Are dark hulls hotter?

[Cadence]

Originally Posted by belizesailor

Have a buddy who is a coatings chemist for Sherwin Williams. He was involved in developing dark paints for military applications with IR signatures similar to vegetation.

Just by chance I introduced him to Chris White last year...I've heard that as a result there may be a dark hulled Chris White design under construction to be painted with these coatings.

If it works, all your friend will get it a pat on the back. I'm sure everything is prepriatory. He may get a raise?

[Sundae Driver]

The same kind of discussion about color for hulls occurs with motorcycle helmets. I'd get that question a lot when I was teaching riding courses here in Virginia. Some said black full face helmets are hotter, where others argued that color made no difference. To find out, experiments were conducted though the data points were small. I guessed that it would not matter since there is a good bit of insulation inside the shell that rests between the rider's head and the outside of the helmet. Outside, sure, the darker one could be hotter (more on that in a bit).

Inside Results: nope. There was no discernible difference on the inside temperature readings. The tests were achieved by placing a black, an arrest me red, and a white helmet in the summer sun and leaving them sit there for hours. We put handy mercury thermometers inside and closed the full faced lids leaving them pointed towards the shadows. The tests were repeated over the course of a few weekends and the thermometers were swapped between the lids.

It turned out that color didn't matter but leaving the helmets on the parking lot caused them to be a lot hotter than when they sat in the grass. The official (highly calibrated) blind touch test showed that black helmets were warmer to the touch than white though. We had the students close their eyes and feel both and say which one if either felt warmer. Sometimes we would present them with the same lid just to test their honesty. This was done in full view of the other students so, they knew we were being tricky...

I own black, red, and white helmets but tend to choose the black one most often just because I like the look.

Kindest,

Sundae

[S/V Illusion]

Bottom line appears to be -

People with vanilla boats like them and think colors increase heat, and

People with 'colored' boats like them and think it makes no difference and prefer non- vanilla.

An epiphany?

[four winds]

I recall someone saying it's probably hotter but fine for them. Because they preferred a dark colored boat regardless.

[skipmac]

I bought a black boat and loved it. The awlgrip job was beautiful. A few years later the paint job was damaged by an idiot's dinghy so I repainted it white but left a stripe of the original black for trim.

The boat was balsa cored hull and deck.

Below decks you could feel exactly where the stripe was on the outside. Like holding your hand up to a radiant heater.

Good ventilation kept the interior cool enough but just that one black stripe absolutely made it hotter below.

[s/v Jedi]

Not only is a darker hull hotter, it is amazing how little color becomes much hotter. A light gray is much hotter than white.

Some core materials or putties can't be used under a dark color paint. An example is West System Ultralight fairing filler.

[Bregts]

Originally Posted by s/v Jedi

. A light gray is much hotter than white.

My steel insulated deck was painted light gray, after painting it white my inside/cabin temperature went down 3 degrees celcius in the same weather. A big difference in comfort.

[s/v Jedi]

Originally Posted by Bregts

My steel insulated deck was painted light gray, after painting it white my inside/cabin temperature went down 3 degrees celcius in the same weather. A big difference in comfort.

Exactly. I once had light gray decks with a white superstructure and while I could walk barefoot on the white part, you could fry an egg on the light gray.

[southern blue]

yes dark hulls are hotter but i prefer to vent i own a adams 40 in midnight blue with sand deek and trim.

[CLady]

My dark blue hulled boat that gets warmer than white ones grows things faster
from the water line down. :/

[poiu]

Originally Posted by s/v Jedi

Not only is a darker hull hotter, it is amazing how little color becomes much hotter. A light gray is much hotter than white.

Some core materials or putties can't be used under a dark color paint. An example is West System Ultralight fairing filler.

There is a huge difference as you say between colours and even between shades of white. To get the best heat reflectance and emissivity you need just the right one. I saw a chart once by awlgrip. Out of a dozen shades of white, there was a clear winner. They may be able to provide the data. I searched the Web, but couldn't find it.

[Sea Frog]

Actually there is a product especially developed for marine use. Nippon Ever Cool. There is a temp chart showing the effect of paint, very interesting. I am not sure you can use it for hulls though...

[robert sailor]

Originally Posted by Sundae Driver

The same kind of discussion about color for hulls occurs with motorcycle helmets. I'd get that question a lot when I was teaching riding courses here in Virginia. Some said black full face helmets are hotter, where others argued that color made no difference. To find out, experiments were conducted though the data points were small. I guessed that it would not matter since there is a good bit of insulation inside the shell that rests between the rider's head and the outside of the helmet. Outside, sure, the darker one could be hotter (more on that in a bit).

Inside Results: nope. There was no discernible difference on the inside temperature readings. The tests were achieved by placing a black, an arrest me red, and a white helmet in the summer sun and leaving them sit there for hours. We put handy mercury thermometers inside and closed the full faced lids leaving them pointed towards the shadows. The tests were repeated over the course of a few weekends and the thermometers were swapped between the lids.

It turned out that color didn't matter but leaving the helmets on the parking lot caused them to be a lot hotter than when they sat in the grass. The official (highly calibrated) blind touch test showed that black helmets were warmer to the touch than white though. We had the students close their eyes and feel both and say which one if either felt warmer. Sometimes we would present them with the same lid just to test their honesty. This was done in full view of the other students so, they knew we were being tricky...

I own black, red, and white helmets but tend to choose the black one most often just because I like the look.

Kindest,

Sundae

If you made your choice based on visibility (safety) then you would choose white. Black is the worst color for being seen.

[GordMay]

Greetings and welcome aboard the CF, southern blue.

[Duct Tape]

A couple of years ago there were two big Royal Huisman ketches anchored next to each other in Antigua. Both had recently completed paint jobs. One dark blue and one white. The crew on the blue one ( me ) started to wonder how much hotter our hull exterior was compared to the White one. Jumping into the tender with an infrared thermo. I took some readings. The blue hull measured on the beam at 1400 was 77C. The White one was 58C. I was not surprised that the darker hull's exterior was hotter. I was surprised by the difference though.