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Old 29-06-2022, 04:58   #1
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Bottom paint on polyethylene hull

Any ideas or experience on the practicality of painting a polyethylene hull (kayak) with bottom paint? Goal being to leave boat in the water.
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Old 29-06-2022, 05:20   #2
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Re: Bottom paint on polyethylene hull

A polyethylene kayak should be easy to paint, using whatever paint, and application method, you choose.
The results will be the same*, no matter what you chose, so I’d pick the very cheapest paint & easiest method.

* A peeling, flaking, mess.
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Old 29-06-2022, 09:24   #3
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Re: Bottom paint on polyethylene hull

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Originally Posted by GordMay View Post
A polyethylene kayak should be easy to paint, using whatever paint, and application method, you choose.
The results will be the same*, no matter what you chose, so Id pick the very cheapest paint & easiest method.

* A peeling, flaking, mess.
Should this thread be moved to the joke page?
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Old 29-06-2022, 13:07   #4
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Re: Bottom paint on polyethylene hull

What reason would you have for doing this?
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Old 29-06-2022, 15:46   #5
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Re: Bottom paint on polyethylene hull

For use as dinghy? Also check to see there are a few boat manufacturers who use the roto molding process of a plastic hull. My guess is the prep and primer coat are going to be key steps. Was 'Boss' boats that did that roto process for a few years?
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Old 29-06-2022, 15:52   #6
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Re: Bottom paint on polyethylene hull

No I mean, why paint it? What advantage do you imagine you would gain?
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Old 29-06-2022, 16:18   #7
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Re: Bottom paint on polyethylene hull

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Originally Posted by massnspace View Post
Any ideas or experience on the practicality of painting a polyethylene hull (kayak) with bottom paint? Goal being to leave boat in the water.

"goal being to leave boat(kayak) in water"


I have a 12ft polyethylene tender.Too large & too heavy to haul aboard,so it floats all summer & grasses up.
I painted the bottom with cheapest latex antifouling paint & that ended the fouling. However,nothing sticks to poly very well. The a/f paint stayed on very well as long as boat was in water. Hauling the boat out scrapes the paint off very easily-no big deal in most cases-easy to touch up next spring.
But don't drag it across the dock,your deck, or anything else you do not want paint on.
Cheers/Len
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Old 30-06-2022, 05:45   #8
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Re: Bottom paint on polyethylene hull

The manatee crew is researching this exact antifouling application. So far, this looks to be a solution.
Alcohol wash. Sand 60 to 80 ...probably 80 is best. Alcohol wash.
3M Tape Primer. $200 per gallon.
Apparently this 3M product is well regarded in the automotive world for adhesion.
Next a latex antifouling.
The crew will do test panels with and without an epoxy primer under the antifouling.
The results will be available in exchange for pizza gift cards.
On a Polycraft 300 Tuffy tender I thought pressure washing would suffice. Maybe the test is just a guise to get free pizza.
Captain Mark
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Old 30-06-2022, 09:46   #9
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Re: Bottom paint on polyethylene hull

Thanks to those who responded so far in a thoughtful manner, and of course it is easy to ignore the snarky answers and those questioning the why after I clearly stated the reason in my original post.

I will add that the boat will have to be pulled for half the year, so looking for a paint that can also remain effective when out of the water.
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Old 30-06-2022, 10:25   #10
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Re: Bottom paint on polyethylene hull

Flame treatment improves the adhesion qualities of polymers, like polyethylene, polyolefins, & polyacetals, prior to the application of coatings, like paint, and adhesives. For the flame to be effective, it must be oxidizing, represented by a blue flame, on butane, propane, natural gas/methane, and coal gas.
It’s really tricky, to get it just right. I wasn't being snarky - I meant it - painting PE/PU/PET is almost always unsuccessful.
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Old 30-06-2022, 13:46   #11
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Re: Bottom paint on polyethylene hull

The why is still not explicitly answered,

leaving it in the water gives context, but not the actual reason.

I'm not being snarky, sincerely want to know.

If it's because stuff may grow on the outside if the hull, I have never seen that happen with polyethylene.
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Old 30-06-2022, 14:32   #12
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Re: Bottom paint on polyethylene hull

So far as I know, NOTHING sticks to polyethylene very well.

Haul the kayak on deck at night, all nights, though, and the biofouling should almost all disappear.

Where the waters are nutritious, biofouling will occur, and the all night rest will really keep it down.

If you're at a dock, a fresh water rinse off will help, too.

Ann
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Old 30-06-2022, 16:20   #13
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Re: Bottom paint on polyethylene hull

I used to have a 8 ft plastic (PE) dinghy (Nylex Pioneer) that I used daily, just too heavy and hard to hoist on deck each time, so I left it in the water, but..... I had to clean it on the beach each week with a scourer, and if I left it for 7 or 8 days I needed a scraper to get the barnacles off.

In the end I slapped on some left over antifoul. I found that often on the slipway people had some leftover stuff ie 0.5 lt or so. So there was no cost no me (just to the environment I suppose).

A quarter of that antifoul fell off the dinghy each month, so I slapped more on. Unsightly, but at least the dinghy was never stolen.

Really nothing sticks to plastic to my knowledge, except for barnacles. I am sure chemical paint scientists could find out what is involved in that attachment process, and copy that, but...... many paint companies would go out of business as the old paint would stick for many years or forever.

To the Manatee crew: OK I will bring the pizza, you have the beer cold please.
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Old 30-06-2022, 20:38   #14
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Re: Bottom paint on polyethylene hull

In North Florida the marina builders drive a steel pipe then slip a black plastic tube over it. Im not sure which plastic but its very slippery.
Stays clean for a few weeks but then the small barnacles grab onto it.
Almost everything in the marine environment gets covered by a biofilm within days. What comes next depends on a huge number of variables but the idea that plastic is not going to be the next home for someone swimming around just looking to settle down and start a family? Nope. Barnacles actually walk around looking for a home.
Maybe something like Teflon is slippery enough but well have to research it.
If your plastic boat or kayak sits still, biofilm will attach and there are a lot of plants and animals which will follow.
We are not sure what system of coatings we will put on the bottom of our Polycraft Tuffy dinghy but I cant trust the manatee crew with a high pressure washer or anything with the words high pressure or caution on the tag.
Will look into this further.
Happy 4th of July. No doubt you will see some of my crew at the emergency room. Mark
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Old 01-07-2022, 02:02   #15
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Re: Bottom paint on polyethylene hull

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Originally Posted by JPA Cate View Post
So far as I know, NOTHING sticks to polyethylene very well.

Haul the kayak on deck at night, all nights, though, and the biofouling should almost all disappear.

Where the waters are nutritious, biofouling will occur, and the all night rest will really keep it down.

If you're at a dock, a fresh water rinse off will help, too.

Ann
Have a look at the Polycraft website, under FAQ, there are full instructions for antifouling. Poly boats are one of the most favoured commuter boats for people who live "offshore" in Pittwater NSW, they are all sucessfully antifouled,
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