Hull color

[gboat5]

I’m looking to purchase and live aboard in FL/Caribbean very soon. As the cool months are almost non existent does hull color significantly alter the interior temperature. I’m specifically looking at a beautiful 37 with a black hull.
Thanks!!!!

[Cyrus Safdari]

Yes, just compare a dark car parked in the sun to a light one. Dark colors also fade, and show dirt n scratches. Dark decks including teak get too hot to walk on too

[capt jgw]

My boat was originally white but I painted it forest green. Looked really nice but in the late afternoon with the sun at a low angle it got really hot inside. And we're on Lake Michigan. Would be way worse in the tropics. Eventually went back to white.

[steve77]

I don’t think the car analogy is applicable. The deck and cabin top are light colored, correct? Sunlight on the hull (topsides) will be minimal during the heat of the day. Yes, a dark colored hull will be warmer, but not to the extent a dark colored car is.

NOW, if you have a boat with a dark hull and sprayed-in insulation (like we do) then there is no interior heating at all. Check if the boat you are interested in is insulated. You may be pleasantly surprised.

Cheers!

Steve

[S/V Illusion]

I was worried about my new black car in Florida but find it no hotter than my prior light grey color - no discernible difference - they are both hot after being parked outside.

We have never liked the ubiquitous vanilla hulls. If there is a difference in radiated heat, my opinion is the prettier topsides is worth it.

I’ve measured the hull temp inside my dock neighbor’s vanilla boat with infrared temp gun and compared it with ours. Not a statistically valid assessment, however, the difference was uniformly less than 4 degrees.

[Shrew]

Just to add some additional anecdotal feedback to muddy the waters...

I had an acquaintance who had a white hull with a sizable navy blue stripe. From inside he claimed he could feel the difference in heat where the blue stripe was when he held his hand against the hull from the inside.

Does that translate to higher ambient internal temperatures?

[gboat5]

Thanks for the feedback, and yes all the topsides are white. The black hull with red rust colored bottom paint looks really cool, so I’ll deal with the 4’ temp difference. This is my divorce present to myself and a big F U to the wife who bitched about my boat ownership for our entire marriage (it needs to look cool, and expensive) lol!!!

Just wanted to make sure I wasn’t buying a solar oven.

[Cyrus Safdari]

It isn't just 4' and there are other issues:

The Awlgrip lady says:

"dark hull gets three times hotter in surface temperature than a white hull, and, as a result, the resin in the hull continues to cure in the heat...and shrinks. This leads to fiberglass printthrough"
https://www.passagemaker.com/.amp/te...ats-themselves

And more

I’ve measured the temperature of dark-colored hulls and light-colored hulls simultaneously and side by side: While white or gray topped out at 90°F (32.2°C), black or dark blue reached 130°F (54.4°C). The heating, nearly always uneven, leads to substantial hull and deck expansion and contraction, which in turn stresses bedded hardware, and in my opinion increases the likelihood of leaks.

[Digdug]

Not to mention that oxidation is much more visible on darker hulls. They have to be protected with wax or they begin to look faded and will require a time consuming buffing and full detail to restore the finish. I have a dark blue hull that I wax twice a year with collonite fleetwax. It is not an easy job. There are two other blue boats near my slip that are completely faded and look very tired and worn out.

[LittleWing77]

White hull and white T-shirts only in the tropics!

(If you really love the boat, you can always repaint....) ; )

Fair winds,
LittleWing

[chouliha]

We did a 6 year trip thru the SP and our boat was mint green. The second trip south (now 14 years +) we left with the hull painted white. A HUGE difference in interior temps. We also gave it the best test and that was 4 summers in the Sea of Cortez. You want hot it’s so hot even our white decks would scorch your feet.

[S/V Illusion]

Nobody likes vanilla. Besides, it’s funny seeing people leave their vanilla boat only to get into their black car.

[barnakiel]

No. The deck is not black, or is it.


Do not listen to 'black is hot' as it only marginally can be.


Reason 1 - most topsides these days are sandwich. Better insulation than an average fridge.


Reason 2 - topsides are vertical and or inversed and exposed only to some amount of the reflected radiation.


Reason 3 - it is mostly water temperature and air movement that create comfort and discomfort. Water will be about 30 degrees centigrade and about same will be temperature onboard, it will feel less only of you have good canvas awnings hung quite high above the deck and plenty of opened ports and hatches.



If in doubt place a light meter flat in the tropics then hang it anywhere vertical see the difference for yourself.


What WILL make the boat hotter is actually a teak deck - it is gray and catches 100% of the radiation. Then again - very very many decks today are .... also sandwich!!!


I tell you this from a black hulled boat that has sailed 7 years in the equatorial tropics and spent 4 full seasons in the Carib. NO ISSUE (and an older, no sandwich boat...)


If you want a cool boat - get one with plenty of opening large ports! This is how you make it cool in the tropics - by creating plenty of unobstructed air movement.


Have fun shopping. Black is sexy ;-)



barnakiel
onboard a black hulled boat, in the tropics

[barnakiel]

And for those of us who like empirical and sensory learning: we take a polished shiny SS plate (highly reflective and not black!) and place it on a sheet of dense foam - flat and facing the sun on a sunny day in the tropics.


Now wait 30 minutes, now place your hand on the plate. How come the plate got THAT hot???


Well, colour is not what dictates how hot a surface gets, neither main nor only factor.


BTW to my above post - the difference between a flat surface (direct sun) and a vertical one (direct sun at cos of the angle+reflected sun) is roughly 1 to 12. Topside color is nearly insignificant because some 95% of heat energy comes to the boat from above.


BTW2 the light meter can be substituted with a solar panel and amp meter.



Cheers,
b.