Originally Posted by Max...
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.