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Chas231

Wood finishing

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Rather than paint, decided to strip the hull with mahogany strips. Happy with the result so far, but am having a finishing issue. Applied three coats of epoxy resin with good results - very clear and glossy. Because I understand resin is not UV resistant, wanted to apply varnish on top of the resin. The store didn't have gallons of varnish, so Minwax Urethane was chosen. According to the label it is extremely durable and UV resistant. Our result was terrible. Today, two days after application, the finish had turned milky white and was peeling off. We were able to remove the finish with a power washer and Scotch Brite pads. Except for some minor scuffing, I'm back to a nice shiny resin finish. I'm thinking I'll scuff the finish with a light sanding and apply one more coat of resin. Was my mistake using urethane and not varnish? The weather was damp, but the varnish had dried to a nice glossy finish before going bad.

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It depends on which MinWax product you used. I'll assume it's their  Helmsman Spar Urethane. This stuff really isn't very good, though some up north have had some luck with it on the interiors of their boats, as an exterior coating, it doesn't last long. You milky application sounds like moisture got at it, before it was hard enough to resist it. Morning or evening dew can cause this. Prep can also be an issue.

 

Was the epoxy well toothed up, say with 220 or 280 grit wet, before the finish went on? What were the environmental conditions when you did the job and how long before the morning or evening dew arrived?

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Did you wash the boat with water and a scotts brite pad after the epoxy was applied.  It could be a amine blush problem.  Or the epoxy wasn't fully cured yet.  I had problems with Epiphanes varnish over West System epoxy.  The varnish never cured.  After two weeks it was still sticky.

 

Egbert

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With all due respect to your work and effort, you have surely modified the finely  tuned design, which depends on what the industry considers to be a lightweight hull by comparison to other similar sized boats. So the current weight is important to know as it relates to the power plant too, which Tom has honed in on with the smallest outboards for these sized boats .

 

 

I would surely weigh the boat as it sits on the trailer now.  What engine are you using?  You have added a ton of weight to your hull, and should really know how to proceed, so you are not disappointed in the final performance numbers and even fuel burns. This also deals with the sized fuel tank that you have chosen, giving you the range that you may need for some desired cruising distances without carrying a bunch of jerry jugs.

 

As it relates to the finish work, there is nothing wrong with using the Helmsman. But there are some issues with coating epoxy finishes  with certain types of spar varnishes. We always use Captains Varnish, which is of course more expensive, but surely well worth the money for long term.

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 We always use Captains Varnish, which is of course more expensive, but surely well worth the money for long term.

 

I always use good old fashion oil based Captains varnish , over epoxy for plywood and alone over solid wood.  Not only is it long term as Oyster mentions, but easily repairable as well as removable with heat.

 

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I visited the Southport boat show yesterday and visited this boat.  If I may be bold about this wood and varnish issue, frankly you are wasting your money and time on this added veneer and any product that you use on it, forgetting the added weight to the hull.  I would strongly consider removing the current wood and at least start over with some assistance and guidance from a wood worker in the boating industry for a day or so

 

 

Please reconsider adding wood on the starboard side until you at least redo the port side correctly if you really want the wood exterior. Frankly your starboard side looks good enough to apply paint to it, even a semi gloss too, and you move along to completing the boat in short order after removing your wood and just painting the port side  Most boats that use a solid wood veneer on the exterior of a hull use approx. 1/4" veneers and then sand them down after gluing them up with closed joints. You can do these on a diagonal, but normally these are applied horizontally to the hull lay up.

 

You will not be able to keep varnish on  the edges of the veneers along the seam voids, since you will not be sanding all of those edges as you continue to apply your finish material. You will be varnishing smooth surfaces. But I question the fastener holes in the faces of your veneers. Those fasteners broke the face of your inside hull. So its quite possible that those inner holes are no longer sealed either.  If you would like some help in improving your job if you continue to want a varnished veneer, by all means let me know and I will come down for a day and go over this with you. 

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Thanks guys. All good advice. I think the varnish issue was the result of a number of factors, mainly as a result of rushing. I understand the mahogany veneer is basically cosmetics. I like it and plan to keep it. The strips are milled to 1/4". The added wood weight for both sides and the transom amounts to about 112 lbs. It will compromise performance marginally, but worth it for the appearance in our minds.

