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Old 30-01-2013, 10:39   #16
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Re: blue hull concerns

The Light Reflecting Value (LRV) gives you an idea of how hot your boat is going to be. What isn't reflected is absorbed.

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Old 30-01-2013, 10:52   #17
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pirate Re: Blue Hull Concerns

Kinda make one wonder why the Bedouins and others use dark colours...
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Old 30-01-2013, 10:52   #18
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Re: Blue Hull Concerns

I had a black boat that we lived on in the Caribbean for several years. Eventually painted it white when planning to sell, because I know a lot of people are concerned about the heat issue. So up North, dark hulls are beautiful and can add to resale value, down south it can hurt resale value.

The darker paint will fade faster and need to be repainted sooner. I found that it didn't make a terribly large difference in the boats interior temperature, I suspect that sun shining on the deck makes a much bigger difference than the sides of the boat. A decently ventilated boat with air flowing through it will be fine no matter what the color. The biggest issue we had was with the outboard lockers. They got 'really hot', and we had to be very selective about what things could be stored in them.
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Old 30-01-2013, 11:05   #19
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Re: Blue Hull Concerns

Roughly 50 % of solar radiation (visible & near infrared) is absorbed at the earth’s surface.
Black surfaces usually absorb up to 90 % of this energy and therefore get hot.
White surfaces, on the other hand, absorb only up to 25 % and tend to stay much cooler.
The physics are analogous to sitting in the sun wearing black clothing versus wearing white clothing – you will feel the heat difference.

In addition the 'LRV' Donradcliff mentioned, also Google:
Total Solar Reflectance (TSR)
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Old 30-01-2013, 11:11   #20
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Re: Blue Hull Concerns

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Originally Posted by Seafarer24 View Post
The red end of the color spectrum absorbs light / generates heat much better than the blue end. Yellow would be hotter than the same shade/tint of Blue.
NOT!

This is why I chose yellow (w/o going to white) with light gray decks to paint the boat.

Which colors absorb more sunlight? - YouTube
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Old 30-01-2013, 11:19   #21
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Re: Blue Hull Concerns

If you go with blue, make sure you add extra insulation to the reefer box if it is located on the outboard side against the hull side.
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Old 30-01-2013, 11:26   #22
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Re: Blue Hull Concerns

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Originally Posted by boatman61 View Post
Kinda make one wonder why the Bedouins and others use dark colours...
The same reason I use a dark blue sumbrella bimini. The heat does not pass thru it. It absorbs the heat. How many white bimini's are out there.

The cloth does not transfer the heat, where as FG will.

The other thing too, is shinny will reflect the rays and flat colors absorb. So if you have a shinny white next to a flat white. The flat white will be hotter.
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Old 30-01-2013, 11:33   #23
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Re: Blue Hull Concerns

I also owned a flag blue hull. Beautiful but a substantial maintenance problem.

Dark hulls show salt. The only way to have the flawless blue of the boat show boat is to wash the hull down in the slip after each trip. Once dried, the salt is quite hard to remove.

Even if you don't care about the white haze of salt, it is like sandpaper. A fender rubbing on a salt encrusted hull will damage it. Some dark boats hang canvas pads between the hull and fenders.

Finally, launch drivers and boat yards absolutely believe that dark hulls can be scratched without anything coming in contact. As proof they offer up "It wasn't me" when shown a scratch.
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Old 30-01-2013, 12:07   #24
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Re: Blue Hull Concerns

We never had problems with colour fading or easy scratches.. Neither had to do much polishing. Salt wasn't hard to remove either - a simple washdown would work just fine.

It might be the difference between coloured gelcoat and Awlgrip. We had Awlgrip.

Though we did end up with honeycombed sides (that's on Jeanneau factory applied, for Boatman ).
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Old 30-01-2013, 12:40   #25
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Re: Blue Hull Concerns

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Originally Posted by delmarrey View Post
The same reason I use a dark blue sumbrella bimini. The heat does not pass thru it. It absorbs the heat. How many white bimini's are out there.

The cloth does not transfer the heat, where as FG will.

The other thing too, is shinny will reflect the rays and flat colors absorb. So if you have a shinny white next to a flat white. The flat white will be hotter.
Consider this...the coolest Bimini fabric color is white on the outside with a dark color inside. The white color reflects most rays with the dark color inside blocking UV from penetrating through.

Ever sit under a dark blue Bimini on a hot sunny day and feel the heat being radiated downward?
Of course, if the wind is blowing the radiated heat will be blown away...thus dark fabric works well in tradewind locations. A white color fabric on the outside would make it more efficient.

Practical Sailor confirms this theory during a test of bimini/dodger fabric types.

Ronbo
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Old 30-01-2013, 12:46   #26
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Re: Blue Hull Concerns

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Originally Posted by ronbo1 View Post
Consider this...the coolest Bimini fabric color is white on the outside with a dark color inside. The white color reflects most rays with the dark color inside blocking UV from penetrating through.

Ever sit under a dark blue Bimini on a hot sunny day and feel the heat being radiated downward?
Of course, if the wind is blowing the radiated heat will be blown away...thus dark fabric works well in tradewind locations. A white color fabric on the outside would make it more efficient.

Practical Sailor confirms this theory during a test of bimini/dodger fabric types.

Ronbo
I'd agree! Just don't want to have to write a book. Hope'n people will use thar nogg'n.
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Old 30-01-2013, 13:19   #27
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pirate Re: Blue Hull Concerns

Dark hull... light topsides...

Anyway I like dark colours....
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Old 30-01-2013, 13:59   #28
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Re: Blue Hull Concerns

Hot or not, more maintenance or less, doesn't matter. You have to do whatever keeps your wife happy.
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Old 30-01-2013, 14:29   #29
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Re: Blue Hull Concerns

I bought a black hulled boat once. Was hot as hell so finally painted it white but left a small strip black around the rub rail because it looked nice. On the inside you could feel exactly where the black strip was by waving your hand up and down a couple of feet from the hull. The heat radiated from the black section like heat from an electric space heater.

The white decks helped but forget a dark hull unless as Bash says, you never sail further south than Newport or you run an air conditioner (and generator) non stop.
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Old 30-01-2013, 14:36   #30
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Re: Blue Hull Concerns

Quote:
Originally Posted by skipmac View Post
I bought a black hulled boat once. Was hot as hell so finally painted it white but left a small strip black around the rub rail because it looked nice. On the inside you could feel exactly where the black strip was by waving your hand up and down a couple of feet from the hull. The heat radiated from the black section like heat from an electric space heater.

The white decks helped but forget a dark hull unless as Bash says, you never sail further south than Newport or you run an air conditioner (and generator) non stop.
We have a six-inch navy blue bootstrip on our hull, and in the summer we can feel its location from the inside of the hull. Wonderblond first discovered this while changing the sheets one day, and she immediately shut down the batteries because she thought a circuit was overheating.
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