Basic Painting Questions

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Re: Basic Painting Questions

Postby GreenLake » Mon Jul 06, 2020 9:54 pm

Update on the gelcoat experiment.

I've now done the rear third of the cockpit (between the seats). It had everything from exposed laminate to several layers of failed paint (plus drips from decades ago when the seats were painted). I mixed 10oz of white gelcoat (with wax!) with a few dollops of black tinting agent to get a basic medium gray. After adding 12 drops of catalyst / oz, and mixing well, I dumped all of it into the cockpit and used a spreader to distribute.

As an extra precaution, I sprayed a thin film of mold release using one of those paint sprayers with disposable cartridges.

Result is a bit rough in places but if I want "really nice" I have a set of floorboards to cover it up. As it appears at quick check, no problem with curing and it looks so much better than before. I'd have to work on my technique a bit before trying a deck or surface like that, but because the underlying surface was never totally smooth to begin with, "perfection" wasn't an option but "durability" is a goal. Gelcoat, because it cures by catalyst, can be applied in thicker layers than paint and I'm pretty confident that I'm not going to wear through this new coating.

The question remains what I'm going to do with CB trunk and the less critical areas of the cockpit (such as upper ends of cuddy walls and some of the transom areas). I'll probably extend the gelcoat in all places that can end up with standing water anytime a tarp fails and use paint for the remainder. The CB trunk has failing/flaking paint on it today, in the cuddy, protected from UV, the old paint is in very good shape, except that it's now a slightly different color. My conclusion is that with some practice and good gelcoat (like Evercoat premium one step which I used today) gelcoat can be an alternative to painting the cockpit floor.
~ green ~ lake ~ ~
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Re: Basic Painting Questions

Postby marcusg » Mon Jul 06, 2020 10:41 pm

Cool. Just got my new-used sander today (a 3.3 amp Bosch) so should be able to bang out the rest of the sanding in the next few days.

So could I paint the floor to get it to match the rest of the boat/cuddy, or is there a disadvantage to painting over the gel coat?
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Re: Basic Painting Questions

Postby GreenLake » Tue Jul 07, 2020 3:44 am

Paint can be pretty durable as well. However, unlike gelcoat, even if you knew a paint that lasted 20 years you couldn't buy it today, because practically all paints had to be reformulated. So the trick is knowing which paint to use. The one paint that I've used myself and that (once it's had a week(!) to cure) has been really tough is EasyPoxy from Pettit. I wouldn't hesitate to use that over gelcoat. (If you don't let it cure, you may find it very soft initially and if you try to use it at that point can probably damage it easily).

There may be other candidates, but none that I've tried.
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Re: Basic Painting Questions

Postby jalmeida51 » Tue Jul 07, 2020 9:57 am

I painted my bilge with Interlux inter deck one part polyurethane about 2 years ago and it has stood up excellent. I did add some silicone sand to increase the antiskid. The paint does have sand in it but I wanted a more rougher finish, I have no floor boards. It took 3 days between coats to dry. The previous owner painted the bilge and his paint peeled anywhere the water collects. Plus it was very slippery under foot. I gave the inter-deck 8 days to make sure it was completely dry. I did apply 2 coats.

I was told by a fiberglass repairmen you can apply paint over gelcoat but you shouldn't apply gelcoat over paint. He told me sometimes no problems other times problems.

Good luck on your project, John
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Re: Basic Painting Questions

Postby marcusg » Sun Jul 12, 2020 7:52 pm

So I've priced out my budget for all the paint and tools and fiberglass repair compounds for the cockpit, transom, and deck. Right now I'm going to skip doing the topside as that's looking in really good condition. Ideally, I can skip the bottom too, except for a couple small repairs, but then there's this...an approximately 4" crack that goes all the way through the balsa of the bottom. Must have hit a rock last season when wife and I thought 50 mph winds meant easy sailing (and we just got tossed around the cove by the boat launch and never got into the lake.) Here's a vid for specifics.

https://drive.google.com/file/d/1nXn4MZ ... sp=sharing

My question: I'd assumed I would have to treat this like a hole and cut it out, put in some laminated mat as backing, put that under tension to a concrete block outside the boat, and then do the 1:12, increasing layers of matting, normal repair treatment. But do I need to treat is as a hole? I mean, the lower balsa does have an "overbite" over the top edge of the crack, but it's still just a crack, right? Could I not sand it down and then use some kind of epoxy over it to just strengthen what's there, and then fair it? Would save me a bunch of time, especially since I'd like to do this first, so I know I have a sound boat before spending ~$1k on stuff, including a motor, for above the topside.
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Re: Basic Painting Questions

Postby GreenLake » Mon Jul 13, 2020 12:36 am

Marcus, that crack is eerily similar to the damage my boat sustained some years back.

