Pressure

Yabadabadoo · 06 August 2019, 18:05

Is there a rule of thumb for inflatables and pressure loss?

I would assume that all factory new SIBS/inflatables would hold air perfectly and as the valves age in years might need topping up a little?

Or that doesn’t happen and a leak is a leak and a faulty valve is a faulty valve.

Pressure testing must need to be done with tubes in same state as when blown up? So, blown up on a sunny day as day gets hotter air expands, would contract again as temp drops to same state as started?

Reason being is that I’m prepared to blow up the boat I’m selling and leave it for 24 hours to monitor pressure for my own peace of mind really before the buyer collects.

Not knowing the above, if I see a pressure drop would that indicate a faulty or old age. Curious to know in any case.

ShinyShoe · 06 August 2019, 18:53

If the temperature doesn't change, a good tube should hold pressure for weeks. But. If you have PRVs then if the pressure rises in the heat, the PRV releases and then as the Temperature drops the pressure drops.

I'd expect for a loss of pressure in 24hrs an identifiable leak to be found unless there was a lot of ultra small porous bits.

If I was buying a well used RIB I'd be expecting to hold air for over a week

Fenlander · 06 August 2019, 19:21

It's difficult as many of us daily setup guys rarely have their SIBs left inflated for long enough in one go to honestly answer a buyers question... "does it keep the same pressure for weeks at a time". Two weeks is the most mine has been left inflated for and it all held over that period apart from one floor side that turned out to have a sharp stone pinprick.

To be totally sure you'd need to inflate it... let the pumped in air settle until next day... take the air temp... wait a week min until a day with same temp... lot of faff.

Yabadabadoo · 06 August 2019, 20:58

Thanks for the replies.

Well it’s good to know overall as knowledge gained. With no fault or damage my car/van/bike tyres do go down over time a little but different sort of impact and use.

I’m not going to be mucking about for a week, I think 24~36 hours or so test is good enough. Had the sib in use as a tender for the flappy thing over the weekend, 3 days of use and some of it on a buoy didn’t show up a defect certainly to my thump test. Now regret no using that time to measure the pressure!

Fenlander · 06 August 2019, 21:07

You have s sailing boat now?

Yabadabadoo · 06 August 2019, 21:19

I have access to a small (19’) twin keeled sailing boat that and the combination of its older than me owner who needs a hand has seen me do some east coast sailing. I’ll get banned for that!

Further ban territory and maybe a reprieve have not been out on the sib once this year. Have been looking at the dark side of bigger stand up inside with tables flappy things..

Have given myself a-stern talking to and doubled resolve to get boat pumped up and out on water!

Locozodiac · 06 August 2019, 21:24

No Sib nor Rib will hold its factory recommended working pressure it was inflated to provided it has 0 air leaks due to atmospheric temp variations specially on cold days. A reinflation is needed if wanting top water performance.

Happy Boating

Fenlander · 06 August 2019, 21:24

We keep toying with such ideas mostly encouraged by Mrs F. Ideas and dreams are cheap entertainment!

jeffstevens763@g · 06 August 2019, 21:31

I pump my boat up once a year and leave it if we have 30 degree weather I dump air then pump up before a trip and never had a problem do the maths and you will br supprised on the the effects of heat verses pressure. You'll fing that taking most valve caps off will allow moats to leak enough to relieve pressure.
I ve just done a trip round Jura we had rain, wind & hot weather I didn't even touch my tubes no need.

Locozodiac · 07 August 2019, 18:24

I used to reinflate all my Sibs when used to al least 3.0 PSI after some minutes water rest for overall pressure to stabilize as the sibs were taken out of water at the end of each outing and sheltered in a shaded garage till next outing.

A correctly inflated Sib with a pressure gauge performs much better than a marshmellow one, yields better fuel economy and better glide due to reduced tube and hull water drag.

The issue with air decks is that needs to be inflated to at least 10-12 PSI for top water performance at speed, if not will feel water rolling under keel and air deck at plane along unwanted water drag and less water glide efficiency.

Happy Boating

billows · 09 August 2019, 12:10

Quote:

Originally Posted by jeffstevens763@g

I pump my boat up once a year and leave it if we have 30 degree weather I dump air then pump up before a trip and never had a problem do the maths and you will br supprised on the the effects of heat verses pressure. You'll fing that taking most valve caps off will allow moats to leak enough to relieve pressure.
I ve just done a trip round Jura we had rain, wind & hot weather I didn't even touch my tubes no need.

I pumped my elderly sib up to recommended pressure and put a tarpaulin on it thinking it would be cooler out of direct sunlight but the seams leaked in hot weather due heat and increase in pressure
Fixed but not a good luck with 4 big patches