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Core Sound 20 Mark 3 Build - Chesapeake, VA


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Amos,

 

Back in 93 I used Brightside directly over epoxy. I think that I was using SystemThree epoxy at the time. I believe that the paint reacted with the amines in the epoxy which prevented it from curing. It almost cured at the surface but it was clear that it was soft under the surface. Fortunately I stopped before removing the paint became a major problem. I took the boat to the Wooden Boat show at Newport where the Interlux people got an earful from me. I felt that they knew about it as they said that you should never put Brightside directly over epoxy. They later put it on the can and on paint guides. They want you to paint the epoxy with their epoxy barrier coat before you use Brightside.

 

Anytime that you want to try a new one part paint over epoxy, you should always do a test sample before you create a big problem. I ended up using latex exterior gloss on the interior of that boat. It was never very glossy or very tough and it could stain but the best part was that before a boat show, I opened the can of paint and dabbed at any wear or stain marks and it dried in 10 minutes and it all looked fresh with no sign of a repair and I cleaned up with water.

 

Jay painted the inside of his 20 mk3 with latex and I thought that it looked pretty good. I was talking to Tom about it at the messabout, he told me that he used Brightside on the inside of Liz and had issues with mildew. I plan to eventually paint some of the interior of Carlita with Latex but I definitely will not be painting inside my lockers.

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Nice work Amos.  You'll find the shelving very useful.   For builders who haven't installed the sheer strakes -- it's much easier to install the shelf-supporting cleats before doing the s-st

Small gear hammocks set in out of the way places work well too.  

More mods:   Installed a GPS holder using RAM mounts (highly recommend RAM mounts, the swivel balls aren't just plastic; they have an aluminum core, and the GPS mount has little roller beari

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I've had the same problem when painting a primer over WEST Sytems epoxy. I painted the whole boat (Bolger Junebug) before I realized it was never going to dry properly. I had to strip it all off and put on a coat of Interlux 2-part epoxy primer. I think it was called 404/414. The epoxy primer adhered tenaciously and the Brightsides I put over it dried just fine. 

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I really appreciate all the replies; I'm just going to sand it all off.  It sands really easy!  I'm glad I didn't paint a larger area.  Good point Mr. Graham concerning testing a new paint before using it on the boat; lesson learned the hard way on my part.

 

I should probably just switch to the two-part marine paint.  That can be applied directly over sanded epoxy, correct?

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Amos, even if the paint can go directly over epoxy I really think that a primer undercoat is a good idea, it makes the finish harder and more resistant to scuffing and by interacting with the finish coat it also makes the finish harder. For this reason I think it a good idea to decide on an epoxy/paint system that is fully compatible and stick with that. Money well spent in the long run.

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I've run into this problem a few times and it affects the alkyds. As to which are susceptible to this issue is a trial and painful error thing, so just don't. It does seem the more modified the alkyd, the more common this issue can crop up and it is the amine groups/environmental interaction, screwing with the cure process, but it only occurs on not truly cured epoxy (painted less than a few weeks after the goo went on). Most single part (alkyd) paints will go over freshly cured, cleaned and scuffed epoxy, but it's a crap shoot, unless you have experence with the combination. I did a few tests a number of years ago, when I first encountered this concern and epoxy that had several weeks of cure didn't react with the paint cure, though did if applied within the few week window I mentioned.

 

This said, there's no reason to save the primer step. You're not really saving anything, because you'll need to fair and smooth the surface anyway, which is best done with primer. Secondly, you do want a good "tie" coat, between the epoxy and the finish coats. I have never seen this issue crop up on water based or borne (yeah, there's a difference) finish paints, over fresh (still chemically active) epoxy.

 

All of the paint formulators will tell you to use their primers under their top coats, but this is simply a marketing ploy, not valid chemistry. In a nutshell, use a good primer over epoxy (or anything else, unless clear coating), simply because it's necessary for a good paint job. Making surfaces smooth and fair is much easier and making a finish coating last and look good needs primer. In fact, most of the work is in the primer stage, unless it's to be a show finish, in which case you'll be color sanding the top coats too, but the bulk of the elbow effort is still on the primer.

 

I now use epoxy primers exclusively, for everything. It just sticks better and I've not experienced any compatibility issues, since this decision. Yep, it costs more, but you'll end up with a better result that also lives longer, regardless if it's over an epoxy base or not

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I should probably just switch to the two-part marine paint.  That can be applied directly over sanded epoxy, correct?

 

I tried searching in previous threads for all of our collective wisdom on applying paint over epoxy but I could not find it. The technical details tend to make my head spin.

 

Are you talking about painting the exterior of the boat or just inside these lockers before you close them up?

 

By two-part marine paint I assume you mean the LPU's two part urethane paints like Interlux Perfection or Awlgrip.

 

I used Devthane 379 which is a commercial two part urethane. The thinners/reducers are very strong and the uncured paint is very toxic. You are supposed to be using a supplied air system when applying the paint. The best respirator is not enough. I painted outside using a respirator and it was OK but not when I needed to get down close. I was rolling and tipping, spraying I think you need supplied air. On my Spindrift I ran out of primer and some of the two part urethane is painted directly on the epoxy. I had to apply additional coats of 379 and I remember thinking that I would have been better off getting some additional primer.

 

It is a matter of opinion but I  would not paint anywhere the sun did not shine regularly, but if you feel like you have to I would go with something less toxic. If you have decided on a paint system for the exterior of the boat you might consider using the recommended primer for inside the lockers either alone or topped with a good quality exterior house paint or your Brightsides since you already have it. That would give you some experience with the primer before you get somewhere where it counts. I think it is hard to beat the two part urethanes for exterior surfaces but thier toxicity gives the nod to other options when painting in enclosed areas.

