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 Post subject: Kit in a roof top box...
PostPosted: Tue Jun 09, 2009 12:46 pm 
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This is a perfect place to carry about half my stuff... But - I know how twitchy you guys get about leaving your kit in a hot car, so I decided to tamp some myths..

It is without dispute that this box, when it was colored Black, was almost as hot as a pizza oven on a sunny day. A black box make a great solar collector. I wanted to change that...

People think anything reflective, like Silver, is ..well; 'Reflective'. It reflects light, if that makes you feel better... I used this silver because I was shooting a 8M rowing shell at the same time, not because it was the best choice.

White would be the best choice. White has the least pigmentation, which absorbs fewer Infrared rays than any other color. Silver is little more than shade of Black with a given percentage of metallic particles mixed in.

Still, I wanted to see what was going on. I have recorded temps in aircraft with a variety of coverings, so this was pretty simple. The heat of the day peaks about 2pm on average..

At 2:15 the ambient temperature was 83f - 28c ..and the winds not strong enough to fly a 2M trainer ...

The most exposed surface temperature was 108f - 42c ... of the objects inside, the hottest was an orange skimboard at 115f - 46c ..the least hot was a harness at 93f - 34c. (everything inside had been sealed within for at least two hours prior - there is no ventilation.)

It is the temperature of the inside of the lid that means the most to stuff on the inside... The lid is made of some sort of vacuum-formed plastic and is quite dense. It is only about 3mils thick which is good... The temp inside the lid was 132f - 55.5c

One reason the outside and inside temperatures vary is that the breeze, however light, pulls the heat away from the outside. The inside air is dead calm.

The reason the skimboard was hotter than the harness, was the skimboard is quite dense and the foam-core harness less so. The harness cannot hold heat as well.

If you lived in an area of really high heat - it would be best to line the underside of the lid with 5mil of closed cel foam. The lid currently radiates heat to the objects in the box just like an electric space heater . The foam would dampen that.

And yes I leave kites in there pretty much all Summer. I open the lid if it is really hot.

Jim


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 Post subject: Re: Kit in a roof top box...
PostPosted: Tue Jun 09, 2009 1:50 pm 
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i've actaully thought about this....

any thoughts about adding a vent or something on the bottom?

i've even contemplated adding some type of water proof plug that could be opened on hot days to help it vent.


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 Post subject: Re: Kit in a roof top box...
PostPosted: Tue Jun 09, 2009 3:23 pm 
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Thanks for the information.
I know you recommended foam but I am curious if you have experience with the rolls of thin silver (mylar?) coated bubble wrap type insulation?
I have some lying around and it comes to mind as potentially a good liner for this type of thing....


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 Post subject: Re: Kit in a roof top box...
PostPosted: Tue Jun 09, 2009 4:17 pm 
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Thanks for bumping that. I've been thinking about painting the box top white for the very same reason. The only thing worse than leaky valves is shrinking of your expensive pre-stretch spectra lines (all high quality kite lines + a zillion bridle lines for the foil kiter.)

I did drill about a zillion holes in the bottom with a 4 mm drill bit - mostly so stuff would dry. It did OK. Then I got a hole saw drill bit - about 25 mm and drilled a bunch more holes. The ventilation is much better and my harness and swim trunks dry out. I assume the ventilation helps keep things cooler. I think I'm going to get some white spray paint.

Jake


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 Post subject: Re: Kit in a roof top box...
PostPosted: Tue Jun 09, 2009 6:43 pm 
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Dude!,to discover that light colours and some foam will isolate from heat your roof torpedo not necessary to play to Myth Busters.......


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 Post subject: Re: Kit in a roof top box...
PostPosted: Tue Jun 09, 2009 8:15 pm 
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jakemoore wrote:
Thanks for bumping that. I've been thinking about painting the box top white for the very same reason. The only thing worse than leaky valves is shrinking of your expensive pre-stretch spectra lines (all high quality kite lines + a zillion bridle lines for the foil kiter.)

I did drill about a zillion holes in the bottom with a 4 mm drill bit - mostly so stuff would dry. It did OK. Then I got a hole saw drill bit - about 25 mm and drilled a bunch more holes. The ventilation is much better and my harness and swim trunks dry out. I assume the ventilation helps keep things cooler. I think I'm going to get some white spray paint.

Jake


any noticable wind noise difference?


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 Post subject: Re: Kit in a roof top box...
PostPosted: Tue Jun 09, 2009 8:46 pm 
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Location: Upper Padre . . . . --> Oleander
The noise is not so bad, but I am not very sensitive to these things. I don't think it made a big difference.


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 Post subject: Re: Kit in a roof top box...
PostPosted: Tue Jun 09, 2009 10:46 pm 
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DUDE! ...not all our Mommys' told us how smart and special we are.

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BWD ... it is perfect. The more air between two solid surfaces the better.

If vented, you really want two. I put this type into a boat cover because it sits out and condensation is an issue for varnish, less so heat. (make sure it has screen material to keep out nesting hornets...)

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Jim


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 Post subject: Re: Kit in a roof top box...
PostPosted: Wed Jun 10, 2009 12:02 am 
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doesn't hot air raises? so any kind of vent should go at the top,no? another way to keep your gear cool is to put the darker tints on the car/van/suv.What i do to keep my gear nice and cool is to take them out the car all together,i only keep gear in the ride when the wind is up for multiple days


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 Post subject: Re: Kit in a roof top box...
PostPosted: Wed Jun 10, 2009 2:44 am 
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Did you by any chance ever check the temp in a black box on a similar day?

I have a black Yakima carrier. I don't think they offered it in white...maybe silver. White would be best, but man that would be an ugly thing to carry around.

In any event, while concerned, I haven't had any issues with the black carrier yet. I think some type of water resistant vents would be a great idea. Get the hot air out, but keep the rain from coming in.


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