RE: [PSUBS-MAILIST] Nice Sub Bill!

[Alec Smyth <Asmyth@changepoint.com>]

I plugged these dimensions into my spreadsheet and got the following:

no stiffeners = 85'
1 stiffener = 205'
2 stiffeners = 329' 

Using:
Yield strength 70K
Young's Modulus 29M
Poisson's ratio 0.3

Which sort of correlates to Phil's numbers, but precisely. Phil, am I within
your "margin of error"? The fact your numbers were so nice and round leads
me to hope you're applying some rule of thumb. 

rgds,

- Alec


-----Original Message-----
From: Phil Nuytten [mailto:72020.572@compuserve.com]
Sent: Sunday, June 10, 2001 8:36 PM
To: INTERNET:personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Nice Sub Bill!


Hi, Bill:
        Just as a guide . . . for your mild steel 15' X 46" X .27 hull -
the calculated depth before the hull  turns into a halibut from assymetric
buckling is:
Unstiffened: 100 feet
Single stiffener: ( unsupported section = 90"): 200 feet
Three stiffeners, ( unsupported section= 45") 400  feet
Cut these approximate values in half to get the safe working depth . . with
no stiffeners you're looking at 50 feet and so on.If you can't afford the
space inside, put them externally - but remember to cap the perpendicular
with a flat band so that you have a 'T' section. If you want to avoid
either a doubler ( the traditional fix) under your 'conning tower' or a
series of gussets, you can put a wide horseshoe - shaped stiffener right in
the 'V' - so the stiffener is at 1:30 if the side of the 'conning tower' is
12:00 and the flat of the hull is 3:00 (  assuming that your trunk ends in
a point on each side of the hull.) By the way, a 46" dia. hull by 15' is
pretty big.  A more usual length is 10 - 12' What's goin' in there besides
you?
Phil Nuytten