Core Sound 20 Hull #102

[tom151]

Jeff's discussion of epoxy degradation on the other thread got me wondering... <<snip>>  I know that UV rays can bounce/reflect off surfaces, so perhaps enough UV might bounce off the cockpit interior and still reach the underside of the deck to degrade it? I'm inclined to think this is unlikely, but then again...  Anyone know or have opinions about this?

I got a big lesson in UV degradation while rehabbing my last boat -- attached is a picture of the seatback coaming I was working on when I realized the fiberglass/epoxy covering  was separated from the Okume. There was virtually no bond remaining between the epoxy/glass sheathing and the underlying plywood.

After stripping off this area shown I noticed that a discoloration pattern in the underlying Okume matched the varying thicknesses of paint and the mounted hardware.  It amazed me how this patern matched the various thicknesses of covering materials.

I tried to add notes to the picture - hope it's readable on the forum.

You should be able to see where the UV bleached all the color out of the Okume through the 'paint only' areas (it was actually two coats of primer and two coats of paint)

The areas noted as 'nonskid' had two additional coats of paint with ultrra fine sand particles sprinkled on -- and you can see that the UV had much less effect on the Okume

The area marked 'genoa track' is where the track was mounted and completely blocked the UV degradation. In this area the epoxy/glass cover on the ply would NOT peel off as it did in the paint only area - where it lifted as if there was virtually no bond remaining.

Hope the picture demonstrates the reality of UV degradation for those interested.

From later research I learned that at least one (name forgotten) boatbuilder uses a black, high-solids primer specifically to protect the underlying fiberglass resin from UV breakdown.

[wkisting]

Hey Tom, what brand of paint did you use? That's really striking how precisely the pattern shows on the stripped wood. I would've thought most brands of marine paint would offer better UV protection.

Ray, do you usually finish off the CS interior with WR-LPU gloss/clearcoat, or do you only use that on the exterior hull?

[tom151]

Hey Tom, what brand of paint did you use? That's really striking how precisely the pattern shows on the stripped wood. I would've thought most brands of marine paint would offer better UV protection.

Who would'a though.. certainly not I. Further to that, other work done on the boat did not reveal delamination in areas the were vertical (as opposed to the deck which is horizontal) and was exposed to the Florida Keys sun for at least 10 years.

The mast, which was stored horizontally for 3 or 4 years, did have some delamination of the glass/epoxy skin from the plywood.

The paint... don't know the manufacturer, it was applied by the original builder - though taking into account the way he chose materials and hardware, it is likely to have been top quality epoxy paint for marine application.

[wkisting]

Aha! I just realized the WR-155 and SilverTip Yacht Primer are not the same thing... so I guess I'm actually using the new version. That means my comments above apply to the new version, not the older WR-155. I've never used the old, but I was pleased with the "build" of the SilverTip.

I applied the paint today. Roughed up the primer VERY lightly with 150-grit, wiped it down with acetone, then rolled on the WR-LPU. The WR-LPU is not as user-friendly as the SilverTip, but still good. It reminds me very much of high-quality latex paint, but it shares latex paint's tendency to "gather" at corners and edges. It will look nice and flat, but slowly seep into a little run mark. So you have to be more vigilant than with the primer, which stays put nicely. I'll have a few small runs to sand off when it cures, but nothing too bad. I really like the color Whidbey White, which is a very nice off-white with a hint of gray... though I suspect it will be a tad bright in the sunlight. We'll probably make tan or brown seat cushions to knock down the shine and soften the ride on our rears. 

Again, thanks Ray for steering me to this brand/type of paint. I'm very pleased with it.

[Randy C.]

Wes,

The interior is looking good. What is the purpose of the blue painters tape?

Randy

[wkisting]

Randy, I used the painter's tape to keep the paint off the surfaces where the deck will need to be glued onto the deck framing. Basically, I just masked off the top of each framing member, and the inside face of the cockpit rim, which will attach to the back of the coaming.

Ray, I use acetone because I've had a few bad experiences with microfiber towels not getting enough dust up. No problems on this boat, but on our last one, I had to re-sand and repaint an area because the microfiber just didn't do the trick getting all the dust off (resulting in poor paint adhesion). Acetone gives a bit of wetness that collects the dust onto the rag or into little balls that are easily sucked up by the vaccuum. I haven't actually tried wetting a microfiber towel... don't know why that never occurred to me. But I like the acetone because it evaporates so quickly (near-instantaneous). When I work with it, I have LOTS of ventilation... garage open, two fans running, etc. The only place I notice the fumes is working down in the little cubby between the forward seats (near the reinforcement stringers) because the bridge of the seats holds the fumes in there.

