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Re: [PSUBS-MAILIST] V.A.S.T. Mk III to K-250 conversion.
Ian,
You can definitely retrofit the ribs, internal or external. They can be
installed in segments and don't have to be one single piece. I don't
think any left over metal from cutting out the integral VBT is going to
provide reinforcement. The two existing ribs provide you with a 44 inch
cylinder based upon the K250 plans. According to the un-stiffened hull
calculator on the web site, that would take you to a maximum of 285 feet
given the 1/4 inch thick hull. Depending how deep you want to dive, a
130 foot self-imposed limit should give you an adequate margin of safety
without worrying about retrofitting ribs. Adding three T-ribs, one in
the center of the conning tower and one additional rib on either side at
12inch on center, will get you to 250 feet with a margin of safety of
about 2.5 according to the hull spreadsheet on the website.
Jon
On 10/16/2010 12:46 AM, irox wrote:
Hi,
I wondering if anybody here has any ideas or insight on this topic.
One of the big differences between the VAST Mk III and the K-250
is that the Mk III VBTs are built into the pressure hull interior
on either side of the conning tower. Essentially there a two foot
by two foot steel plate welded to the inside of the pressure hull
(see Busby p144). The VAST Mk III appears to not have internal
ribbing, other than at each end of the cylinder section of the
pressure hull. Which leaves me thinking that the VBT are also
providing structural support as well.
Since the VBTs are welded from one side only, the welds will not
last as long. Also it is not possible to inspect the inside of
the tanks for corrosion problems. So the tanks must be cut open
for inspection. Installing a K-250 style VBT tank which isn't part
of the pressure hull seems straight forward enough. But what
about the lack of ribbing? can ribbing be refitted? will the
remains of the VBT tank (the structural plates of the VBTs
which are perpendicular to the axis of the pressure hull cylinder)
provide enough re-enforcing?
Hopefully my explanation is understandable. Any advice on how
to deal with this issue much appreciated. Let me know if I am
not making sense and I'll try to explain it better.
Thanks!
Ian.
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