Pressure Relief Valves, what do you think?

[office888]

Originally Posted by Nos4r2

In other words, bugger all

Can't argue that they're not a good idea, because they are. But to think they'll make a difference during the split second when there's an impact you'd probably have to be a bit overconfident in your own logic.

It's the reason why Military and Police tubes have them standard.

https://youtu.be/g9OcKFNEwEg
The hypalon tube has OPVs which is why a seam didn't blow out while he runs it over with his truck.

Zodiac 25 year old PVC UV baked tube = no OPVs, tears open at a weak spot (might be a cut from the undercarriage).

[Pikey Dave]

Originally Posted by office888

It's the reason why Military and Police tubes have them standard.



https://youtu.be/g9OcKFNEwEg

The hypalon tube has OPVs which is why a seam didn't blow out while he runs it over with his truck.



Zodiac 25 year old PVC UV baked tube = no OPVs, tears open at a weak spot (might be a cut from the undercarriage).

If the OPV had let go during the "experiment" the tube would be soft after the fact. The tube appeared to be as tight after as it was before. That experiment is a demonstration of the strength of a Hypalon tube, not the effectiveness of an OPV. The OPV can't dump air fast enough to do what you're claiming. As I said before, to increase the pressure from 2.5 to 13 PSI involves a reduction in size of the tube to a 1/4 of its original size (Boyles law). In a collision, this would happen in a fraction of a second, there's no way could an OPV dump that much air in so short a time.
All IMO of course.

[jeffstevens763@g]

never bothered me this tube pressures & dont suppose anyone bothers to think about their cars tyres in summer with friction added into the equation, still picked this off google 20c increase about 6%

Welcome to pf, the formula is PV = nRT (n is the amount of gas and R is a constant) What this means is that pressure * volume is proportional to temperature. (The temperature has to be absolute ie. = celcius + 273) So if you go from 20->40 C, the pressure * volume increases by (40+273)/(20+273) or about 6%. So if you keep the pressure the same the 1000cc will become about 1060cc. And so you are correct - assuming the temperature is the same, if you half the volume you double the pressure.

Reference https://www.physicsforums.com/thread...h-heat.267530/

[office888]

Originally Posted by Pikey Dave

If the OPV had let go during the "experiment" the tube would be soft after the fact. The tube appeared to be as tight after as it was before. That experiment is a demonstration of the strength of a Hypalon tube, not the effectiveness of an OPV. The OPV can't dump air fast enough to do what you're claiming. As I said before, to increase the pressure from 2.5 to 13 PSI involves a reduction in size of the tube to a 1/4 of its original size (Boyles law). In a collision, this would happen in a fraction of a second, there's no way could an OPV dump that much air in so short a time.
All IMO of course.

Don't focus on the 13 psi, the amount of overpressure would depend on the dynamic stress.

You can hear the OPVs dump a lot of air at about the 0:10 mark.

The 2.0 psi cracking A6 OPV flows 58 cfm @ 6.0 psi.
28.32 * 58 = 1643 lpm
1643 lpm / 60 = 27.4 liters per second
27.4 / 10 = 2.74 liters per 100 milliseconds
= 0.274 liters per 10 milliseconds

Whitewater rafts are equipped with overpressure valves exclusively for high speed collision related reasons.

From leafields website:
A6 Valve Plug
Provides an effective secondary seal on the valve. This is a requirement for some life raft approvals. This cap can also be useful in preventing air loss through the pressure relief valve when an inflatable chamber is experiencing heavy impacts in rough seas which can cause pressure spikes.

[Xk59D]

That is where these guys went wrong, if they had OVP they didn't work too well

https://youtu.be/y6X92PzMBSg

[Pikey Dave]

Stupid is as stupid does[emoji57]

[Maximus]

Originally Posted by Nos4r2

Let it not be said you talk a load of #2....

Don't go you worrying yourself AT ALL on that Score Nos!(why do I always think I've spelt that wrong?)..