I suspect we put the topcoats on a bit thick, which is probably why we had some runs. I was using a short nap roller (3/16" foam-fiber) but it seemed to hold a little more paint than I wanted. I rolled it out thoroughly in the paint tray, but still laid down a lot of paint with each roll. We didn't really thin the paint much... just about 20 ml of water per quart, and only because it's in the 90s here in GA so I wanted to discourage the paint from drying out too quickly. We ended up using exactly three quarts to get two to three coats on the entire interior, plus a bit of the centerboard and the hatch covers. Likewise, we used exactly a gallon of the SilverTip primer to coat all of that as well, since the spec sheets recommended thicker primer coverage than topcoat coverage, and also since we had some touch-up work to do with the primer after sanding.

Here's a pic of the finished interior... keep in mind, looks better in pics. Up close, there's some roughness that makes it not quite professional-grade, but very nice looking nonetheless. If I weren't burned out, the perfectionist in me would do some sanding here and go back over it until it's perfect, but we're anxious to sail it and it's coming out quite nicely so we're going to keep plugging along. I'll come back to finesse the little flaws in the paint in a year or so.

[Randy C.]

Wes,

By the time you get your seat cushions and all your other "stuff" in the boat you probably won't notice the little flaws that you say you have. Looks good from here.

[Charlie Jones]

Sorry Ray, but Acetone has gotten a very bad, but largely untrue rap.

True it isn't good to breathe, but hundreds of thousands of women use it weekly ( or daily) to take the nail polish off their finger nails.

It's actually one of the more benign solvents- more so than Lacquer thinner and certainly more so than Tolene, Zylol or MEK ( NOT MEKP*).

One big problem with Acetone though is it evaporates SO quickly that it can leave residue behind of what you are washing off- not get it off completely.

Of course, when you can use it, washing with water is MUCH more benign than any of the solvents ;D

And as you say, much cheaper.

*MEKP is the catylyst for polyester resins Methyl Ethyl Ketone Peroxide- VERY bad stuff. Also very different from MEK- the P- the  Peroxide in there makes a BIG difference. I don't work with MEKP without gloves on ever. Of course I also wear gloves working with epoxy, but with MEKP I'm extra careful.

[wkisting]

Well, in retrospect Ray, I definitely agree with you about the wisdom and cheapness of using water to clean up instead. But at the time, it didn't even occur to me that since the Systems 3 is water-reducible, residual wetness wouldn't bother it. I'm so accustomed to the notion that the surface must be perfectly dry that it's second nature for me to reach for the acetone.

I did notice, however (after dripping small sweat droplets in just a few places while I was painting) that moisture on the surface does significantly reduce the adhesion of the paint (temporarily), making it difficult to roll on smoothly and evenly. So for any folks who do use water to clean up before painting with it, it is probably best to let the surfaces air-dry for a bit before applying the paint.

[Rod Thompson]

Ray, Wes, is it fair to say that you are getting better coverage than set out in the manufacturer's specs.  Seems to me they say 200-250 sq ft./gallon for the primer and something like 350/gal for the top coat.  Would be nice if their rates are conservative.

[wkisting]

About attaching the deck... Do most of you attach it piece by piece, or would it be better to join 2 symmetrical halves (like the port and starboard halves of the forward deck, or of the aft deck) BEFORE gluing them to the boat?

I guess I should clarify that I'm hoping to attach all the deck panels without using fasteners (i.e., just epoxy glue). I've found that webbing straps wrapped around the boat seem to pull the panels into shape quite nicely. The only place I'm concerned is the centerline on the forward deck within 10" of the bow, where there is a lot of pressure to make a very slight curve down to the side. Everywhere else the deck panels bend into place fairly easily.

[wkisting]

Well, all went very well installing the first two deck panels. I got a terrific fit using no fasteners whatsoever. All it took was some very creative strapping and a lot of masking tape. 

I attached both forward deck panels at the same time, then wrapped with straps to hold the panels down to the curved framing members. Then I ran tape along the edges to ensure all the edges were flush. I used a 2x4 down the centerline to hold the panels flush along the center, and the result was virtually no gap/seam between them. They could be finished bright, but I may still take Ray's advice and install a mahogany overlay to hide it altogether.

The trick to getting this method of attachment to work is that your stringers must be beveled perfectly for a smooth curve so that the panels align with them naturally and easily. Otherwise, tape will not be strong enough to "pull" the panels into shape.

