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Old 24 May 2020, 14:33   #1
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A few inflation questions

Having followed the hole repair guidance in my previous thread, the moment of truth whether I was successful. Inflation time.
I removed the airdeck and inflated the floor and both side tubes with the electric pump that has a digital gauge.
I went all over the tubes, seams, valves and patches with soapy water and didn't see any bubbles.
I left it and returned a couple of hours or so later, connected the pump and both side tubes had lost well over 10%.

Could the pressure difference just be air temperature? The temperature has dropped from 18 to 13.
What is an acceptable pressure loss?
One side tube inflates most of front so which tube should I inflate first?
The valves are the zodiac delrin/boston type are these likely to leak even though I did the soap and water test on these?
Thanks
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Old 24 May 2020, 15:24   #2
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It is possible the elec pump is heating the air which then cools and loses pressure. So I’d take notice more of the pressure loss after the two hour check to perhaps hour three.
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Old 24 May 2020, 15:55   #3
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It's normal to experiment some presure loss, worse during cold temp atmospheric changes , much less during summer time. That's why need to carry a high pressure foot or hand pump to reinflate a single air mat or the double smaller ones from time to time for an oustanding water performance with less hull drag.

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Old 25 May 2020, 01:57   #4
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Two factors:

The act of compression makes the compressed air warm. This heat then dissipates and the pressure drops.

If the ambient temperature falls, the air in the tubes will drop to the same temperature, and the pressure will fall.

If you have found no leak from the tubes or valves, then it seems simply a matter of temperature and pressure being linked.
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Old 25 May 2020, 02:36   #5
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How are you measuring the 10% - with a proper gauge or the built in one on a pump? They are quite likely not up to 10% accuracy compared to a proper measuring device. And 10% on a tube is not much with heat/pressure differences.
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Old 28 May 2020, 11:58   #6
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When I plugged the electric pump back on the pressure it showed on the digital display as it started was showing over 10% less and the pump stayed on until the preset was reached
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Old 28 May 2020, 12:08   #7
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Pressure, temperature, are volume are all linked. For a given mass of gas, change one and the others inevitably change.

So when you compress air, it gets warmer. Leave it to stand for a bit, and that heat dissipates. Therefore the compressed air is getting cooler, and it's pressure reduces.
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