Are dark hulls hotter?

[Rohan]

Originally Posted by Julie Mor

The devil's advocate in me asks, "If dark surfaces are such a problem, why does Oyster install teak decks on their boats?"

Teak is darker than a white deck, but it's still not like dark blue or black. That does make a difference. Wood also acts as it's own insulation, so while it might be hot on your feet on a summer day, the underside of it would not be very hot. On a related note, I have heard that cork decks are much more heat resistant, but I have no experience with this.

On another note, has anyone else noticed that nearly ALL America's cup racing boats have black hulls? Does black make a sailboat go faster? Or maybe at those speeds everyone is freezing so they need all the heat they can get?

[evm1024]

Done a lot of astronomy in days past.... Some fun reading.

There is white and then there is white. White is white because of the pigment used. Some pigments are actually quite "black" at infrared wavelengths and there is a lot more to it....

Observatory Paint.

Here is a pdf that lists a bit about keeping it cool with paint selection:

http://www.basf.pl/ecp1/Poland/pl/**...e_do_farb_.pdf

[colemj]

Originally Posted by Julie Mor

In my empirical testing , which included one blue-hulled Oyster, the results don't support the belief a dark hull in sub tropical waters results in a hot interior.

Is the Oyster hull cored or insulated? If so, then the color doesn't make much difference to the interior heat.

I owned a solid fiberglass dark hull in sub tropical waters and it got hot inside. I painted it white and it no longer got hot.

Mark

[lesterbutch]

In regards to "Julie Mor" if that boat was cooler below then there is NO DOUBT that it was well insulated, you cannot deny the LAWS OF PHYSICS, thats why they are laws! Dark colors absorb more heat than light colors.....

[markpierce]

Originally Posted by robert sailor

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

Darker colors are easier to see in fog. Bright yellow is even better to be seen. Thankfully, boats needn't have only a single color. Multiple colors are best compromise for visibility.




To be less seen, try a blue hull, blue sails, and blue outfit.

[Cadence]

Originally Posted by Rohan

Then wouldn't you choose bright orange for safety? It's a horrible color for a boat though.

That and blue or black bottom paint if you turtle. I wonder why international orange hadn't become a bottom paint?

[geoleo]

Originally Posted by Dr. Sea

I love the appearance of a dark hulled boat, but I wonder about the effect on heat inside the boat. I sail and plan to sail in mostly tropical areas, and I prefer to not be dependent on air conditioning, so a heat gain would not be good. How much heat gain would a dark hull cause?

My wifes hull is dark-and yes it is hot.

[Steadman Uhlich]

I enjoyed reading the previous comments on this subject which interests me.

Unfortunately, while I like to read anecdotes, and I don't doubt that everyone has experienced what they wrote, I know that anecdotes can be a matter of memory and seldom involve side-by-side controlled measurements.


In boats there are many variables: Conditions can change (more or less wind or humidity or water temp or air temp or angles to sun etc.) and one boat may have insulation and another not.

For that reason, I suggest everyone watch the following short video that shows some comparative testing of colors and how they differ in their ability to absorb light energy (sunlight).

Please note that the colors you see in the video are thermal imaging representations, and one should look at the captions to see which color is represented, and look at the linked color page to see the actual colors tested.

Which colors absorb more sunlight?

http://www.youtube.com/watch?v=tKpkJ5wxr-E

Use your word processor to print a page with different color bars and put it under the sun. The temperature difference between different colors reflects the difference in their abilities to absorb light energy. See the color bars used in this video:

Color page: http://3.bp.blogspot.com/-cZnZhrPxp2...4XbCCqBrgo/s20
______________________

In the first video linked above, notice the reflective ability (or the ability to absorb sunlight) of the different colors (see the linked color page to see the real colors on the printed page). These are colors, and unfortunately there is no strip for "white."

Notice the second color strip from the left side.
This corresponds to the color "Yellow." The one that is "coolest" of the colors tested is the color Yellow. In the video's thermal imaging, it appears blue-green, while the "hottest" colors (those that absorb the most sunlight) appear bright yellow-red.

Of the colors tested in this test, the "coolest" colors that reflect the most sunlight were:

Yellow (the coolest)
Red (second coolest, tied with Light Gray)
Light Gray (second coolest, tied with Light Gray)
Magenta

________________

The colors that absorb the most sunlight (and show in the thermal image as the "hottest" colors) are:

BLACK (The Hottest)
GRAY (Almost the Hottest)
BLUE
GREEN
___________________

My Preference?

I like the look of dark blue boats. It is very likely the boat I get would be white, as that is the most common color for hulls.

But, IF I had a choice for a boat paint job I would choose bright yellow.

For these reasons:
1. Yellow is my personal favorite because I like the color, and I find it cheerful.
2. It reflects sunlight very well and I would like that in the tropics.
3. It is highly visible, especially in a marine environment, and I would like that anywhere.

My second choice would be a red (i.e. International Orange).
1. Red is another one of my "favorite colors. I like the color.
2. It reflects sunlight well, almost as well as Yellow does.
3. It is highly visible, and in fact is often chosen for arctic boats.

________________

This is not Rocket Science.

But, if you want to hear it from a Rocket Scientist, here you go:

Why space rockets are white - do you know?

http://www.youtube.com/watch?v=dxPKCn1troU

[scuba0_1]

I don't know what we are talking about we agree on everything.

Sent from my SM-N910V using Cruisers Sailing Forum mobile app

[Cadence]

It's just a matter of choice. Someone in the tropics might like black and someone in the artic might like white. Not good choices maybe but so what. But that is just my opinion.

[Dr. Sea]

Originally Posted by 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...

I followed the link to the Nippon Paint website. It shows that you can get this paint in colors other than white and that in other colors the Nippon paint is still cooler than the same color in epoxy or polyurethane. It also has a statement that it can be used on all exterior surfaces. But there is no info on other characteristics such as durability or fade resistance.

[Sea Frog]

Originally Posted by Dr. Sea

I followed the link to the Nippon Paint website. It shows that you can get this paint in colors other than white and that in other colors the Nippon paint is still cooler than the same color in epoxy or polyurethane. It also has a statement that it can be used on all exterior surfaces. But there is no info on other characteristics such as durability or fade resistance.

That's why I decided to go with Altiris IR-reflective pigments added to gelcoat. I still did not make up my mind about color though.

[vasariah]

I have got a dark blue hull but with the balsa core to the waterline. I can't see the difference. Previously I had a white hull.

[Whitebread117]

Originally Posted by georgetheleo

My wifes hull is dark-and yes it is hot.

Well played

[savoir]

Originally Posted by Rohan

Teak is darker than a white deck, but it's still not like dark blue or black. That does make a difference. Wood also acts as it's own insulation, so while it might be hot on your feet on a summer day, the underside of it would not be very hot. On a related note, I have heard that cork decks are much more heat resistant, but I have no experience with this.

On another note, has anyone else noticed that nearly ALL America's cup racing boats have black hulls? Does black make a sailboat go faster? Or maybe at those speeds everyone is freezing so they need all the heat they can get?

Carbon fiber is black. If you want the boat any other color you will be adding weight. Looking pretty and making the cabin cooler are not good enough reasons.