they are 100% waterproof
A little paint left wont affect these.
See if you can get the Durabak without the rubber granules, that is why I used the sanitred permaflex.
www.durabak.com (http://www.durabak.com)
www.sanitred.com (http://www.sanitred.com)

[Hal Forsen]

I've seen Sanitred's site and it piqued my interest enough to post a question about it here several months back but nobody bit. Don't know anyone who has used the products. sdowney717
can you tell us about your experiences with this "rubber paint"? Where did you use it? How does it perform? Any cautions?.........
HF

[JimD]

I would be inclined to epoxy it and not worry about a few traces of old primer left in the grain of the wood and then repaint but if the boat is 20 yrs+ and in good condition can't you just put back on what was there before? It seems to have worked well enough. What was incompatable?

[Plantman]

Up until last season the boat was only used as a trailer sailer & never in the water for more than a week or so at a time so marine gloss was used.

[Russell Sova]

I've used Gluvit epoxy, which is a repair epoxy, tinted and painted on the hull. It will take a little longer to cure and especially at lower temperatures. So in other words, be prepared to stand there and touch up runs. But, it is flexible and hard. I never had a problem after using it. There are many other flexible epoxies you could use. I just found that one locally available and found it works very well. I read a book about someone cruising the Carribbean who said it was the best to use so I tried it.

[Dave Carnell]

No coating is completely waterproof. The owner of a houseboat in fresh water reported to me that he painted its bottom with 100% acrylic latex exterior house paint and it worked beautifully with an annual scrubbing off of the slime that grows in fresh water.

[sdowney717]

I bought a 5 gallon pail and it covers like a thick sticky paint. 240 sq feet per gallon. It slowly sets up stickier and stickier and is always dry overnight but it takes at least a week to fully cure.
The solvent is Xylene and you can thin it down up to 20%. But even full strength it penetrates into wood. You can clean up your hands with dish soap, but it is tought stuff and if you get it on your skin it wont come off easily. I leave the brush in a mixed up bucket and stick it in the freezer and can use it for days. It sets up even in real cold weather where epoxy cant work. I have even used it to glue in wood plugs on the frames. It holds the plug and wont pull out when I run the planking screw in.
There are several potential problems in its use.

The surface should be dry. This polyurethane is moisture cured. If the surface is wet it may not stick. Although I did paint it on some damp PT pine and it did stick well.
The surface must be clean not oily. Polyurethanes dont stick to oily surfaces.
The tech people say 30 days to reach its full strength. If you test it right after it sets up overnight, it is rubbery but is not completely hard and stretch it it will break. As time goes by it gets tougher and tougher.
The polyurethane Sanitred Permaflex may somtimes form an orange oil on the surface during its cure.
I have seen it occasionally and I am using the sand colored stuff.
More coats can be applied while the stuff is still sticky and you dont have to worry about the oil byproduct. But if it has dried hard, you either wash it off with soap and water or Xylene when it has an oil formed. Seems like it happens mostly in high humidity and warm temps. Make sure if you wash it off or decide to recoat after it has set up that the surface is not damp or moist from dew etc.... They recommend 2 coats on wood. I have gotten real good coverage with only one coat on wood. And since it soaks into the wood and hardens, I have wondered if this is simply enough.

Some really nice things about it.
It glues wood. I had to pull apart some PT pine and it broke off the side in the wood where it had accidently been stuck. This was on a fresh dry table saw cut.
It soaks into end grain, wicks right in. I had some Douglass fir stringers on my egg harbor. It was like a sponge sucking it up.
It dries glossy like a tough rubber sheet.
At the boat yard, several have asked about it and like it. A man came up and said his boss puts it on the bottom of his boat and he has no barnacles.
When it is dried and you put water on it, it feels slick and slippery like it is oiled.

It only comes in sand black white and light grey.
There are 2 versions of the stuff. One is 100% UV proof and the other is not. I am using the cheaper
non 100% UV proof stuff.

