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Old 19-08-2016, 14:00   #61
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Re: Black boat and the tropics, a good idea?

Buy for $15 IR thermometer and test different colors of cars on full sun.
You'll be suprice how big difference different colours make.
10-15 C easy. You can always keep it black underwater hi hi.
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Old 19-08-2016, 14:03   #62
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Re: Black boat and the tropics, a good idea?

patricia belle is black and comfortable. lung ta was dark blue and painted their hullbeige as they said it was too hot.
as in some years the water never gets much below 80f and in summer itis closer to 100 than 80, the water under the boat doesnt give a rats poo if your hull is white or poo brown or black.
it is hot n humid even at night. despite the nice cooling winds.
remember the air at night also stays fairly warm.
tropics is tropics, not florida, not maryland, but within the tropic of capricorn and tropic of cancer.
temp stays essentially same year round. humidity is only thing to change
there are skirts to put over hull to keep sun off and interior cooler.
but then most yotties donot wish to have the alleged clutter on board that helps reduce the temperature one must endure on boat between water temp and air temp.
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Old 19-08-2016, 14:37   #63
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Re: Black boat and the tropics, a good idea?

Quote:
Originally Posted by LakeSuperior View Post
Jim - you are missing 1/2 the simple physics here. Radiative exchange with your surroundings is a significant factor in comfort and most non-heat transfer lay people miss this part.

So if the air temperature inside is 70 F (due to ventilation) and the inside hull temperature is 80 or 89 F you will be significantly more uncomfortable than if the inside hull temperature is 70 or 75 F.


Also, because the skin layers are relatively thin compared with the hull area only a very small fraction of the heat will be conducted to the seawater. Conduction depends on the cross-sectional area, distance heat must travel, and temperature difference.
Well,let's see...

Radiative exchange does count, and that is why the insulation and or ceilings with air space are important, as I mentioned. These factors isolate the occupant from radiation from a hot hull as well as reducing convective transfer. Further, without doing any calculations, I wonder if the difference in black body radiation from a 70 deg F surface and an 80 degree surface as you postulate is significant? Seems unlikely to me .

The only hull material with enough thermal conductivity to provide any useful cooling is Aluminium. And you are correct in that there is little heat transfer from the deck areas to the sea, but I've done highly scientific tests (placing my hand on aluminium hulls at the WL and at higher points) and there is definitely a temp gradient so some transfer is occurring. Does this have any real affect? I dunno, but it surely can't hurt, especially at lower sun angles.

Jim
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Old 19-08-2016, 16:35   #64
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Re: Black boat and the tropics, a good idea?

I love the look of the dark hulls. Yeah, they're likely a bit hotter, but they look COOL!

On the downside, keeping a dark hull clean & beautiful (i.e., not showing the salt), will take more work. In the Med we see a lot of black or dark blue hulls, but they're often the superyachts with multiple crew busy cleaning the hulls. The rest of us more commonly have white hulls.

Lots has been said about the heat of teak decks too. We've had both white non-slip on a white hull, and teak on a white hull. We noticed no noticeable difference on the interior temp, but the teak decks are definitely hotter to walk on. Still, they look so much nicer I wouldn't give them up.

If you like the boat, I'd go for it.
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Old 19-08-2016, 16:45   #65
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Re: Black boat and the tropics, a good idea?

Black absorbs heat. White reflects it. Only a fool needs additional conversation.
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Old 19-08-2016, 16:57   #66
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Re: Black boat and the tropics, a good idea?

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Originally Posted by tikirawker View Post
Put an offer in about a year ago on this black boat named 'imagine'.
The sale didn't go through as we got freaked out by the 7' draft and they got freaked out by our offer...
The boat had very smooth lines and was gorgeous.
I didn't even consider the extra heat from black paint.
Sometimes things work out for the best and you don't realize it until much later.

To the point of color. I don't even wear dark colored clothing in the daytime while on the boat. The extra heat makes life brutal and miserable.
Finally,this really is a black or white answer black(hot)
white(cool) dress in black and then white in sun,then this becomes a non discussion.I drive two identical cars
Black in winter,silver in summer difference is extreme.
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Old 19-08-2016, 17:38   #67
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Re: Black boat and the tropics, a good idea?

