RE: [PSUBS-MAILIST] rib span

["Alec Smyth" <Asmyth@changepoint.com>]

Jon,

I ran two scenarios:

1) Using 0.25" plate, and the T stiffeners of the following dimensions:
web thickness = 0.25
web depth = 1.5
flange thickness = 0.25
flange width = 1.5

"Web" refers to the "vertical" part of the T, "flange" to the "hat".

result --> failure at 969' through general instability



2) Using 0.375" plate, and the T stiffeners as follows:
web thickness = 0.375
web depth = 1.5
flange thickness = 0.375
flange width = 1.5

result --> failure at 1,684' through general instability


That's quite a difference, no?

Alec



-----Original Message-----
From: Jonathan Wallace [mailto:jon@psubs.org] 
Sent: Thursday, August 21, 2003 10:12 AM
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] rib span


Hi all,

I heard a few people at the convention commenting on how they would like
a K-600 but that Kittredge won't release the plans he has.  However, my
crush depth calculator is showing that ribs spaced 12" apart using .25
steel with an 18" radius collapses at 1900 feet.  That's a 3 to 1 safety
margin.

I don't know what rib spacing the K-350 plans call for, but it occurs to
me that if the calculations are correct people might modify the rib
spacing to reach a deeper depth using a good safety margin.  In other
words, a thicker hull (.375 instead of .25) is not absolutely necessary
for a deeper diving vehicle.

Can someone else:
1) confirm my calculations using modulus of 30 million and poisson's
ratio of .3
2) tell me what the rib spacing is on the k-350 (if I had thought of
this earlier I would have measured the Lake Diver)
3) poke holes in my conclusion

Thanks,
Jon