I was wondering about the pressure margins in the tubes on an inflatable boat (RIB).
In the course of a day the air temperature can probably change 15-30 deg F or more (depending where you live and the season). The rule of thumb for tires is that a 10 deg F change in temp will change the pressure by 1 psi. For a high pressure thing like a tire this is not particularly significant. But with a low pressure boat tube a 1 psi change is ~28% (for a 3.5 psi tube). If a tube is under inflated by 1 psi you'd probably notice. A 20 deg temp change will change the pressure by about 50%. It is quite possible for the tube pressure to get up to 5-6 psi due to temperature changes. And we aren't counting heating effects on the tubes from direct sun exposure.
Say I start out early in the day and it's cool and cloudy. I make sure my tubes are firm when I start out. Then later in the day it warms up and the sun comes out (plus I have red tubes). I could end up with my tubes at twice the recommended pressure (or more).
Does the manufacturer of the tube design them with sufficient margin to account for temperature changes? Or must I monitor the tube pressure and adjust it as necessary during the course of the day (release some pressure as the temp rises and the add some back as the day cools)?
Perhaps the rule of thumb for tires does not apply to boat tubes. Maybe I should fill them with nitrogen to reduce this effect (like is done with aircraft tires).
What do others do about this?
Perhaps I'm concerned about something that's not really an issue.
In the course of a day the air temperature can probably change 15-30 deg F or more (depending where you live and the season). The rule of thumb for tires is that a 10 deg F change in temp will change the pressure by 1 psi. For a high pressure thing like a tire this is not particularly significant. But with a low pressure boat tube a 1 psi change is ~28% (for a 3.5 psi tube). If a tube is under inflated by 1 psi you'd probably notice. A 20 deg temp change will change the pressure by about 50%. It is quite possible for the tube pressure to get up to 5-6 psi due to temperature changes. And we aren't counting heating effects on the tubes from direct sun exposure.
Say I start out early in the day and it's cool and cloudy. I make sure my tubes are firm when I start out. Then later in the day it warms up and the sun comes out (plus I have red tubes). I could end up with my tubes at twice the recommended pressure (or more).
Does the manufacturer of the tube design them with sufficient margin to account for temperature changes? Or must I monitor the tube pressure and adjust it as necessary during the course of the day (release some pressure as the temp rises and the add some back as the day cools)?
Perhaps the rule of thumb for tires does not apply to boat tubes. Maybe I should fill them with nitrogen to reduce this effect (like is done with aircraft tires).
What do others do about this?
Perhaps I'm concerned about something that's not really an issue.
