Inside your boat....hotter or cooler than outdoor temps?

[lesterbutch]

It's nice if your boat has A/C but many older boats don't! So of course many will say " get A/C! But that may not be possible due to space requirements, availability of adequate power, etc. I'm afraid many of us just have to get by with passive methods of cooling!

[sailorboy1]

and even with air conditioning a sun shade to keep the sun off the deck makes a big difference!

The only people in hot areas who say air conditioning on the boat isn't worth are those don't have it. We need to travel the next couple days and the trip could take 3-4 days if we push, or 7+ dats if we go slow and mellow. At the end of the trip we are going into a slip for the next 3 months, which mean air conditioning without ut having to run the generator that we only run in the day. So I ask my wife "You want to go fast or slow?". She quickly said "fast".

[LakeSuperior]

Originally Posted by mikedefieslife

Of course the white hull will also retain more of the heat it does absorb, where as a darker one will radiate it back into the atmosphere.

Thickness is more important than colour. At least in a study of clothing worn by Bedouin tribes in the Sahara, who nearly all wear dark clothing.

Still, I know I'd much rather walk on a white deck than a dark coloured one.

Sorry Mike, not correct. The heat is radiated in accordance with the Planck function. For a non-black body (non-perfect radiators) the amount also depends on the surface emissivity in the long wave spectral region. Long wavelengths for this application are from 8-12 micrometers.

In general, both black and white colors have the same long wave emissivity, 0.94. Consequently, if they are both at the same temperature they will both radiate the same amount of energy.

Because the black hull absorbs more solar energy than the white hull it will be warmer.

The visible band is 0.4 to 0.7 micrometers. This band is where you see the color (and it absorbs and reflects solar energy). Almost no heat is radiated here for ambient temperatures.

[Dave22q]

Of course, white surfaces reflect heat and stay cooler than dark ones. However, the surface exposed to the sun is almost 100% deck. The hull is close enough to vertical that it's contribution to heat below decks is negligible. I also doubt that hull color has any impact on direct heat transmission from the water to the boat interior.

[zeehag]

for those with dark colored hulls there are cool sun skirts to use while anchored or in a marina in tropical summers.
they look good and work well so you can have your black or blue or red or whatever colored hull and not die in hot weather areas.
currently i use a window unit temp mount air conditioner, but i have discovered other options for m e..reasonably priced , miraculously--- built in central air or a cruise air overhead unit.... debating each with my mechanic who found the central air one--he has 3, i get good deal.

[Dave22q]

Originally Posted by Leo Ticheli

Does this have any practical value on our sailboats? Perhaps if the bottles could be cut much shorter and glued together then placed in the opening of the wind scoop it could work.

They screw plastic bottles to a piece of cardboard and hang it in the window. The air flows differently now.

I understand that storage space is no small concern and I'm not all that confident it could make a significant, if any difference. Thoughts from smarter physics minds than mine?

I believe there would be a huge market for a small, 12v air conditioner, just powerful enough to cool a single cabin. With solar growing cheaper, the batteries could be charged during the day and then run the machine at night.

If anyone knows of such a device, I'm past ready to sign up!

Fair winds,

Leo

"a small, 12v air conditioner" would be larger than a refrigerator motor/radiator and probably a lot more expensive. It would need to be designed for long cooling cycles unlike an insulated refrigerator or freezer. I'm not seeing costs below a hundreds of dollars, ever.

[S/V Illusion]

How much a dark colored topsides contributes to heat is arguable and can't be calculated. What is indisputable is how much prettier your favorite color looks compared with vanilla.

[Leo Ticheli]

There is this: My Site - The Zero Breeze It's smaller than a refrigerator.

OK, as of yet only promised, and it could turn out to be vaporware, but if it will cool one of the cabins, and costs the estimated $500.00 US, I'll be signing up. They claim to have delivered 50 units already. I'm tempted to pre-order, but I've been burned once doing that.

Another idea is from this guy:

https://www.youtube.com/watch?v=GVZnmtendbE&t=67s

Not a lot of cooling, but perhaps enough; at least it's working for him. I imagine you could mount it in a hatch and top it will a solar panel for daytime power.

