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as it
seems we are back to the same old discussion.... i thought i would put my
thoughts in too.
while
it does initially seem a great and cheap way to get a hull that already looks
the part, it is worth using the pop bottle analogy.
take
your bottle of coke and shake vigorously. it is capable of withstanding a
great deal of presure from within without bursting.
now
take your empty bottle and submerge it in the bath tub..... it will already
start to buckle and even at small depths will be visibly
compressed.
now
take that and imagine the propane tank! forget that the tank is metal, it
is going to be the exact same effect only scaled up slightly. if max depth
required is just beneath the surface then it might be worth it but would you
want to risk your life in a big pop bottle? what price would you put on
your life... £500 for a 5 metre propane tank or £2000 for a 100 metre plus
hull?
i
assume that it may be possible to have a 1 atm wet sub, that is totally sealed
and then able to take the external pressure but then to be honest... what is the
point?
steve
- uk
i have
no direct experience trying this but anyone looking into this seriously needs to
trawl through the archives! maybe there should be a link to all propane
related material on the main page?
myles
that is best guess numbers without knowing the
material and thickness, the shape of the head and so on.
i put the end caps for mine
out to bid. for one inch end cap 36 inch dia with a min thickness of 3/4
cost 980.00ea the shell rolled and rings tacked 3500.00. that is cheap
insurance. that is for a hull with a 1000ft operational limit.
save money in other areas.
rick m
rick m
----- Original Message -----
Sent: Monday, October 31, 2005 6:55
AM
Subject: Re: [PSUBS-MAILIST] Propane
tanks
Rick,
So, according to your
calculations, we are talking a safe operational depth of 20M ?
Myles.
----- Original Message -----
Sent: Sunday, October 30, 2005 11:37
PM
Subject: Re: [PSUBS-MAILIST] Propane
tanks
shipmates
i posted to qiuckly
the numbers i gave you are for maximum allowable working pressure not
failure.
rick m
----- Original Message -----
Sent: Sunday, October 30, 2005 8:12
PM
Subject: Re: [PSUBS-MAILIST]
Propane tanks
guys
i know that propane tank seam to be
an easy way to start. But the cost of the hull tube conponents are a
small frastion of the total cost. and you still have to weld the rest of
it together. buy decent end cap and shells. For the cost testing the
tank material you can buy the hull.
rick m
----- Original Message -----
Sent: Sunday, October 30, 2005
7:26 PM
Subject: Re: [PSUBS-MAILIST]
Propane tanks
From a manufacturer: Tanks are rated at 250 psig from -20° F. to
125° F. All tanks may be evacuated to a full (14.7 psi) vacuum.
I'd be curious as to what depth guys
are getting on a new 500 gal propane tank (without ribs). 10M
?, 25 M ??
Myles.
----- Original Message -----
Sent: Sunday, October 30,
2005 5:41 PM
Subject: Re: [PSUBS-MAILIST]
Propane tanks
Hi Myles,
I've cut a couple, 250 gallon or so, I
think were over 1/8th.
Newer and smaller tanks have thinner walls. Could be the
steel is stronger, could be they are not as overbuilt as the old
school stuff?
Anybody else have experience here?
-PK
Peter,
Is that some sort of
custom tank ? It seems to me they aren't that thick.
Don't quote me, I've never cut into one but I thought they were
closer to 1/8 " I'm referring to your run of the mill
residential tanks.
Myles.
----- Original Message -----
Sent: Saturday, October
29, 2005 10:37 PM
Subject: Re:
[PSUBS-MAILIST] Propane tanks
My propane tank sub has been to 300 feet. One thousand
gallons, 4 by 10 feet, 1/2 in thick cylinder with 5/8 inch end
caps. No reinforcing rings.
Peter K.
Hi Myles.
I would definately consider one
for an ambient, but no way for a 1 atm. There was some
discussion here a long time ago about
how the tank's holding internal
propane pressure did not necessarily cross over to keeping
pressure out the same way. I can't recall
what was said though, but I
remember it was discussed. Some guys have built them (1 atm)
and I have seen some for sale made from propane
tanks. But I'd want a thicker
hull for a 1 atm if it was me. I wouldn't trust a propane
tank hull, even with reinforcement rings.
I mean, if you are going to
build a 1 atm with all the trouble it takes....you might as
well make it where it can go
relatively deep and build it with a thick pressure
hull
and get down 600 feet or
more. Most of the good non picked over wrecks are
deeper than scuba depths because the divers have already
picked most of them over.
Most wrecks (okay not all) at
scuba depths have already been found too and there isn't
much to discover new unless you go beyond scuba
depths.
But for an ambient? Like I said
I think it would be great for that for all the reasons you
listed. I think it would be very durable for an ambient and
if
you are still contemplating
building an ambient, that would be an inexpensive way to
go.
Bill.
----- Original Message -----
Sent: Saturday,
October 29, 2005 8:39 AM
Subject: Re:
[PSUBS-MAILIST] Propane tanks
Bill.
Yes,
agreed. When I was looking into the feasibility of a
propane tank pressure hull, I was certainly only thinking
of a new one. There is no way in hell I would put my
torch to a used one. The reason I was considering
one as a possibility is because:
1) I'm not looking to
go very deep.
2) They are, by their
very nature, pressure vessels complete with hemi-spherical
end caps.
3) Cost. Being
mass produced, you would expect them to be relatively
cheaper than a scratch build.
4)
Availability.
5) Convenience of
having a pressure hull with end caps already.
Having said all that, if I'm
taking the time to cut, grind, and weld, I was just as
soon scratch build a hull that is a little more
durable.
I don't know, it was
something I was pondering but I'm leaning towards a
scratch build.
Myles.
----- Original Message
-----
Sent: Saturday,
October 29, 2005 2:29 AM
Subject: Re:
[PSUBS-MAILIST] Propane tanks
Hi Myles.
There have been some subs
made from propane tanks but most of the knowledgeable
subbers shun them.
Because...
1. They can explode from
residual propane when you grind cut or torch them.
2. They are of an unknown
metalic strength.
3. They are usually too
thin for deep dives.
4. The interior of an empty
one may be corroded if the valve was left open and hence
you have something useless when you cut it
open.
There are some other
reasons I have heard of too, but that's all that comes
to mind right now.
If you do use a propane
tank I have always heard to make sure you buy a brand
new one that is shipped to you without any gas ever
having
been put into it. Then it
is safe to grind cut or torch.
I wouldn't use one for a
pressure hull myself, but I think they might be good for
an ambient.
Bill.
----- Original Message
-----
Sent: Friday,
October 28, 2005 8:20 PM
Subject: Re:
[PSUBS-MAILIST] remove me second kind request
Patrick,
Speaking of
propane tanks for pressure hulls, is there any merrit
to that, convenience or expense wise, or is a guy just
as smart to scratch build the hull ?
Have you
done any research on the propane tank thing
?
Myles.
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