Re: Materials/parts, propane tanks.

[shawl@torchlake.com (Jonathan Shawl)]

Good points Ray,
1. Yes ribs are a good idea, if I had them I could go much deeper. Do all his
hulls have ribs?

2. I found that the main reason tanks are retired at my local gas supplier is,
once they are brought back into the yard, usually because a customer switches
companies, they don't want to go to all the trouble of changing all the valves,
which is required after so many years of service, and then striping and
repainting, they would rather write them off and buy a new tank. A new one only
costs them about $700.  If I had enough money I would build with new steel.

3. As far as metallurgy of propane tanks, I talked to someone back when I got my
tank that knew that propane tanks were better than just mild steel plate.  I
didn't go to the extra expense to prove it. What I did was to calculate for low
grade mild steel to be on the safe side. If my calcs. are in err, it is on the
safe side. And for the cost (free) of a used tank, I am happy with a 100'.

>Why fool around with an unknown propane tank?

I know what you mean. I know my propane tank very intimately and would never
think of fooling around with any other tank. ;-)
But seriously For me, it was cost $0 versus $400+?
I was wondering how much are hemispherical heads? I think they add much to the
$400 cost for the tube.
I would think a propane tank is a big head start over using plywood or other off
the wall materials.
Has anyone priced marine plywood lately? WOW? I can't afford it.
Ray Keefer wrote:

> Hi,
>
> > I have not heard of any reason to not use a propane tank, if there is a
> > reason please speak up.
>
> I once asked Kittredge why he didn't like propane tanks. Hear is the relavant
> excerpt from his reply:
>
>  Re propane tanks and why I don't like to see them used:
>         1.  Propane tanks ae for internal pressure.  Submarine hulls are
> designed to resist external pressure.  The latter must be framed in order to
> ba able to compute the collapse depth.
>         2.  There would be a tendency to use an old discarded propane tank
> because they can be purchased cheap.  If it was discarded for propane, why
> would you want to use it to risk your life in it?
>         3.  I know nothing about the metalurgy of propane tanks.  Notch
> toughness, carbon content, etc.  I would have to get the melt number of the
> steel in the tank and do a charpy test.  By the time I got through, I would
> probably spend more money than buying a certified plate of A36 or ASTM
> 516Gr70 (which I like) and having it rolled.  For a K-350 hull (one man) it
> should not cost about $400.  Then it would have to be framed.  Why fool
> around with an unknown propane tank?
>
> Regards,
> Ray