Gas Bags

Tiffy · 10 March 2005, 18:48

Have been trying to work out if you fill the inflatable tubes with
Helium or Ballon Gas will the Rib weigh less , and perhaps go faster. ?
Answers to captiffy13@msn.com
visit www.venturers search and rescue.org.uk

ribraff · 10 March 2005, 18:58

I've thought about this in the past but i think you would have a job keeping Helium in the tubes!

EDDO · 10 March 2005, 20:00

If you started to sound like Joe Pascualli, you would know that you may have a leak.

Swifty · 10 March 2005, 20:24

Fill em with propane and it'll go like a rocket

Simon B · 10 March 2005, 21:51

Propane is as we all know a hydrocarbon gas a bit like petrol vapour, so is therefore heavier than air. My money would be on alternate chambers of the RIB being filled with Hydrogen and Oxygen.

However for max thrust one could employ open ended "tubes" that were packed with solid fuel like a shuttle booster unit...Did I hear some mention a stepped hull?

Brainiacs did a test to see if you filled a parcel with helium you could reduce postage costs, it made the parcel lighter but the gas was more than the postage would have been.

HTH

Jelly · 11 March 2005, 08:41

Tiffy
Your link doesn't work,
What happened to the ex RNLI prototype cabin Rib I think it was called a 'Medina' class you used to have in the Beaulieu river?
As for helium you might well find, (trying to remember chemistry lessons at school) that as the molecules are smaller it might leak out of the hypalon as the weave is designed for air.
Rgds
Jelly

Scary Des · 11 March 2005, 08:50

Quote:

Originally Posted by Jelly

Tiffy
Your link doesn't work,
What happened to the ex RNLI prototype cabin Rib I think it was called a 'Medina' class you used to have in the Medina?
As for helium you might well find, (trying to remember chemistry lessons at school) that as the molecules are smaller it might leak out of the hypalon as the weave is designed for air.
Rgds
Jelly

http://www.venturers-search-and-rescue.org.uk/ is the link

More on there about what happened to the boat

And I think you are right about leaks, but just as a matter of interest, in the automotive world they are talking about using nitrogen to reduce leaks, but that might have more to do with the characteristics of rubber than anything else

Des

keytouch · 11 March 2005, 09:06

could hypalon be lined with some kind of foil?

Cookee · 11 March 2005, 09:11

The amount of helium involved would not make a measurable differance anyway .......... add a load of foil or other barrier to the inside of the tubes would only add to the weight and make it heavier than when you started

Pete7 · 11 March 2005, 12:29

Tiffy, think you posted this about 3 weeks to early.

Breathing quality Helium is about 1p per litre, so thats going to cost a bit with a rib the size of yours.

Its a light gas that can even escape past the seals in diving cylinders that hold air to 300bar perfectly, so the chances of you keeping it in a set of tubes are slim.

It has a greater expansion and contraction rate when the temperature is varied for a given volume.

The cost of permanently hiring cylinders from BOC is expensive and hardly readily available.

Wouldn't want to be asleep in a cabin rib with a leak from the tubes.

Think I will stick to using a mix with 79% Nitrogen in my toobs.

Pete

ashbypower · 11 March 2005, 12:44

Quote:

Originally Posted by Cookee

The amount of helium involved would not make a measurable differance anyway .......... add a load of foil or other barrier to the inside of the tubes would only add to the weight and make it heavier than when you started

Agree, however you'll have a RADAR reflector as well

Brian

Simon B · 11 March 2005, 14:29

Haven't the manufacturers thought of this?