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Singing the Two-part Poly Blues


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I just finished modifications to my Two Paw8, including painting her with Devthane 374 2- part polyurethane.  It came out a horrible mess.  I’m hoping that someone can tell me what went wrong.

 

I mixed the paint 4:1, and allowed it 20 minutes induction time.  I then added 20% thinner (Awlgrip reducer).  I used a mini velour roller and a 3” Corona Urethaner brush to tip it off.  Halfway through the process, I even added about 15% more reducer, to make up for evaporation.  It’s hot and humid, here in the Carolinas— 90+ degrees and about 80% humidity.  But it never laid down.  The brush marks are horrible.  I had simply rolled the first coat, and did not tip.  The orange peel was so bad, I sanded and tipped the final coat.

 

“Final” is the operative.  We leave for a 4-week vacation in 7 days.  There is no time to amend my sinful ways.  I will be using her as-is, and putting my shame on display to the world.

 

What did I do wrong?  I need a mentor to begin spraying these boats.  That’s what they deserve. Am I stuck with this until then?

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Don- Are you sure you have the correct thinner?  It is clearly drying to quickly.  I am no expert but have done a bit of painting with LP.  The hardest thing is not to overwork it when applying.  It seems like magic to me if do a light tip and let the brush marks shrink up.  Maybe enjoy your trip and try again in the Fall when the temps are cooler.

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I am also not an expert but I agree with Kennneee that things are moving too fast. I have had similar experience and also the one where it seems like magic. Remember, the largest area you have shown us is only visible to the fish and the rest easily passes the 10-foot rule. That’s what I keep telling myself about my boat(s).

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B&B recommends the Awlgrip thinner.  I had a quart of N333, which I used on the interior and first coat.  About the same performance, except the interior was better.  I think it was the heat and maybe humidity.

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Don

i know what your going thru but I think I found the best solution for me iam painting my cs with devthane 379 using 379/359h hardner I believe it’s close to the Same two part as 374 both are 2 part epoxy I tried acetone as a thinner it’s to fast in warm weather I got ahold of the paint dealer he said that I should use devoe t17 thinner this is made specifically for devthane paints to slow down the flash off time to allow the paint to flow out I thin x 20% or a count of 5 or 6 count dripping off the paint stick, also I have the best results with a solvent proof foam roller and then tipping  it still is not without some brush marks but it seems to give the best results hope this will lead to some peace of mind by the way you will have to sand the hull down so as to remove the brush marks already there 400 grit wet/dry should do the trick quick enough and give good bite for the new paint.

ps

as much as I tried you can not do this in one coat let the paint cure at least 3days before sanding should give really good coverage 3coats

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Don, I have always used Devoe polyurethane (379) and believe you me - I sympathize . Bear in mind that polyurethanes are moisture and temperature activated. In summer it can be a trial. Spraying always worked the  best for me because it goes on fast and even. It may help to get your gear set up the night before ( including lights) and then get up at four in the morning, throw your paint together and go at it. If you use HVLP sprayer you may need to run your hose through bucket of ice to keep the air hose cool. The turbine has a tendency to heat up the air supply causing the paint to flash set and you'll get a nice orange peel or powder coat effect. Good luck PeterP

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3 hours ago, AmosSwogger said:

Letting it sit 20 minutes after mixing is unnecessary in my opinion.  This may be allowing too much thinner to evaporate.

The 20 minute induction time is before the thinner is added and is explicitly called for by the manufacturer.

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When I have to use epoxy in really hot weather, I place the cans/jugs in a water/ice bath before mixing.  This at least gives me a head start. It may be a bit thick in the cold state, but warms very quickly as I spread it out. I don't know if some variation on this cooling idea would help.

 

Another thought is to become 2 people, one to roll and one to tip. ?

 

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On 7/10/2022 at 3:24 PM, Mike Vacanti said:

The 20 minute induction time is before the thinner is added and is explicitly called for by the manufacturer.

I added the thinner after the induction time at a 20% rate.  I added about 10% more halfway through the process.  I used Awlgrip’s thinner product, because Alan said that it produced better results than Devoe’s thinner.

 

I wish someone would teach me how to spray these boats…

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Just like to add, Awlgrip has several types of reducers,  looks like the reducer flashed before the flow.  I have had reasonable success with Awlgrip T-0005.   A quick buz with the DA sander and it is called “an extended primer coat”

 

BTW,  Carol has been sick so I haven’t been to the Flinders in almost 2 weeks, it currently is in a marina in Madisonville La,  plan to post some pictures without it under sail…..well directionally drifting.   Either it is 50kts or 1.2 kts here mid summer! 

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