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any physicists out there?
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bluefish1



Joined: 24 Dec 2013
Posts: 1229

PostPosted: Sun May 12, 2019 4:03 pm    Post subject: any physicists out there? Reply with quote

The more I looked into this, the more confused I am about heat and colors.

First of all, please tell me if I am overly concerned. My goal is to keep a new SUP on a dock all Summer so not to carry it a long way for each use. It is red on one side, white on the other. Itís a Bic Ace-Tec construction, no vent.

If I leave it in the sun all Summer with the white side up am I at risk of delamination or are most modern boards immune? Iíve heard of inside of hot cars, on hot sand, but this is just mounted over water on a dock, just direct Sun and air temperature.

I am not concerned about cosmetic fading or looks, just outright damage.

If I were to try and make a cover for the Sunny side, what material? I started looking into and this is where I got confused.

Some say silver reflective is the worst because it retains heat (like metal). Especially if it has insulation under (like most board bags). I would think it reflects all the energy?

One board bag company says light grey absorbs least heat
One company says white.
Spacesuits have always been white. Not reflective, light grey or silver but white. The tiles on underside of space shuttle are black as they try and absorb the heat of re entry?

Iím starting to think just leave the white side up all Summer and forget about it?

Any physicists out there?
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westender



Joined: 02 Aug 2007
Posts: 1156
Location: Portland / Gorge

PostPosted: Sun May 12, 2019 4:28 pm    Post subject: Reply with quote

Any material you can position so it's not touching the board that will keep the solar radiation off of it should do the job. Maybe like a tarp and tree branches. I have no degree. Go to a parking lot on a hot day and touch vehicles with the colors you're interested in. https://www.google.com/amp/s/www.space.com/amp/25844-spacesuit-evolution-space-tech-photos.html
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U2U2U2



Joined: 06 Jul 2001
Posts: 5013
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Sun May 12, 2019 6:10 pm    Post subject: Reply with quote

Sink it under the dock when not in use.
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carl



Joined: 25 Feb 1997
Posts: 2652
Location: SF bay area

PostPosted: Sun May 12, 2019 7:25 pm    Post subject: Reply with quote

I would think the ASA plastic layer on the Bic would get brittle and start to delam because of constant UV rays of the sun. Cover it with something light colored to keep it out of the sun. As for heat, I used to keep an older Bic in a hot car. It didn't delam but it did split in a small area on the seam.
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manuel



Joined: 08 Oct 2007
Posts: 909

PostPosted: Sun May 12, 2019 9:32 pm    Post subject: Reply with quote

One board painted red over and white under was left on the roof of a hotel here.
I believe on its side? It was delaminated, did it happen before or after? I don't know.

Another board (mostly white) was left out in the sun too but on the beach standing up. It lost all of its color so now we can see the epoxy and carbon kevlar construction. No delam here and apparently not a problem regarding boards left out in the sun here (DR)...

I'd say avoid sun at all cost, prefer white for sure.
Cover and let air flow around it.

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bluefish1



Joined: 24 Dec 2013
Posts: 1229

PostPosted: Mon May 13, 2019 6:29 am    Post subject: Reply with quote

Do we think an air space is critical? I have some old 2 sided foil bubble wrap they sell at Menards. Was thinking of using that to cover it but then I read that is the worst.

Maybe just a breathable canvas cover? Under the dock won't work because of wave action.

On shore and tress are not an option.
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westender



Joined: 02 Aug 2007
Posts: 1156
Location: Portland / Gorge

PostPosted: Mon May 13, 2019 6:36 am    Post subject: Reply with quote

I would be more concerned about the ventilation gap than the solar shield color.
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Brian_S



Joined: 11 Jun 2005
Posts: 216
Location: SE Michigan

PostPosted: Mon May 13, 2019 12:13 pm    Post subject: Reply with quote

Not a physicist, but an engineer with some experience in radiation heat transfer.
I'm with Westender on this one. A sun shield of any color that blocks the sunlight (and doesn't touch the board) will help protect the board better than putting it into a cover that touches the board. In other words, 'shade' the board with something.

The foil reflective board bags are good, but the board will still get warm inside. I did run an experiment a few years back to measure the board skin temp on a white board in and out of a foil board bag. Can't recall any of the numbers, and the bags worked well, but the board will still get warm in the board bag. And then leaving a wet board in a warm board bag can do things to the paint a grow mold.

Also, white colors can deceiving since our eyes see only a small part of the spectrum. White snow, for example, reflects sunlight in the visible spectrum and absorbs sunlight in the IR spectrum.

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U2U2U2



Joined: 06 Jul 2001
Posts: 5013
Location: Shipsterns Bluff, Tasmania. Colorado

PostPosted: Mon May 13, 2019 12:26 pm    Post subject: Reply with quote

ď in other words Shade the board with something ď
Just like I said put it under the dock

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nw30



Joined: 21 Dec 2008
Posts: 5696
Location: The eye of the universe, Cen. Cal. coast

PostPosted: Mon May 13, 2019 1:02 pm    Post subject: Reply with quote

The UV penetration would be a bigger problem than the sun's heat on a white surface, over a period of time.
Also you have to consider the color of the dock, if it's dark, it will get hot, so I wouldn't want to put the board on the dock unless it is shaded.
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