For the story and how I fixed it, see "Gored: crack repair".

The TLDR:
(1) you don't need to cut a larger hole than the one that's there, you just have to get the crack and adjacent damaged laminate (in both dimensions!) ground away until you're left with a shallow groove (that may have edges that don't quite meed, so, yes, it's a hole).

(2) you may find that the edges will no longer line up due to tension in the hull; you'll need a bit of a backing plate in that case

(3) You can insert a piece of flat fiberglass (laminated on your work bench) through the crack and either use a central wire over a wooden cross piece or deck screws all around to pull it against the hull and pull the hull into alignment (you'll use a bit of epoxy as a glue, once that's set, you can remove screws/wire).

(4) If you don't need a backing plate, you don't need one. But if you do, it'll make the repair a bit stronger.

(5) The repair I wrote up took part of one weekend, in 3 or so chunks of time. Really not that involved to do it.

It's definitely a no-no to just "fill" the crack with some epoxy. I had a nickel-sized circular hole below the waterline that some PO "fixed" with caulk. One day, with the boat on the hard, I put my finger through. I don't want to imagine this happening on the water . . .

You keep mentioning "balsa". Does your boat have a wooden core?
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Re: Basic Painting Questions

Postby marcusg » Tue Jul 14, 2020 10:02 am

Thanks Greenlake, yeah your example looks pretty similar, except that, like you said, whatever interior patch/backing I apply will need to be inserted from the outside.

In your write up you said you "sawed" open the crack to remove damaged glass/even out the criss-cross overbite. What saw did you use? I know a lot of instructions say to use a router but I don't have access to that, and I wonder if I could just use my orbital with 40 grit to grind down the fiberglass or if sanding cross-sectionally hurts the glass' strength.

I also worry about using a saw because I don't know what's immediately behind the hull there. Like some kind of structural members maybe?

Oh and I actually think I was wrong about the balsa core thing. It's just that the fiberglass along the crack looked a little brown colored and the texture reminded me of wood. I'm very new to working with fiberglass and all this. I figured because the transom/floor had wood under the laminate, the whole boat must do that.

I also wonder if I can use your strategy, since I won't necessarily be able to get such a big interior patch as you did to provide so much strength? Wouldn't I then have to do more of a 12:1 bevel on the outside and slowly build it up with matting and epoxy?

Another idea: My sailstar is built differently than the DS in that the cuddy isn't right up next to the walls with only a bulkhead separating it. The cuddy is actually raised about 8" off the cabin floor, but it seems there's an old patched-over access hatch into the interior hull of the boat, that I could maybe cut open and get access to the interior hull wall. I'm not totally averse to cutting that open, but it's just intimidating to create more work and stuff to patch and I don't know how I would then patch that to be very stable since I obviously can't put a patch below the cuddy floor. I can take a pic of this later - basically there's a 2' square of cracking in the cuddy floor where the paint is broken off (looks unintentional) where I suspect somebody opened it up at one point.
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Re: Basic Painting Questions

Postby GreenLake » Tue Jul 14, 2020 10:50 am

Marcus. glad we got the confusion re balsa out of the way. Broken laminate will show exposed fibers or look "milky". Solid laminate will appear dark (unless backlit, in which case it may simply look translucent, or show the color of its background).

For removing fiberglass you can use any cutting / abrasive tool that won't get dull from the glass. You can use a disk/orbital sander with 40 grit (or less) to cut the shallow V. The only thing you might like to avoid is creating excessive heat. You will find the that area of damaged laminate extends beyond the visible edge of the crack.

If your crack has a bit of "overbite" you need to sand/grind that area away completely, otherwise the two sides won't ever align. An angle grinder would work, for example, even your sander if held at a steeper angle. Really anything you have (or are willing to purchase) and can bring to bear that doesn't penetrate very deeply. Nothing wrong, btw, with drilling a hole or two right there and probing with a wire to get an idea of clearance.
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Re: Basic Painting Questions

Postby Abaird62 » Wed Jul 22, 2020 9:06 pm

Hi!

Using the parameters you have, I would reccomend Rustoleum Topside Paint. $16.99 /gt. It does a good job. I rolled the interior with 2 quarts. 1 1/2 qts for the top. It covers very well. You can find it at some lowes, and Home Depots.


