Rapid dinghy inflation - from a safety perspective

[webcraft]

Not owning a liferaft, our aging Avon rubadub would be our ultimate refuge in the event of the boat disappearing unexpectedly from under. However, submergence would need to be very slow and Titanic-like to allow time to inflate the Avon with the aged footpump.

A 12V electrical inflator is obviously a waste of time as there is a high probability of the batteries being underwater by this time.

So - what about using compressed air? How big a cylinder would be needed, and are there any potential snags or hazards with this idea? Maybe some of the divers out there have tried this from their cylinders?

I thought a small dedicated cylinder and hose kept in the vicinity might be a sensible idea, but I'm now ready to be told why it's not . . . because if it was a good idea surely someone would be selling it by now?

- Nick



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[Robin]

Avon used to offer such a piece of kit as does Tinker (Henshaw Inflatables). Maybe you could buy something from them that you could fit (or try the local liferaft/dinghy servicing people?

The other option is to carry the dinghy half inflated on deck (Avons claim this will support the full quoted crew compliment) and pump it up when aboard if needed albeit with difficulty! We use a Bravo footpump (Avon offered them too as an option) which has 3 connections, one for max air input for initial pumping, one for max pressure for top up (like low gear!) and the other for pumping the air out (very useful). The Bravo is much faster than the old wood Avon pump especially in the hands of a frightened matelot....

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[Rich_F]

A couple of months ago in PBO there was a "Practical Project" for a rechargable, rapid-inflation electric pump. This might be a useful bit of kit to knock up, as it would be good both in an emergency, and for day-to-day use.

Not as fast as compressed air, of course, but hopefully faster than manual pumping.

A second useful addition would be a one-many tube/manifold that allows you to inflate all chambers at the same time. That way, in an emergency, you could start the inflation going, then rush off to panic elsewhere.

Of course, if sinking is so fast that you can't inflate on deck, then an electric solution is probably not ideal!

Rich

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[tcm]

I'm afraid i would very strongly recommend a liferaft.

Yep, the ruberdub is a start, but if there's a fire you need to get off immediately annd last one lobs in the liferaft (so why do some mount the liferaft way up high?)

If the boat is sinking, then from my experience you use/need effort to stop it sinking if poss, if not to then call the lifeboats.

Oh go on, buy one. A low-freboard rubberdub is no good at all in anything but good weather whn you are less likely to need it. You can squeeze six in a four-man, eight in a sixman for anything cept very offshore.


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[AlexL]

My perspecitve on this as a diver would be that the reason why such a system not sold is that it would be a tad expensive.
Dive cylinders are typically pumped to 230 bar - which would probably turn the dinghy into a rubber grenade! however a scuba regulator 1st stage, which sits on top of the tank reduces this to about 9 bar which would be altogether more usable, and the hoses which we use to connect the scuba unit to the BCD and Drysuit have a kind of push fit connector on the end. I guess you could fit a suitable connector to the dinghy.
Scuba tanks come in all shapes and sizes, Many divers use a 3liter 'pony' bottle for emergency use which will supply 3lires*200bar = 600 liters of air at atmospheric pressure, there are also small bottles for drysuit inflation and surface marker buoy inflation.
However this little lot is going to cost well over a hundred quid - maybe nearer 150 and the scuba tanks need testing every couple of years. If you are already a diver and have the gear it may be worth considering, but other wise it might be a bit expensive.

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[Tomsk]

Have you considered using the aircylinder and airpump from an HGV?

Run your enging to pump up the aircylinder initially then off you go. If you need to inflate the dinghy use the airbag (with suitable adapter of course), or just run the air pump straight of the engine.

<hr width=100% size=1>Tomsk -

What the hell... it's only money!<P ID="edit"><FONT SIZE=-1>Edited by Tomsk on 10/05/2004 11:16 (server time).</FONT></P>

 

[Gordonmc]

Great minds...

I posed this question on the forum some time ago and the consensus seemed to be the cost of a system that could keep a compressed air delivery system from over-inflating the dinghy would not be viable.
Since then I have seen a fast inflation device running off a compressed air engine starter... but that won't help on most boats and in an emergency you can assume the engine is duff in any case.
As a half-way house I invested £10 on a Homebase cylinder hand pump which takes the same hose and fittings as my old footpump. These things blow on each stroke and inflate the dinghy in half the time. You can also use them sitting down which is handy on a bouncy foredeck.

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[claymore]

I would also like to add that if one were to find that one had excess air left having inflated the dinghy one could also stuff the tube up one's jacksie and gain extra bouyancy and possibly a tad of propulsion.
When are you thinking of sinking Webbie old chap so that I can be in the vicinity and watch the proceedings.

<hr width=100% size=1>regards
Claymore
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[steve_cronin]

Been there and done it

Since I had a good supply of co2 extinguishers and two old inflatables I experimented with bits and bieces.

