Re: Pressure hull calc's

[protek@shreve.net]

    The thing on ballast tanks got me warmed up.  :-)  I just wanted to
throw in a couple of thoughts here.  First, the calculations for crush
depth may be assuming a perfect hull.  Most welded hulls have a certain
degree of "out of round" and this can change the operating depth
considerably.  Second, in many cases, the compromise comes in the interface
of the hull to the sail itself.  This is a common failure point due to how
the stress is distrubuted at this junction.  I used bracing in this area
for my sub, but I chose to make the sail (conning tower) out of thick steel
(approx. 0.65 inch thickness).  I also extended this sail down below the
hull line everal inches all around for extra strength.

    BTW, did anyone get infected with the happy99.exe virus that attached
itself to my email the other day?  I certainly hope not.  As I mentioned
earlier, McAfee did not see it after I bought it and got the latest update
from the web.  McAfee got a "Hot" note from me on this issue.  I think
Norton will see it or at least that is what I have heard.  Wish I had
purchased Norton's Virus program.

Gary Boucher


At 05:31 AM 5/6/99 EDT, you wrote:
>
>In a message dated 5/6/99 4:40:16 AM, rmorrisson@unidial.com writes:
>
><<I have been playing around with a hull strength program and decided to
>test it out with the numbers Vance said he was considering for his
>boat.  In a formula attributed to Roark, "Formulas for stress and
>strain", 1961, the crush depth for a 42" hull with .25" wall and ribs on
>12" centers would be 1505'. >>
>
>Dick,
>	I think I was extolling the virtues of George's 1/4" hulls at the 
>time, but would not build so light for deep water.  1/2" or 9/16" shell 
>thickness with 1/4 wall (3" ribs) will be required, I think.  There is a
good 
>bit of information on rib structure in Submersible Vehicle Systems Design 
>published by the Society of Naval Architects and Marine Engineers in 1990.
 I 
>haven't seen the program you are talking about.
>Fun with figures, eh?
>Vance
>
>