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Old 11 August 2007, 13:24   #1
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Tubes, How hard?

I am sure this has been covered before, but I can't find a thread!

The question is, how hard should my tubes be? They are black and are very susceptible to heating in the sun. I find they are really hard in the heat of the day, but quite floppy in the early morning.

Should I pump up when it is cold and relieve the pressure when it is sunny?

We went back to Cowes late at night recently and they were so floppy I was concerned about damage?

Would appreciate input, please.

Thanks!

Tony
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Old 11 August 2007, 14:01   #2
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Yup, have same problem " allways floppy in the morning"
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Old 11 August 2007, 16:39   #3
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I have a pressure guage that came with my Zodiac. I use a footpump to inflate and when it is difficult to push down, that is usually the right pressure according to the guage. The tubes feel hard. In the heat they do get firmer and in the cold they go softer but i recon on the water they are in contact with 15-18C so they should be fine even on a hot day. I have heard of pressure relief valves but dont use them so cant comment on their effectiveness. i wonder at what pressure they release air? in the UK that will not happen that often! Still raining in Scotland and not so ruddy warm!
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Old 11 August 2007, 16:43   #4
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Quote:
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I have a pressure guage that came with my Zodiac. I use a footpump to inflate and when it is difficult to push down, that is usually the right pressure according to the guage.
Do you have any idea what pressure that is??

Thanks
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Old 11 August 2007, 16:47   #5
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Quote:
Originally Posted by Red Fox View Post
I have a pressure guage that came with my Zodiac. I use a footpump to inflate and when it is difficult to push down, that is usually the right pressure according to the guage. The tubes feel hard. In the heat they do get firmer and in the cold they go softer but i recon on the water they are in contact with 15-18C so they should be fine even on a hot day. I have heard of pressure relief valves but dont use them so cant comment on their effectiveness. i wonder at what pressure they release air? in the UK that will not happen that often! Still raining in Scotland and not so ruddy warm!

My RIB has pressure relief valves and you would be suprised how much air they vent off. I have seen RIBs without them pop the seams.

Personally I believe tubes should be as soft as you can get away with without them flopping all over the place - it's much easier to burst a balloon blown up as hard as you can than one that's only 1/2 inflated!!!
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Old 11 August 2007, 16:48   #6
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Tony,

I think I read somewhere about 2-3PSI is about right, but can't remember where, sure it was on here.

Do you have pressure relief valves? I find that after a hot day, sometimes in the evenings etc my tubes are soft, as the relief valcves have let air out. Hence need topping up for a late run back or early in the mornings. I ran with softish tubes once, too soft, ride changes and sure not good for boat if you keep doing it.

KR

Neil
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Old 11 August 2007, 17:07   #7
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Quote:
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Do you have any idea what pressure that is??

Thanks
sorry no, it just has +/- and a green zone for correct. So how do the pressure relief valves vent? Do you set them to go off at a certain pressure? If so what is it?
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Old 11 August 2007, 17:58   #8
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My Polaris (hypalon) has a pressure of 2.5 psi max.

My buddy's Avon (hypalon) uses closer to 4 (I think; that's what they told me.)

My other buddy's Zodiac (PVC) runs around 3.5, as I recall.

YMMV.

jky



My old Achilles SIB (also hypalon) ran 4 to 4.5 psi.
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Old 12 August 2007, 01:17   #9
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My Searider still has Avons original plate which recomends 2-3 PSI.

Ian
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Old 12 August 2007, 02:13   #10
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Heat makes mine go floppy!!

well indirectly!
My XS-Rib was fitted with pressure relief valves, as it get toasty quite often over here in Sunny California.
Only problem is, they do their job and vent off excess,but then when it cools down at night ,the tubes tend to get the "floppies".
So its usually a little top up next morning before it heats up,just so its not flopping around on the trailer.
3.5psi seems good
Luckily had an old low pressure /high volume spray unit that puts out about 10 psi. So I made up an angled inflator adapter from some PVC , to go on the end of the spray hose , which is great for quickly topping up the tubes before leaving home.
cheers Dal
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Old 12 August 2007, 12:40   #11
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When I had my temporary botch up repair in place recently it was filled with a tyre valve so I could measure it and 3psi was nice and firm and I thought probably about right for "feel" - but you need to start with the tube pretty hard here as the water temp can be down to 2 or 3 deg C in the winter and it soon takes the heat out of the air inside the tube when you get under way.

I think running them under inflated would probably damage the tubes as the fabric would flex in places it wasn't designed to - the air pressure seems to give the tube "structure" if I can put it that way.
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Old 12 August 2007, 14:19   #12
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normal use 1.5psi , race boat as hard as possible ,hypalon fabric is only gaurenteed to be airtight upto 4psi
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Old 12 August 2007, 16:38   #13
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Do I have pressure relief valves?

Can anyone tell me if I have pressure relief valves? How can I tell? They look like standard Leafield C7 valves similar to those on the Henfield web site.

If I can do it, and I don't have them, I would really like to fit relief valves, so i don't damage the tubes in the sun! Can this be done?

I guess I should have found this out months ago!

Now I am concerned.
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Old 12 August 2007, 16:47   #14
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Having my old RIB up the drive I would give them a gentle squeez when walking by. If they were too hard I would deflate them a little and too soft (in Winter) would inflate. I guess it's a little more difficult with a RIB on a mooring or lockup. Best to err on the side of caution and deflate them after each day of use. Only takes 5 mins blowing them up anyway.
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Old 12 August 2007, 16:55   #15
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if you have 5 air chambers with 5 valves you do not have pressure relief valves .they can be fitted as an afterthought
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Old 12 August 2007, 17:06   #16
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if you have 5 air chambers with 5 valves you do not have pressure relief valves .they can be fitted as an afterthought
By replacing just the valve tops or the whole fitting (cut and glue job)?
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Old 12 August 2007, 17:11   #17
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you cant change top as c7 is fill valve ,a6 is relief valve separate units .cut ,reinforce and fit a6 valves
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Old 12 August 2007, 17:25   #18
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What angle on the tubes would you fit relief valves Paul?

Downward or at 90 degrees to the floor? (I guess upwards would be a bad idea?!)
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Old 13 August 2007, 07:49   #19
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normally 90 degrees or less to floor
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Old 13 August 2007, 08:06   #20
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So I conclude that I don't have relief valves and should be looking at two PSI. Thanks to everyone!
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