 

The primer for Devthane was a two part epoxy primer which I believe may be similar to the Awlgrip primer 555, and the Interlux Primekote. I thought the Devoe primer was difficult to apply. Over one of the two part epoxy primers you could probably put a variety of paints but the problem is once you stray form the manufacturers recommendations you are rolling the dice.

 

The other issue is that the epoxy that you are painting over though it has hardened it has not fully cured so the more time and warmth you can put between applying the final coat of epoxy and the primer the better off you are.

 

Keep the questions coming we are rooting for you.

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Thank you for the detailed replies; this is a great forum.

 

I don't have a sprayer so I'm just rolling or brushing and then tipping.

 

I realize most don't paint these storage areas; I was just trying to get familiar with the paint by using it in an area that won't be seen before using it in the cabin.  You guys are right, the epoxy I painted over was only four days old.

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Has anyone tried an epoxy primer from a "local source" like an automotive product, or Sherwin Williams? And one that can be bought in less than a gallon quantity? Ya don't need that much for a canoe or similar small project. I realize that you can order a marine product, but you have to add the shipping and hazmat cost on top of the already high cost of the primer.

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I often use tinted or fully pigmented epoxy in lockers, cabinetry and buoyancy chambers. This is because it's difficult to paint in these spaces once installed, but they still need encapsulation, so once the initial raw wood coating is down, I add pigment. Most times I add enough pigment to lighten the wood significantly, but not so much to hide the grain, putty over seams or fastener heads. My logic is so I can see what's going on with the surface, in the event of a leak or damage. If the area is fully painted, you can't see what's happening until the paint starts to bubble and lift, when you have a lot more to contend with, compaired to catching it when the issue is relatively fresh. Many of these location will never see paint or some color again, mostly because it's too hard to paint these areas. 

 

I don't think LPU's or even the WR-LPU's are particularly backyard builder friendly. I've grown to dislike the WR-LPU's and haven't used them in several years. Single part polyurethanes are nearly as good, typically more than 1/2 or more the price of LPU's and you can use conventional application techniques, without the need for $1,200 in equipment (sprayers, big enough compressor, respirator, etc.). I had to build a new compressor, to replace my freshly dead one. I was able to reuse the 80 gallon tank, water and particulate traps, etc., but I needed a new 5 HP compressor and motor. Price out what a 5 HP electric motor and even a basic single stage 5 HP compressor cost and you'll see how quickly it goes up. I got a real good two stage, though I could have gotten a Harbor Freight single stage for 1/2 as much. My new FINI two stage, 2 cylinder, 175, PSI and 18 CFM at 90 PSI and 16 CFM at 40 PSI will squirt some paint, but compared to a cheap one (Harbor Freight about 1/2 it's price), it'll work continuously, whereas the HF unit will crack its head or toss it's poorly cast fan (or something) in no time. 

 

No home builder needs a bullet proof spray setup, but if you plan on serious painting . . .

 

When it comes to paints and primers, look up the MDS and check out it's contents. Solids count, particulates, vehicle and resin types, etc. You'll notice similarities between the various formulators. Staying within brand isn't necessary and you'll never get an honest answer from a formulator's rep or tech guy. So, if you have one brand that uses mineral spirits for clean up, but the top coat you want to use suggests toluene, you might want to keep looking. If not that comfortable with the chemistry stuff, you can always stick with the same formulator's recommendations. If you paint a lot, you'll learn much of this chemistry stuff, even if you didn't want too.

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I scraped and sanded off most of the paint today; took about 2 hours.  A thin flexible cabinet scraper worked best.  One more session should finish the job.  The paint was soft and gummy.

 

20161212_194640_zpsfx2piaes.jpg

 

Just to satisfy my curiosity I'm going to do a few tests with the paint on scrap pieces to see if I can duplicate the problem.

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I had this problem when I painted enamel paint over epoxy on Turtler. It wouldn't dry hard even after a few days. Not knowing any better, I added another coat thinking it might help to cure the first coat. It actually seemed to work. This dried and hardened as it should have. After using the boat for over a year, the paint doesn't seem to wear ant differently that it should.

 

Note to the rest of y'all---DON'T TRY THIS ON YOUR BOAT! God seems to protect little kids and boatbuilders from their sins. But it takes a lot of FAITH to make it work....

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  • 2 weeks later...

If I'm reading the plans right, the tabernacle is made from 3/4" thick stock.  Is that correct?  It looks like it is made from 1' stock when I look at pictures here on the forum, but that could just  be the camera perspective.

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I'm starting work on the hatches, I'm glueing them up in stages.  Lightly clamping the innner pieces around a board cut to the inner dimension helped keep everything square when I tacked them together.  This is probably unnecessary but it worked well for me.

 

20161231_105758_zpseprt3yxq.jpg

 

 

I assembled the outer coamings seperately; the workbench top helped keep everything flat. 

 

20170101_084902_zpsi2tzjy4m.jpg

 

 

Now I need to attach the two assemblies.  This brings up several questions.

 

 

What is the purpose of the 1/8" spacer called for in the plans (see pictures below)?  Is it to gain clearance and set the hatch back slightly so the hatch lid closes better?

 

20170101_195349_zpsreanb2pz.jpg

 

20170101_195717_zpscyzhrgnz.jpg

 

If the spacer is glued onto the "inside coaming inboard" than do the the outside coamings need to protrude 1/8' past the "inside coaming inboards" like this?

 

20170101_194600_zpstn7dnrff.jpg

 

 

Or should they be in the same plane like this:

 

20170101_195527_zpsy4tq309n.jpg

 

 

 

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