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Old 14-07-2017, 16:11   #46
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Re: Inside your boat....hotter or cooler than outdoor temps?

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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.
Let's ignore the testing bias of someone who spent a lot of money and/or time residing your house and focus on your first declarative statement - "dark surfaces make a significant difference".

How do you know that? What empirical data exists to support that statement? Whatevidence exists to substantiate that hypothesis?

Absent any evidence I've ever read, this falls into the category of one of those urban myths that are often repeated but never proven.

Please don't tell us it's only your opinion...
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Old 14-07-2017, 16:26   #47
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Re: Inside your boat....hotter or cooler than outdoor temps?

Go step on black asphalt at 2PM, then white concrete.
Tell me which one burns you feet.
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Old 14-07-2017, 17:06   #48
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Re: Inside your boat....hotter or cooler than outdoor temps?

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Go step on black asphalt at 2PM, then white concrete.
Tell me which one burns you feet.
Or, hop into your car that's been baking in the Florida sun and slide your legs not covered by your swim suit onto the black leather seat. Yikes.

Now that I'm a Florida boy, I bought a white car with light-colored seats.

Fair winds,

Leo
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Old 14-07-2017, 17:18   #49
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Re: Inside your boat....hotter or cooler than outdoor temps?

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Originally Posted by a64pilot View Post
Go step on black asphalt at 2PM, then white concrete.
Tell me which one burns you feet.
Nice trick but gravity defying as we're talking about the topsides, a vertical surface, with incidental exposure to the sun. A black topsides is arguably less hot than a white (horizontal) deck.
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Old 14-07-2017, 17:20   #50
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Re: Inside your boat....hotter or cooler than outdoor temps?

Let's try to use measurements with meaning. Like the TSI (testicles sweat index)!
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Old 14-07-2017, 17:22   #51
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Re: Inside your boat....hotter or cooler than outdoor temps?

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Originally Posted by S/V Illusion View Post
Nice trick but gravity defying as we're talking about the topsides, a vertical surface, with incidental exposure to the sun. A black topsides is arguably less hot than a white (horizontal) deck.
Really? ask someone with teak decks if they are hot in the summer.

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Old 14-07-2017, 17:32   #52
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Re: Inside your boat....hotter or cooler than outdoor temps?

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Originally Posted by Leo Ticheli View Post
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
Peltier cooling is very energy inefficient.
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Old 14-07-2017, 17:43   #53
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Re: Inside your boat....hotter or cooler than outdoor temps?

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Originally Posted by S/V Illusion View Post
Let's ignore the testing bias of someone who spent a lot of money and/or time residing your house and focus on your first declarative statement - "dark surfaces make a significant difference".

How do you know that? What empirical data exists to support that statement? Whatevidence exists to substantiate that hypothesis?

Absent any evidence I've ever read, this falls into the category of one of those urban myths that are often repeated but never proven.

Please don't tell us it's only your opinion...
You would fare better claiming that the earth is flat. This is so absolutely elementary.
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Old 14-07-2017, 18:39   #54
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Re: Inside your boat....hotter or cooler than outdoor temps?

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You would fare better claiming that the earth is flat. This is so absolutely elementary.
Nonsense. The argument being postulated here that dark topsides are hotter is totally unfounded. I could make silly analogies of intuitive evidence like someone did about black asphalt - the tiles on the Space Shuttle are black and don't conduct or radiate heat - but that isn't relevant either.

If you can show evidence other thanperception that dark hulls are any different than vanilla, I'd agree. Perceptions don't matter except in fairy tales.
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Old 14-07-2017, 18:50   #55
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Re: Inside your boat....hotter or cooler than outdoor temps?

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Peltier cooling is very energy inefficient.
Absolutely. However, efficiency matters only if you are either paying for the energy or you don't have enough "free energy."

Now I don't know if a Peltier cooler will actually make a significant difference in cooling a cabin, but as long as I can power it with solar, it's relative efficiency is not very important.

If to cool effectively, a Peltier cooler takes a huge solar array, then your caution is quite valid.

Fair winds,

Leo
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Old 14-07-2017, 21:23   #56
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Re: Inside your boat....hotter or cooler than outdoor temps?