Pros : It did't break the bank.
Cleans with soap and water, (Maybe a little kerosene helps too)
Covers well.
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Re: Basic Painting Questions

Postby marcusg » Thu Jul 23, 2020 1:47 pm

This morning I got the lovely experience of wearing a Tyvek suit, half face respirator, and goggles to sand a boat bottom on a hut summer day! :)

Here's what the crack looks like ground out. Turns out there was a perpendicular crack on the mid-lower left so I had to extend my sanding in that direction also. 40 grit sander worked fine, just took a while and a few discs as the edges got worn out quick.

boat repair (Small).JPG
boat repair (Small).JPG (97.43 KiB) Viewed 576 times


My question now is: what about that foam? (I'm assuming everywhere below the waterline on the boat looks like this?) Had it just been hollow space behind there, installing a backing patch of laminate would seem easy. The foam is pretty tight against the hull, but I can push on it with a screw driver or cut it out or what have you. I imagine I wouldn't want to cut out too much though, right?

Also, Greenlake, in your "Gored" repair, it seems like you didn't do the traditional 1:12 taper. Is that so, and was it because the crack was so narrow and also backed by the laminate patch? I'm wondering if I should give mine more of a taper since it seems wider than yours?
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Re: Basic Painting Questions

Postby GreenLake » Thu Jul 23, 2020 9:12 pm

The foam is good, because it gives a place for the repair to rest against (and it's probably helping the two edges stay reasonably aligned). Just cover it with something like a sheet of plastic, so it doesn't get resin-soaked.

You are correct, it will make it tricky to put a "patch" from the inside, but even so, the repair will most likely be plenty strong. If you feel better about a 1:12 taper, then, by all means sand some of the narrower spots to where you get closer to 1:12.

Finally, if any of that dark stuff is paint, I suggest you sand just the paint off for about 2" around the repair. That will allow for better fairing of your repair when done.

PS: while you could slice a backing patch into 2" strips and wiggle them between foam and hull (with glue on), I'm not sure what that ultimately buys you. The foam already supports the area by preventing it from flexing. What do you think?
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Re: Basic Painting Questions

Postby marcusg » Thu Jul 23, 2020 9:41 pm

So what I hear you suggesting is to essentially use the foam as the counterforce against the exterior repair, so therefore I wouldn't need an interior patch doing that?

That sounds great, except that the foam isn't totally flush with the hull anymore where the crack was, as I ground some of it away (not much, maybe 1/4 - 1/2 inch) in order to sand off the fiberglass. My worry would be that this would create a "weak point" exactly where the patch is that could be easily pushed in. I suppose that's all the more reason to do a 1:12 taper?

A couple ideas:
-Use very hard plastic sheet as the epoxy barrier between interior hull and foam, which would be easier to jam in between foam and hull and would itself give some strength/backing to repair.
-Fill in the foam cavity that I sanded away with some kind of household product like that spray foam for filling cracks and such. Then try best I can to sand it flush with interior hull?

What you think? Also, any recommendations for epoxy brands for repairs?
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Re: Basic Painting Questions

Postby GreenLake » Fri Jul 24, 2020 1:57 am

At this point you are overthinking it. :D :D

To make a neat job with the same thickness laminate, you might use the plastic window of some retail packaging. That's flexible enough to squeeze in there and firm enough to bridge the hole while your epoxy is curing -- after that, your repair will be nice and strong and you won't be able to dent it (other than by using a tool or a rock). Don't worry if there's a small cavity. (The support the foam gives is for flexing of the whole side of the hull. When that's absent, there won't be any flexing at your repair site either).

You may need to divide the plastic sheet into two or three parts. Don't worry about any gaps < 1/4" or any overlaps.

More important, but far is t to make sure you get a super bond and strong laminate for your repair:
  • make sure you have de-waxed the repair area before final sanding (or all your sanding grooves will have wax in them).
  • make sure the epoxy is mixed accurately and stirred well; scrape side/bottom of container while mixing or you'll get a reservoir of badly mixed resin there
  • make sure your ration of glass to epoxy is high (don't over-saturate)
  • make sure your glass is wetter evenly out w/o white patches
  • make sure your layers of cloth proceed from largest to smallest (like nested U's).
~ green ~ lake ~ ~
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Re: Basic Painting Questions

Postby marcusg » Fri Jul 24, 2020 9:21 am

Ok cool, sounds good. Is that largest to smallest from interior to exterior or vice versa?
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Re: Basic Painting Questions

Postby GreenLake » Fri Jul 24, 2020 9:55 am

largest first.

yes, not what you might think, but that's the recommended order.
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