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Old 17 January 2008, 15:39   #11
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Cheaper than I thought!

My question was really...... has anyone ever tried it?.
I'm sure some crazy naval architect has had access to the required seaming/valve technology and budget to give it a go.
Ignoring the problems of sealing. The weight difference is tiny. In a typical 6.5 m rib the tubes will (roughly) have a volume of 3000-4000 L. So at best would save you about 4 kg of weight. Thats about the same as one small spare (car sized) fuel can, or everyone on the boat going to the toilet before they leave, or probably completely drying the inside of the boat and bildge.
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Old 17 January 2008, 17:05   #12
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I did some digging around in the garage and found a 1 ltr. nitrogen tank rated to 3000psi. It has a regulator on it bringing down to 800psi, a pressure gauge and safety valve. If I can fill it to 2000psi this would seem to give a useful volume of gas at 2psi. Any math. whiz kid want to run a sanity check on this?
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Old 17 January 2008, 17:11   #13
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I did some digging around in the garage and found a 1 ltr. nitrogen tank rated to 3000psi. It has a regulator on it bringing down to 800psi, a pressure gauge and safety valve. If I can fill it to 2000psi this would seem to give a useful volume of gas at 2psi. Any math. whiz kid want to run a sanity check on this?
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Old 17 January 2008, 17:39   #14
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Could well be wrong here, but i think at atmospheric pressure (14.7 PSI) you would get 130L (ish) from the full tank. (you get 660L from a 5L oxygen tank)

Not sure what you would get at 2psi - 1000 ish

Tim
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Old 17 January 2008, 18:15   #15
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want to run a sanity check on this?
I think you will need about 30 of them to pump your tubes up from flat.

Pete
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Old 17 January 2008, 18:43   #16
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I think you will need about 30 of them to pump your tubes up from flat.

Pete
I got 20 of them but it obviously depends what assumptions you make about limey's tubes. (I was assuming 50cm diam and total 15m long).
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Old 17 January 2008, 19:13   #17
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I got 20 of them but it obviously depends what assumptions you make about limey's tubes. (I was assuming 50cm diam and total 15m long).
That's about right and as already stated I only intend to use nitrogen tank to top off rather than carry a 12v. pump. I carry a stirup type pump also but the ally tank would be a lot easier. Just found out I can fill the tank for about 2 bucks at the paintball range at the end of my road. Thanks for the input. BTW, if the tubes are totally flat I use my big arse compressor to fill them. Just a tip if using a compressor you need to make an expansion chamber in the fill tube as high pressure air will damage the tube valve and do not use a fixed attachment just a push fit so you have to hold it in place. Otherwise a small distraction could end up with burst tubes.
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Old 18 January 2008, 04:27   #18
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I got 20 of them but it obviously depends what assumptions you make about limey's tubes. (I was assuming 50cm diam and total 15m long).
Yep plus I added the pressure to raise above atmospheric and a fudge factor because there will be some leakage changing over cylinders.

Still think a foot pump is a better solution, its free with unlimited supply of gas and good exercise which some of those colonists could do with

Pete
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