It comes with a small can of catalyst and a small can of accelerator. For a 20 oz mix you would add 1 to 2 teaspoons of catalyst and 2-4 teaspoons of accelerator. The stuff sets up even without these things but they claim it wont reach its advertised potential unless you add it. So far I have been pleased with it. Feel free to ask me anything else about it.

[Wild Wassa]

Originally posted by sdowney717:
"It only comes in sand, black, white and light grey."

It does come in white. White can be tinted. With poly when I've wanted the paint tinted, I've used acrylic tints, definitely don't use oil based tints. It always pays to check with the manufacturer if there are any special instructions, like the inclusion of wetting agents, if you are colouring with powder pigments etc.

Warren.

[Hal Forsen]

What all have you used it for?
HF

[Bear's Oil]

Its nice to be able to afford stuff that says "marine" on it, but... Years ago I used Sherwinn-Williams porch and floor enamel (first coat thinned 50%)with never a problem. S&W tractor and implement enamel if I wanted jazzier colors. Think I might go the latex house paint route now.

[sdowney717]

Most everything on or in the bottom
I am currently rebuilding the bottom of my 1970 37 Egg Harbor. It all started with a simple refastening job. After a while I discovered screw holes that would not hold screws. So I deplanked the forward part, pluged and fixed the frames and replanked. Then I moved onto the aft area. Every frame from stern to mid section was rotted. I ended up replacing 14 bottom frames.
I also replaced one floor behind the generator in the lazorette. Managed to shove it in sideways from the bottom of the boat. These floors sit on top of the keelson and run to each side where a large stringer sits on top of them.

Now this boat has large oak floors that extend across the bottom of the boat from side to side. And it has gussets supporting the frames at the turn of the bilge. What I did was cut every frame out near the ends of the floors and screwed the old frames into the floors. I then ripped some arsenic PT pine into frame sections recreated those nice round ends for the pockets and screwed these into the oak floors all the way to the keelson. I used regular stainless 3 inch #10 deck screws to attach the frames to the floors. I believe that this wont crevice corrode since it will not be underwater, as it should get plenty of air and should stay dry.

Everything was cleaned and separately coated with permaflex including the inside of the planks and attached back on with #14 1 1/2 inch SB square drive screws.

I also found a significant amount of angel hair weepage rot starting to get going all over the shaft log and one of the floors where a long bronze bolt holds the shaft log to floor had allowed a lot of weepage. Weepage rot is really awful, it goes deep into the wood and shreds it into a fibrous stringy weak mess.

[sdowney717]

I asked them about coloring it and they will make any color you want for orders of 12000 gallons or more! I suggested they add blue to their choices.
By the way, this stuff is self leveling and forms a nice smooth suface on smooth wood. If you paint it on wood with lots of loose fibers, every loose fiber on the board stands up and the surface is quite rough.
I think you could probably tint it but I am not sure with what. I chose the sand color. It is a neutral light tan color. I know Durabak www.durabak.com (http://www.durabak.com) comes in many colors but it has rubber granules in it and is generally a lot more expensive. This sanitred permaflex is really smooth and slick. I plan on using it for bottom paint. The company says barnacles wont stick to the surface.

[Richard Smith]

Here is a related product: http://www.rotdoctor.com/poly/polymain.html#uniflex

[sdowney717]

Yes the products appear similar.
I have found pot life to be as long as several days with the sanitred permaflex, it does not heat up when curing that I have noticed. It is very easy to mix, the catalyst and accelerator are like water. And the final product has 500% elongation before tearing. I notice some of their products require a primeing using CPES. Only one seems close and that is Elastostuf 120. Sanitred also claims no need for any bottom paint on the boat. The cured surface is slick and smooth, when wet it feels oiled. You can get it in aromatic or aliphatic versions as well.

[paul oman]

very few coatings are approved for constant submersion. Epoxies are one of them.

I tried/tested a rubber paint this year. -- coated a rock and left in my goldfish pond for about 5 months. Also coated the exterior epoxy paint on the bottom of my dinghy and left floating in my backyard pond for about 3 months. Both came out fine without blisters, cracks, etc.

paul oman
progressive epoxy polymers