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Originally Posted by dwedeking2 View Post
I live on a boat in Florida without AC. When down below airflow is very important. I have no problem when there's a nice air stream through the cabin is no problem. When the wind is hitting from the wrong direction (I'm at a dock so don't shift with the wind) it can be rough.


We did that one year in Florida and never again. Since then we find an affordable marina, buy some portable AC and plug in until mid-October. Then either sell or donate the AC. Rinse and repeat.

In our next boat we will have enough AC to freeze saltwater.
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Old 14-07-2017, 22:18   #57
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Re: Inside your boat....hotter or cooler than outdoor temps?

If you are fortunate enough to have cabin overheads that are removable, then, in addition to having access for electrical wiring and lighting, you can install insulation. I started with a quarter-inch foam/Mylar sheet insulation against the underside of the deck. I held it in place with double stick tape squares. That alone yielded an instant ten degree temp difference. Then I added a half inch pink foam insulation sheet available from Home Depot, also held in place with the double sided tape squares. Then the Formica covered doorskin plywood, sealed in epoxy, was screwed into place and teak trim installed. Dramatic heat reduction, as well as retention in winter.
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Old 15-07-2017, 04:31   #58
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Re: Inside your boat....hotter or cooler than outdoor temps?

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Originally Posted by Roy M View Post
If you are fortunate enough to have cabin overheads that are removable, then, in addition to having access for electrical wiring and lighting, you can install insulation. I started with a quarter-inch foam/Mylar sheet insulation against the underside of the deck. I held it in place with double stick tape squares. That alone yielded an instant ten degree temp difference. Then I added a half inch pink foam insulation sheet available from Home Depot, also held in place with the double sided tape squares. Then the Formica covered doorskin plywood, sealed in epoxy, was screwed into place and teak trim installed. Dramatic heat reduction, as well as retention in winter.
Thank you, Roy! I'm a big fan of the foam/Mylar insulation and I'll give it a try on my boat. I completely cured a problem of air conditioner condensation in my lazarets by wrapping the ducts with it. I've also used it with aluminum tape to make pouches to protect equipment.

Fair winds,

Leo
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Old 17-07-2017, 04:40   #59
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Re: Inside your boat....hotter or cooler than outdoor temps?

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Originally Posted by S/V Illusion View Post
Nonsense. The argument being postulated here that dark topsides are hotter is totally unfounded. I could make silly analogies of intuitive evidence like someone did about black asphalt - the tiles on the Space Shuttle are black and don't conduct or radiate heat - but that isn't relevant either.

If you can show evidence other thanperception that dark hulls are any different than vanilla, I'd agree. Perceptions don't matter except in fairy tales.
Illusion, you are unaware and do not understand basic physics/engineering principles of heat transfer that are well known. For example, contrary to your statement the primary mechanism that shuttle tiles use to shed heat on re-entry is radiation.

Unless there is a special type of coating on the topsides the dark topsides get hotter than a white one. This difference can be significant. If the hull is cored then the temperature of the inside of the hull will not get as hot.
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Old 17-07-2017, 05:14   #60
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Re: Inside your boat....hotter or cooler than outdoor temps?

I live in the tropics. The summers are HOT! I have no AC on my boat and have never felt the need for it. However, I have a scheme to keep the boat cool in the summer. I use big awnings to keep the sun off the deck. These awnings are suspended over the deck, allowing the breeze to flow under it and through the hatches. I can keep all the hatches open in the rain (very important!). I also have lots of hatches that can be opened in either direction. My boat is white. My deck is off-white. Even the slightly beige colour of the deck will heat up if exposed to the sun at noon. I never stay in marinas, so I have the advantage of anchoring in the breeze. I have fans in all sleeping areas and galley, but seldom use them. My deck is Divinicell cored and has an insulated headliner, which also helps. I find the boat remains cool during the day. By the end of the day (sundown) the boat will normally feel warmer inside than outside air, but that's because the air temperature drops in the evening and the boat retains the heat for a while. By bedtime it has already cooled down again. There is no question that without the awnings, hatches, white paint/decks etc. the boat would be unbearable in the summer.
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