Here's two pics... before and after.

[Norman Colter]

Nicely done Wes,

  I would have called that pic "I've got the tape, might as well use it"  ;D

Norm

[JeffM]

I remember that day: dozens of screws (ss, and they stayed), lots of epoxy and silica, and every heavy object I could lay hands on!  My decks are white non-skid--a very fortunate decision on my part.

[wkisting]

Time commitment to clamp the panels down wasn't too bad... probably about 30 minutes from the time I started wetting things out (prior to gluing) to the time I finished laying the tape (for both sides). But I thought it through carefully in my head first, so I knew exactly what I wanted to accomplish with the straps, tape, and board before doing it. Also, I have to work fast because the weather is really hot in GA now... so I've been keeping my epoxy in the air-conditioned house to give me a bit more working time. It's still gelling in under 10 minutes, and cured hard in about 2.5 hours instead of the usual 6 (I'm using the slow cure hardener from Raka).

I'm letting each pair of panels cure overnight before proceeding to the next two panels. This lets me line up the butt joins very carefully. They're not quite perfect, but they're coming out really darn tight and nice looking. I also like going slow so I can play with the panel fit to find the best color/grain orientation. Anyway, I attached the two side panels today, and tomorrow evening I'll put on the aft portion of the deck. I think I'll be able to do the whole lot with just clamps, straps, and tape. The fore deck had the most challenging curves, but that came out fine. The rest should be easier.

While I was waiting for the seal coats on the underside of the panels to dry today, I had time to build the masts. Took only about 4 hours start to finish to make the fiberglass bushings and fit the aluminum sections together. I went for a tight fit and then pounded the sections together carefully with a rubber mallet. I still have to make the tapered wedges for the sailtrack, but I was surprised and delighted with how quickly and securely they went together. One trick I learned--that maybe everyone else already knows--is to wrap the bushings slightly thicker than needed (I cut a small block of wood to use for thickness reference while wrapping the tape), then use a block plane to shave them down gradually to a perfect fit. Also, I pre-wet the tape before wrapping it, which was much easier than trying to wrap it dry and then wet it out on the aluminum.

[wkisting]

Yes on the mast track. Which edges need chamfering? (Where the ends join? Or along the full length of the track? Clarify?)

What is the ideal way to run the lines on the aft deck for the mizzen sheet? I'm trying to envision where I'll need reinforcement doublers for the hardware. I've noticed that the plans show the mizzen sheet running to a block right on either side of the tiller, but in some pics, a few builders have run the lines to the far corners instead (i.e., the outboard corners). Does it matter? I'm just wondering if there's a reason some folks have strayed from the plans. Or perhaps my plan sheet is old.

Will probably install the aft deck tonight. I can't believe how well the seams are coming out. Took some creative cutting, but I've managed to line up the grain pattern pretty well to make the entire deck look like it all flows, like one large chunk of wood. Not perfect, but keep in mind, these are all from different sheets of plywood. Fortunately, I was smart enough to select three sheets of ply for the deck back at the beginning of the project. I matched grains, envisioned cuts, and set aside the best matched three for color/grain. Some pics below of my seams... boring stuff, I know, but I'm proud of them. 

[wkisting]

What kind/size of rivets do you use for attachment? That may be a stupid question, but I've never used a rivet gun and will have to buy one for attaching the sail track. What should I look for?

Thanks!

[wkisting]

Got the deck installed and the first soak-in coat of epoxy on. We'll add a layer of 4 oz. glass next (when the first coat is semi-cured) because the Okoume dents very easily and the glass will give it a bit of extra durability from nicks and scrapes. Here's some pics...

Also, where do I need to add reinforcements for running the blocks/lines on the aft deck? And what should I use for reinforcement: a layer of 3/8" ply or 1x Douglas Fir lumber? I've seen some folks run their mizzen sheet to blocks right on either side of the tiller (as shown in the plans), but others place the blocks at the outboard corners of the aft deck. Does it matter? Is one setup preferable?

Thanks!

[Randy C.]

Wes,

Looks GREAT!!! You'll be sailing in no time!!!

[wkisting]

Speaking of hatches (deck hatches, not seat lockers)... how high should the rim of each hatch protrude above deck in order to keep reasonably dry below? I installed the rims tonight and mine stick up 1-3/4" above the deck, but it looks a bit high to my eye so I'm wondering if I should cut it down. My plan sheets do not specify a height for the rims of these hatches, but I don't want to cut it so short that it leaks.