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Old 02 July 2009, 02:19   #1
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Grr tubes + temperatures

Hi Guys,

I've had a quick read of a few things on here but it always seems to point to a leak!

Yesterday we took the old humber out diving for the first time.
Before going out the tubes were nice and solid, they dropped a tiny bit when she was on the water, but when we came up after diving (20 mins) I would say they were 1/3-1/2 flat.....
Once home again on the trailer after 10 mins they were hard again.

Now this is all tubes so it is obviously a temperature issue... my question is- am I not blowing them up enough to start with? Its a 1984 and doesn't appear to have pressure release valves so I don't want to blow my tubes up when it gets really hot!
But at the same time is was a little hairy yesterday with 1/2 inflated tubes!
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Old 02 July 2009, 03:20   #2
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Going soft is a common problem for me. Yesterday midday - mine were very hard - by 8pm & after a 10 mile run with breeze & spray youd think they were punctured, but its all down to the temp ! The only thing you can do is infate them on the water as needed. I'd be surprised if it ever gets hot enough to burst them in the UK ( apart from maybe 1 day a year) . I've never seen it & never heard of it happening to anyone.

I'd blow them up hard after 10 minutes afloat to get them ' right'. It may not help if you have wet divers / gear on the tubes as this will cool them alot compared a dry tube in the sun. As you will know water takes the heat away alot faster than the air - is it 50x ?
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Old 02 July 2009, 03:26   #3
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I think the best you can do it to have them at a minimum useable pressure when cold, hopefully one of the tube guys will be along to confirm that this should not cause an over-pressure situation when hot.
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Old 02 July 2009, 03:53   #4
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remember when i had my first boat (black tubes) scared the bejesus out of me first time when i was going down southampton water and looked at the tubes as they were almost flat!!

they had pressure release valves which made it worse cos as they expanded they let air out to keep pressure but of course when they cooled down, there was almost nothing left!!!

Strangly the next two boats didnt have any problem at all, even in the really hot weather!!
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Old 02 July 2009, 04:07   #5
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Quote:
Originally Posted by Blackroady View Post
As you will know water takes the heat away alot faster than the air - is it 50x ?
I am no expert but I think it is 25x
I think it is the same for sound as well?

Lee
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Old 02 July 2009, 04:16   #6
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had a new black tubed rib outside on monday tubes blown up hard when inside temp 21approx took temp of tube outside too hot to touch 61 degrees .tubes are fine didnt even blow off pressure relief valves
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Old 02 July 2009, 04:40   #7
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I am no expert but I think it is 25x
I think it is the same for sound as well?

Lee
Your heat factor is correct: the thermal conductivity of water is 0.6 and air is 0.025 which is actually 24x.

The speed of sound through salt water is only 4x faster than air (at 1,560 m/s as opposed to 343 m/s).
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Old 02 July 2009, 05:06   #8
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I knew it was alot ! my guess was based on a conversation years ago when I considered getting in to diving on a more than ' i'm on holiday in a nice place' type of way. As you can tell I didn't take it far.

Hopefully it gives a good indication of how much water will cool you / the tubes compared to being in the sun / air. As Paul said tubes can be too hot to touch & are fine - a quick rain shower / bit of spray and they very soon cool of.

I'd guess if running with big divers etc then more of them will contact the water, more cooling, more divers - more water running over top of tubes , more cooling , etc etc .
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Old 02 July 2009, 05:45   #9
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thats why lifeboats are pumped up solid in the boat house ,though i suppose if you inflate a boat at a high altitude there should be more volume in it at sea level , i wondered why some of the diving clubs that come from higher altitudes have no bother ,Bradford b.s.a.c . club house is about 2000 ft above sea level ,
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Old 02 July 2009, 06:03   #10
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though i suppose if you inflate a boat at a high altitude there should be more volume in it at sea level , i wondered why some of the diving clubs that come from higher altitudes have no bother ,Bradford b.s.a.c . club house is about 2000 ft above sea level ,
I think you'll find it is the reverse.