First if you just blast raw co2 from the cylinder into the inflatable, two nasty consequences ensue. First if liquid gas enters the boat it will freeze the fabric and make it succeptible to cracking - however IOM it soon welds itself together again invisibly if you're lucky and the cracks are minor. Secondly, and liquid gas soon boils and expands greatly so you end up with a very much over inflated boat -which could burst. Also you can end up freezing your own hand onto tany metal of the connectors.

A proper system needs an expansion chamber for the liquid gas to expand as it reaches is gaseous state, This needs to be in the pipework and again to avoid injury it needs to be insulated. I used a simple jet running into a coil of spirally re-inforced air hose and this worked fine./

The practicalities of stowing a heavy cylinder soon made the scheme seem not worthwhile so I abandoned it.

Steve Cronin



<hr width=100% size=1>The above is, like any other post here, only a personal opinion

 

[TheBoatman]

I think you need to be very careful with this one as all liferafts are fitted with valves that let excess air escape. Blowing a rubberdubb up with compressed air could result in blowing the whole thing to bits. I would have to say that if you are concedering using this thing as a life raft which is was never built for you may wish to buy a purpose made liferaft?

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[webcraft]

Thanks Boatman & TCM for pointing out that a proper liferaft is the best solution . . . I already know that, but finances do not permit this option and so I do not intend to buy one this year - unforseen windfalls excepted.

Hopefully if I sink Claymore will have come to come and watch, and after the fun is over I'm sure he will pull us out of the oggin for a small consideration, and time spent trying to pretend our ancient Avon is a fully RORC compliant liferaft will be kept to a minimum.

As regards overinflation and over-rapid inflation - I can see how this would be a problem. Perhaps a cylinder which only has enough air to almost inflate the dinghy . . . but from the replies others of you have thought about this and found it impractical.

Keeping the dinghy partially inflated is not much of an idea either - on a small boat it takes up too much foredeck space, and is likely to catch genoa sheets and necessitate unnecessary trips to the foredeck - not a problem in reasonable conditions, apart from the irritation factor, but definitely not wanted when conditions deteriorate.

So - next question - what is the best pump available in terms of volume of air delivered vs stowage space require. As I said in my original post, electric is probably not a sensible option for emergency situations.

- Nick

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[StephenW]

If you are unable to inflate because the batteries are submerged you are anticipating pretty dire conditions and very little preparation before evacuation. More likely is that betteries will be OK when you become aware of potential danger - so time to inflate using an excellent bit of kit called an LVM high speed inflator (also used to jack animals out of ditches using air-jacks!).

Will take about 3-4 minutes tops to inflate your rubber duck. We have one and it means you use the tender when you otherwise wouldn't bother mucking about blowing it up. It's 12v and crocodile clips onto the battery as the short duration load is quite high.

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[LadyInBed]

If you went the LVM route and don’t think that the boat battery will hack it, you could buy one of those ‘car starter battery packs’. You would then also have an emergency starter battery for the engine.

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[webcraft]

Not owning a liferaft, our aging Avon rubadub would be our ultimate refuge in the event of the boat disappearing unexpectedly from under. However, submergence would need to be very slow and Titanic-like to allow time to inflate the Avon with the aged footpump.

A 12V electrical inflator is obviously a waste of time as there is a high probability of the batteries being underwater by this time.

So - what about using compressed air? How big a cylinder would be needed, and are there any potential snags or hazards with this idea? Maybe some of the divers out there have tried this from their cylinders?

I thought a small dedicated cylinder and hose kept in the vicinity might be a sensible idea, but I'm now ready to be told why it's not . . . because if it was a good idea surely someone would be selling it by now?

- Nick



<hr width=100% size=1><font size=1><A target="_blank" HREF=BlueMoment - UK Sail Cruising>BlueMoment - UK Sail Cruising</A></font size=1>

Wow.. . . someone liked this post 20 years after I made it. A bit of a delayed reaction!

— W

 

[justanothersailboat]

It's a natural thing to wonder whether the dinghy could be made to do. Or I hope it is!

In that 20 years, have you needed the emergency-inflation dinghy... or a liferaft?

 

[penberth3]

Wow.. . . someone liked this post 20 years after I made it. A bit of a delayed reaction!

— W

That's good! It means someone has used the "Search" function instead of starting another thread about rubber things.

 

[Dellquay13]

Wow.. . . someone liked this post 20 years after I made it. A bit of a delayed reaction!

— W

Are AI internet search ‘bots getting advanced enough to be having a genuine interest in taking up sailing?

 

[johnalison]

Wow.. . . someone liked this post 20 years after I made it. A bit of a delayed reaction!

— W

Why do I have this image of a forum member sitting at his computer and trawling through his 20-yr-old posts to see if they've been liked or not?

 

[justanothersailboat]

The forum does just tell you... it's not like you have to go looking

 

[Mark-1]

That's good! It means someone has used the "Search" function instead of starting another thread about rubber things.

It was me, and I did. Sadly it didn't quite answer my question and wasn't quite specific enough for me to add my question to it so I started another thread about rubber things.

I thought the like would be a nice way to show my appreciation to the OP without reviving the thread.