My black hulled boat has spent over 800 days in the tropics with no blistering and looks great. If you're going to the tropics and are afraid of heat might I suggest Kodiac
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Old 19-08-2016, 17:38   #68
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Re: Black boat and the tropics, a good idea?

Our boat is black and we live in between the tropics full time.

I think black and shiny with some insulation inside is zero problem (this is what our boat is like). Our low topsides may be helping too (only 2 ft of it).

BUT black and no gloss and metal and no insulation inside will definitely get hot.

Topsides do not get all that much radiation as tropical sun is mostly overhead. Now a grey unpainted aluminum deck is quite a different thing. And teak deck laid on non-cored grp is ...

So, to sum it up, black is OK but if you want to be 100% out of the zone you want a white shiny boat with white decks and plenty of awning when docked/anchored.

Cheers,
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Old 19-08-2016, 17:54   #69
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Re: Black boat and the tropics, a good idea?

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Originally Posted by UNCIVILIZED View Post
Mark J I dare you to go out on a 30 deg. C day & stand for 3min. on both; a patch of (light grey) concrete which has been in the direct sun for several hours, & then do the same in an (black) asphalt parking lot.

Hint: have a friend standing by to take you to the Emergency Room for severe burns on your feet. Mostly from the asphalt.
Except very few DECKS are black.

Black boats implies (to me) black topsides.

You are right that a black deck could be a horror.

Somehow, the substrate material counts (even though I do not know the scientific explanation).

My experiment for you: stand on a white plastic deck then stand of a mirror finished SS plate glued to this deck. Which will be warmer?

How come since mirror gloss SS should reflect most of the sun???

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Old 19-08-2016, 18:01   #70
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Re: Black boat and the tropics, a good idea?

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Originally Posted by reed1v View Post
Lots of research on black fiberglass hulls in the tropics. Bottom line: not good. Has structural impacts.
Googled. Found nothing of note.

Links?

White decks cause glare which causes eye cancer.

Googled. Found nothing.

Cheers,
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Old 19-08-2016, 18:23   #71
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Re: Black boat and the tropics, a good idea?

Painting a wood boat black, is a very bad idea. I know two who did and it didn't last a year with all the seams opening up. Looked good.
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Old 19-08-2016, 18:27   #72
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Re: Black boat and the tropics, a good idea?

My hull is black. But my Hull is also insulated everywhere above the waterline with the exception of the wet lockers. No problems with the heat with one exception - The refrigerator will run longer and harder if the sun is shining on that side of the hull (port).
My solution is to use a car windshield reflector tied on to lines and tossed over the side to shade that part of the hull when at anchor. It works great. And if I'm at anchor I have a tent cover I can use that funnels the wind into the hatches and shades the deck.
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Old 19-08-2016, 18:32   #73
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Re: Black boat and the tropics, a good idea?

we changed from dark blue nonslip deck paint to white and mixed aluminium in the dodger grey paint to reflect heat and improve radar footprint approx -8 degrees cooler in full sun / at the moment 30 degrees inside the boat / the tide is still coming in / the hull will cool down slightly when she floats / water temp is between 18 - 25 degrees /be a shame for you to miss out on a good boat for the cost of a coat of paint / perhaps paint the decks first then next season the upper hull / we used black anti-foul for 15 years didn't notice any difference in heat after changing to diy hard copper
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Old 19-08-2016, 21:14   #74
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Re: Black boat and the tropics, a good idea?

Quote:
Originally Posted by Tikka View Post
Buy for $15 IR thermometer and test different colors of cars on full sun.
You'll be suprice how big difference different colours make.
10-15 C easy. You can always keep it black underwater hi hi.
You wanna really test your IR thermometer??? Over here we measure the surface temperature of our metal clad buildings, almost all of which are about 18% reflectance. During the heat of the day with an average shade temperature of 120 degrees F, we've IR measured the surface at 160 degrees!

At these extreme temps I doubt black versus white makes much of a difference in reality - it's just too damn hot!
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Old 19-08-2016, 22:03   #75
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Re: Black boat and the tropics, a good idea?

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I would doubt you would notice a difference. Maybe a scientific digital thermometer could... but really... you and I? On a Blind RTC? I doubt it.

If everyone tells u a black boat is hotter you will sweat more... but Pavlovs dog does too...

Buy what you want and learn to be man enough not to worry about .2 of a degree

If its your wife who gets hot, I know a great solution
You can't be serious! - perhaps you meant 20C?
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