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Old 10 June 2015, 13:39   #11
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Originally Posted by Max... View Post
That's pretty significant, here in the UK it can easily (well, alright once in a blue moon) be say 12 deg C first thing when you check tubes in the morning and double to 25 deg C early afternoon. That's just the measured air temperature though, surely the direct sun acting directly on the tubes will raise it more??
You are completely correct, sun will raise the material temperature.

Today in Charleston : 87F (30.6C), scattered clouds at 12:30

I used an infrared temperature gauge on both of my inflatable boats.

My FC470 (black hypalon) registered 157F peak (69.4C)
My other boat (light gray hypalon) registered 127F peak (52.8C)

My FC470, has overpressure valves all over the place, so I don't really worry about it. Plus, it has enough seam leaks at pressure (the downside of a beat up, former military hypalon boat that probably got dropped out of an airplane a few times!) where it loses 10% of its pressure in a day until it gets down to about 1.5 psi tube pressure.

My other boat does not have overpressure valves, so I air it down to about 2 psi before I store it.

However, once the boat is in the water, the material will begin to cool, and the pressure will drop dramatically. Same goes vice versa...if you pull your boat up on the beach in the midday sun, the temperature/pressure will increase.

This is why I tell people a pressure gauge & an electric pump is probably their best investment for inflatable boat ownership.
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Old 10 June 2015, 19:41   #12
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That's pretty significant, here in the UK it can easily (well, alright once in a blue moon) be say 12 deg C first thing when you check tubes in the morning and double to 25 deg C early afternoon.
I just made a run from Albion, CA (near Mendocino) to Oakland; temps went from upper 50's (F) at Albion to about 110F in Booneville, and back to about 80F in Oakland (with a drop to about 70 in Richmond.) Started with a tube pressure of (at a guess) about 2 psi, dropped it again in Booneville (they were really tight); got home with fairly soft saggy tubes. Beats repairing blown seams though.

jky
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Old 10 June 2015, 20:21   #13
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That's California. I do the long beach @ 50F and foggy to the valley @110f and back to Ventura @50. Makes for a couple stops to deflate and inflate. I'd be interested to see how that works now that I have a pressure gauge.

Jason
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Old 10 June 2015, 22:34   #14
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What's a good gauge, and how do you put air in your tubes?
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Old 11 June 2015, 00:14   #15
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thanks guys for all the responses, interesting info
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Old 11 June 2015, 00:42   #16
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I got this one. It's a low pressure gauge which is what I wanted.

http://rivergear.com/product.php?productid=54

I have an electric air pump now. The fancy two stage 12v one wired in the boat. Can't recall the brand right this second. The popular one on here.

Jason
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Old 11 June 2015, 06:27   #17
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-1 degree Celsius = -4 millibar pressure change.

100F to 80F = 6.666 Celsius. Thus, your boat should have lost 26.664 millibar of pressure (or 0.39 psi).

Same goes for barometric pressure. -1 millibar of barometric pressure = +1 millibar of tube pressure.
Nah,

P2 = P1 T2 / T1

T has to be in Kelvin.

(for 100F falling to 80F...)

P2 = P1 * 300/311

So the pressure change is 3.6%... probably less than the accuracy of most cheap gauges!
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Old 11 June 2015, 06:36   #18
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Yes, but looking at the whole picture, that's just the air temp Poly - as ofice888 posted the actual temp the tubes heat up to when exposed to the sun is much more (significant).
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Old 11 June 2015, 06:49   #19
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Also have a look at how the partial presure of water changes with temp, apply Henry's law and work out what that does to the overall pressure if you have some liquid water in your tubes.
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Old 11 June 2015, 10:15   #20
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What's a good gauge, and how do you put air in your tubes?
I have a Bravo 12HP wired into the boat, with enough garden hose tacked on to reach all the valves.

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