Curious about the Club House, the town is at less than 500ft, is it well up the Pennines then?
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Old 02 July 2009, 06:32   #11
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I think you'll find it is the reverse.

Curious about the Club House, the town is at less than 500ft, is it well up the Pennines then?
i know their club house and where their boats are kept is up at at ,mountain ,Queeensbury , about 4 miles west outside Bradford city center.think it highest village in yorks as they look down into the city ,on a clear day you can see 3 uk national parks ,look over at Derbyshire ,yorkshire and out to humberside ,guy recons that they can get more volume in for a given pressure as the air is less dense up there ,might be an urban myth or joke .
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Old 02 July 2009, 06:49   #12
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I've had the pressure release valve go off in my Bow section.

the relavent point is that for some reason it didn't stop when the pressure was back down to what it should be, but let far more air out than that.
It required a lot of pumping in hot weather to get it back up.(Ooer missus)

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Old 02 July 2009, 07:30   #13
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I always carry a plastic stirrup pump in the console. It is dual action so even with my big boat it is very easy to chuck some extra air in.

Even though I have bright tubes and pressure relief vavles I let some air out manually yesterday - they were drum tight. As it's easier to burst a balloon when it's blown up to it's limit I suspect the same is true of tubes!!!
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Old 02 July 2009, 07:50   #14
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i know their club house and where their boats are kept is up at at ,mountain ,Queeensbury , about 4 miles west outside Bradford city center.think it highest village in yorks as they look down into the city ,on a clear day you can see 3 uk national parks ,look over at Derbyshire ,yorkshire and out to humberside ,guy recons that they can get more volume in for a given pressure as the air is less dense up there ,might be an urban myth or joke .
Volume will be limited by the tubes - but as air is compresable, the variable become pressure ( either by heating or changing atmospheric pressure) - you can get differing pressure for the same volume - pressure changes as you go up / down .Up = less atmospheric pressure - so stuff inflated lower gets harder . If you inflate at altitude and come down pressure increases so stuff goes soft.

Thats why if you dive gases expand / come out of solution (you get harder - until you pop ) as you rise to the surface etc etc . Same as water boiling at lower temps at less pressure - the gas just 'appears' -hopefully not inside you , or at a rate you cant deal with !
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Old 02 July 2009, 09:31   #15
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Volume will be limited by the tubes - but as air is compresable, the variable become pressure ( either by heating or changing atmospheric pressure) - you can get differing pressure for the same volume - pressure changes as you go up / down .Up = less atmospheric pressure - so stuff inflated lower gets harder . If you inflate at altitude and come down pressure increases so stuff goes soft.

Thats why if you dive gases expand / come out of solution (you get harder - until you pop ) as you rise to the surface etc etc . Same as water boiling at lower temps at less pressure - the gas just 'appears' -hopefully not inside you , or at a rate you cant deal with !
He probely means then, that there really hard when setting off but when at sea level they go flat .hope they let some out then on the way back up ,lol
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Old 02 July 2009, 13:20   #16
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Hey guys,

Thanks for the info (lots of it!)
I can't see the change in altitude being an issue, its almost certainly the temperature as the tubes are fine until its been on the water for a while.

I'll wait for a hot day and blow them up as far as I dare at home and then see how they hold up!!

I think I might just be being too scaredy with how much air I put in them!
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Old 03 July 2009, 20:52   #17
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I have the same problem here - even in the summer the Antarctic currents mean the water temps are always low - about 5 deg a lot of the time I think. A rock hard tube on a sunny day goes quite limp in the water - often have to pump them up a bit. It isn't helped by the fact the tubes don't hold high pressure well - must be slightly porous I guess - if you get a hot day with strong sunshine and then a cold day the tubes will look quite soft and need pumping up before use. I can live with it - a pump always lives in the console and it takes about 20 pumps into each chamber which only takes a couple of minutes. The two rear chambers (Paul Tilley's sausages) hold air perfectly and have pressure relief valves so I leave them hard all the time.
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