Fair (cool) winds,

Leo

[LakeSuperior]

Originally Posted by S/V Illusion

How much a dark colored topsides contributes to heat is arguable and can't be calculated. What is indisputable is how much prettier your favorite color looks compared with vanilla.

Engineers do these calculations every day. The color of the deck can make a big difference. The hull not so much during the high solar hours, especially if cored.

[softdown]

Dark surfaces make a very significant difference in indoor temps whether the surface is vertical or horizontal. But 5 degrees can make a big difference in perceived comfort. 75F indoors is comfortable, 80F indoors is not. Humidity also plays a significant role. Along with air movement and numerous other individual factors.

I remember changing from white shingles to dark tan shingles. Suddenly the house felt uncomfortably warm though the real difference was likely only 3 or 4 degrees...if that. The attic was not well insulated at that time.

I still think I may be unto something with a freshwater mister on the outside of the cabin. Knowing that 3-4 degrees makes a huge difference in comfort.

[LakeSuperior]

Originally Posted by softdown

I still think I may be unto something with a freshwater mister on the outside of the cabin. Knowing that 3-4 degrees makes a huge difference in comfort.

...a freshwater mistress?

[softdown]

Originally Posted by Leo Ticheli

There is this: My Site - The Zero Breeze It's smaller than a refrigerator.

OK, as of yet only promised, and it could turn out to be vaporware, but if it will cool one of the cabins, and costs the estimated $500.00 US, I'll be signing up. They claim to have delivered 50 units already. I'm tempted to pre-order, but I've been burned once doing that.

Another idea is from this guy:

Not a lot of cooling, but perhaps enough; at least it's working for him. I imagine you could mount it in a hatch and top it will a solar panel for daytime power.

Fair (cool) winds,

Leo

That bloke posted a youtube video before bothering to test the unit....by his own admission. How hard is testing the unit? I therefor smell a rat.

[softdown]

Originally Posted by LakeSuperior

...a freshwater mistress?

Preferably less than 130 pounds due to thermal mass...or something like that.

[Leo Ticheli]

If you search a bit more, you'll find other videos from Alan Marine and he apparently has had success with his units. I probably should have provided a link to an earlier video, but you can find them easily. He does disclaim that they are not equal to compressor air conditioners, but that they remove humidity and cool his boat to a level he's comfortable with.

As he sells neither the units nor the plans, I don't believe he has nefarious motives. At one time he put his plans on line, but after discovering that others were "appropriating" them and offering them for sale, he took them down.

I may play around with trying to build one, although it's quite hot and humid where I sail, so it may just be more entertainment then salve.

Fair winds,

Leo

[zeehag]

fact---lg 5000 btu window unit is less than 200 usd. so damned expoensive that folks wouold rather argue of-ver having and not having air an d where to put it ohmygodsihavenoroomosis and the rest.. folks buy 8000 btu units and place them in overhead hatches or in companionways. i am fportunate to be able to find 5000 btu units of 11 inch height and 11.5 inch height for my formosa windows in dinette. and wow i had a frame made for it so it doesnt look like total crap. ohmygods.
does not take much . \then mebbe you could be able to convince the lady to do ye. damn such hardheaded idiocy over a mere comfort and get laid item. wake up boys. low season(cane season) marina rent is lower than winter, high season rates by more money than you can count.
if you have to choose between fridge and air, choose air to keep, as it is easier to be comfortable with air -- many foods keep well without fridge and fish under boat count as dinner. donot even try to impress a lady with toxic water below your boat. it just willnot work. but... air over fridge. how do i know this\??i am a very well spoiled and experienced lady sailing and repairing a 41 formosa with no fridge but has 5000 btu air. yup. niiiiice. .
i only have air and fridge in marinas. anchored i have neither fridge nor air. 2011 i bought my first air conditioner for marina use... 2015 i bought my first fridge for summer use . each season is approx 6 months in duration and follow furycame season.
oh yeah i found the lg 5000 with remote is a lot more fun than the one i need to climb onto the dinette berth to change. nice feature. surprisingly less money than the non remote version.