Those in the "Know"..."Know"....IF you Know what I mean

[Maximus]

Blimey...the poor O.P must wonder what he started...funny thing is I think we do agree they are a good idea!??...
Maybe as well a the Flu..a bit "Cabin fever" going around

[Nos4r2]

Originally Posted by Maximus

Blimey...the poor O.P must wonder what he started...funny thing is I think we do agree they are a good idea!??...
Maybe as well a the Flu..a bit "Cabin fever" going around

Yep, they are definitely a good idea
Definitely cabin fever too.
I'm bloody itching to get the boat out at the moment. The freezing weather has caused me some tyre valve problems and I'm stuck with 2 flat trailer tyres.
I need it to freeze properly so I can jack it up and change them!

[Poly]

Jeff - I have said this many times - people don’t believe it! Moisture of course doesn’t obey the ideal gas laws. The reality is if tubes burst from heat it is almost always at seams - which is a glue softening issue not a pressure issue really. This is an argument for welded tubes but that goes against the mantra of hypalon is always best!

[jeffstevens763@g]

Originally Posted by Poly

Jeff - I have said this many times - people don’t believe it! Moisture of course doesn’t obey the ideal gas laws. The reality is if tubes burst from heat it is almost always at seams - which is a glue softening issue not a pressure issue really. This is an argument for welded tubes but that goes against the mantra of hypalon is always best!

Tube state is a factor but if your tube working pressure is 3 psi your going to pump up to that regardless, as condition unless obvious is unknown, as the OP as stated they hold air remarkably well he is aware of possible strain that's why he's asking and yes PRV'S are great but my point is a 6% pressure increase @20c about 0.2 psi. whilst stood drop the pressure I think I read somewhere a 1 cm depression in the tube pressed by your finger is about 2.5 psi which means the tube is still in a full state giving room for about 15% volume increase. Also on new tubes test pressure is greater not saying that should be used on old tubes. All I am saying is we pump up with cheap gauges that arnt calibrated so are we at 3 psi in the first place? Do PRV,S blow off at the required pressure as they get older?, should we leave our tubes at max pressure regardless of temp increase.i ve been using inflateables for forty years only one boat I've had with PRV,S nice to have but not a nesseserty IMO or all tubes would be fitted with them.

[Maximus]

Originally Posted by Poly

Jeff - I have said this many times - people don’t believe it! Moisture of course doesn’t obey the ideal gas laws. The reality is if tubes burst from heat it is almost always at seams - which is a glue softening issue not a pressure issue really. This is an argument for welded tubes but that goes against the mantra of hypalon is always best!

You do love splitting Hairs Poly...But the fact remains Hypalon IS Best! for RIBS ...by quite a long way

[Poly]

Originally Posted by Maximus

You do love splitting Hairs Poly...But the fact remains Hypalon IS Best! for RIBS ...by quite a long way

Well you never let logic get in the way of an argument eh!

[Maximus]

Originally Posted by Poly

Well you never let logic get in the way of an argument eh!

If I can ever figure out you're argument actually IS..I'm very happy to par take
If you think PVC ect is Superior to Hyperlon?....
Crack on with your Case!

[beamishken]

Originally Posted by Maximus

You do love splitting Hairs Poly...But the fact remains Hypalon IS Best! for RIBS ...by quite a long way

I personally prefer hypalon but I can see the benefit of polyeurothane with welded seams (Not pvc) our sailing club have 4 boats 3 are hypalon 1 was polyurethane last year the polyeurothane boat, an XS failrd at the tube seams xs volunteered to tube the boat in a material of the club's choice for half price we chose hypalon and are very pleased with the outcome.
However before the retube the XS looked cosmetically in far better condition than the hypalon ribcrafts, it had stood up to the club abuse and abrasion cosmetically far better than the hypalon
XS assured me the glue seam issue is now a thing of the past due to new materials and welded seams
I'm not saying polyeurothane will overtake hypalon but I think the gap is closing with the advent of welded seams and the claimed cureing of the glued seam issue
I guess time will tell.
For now I'm still in the hypalon camp

[Poly]

Originally Posted by Maximus

If I can ever figure out you're argument actually IS..I'm very happy to par take
If you think PVC ect is Superior to Hyperlon?....
Crack on with your Case!