The fastener holes left after removing the brads will have to be addressed. The holes don't go through the hull, but they do penetrate about 1/4" into the hull. It appears to me that the resin sealed the holes in the mahogany, but it's doubtful the hull has been sealed completely. Removing the veneer strips and sealing the holes may be the only option? How about covering the veneer mahogany with fiberglass? That would re-seal the hull completely from any intrusion.

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Well if you want to glass over the wood, you continue to add weight. But glassing over the wood will require a lot of filler in the voids between the existing veneers and the fastener holes now. But the weight of the wood is just half of the final additional weight. The epoxy used for gluing also adds more weight to the raw material weight. 

 

But if you are talking about glassing over the wood and then paint the glass, the best thing to do is to take a power plane and remove as much of the wood as possible to just above the hull surface, leaving just a wee bit of the wood. Then take a big eight inch soft pad grinder and  finish the job. Then  deal with holes with filler and then use quality high build primers over the hull sides and paint after sanding smooth.

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Glassing would be a great option. 6 ounce cloth should do it. You'll need to remove all traces of varnish before glassing. Three or more coats of epoxy to fill the weave and build a little thickness comes next. I like the big 8 inch pad sander that oyster mentioned. Then you'll have to decide whether you want to use a traditional varnish (I like Captain's Varnish.) or a two part polyurethane. The two part is much more durable, but can be dangerous to your health, especially if sprayed. The guys on here who use these products can advise you much better than I can.

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Here on the Texas coast, with our sun, there are only two varnishes I'll even consider

 

Z-Spar Captains (2015)

 

and Epiphane's

 

The rest are pretty much a waste of time

 

Tried Bristol Finish and it was beautiful-til it failed and had to ALL be removed- UGH!!

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Update:  Chuck has decided on a do over and has removed all the wood lamination.  It is now on the way to the dump. The topsides will be painted as originally intended.  The only remaining issue is whether the staple holes through the Xynole sheath and into the plywood will present any problem.  The few screw holes can be filled in the normal manner.  He will do an experiment to see whether a high build primer will effectively seal the holes and if not, some thickened epoxy will be forced in with a squeegee.  I am pleased that he has chosen to do this since I thought the wood could become a maintenance headache in the future. 

 

For those who have not tried it, filling small holes is not as simple as it might appear.  Thin liquid like epoxy or paint will not cover a hole or a sharp edge as the liquid will pull away from the edge due to surface tension.  The technical term is "surface free energy" and is what determines which material will cling to or be repelled by the other material.  An example is: water beads on wax while addition of soap will allow water spread flow easily over your waxed car.

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To follow up: The mahogany strips came off pretty easily. After sanding the hull was in pretty good shape. The hull had been covered with Xynole and multiple coats of resin, and was not damaged, except for the small holes made by the brads which held the mahogany strips while gluing. The holes and scratches were filled with Interlux Surfacing Putty, then a coat of resin. The hull was finished with a coat of high build primer and three coats of Rustoleum Marine. I'm happy with the final result. Not as pretty as the mahogany, but should be much less maintenance and I'm confident the hull is sealed. Appreciate the help and advice! (Sorry for the upside down pic!)

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Even upside down it looks good.  How did you get the paint on the boat, spraying or rolling?

I had a hard time getting my boat painted, tried rolling and tipping, rolling and rolling and finally it got sprayed with mixed result.  

 

Egbert

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Next time you run into the drying too quick issue with Rusto Marine, add some Penetrol. This is a flow promoter and works very well with straight alkyds like Rusto Marine. I just squirted a boat with it last week and about a 5% cut to get it through the gun and another 5% of Penetrol, to get it to "lay down". The same thing applies to roll and tip, except you probably don't need the initial solvent cut, just the Penetrol.

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Next time you run into the drying too quick issue with Rusto Marine, add some Penetrol. This is a flow promoter and works very well with straight alkyds like Rusto Marine. I just squirted a boat with it last week and about a 5% cut to get it through the gun and another 5% of Penetrol, to get it to "lay down". The same thing applies to roll and tip, except you probably don't need the initial solvent cut, just the Penetrol.

 

That is great advice for any one who uses paints.  Most need some additive for best results in different conditions. All paint manufacturers will offer what they consider best for their particular formula but PAR's advice works well for alkyds.

 

I once tried an experiment where I foam rolled a very thin coat of LPU cut about 40% (if I remember right) over a fresh roll and tip LPU finish on BRS LOON.  The finish came out about like a really good spray job and I will do it again if I use LPU again.  The only drawback I know of is that drying time is increased and dust and bugs might be more of a problem if you work outside.

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