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Old 03-23-2013
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Hull color?

Hey, did I miss something in hull color 101? Was at Soloman's I. today and saw (2) boats on the hard with newly painted 'black' hulls. Wife and I went over to Drum Point, and there were a couple of guys painting a couple of boats there 'black' also? What's up? Does it help with 'growth on the bottom'?
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Old 03-23-2013
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Re: Hull color?

No, has nothing to do with bottom growth. Has a lot to do with the temperature inside the hull in the hot summer sun. The hull might look nice at anchor, but it will be hotter than hell inside.
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Old 03-23-2013
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Re: Hull color?

You know, they did look good, on the hard that is. Four boats in one day is a little much. I would think one once in awhile would be ok, but four in one day, was a bit much for me, LOL!
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Old 03-23-2013
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Re: Hull color?

Topsides or bottom paint?

Topsides it makes for a HOT interior, on the bottom it helps hides the Chesapeake slime.
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Old 03-23-2013
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Re: Hull color?

Nate Herreshoff said this: "There are only two colors to paint a boat, white and black and only a fool would paint a boat black!" . . . or something like that.
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Old 03-23-2013
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Re: Hull color?

Well color me a fool. I am going from dirty white to flag blue. There are really only a few weeks this far north that are really hot.
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Old 03-23-2013
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Re: Hull color?

Darker colored hulls are becoming more popular nowadays. They do look good, but yes are hotter in the summer.
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Old 03-23-2013
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Re: Hull color?

There are several problems in painting a boats topsides a dark color, especially in areas that are hot in the summer ... and besides the heat transfer into the 'insides' that occurs in summer:

The primary problems are the fiberglass matting layer and the very long term cure rate of most polyester resins.
White fiberglass boats typically have a rather thin glass matting layer beneath the gelcoat. The matting layer is to provide a uniform cosmetic base for the gel coat and to ensure that the subsequent final cure of the resins, over years and years of thermal cycling of the topsides, results in and maintains an even flat planar surface and so that the structural roving layers of the laminate don't 'print through' and show up later as hundreds of thousands of small raised 'bumps' on the surface.

Black or dark colored topsides, when built, have extra thick matting layers to provide a 'cushion', the depth of matting sufficient to lessen or prevent 'the bumps' from 'print-through' of the structural roving layers that will develop due to thermal cycling over many years.

Boats that have cored topsides and have been "painted" dark/black can have the coring release from the outer fiberglass laminate structure .... eg. Niagara boats and also many Hunter rudders that have been painted with 'dark' bottom paint, as examples.

Sure dark and black topsides are absolutely beautiful because of their stark contrast between the topsides and the white decks and houses on top. But if you want that dark painted hull to remain dazzlingly beautiful, you'd better have a thick matting layer in that topside laminate structure or you risk having the topsides over time and many thermal swings of the surface develop into something that looks like a teenager who developed a severe case of 'low profile' acne. Before you go through the agony or expense of changing a boats topsides from white to dark color by painting ... simply take a good walk through any boat yard looking for hulls that have been painted black, blue or 'dark'; put your eyeball close to the hull and sight down along parallel to the surface and see what YOUR formerly flat and fair white hull is going to look like after several seasons of thermal cycling at higher temperatures .... and then ask yourself: will you be satisfied with a hull that has zillions of slightly raised little 'bumps' and quite obvious and developed 'hard spots' where any bulkhead is in contact with the topsides/hull? Do take that walk through any boat yard and seek out older black or dark painted topsides boats .... as THAT what youre going to see is a damn good possibility of what your dark painted topsides/hull is going to look like in a few short years.

Last edited by RichH; 03-23-2013 at 11:20 PM.
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Old 03-24-2013
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Re: Hull color?

Hi Rich

Interesting that you mentioned the "bumbs" showing through the gelkote. My boat (a Tayana 37 like yours) is a 1985 vintage and has for the past several years have shown small dimples or "bumbs" in the groves. I know that I have a very thick matt layer on the boat bottom so maybe those bumbs were not caused by thermal cycling. Now if I can figure out a way to be rid of them. The hull gel color is a light beigh and I've seen similar "bumbs" on other T37s with white gels.
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Old 03-24-2013
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Re: Hull color?

Quote:
Originally Posted by lancelot9898 View Post
Hi Rich

Interesting that you mentioned the "bumbs" showing through the gelkote. My boat (a Tayana 37 like yours) is a 1985 vintage and has for the past several years have shown small dimples or "bumbs" in the groves. I know that I have a very thick matt layer on the boat bottom so maybe those bumbs were not caused by thermal cycling. Now if I can figure out a way to be rid of them. The hull gel color is a light beigh and I've seen similar "bumbs" on other T37s with white gels.
A totally different situation on Tayana boats ... probably poor mix of OEM gel/MEK ratios / dirt / and someone forgot to drain the air compressor before spraying the gel, plus they probably let the gel fully 'kick' and then waited a day or so before laying matting, etc. .... I 'think' its principally an adhesion problem due a bad mixing, etc. The gel is VERY thick on a Ty37 ... and that may be part of the 'problem'. The good news is that the matting layer is also quite thick.

Im currently sanding down through and re-doing the gel. That beige is ROYAL PAIN to color match as it rapidly fades when 'new' .... arrrrgh. If you consider to re-gel or repair the gel do get a computer color match ... but you have to cut a 3/4" plug from the hull and send it out .... and then deeply sand down into the adjacent gel to remove deeply faded gel and surface oxidation.


BTW - those Tayana pimples will eventually spread, worsen and increase (not larger sized pimples, just 'more' of them) as the gel ages with sun exposure, so do aggressively power-buff and wax often. If you 'get to' these 'teeny pimples' early, you can simply 'pop' them, fill with epoxy and simply spray repair over the repair with new gel. If you let them 'grow', then youre going to have to sand deeply into the faux strake and redo entirely, ... got the tee shirt. Also, Ive seen these Tayana pimples turn into severe alligator cracking of the gel on older ill-maintained boats.

Im doing mostly long distance cruising, I also know that ALL topside paints can't withstand being immersed for very long times (such as being heeled over for for days and days on end)... so that removes any possibility of painting the topsides for me. Ive been down the road of 'topside' paints on other boats, they simply cant be immersed for long term periods without the potential of 'lifting' ... all the paint tech data states this, and I had to find this out the 'hard way'.

;-)

Last edited by RichH; 03-24-2013 at 02:12 AM.
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