Saying PVC etc lumps PU in the same camp which is just wrong. There is a marketing failure there by not using names that are better differentiated to the lay person. PU and PVC are totally different. Let’s rule PVC out, although It has its place. Early PU boats had issues with gluing, as Ken alludes to. Virtually all PU tubes are now welded. Welded seams don’t fail. Welded seems are easier to quality control and can deliver genuinely air tight boats. There is data around that suggests as Ken’s anecdotal evidence supports, that PU is more abuse resistant. American commercial use seems to have been heading that way for a while now.

So, tell us why modern hypalon boats which have glued seems are definitely better than all other materials and manufacturing techniques again? Is it really just that that’s what we do in the UK and have done for years and so must be the best way.

As far as I can see there are two issues that might make hypalon better:

1. When you puncture it - repair is easier. Perhaps that needs someone to make a welded patch kit /tool? but it’s not impossible to repair anyway. If the abuse resistance is true you’ll get fewer punctures to start with anyway.

2. Because of its reputation it has higher resale value. Although condition matters more so if as ken says the Pu tubes looks better after years of use, that might cancel out. Tubes are probably only 15% ish of the purchase price of a new boat package anyway.

If I was in the market for a new boat and both hypalon and Pu were options I’m not certain which way I’d go. Possibly follow the sheep and go hypalon, then fit PRVs to it because I’m worried on a hot day the glue softens.

[beamishken]

I think poly pretty much nails it there,most of us in the hypalon camp are probably sheep following the crowd

[chipko]

Originally Posted by Maximus

But the fact remains Hypalon IS Best! for RIBS ...by quite a long way

Well I do hope you are wrong as we chose welded PU over a no cost Hypalon option for our XS rib. Liked the idea of less glued joints and superior abrasion resistance of PU. Disadvantages include far less choice of colours and perceived quality when resale time comes.

We also had PRV’s fitted during the build for peace of mind even though we are north uk based! Have actually heard them working whilst waiting to launch on hot sunny days (we wish). I think they also leach a little air over time anyway so be prepared to top up more frequently than tubes without.
Not sure I’d retro fit as seems a fairly complicated/costly affair installing doublers etc.

[jeffstevens763@g]

Always been a hypalon man but when I bought this sib strongen material welded seams was 2/3 the price, it's the same material as gurnard's boat which I think is 12 years old and his boat is immaculate and proberbly had a busyer life than most so worth giving it a try time will tell

[Maximus]

Originally Posted by beamishken

I think poly pretty much nails it there,most of us in the hypalon camp are probably sheep following the crowd

Come on Chaps at least try to engage a just bit of the Ol grey Matter.

Sheep you say?...Following the Crowd? You say

...Oh!! Yes!!...you mean Like ..The Royal Navy...Customs...Police...Fisheries Protection Rescue Services all (including our own R.N.L.I) Special Forces..ect ect ALL over the world.
Who have used and continue to use a time tested product which nothing has really competed with for decades.

Organisations with just maybe a "Tad" more experience?? ..not to mention exhaustively procurement testing......Organisations with Budgets which give them the WIDEST choice possible!!
Yeah..and despite my experience of being in and around many and different types of Inflatables since the 1970's...
I have visited Ribcraft and Henshaws on numerous occasions and seen many other products being manufactured out of Hyperlon..From Truly Huge Fenders for Big Shipping and Super Yaghts to Oil catchment Boons used to capture and Sometimes move oil slicks to in Ocean Swimming/Anti Jellyfish
Devices...All had one thing in common..I'm sure you can guess what that was?....just in case ALL Made from Hyperlon!
I wonder why they in these chastened economic times use something "cheaper...and easier to weld..and repair"??

..yep it's a more expensive..I wonder why no one minds the extra cost?
Because it's the Real world with Real World experience coming to into play.


I'll take that a experience and those endorsements over the dubious limited opinion of someone who stays WELL inshore with a Plastic S.I.B and FunYak.
...EVERY Time