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I just noticed that the prior discussion was on the Member
Forum, so many may have missed it. See the thread below:
-Jim
From: JimToddPsub@aol.com
To: member-forum@psubs.org
Sent: 10/1/2010
2:13:23 P.M. Central Standard Time
Subj: Test depth
U.S. Navy has generally set test depth at 2/3 of design
depth. The European navies more commonly set test depth at
approximately 1/2 of design depth. The Russians ain't
saying.
Design depth is calculated at slightly less than crush
depth. Both are usually calculated depths, not necessarily tested
depths.
I have no idea how this relates to civilian subs or to ABS
or Lloyds standards.
JT
In a message dated 10/1/2010 2:53:32 P.M. Central Daylight Time,
irox@ix.netcom.com writes:
Excellent data point, Vance! The test to twice the
operational depth was
based on some claims I read on the forum (but can't
cite) that people
had tested their vessels two x2 op depth. Also I
recall a discussion (again I
can't cite it) that the 1.25 mil/ABS test
ratio wasn't a large enough
safety ratio for most home made
subs.
Sorry if the term "standard practice" implied anything to do
with
standards. I think "sometimes observed in informal
conversations"
would have been a better term.
Cheers,
Ian.
-----Original Message-----
From:
vbra676539@aol.com
Sent: Oct 1, 2010 12:40 PM
To:
member-forum@psubs.org
Subject: Re: [PSUBS-MEMBER-FORUM] Guideline
Change - Request for Comment
George drop-tested every K-350 built in
his shop in one hole on the west side of Penobscot Bay: just shy of 500
feet. Crush depth was calculated at nearly a thousand feet. One of the last
boats built sat on the bottom of the Sea of Japan at about 600 feet for
several months (chained on the deck of its sunken support ship). Once
salvaged, it was found to be in perfect condition. Not one leak anywhere and
zero hull distortion.
I'm not sure where all this double operational
depth thing came from in the discussion thread. Test depths are normally in
the 125% range, not the 200% range. Crush depths are a different matter, of
course. It seems to me that Perry figured 150% to 175%. The problem is
unrecoverable distortion of the hull. There is measurable compression on
these things, but the steel rebounds as the pressure eases. It's that
non-recovery thing that gives you a ruined hull.
I'm talking about
readily available materials here, not aluminum or mil-spec or titanium,
which pose a whole 'nother set of
demands.
Vance
-----Original
Message-----
From: irox <irox@ix.netcom.com>
To:
member-forum@psubs.org
Sent: Fri, Oct 1, 2010 3:27 pm
Subject:
Re: [PSUBS-MEMBER-FORUM] Guideline Change - Request for
Comment
I believe the
standard practice is to test your sub to
twice the operational depth
(unmanned), this would 500feet
for the K250 and 700feet for the K350 (of
course this
depends on how deep the water you have access is). So
I
don't really understand the reason for de-rating the K
subs.
Cheers,
Ian.
-----Original
Message-----
>From: Alan James
<alanjames@xtra.co.nz>
>Sent: Oct 1, 2010 11:58 AM
>To:
member-forum@psubs.org
>Subject: Re: [PSUBS-MEMBER-FORUM] Guideline
Change - Request for Comment
>
>Hi Jon,
>I don't think you
can take the K350s past track record into account, as
>most of the
diving would probably not have been done at the 350ft depth.
>ABS
probably covers their butt for worst case scenarios like continual
operation
>at 350 ft.
>We have a rule "only dive to half
your test depth" wich is a good back up
>as, despite all the
engineering calculations, their is the human construction
factor.
>It would be silly to ban K250 or K350s diving with the
group as they might
>"comply" under ABS for a shallower depth. Just
put a sticker on them K125
>or K175.
>You may feel to put a
disclaimer on the plans we sell explaining the
discrepancy
>with
ABS.
>Regards Alan
>
>----- Original Message -----
>From: "Jon Wallace" <jonw@psubs.org>
>To:
<member-forum@psubs.org>
>Sent: Saturday, October 02, 2010 5:24
AM
>Subject: [PSUBS-MEMBER-FORUM] Guideline Change - Request for
Comment
>
>
>>
>> This is a Request For
Comment regarding a proposed change to PSUBS
>> standards and
guidelines.
>> All members are encouraged to participate in
discussion of this RFC.
>>
>>
*******************************
>> *** REQUEST FOR COMMENT
***
>> *******************************
>>
>>
PSUBS-RFC-20100001
>>
>> 1. Purpose.
>> To adopt
the 100% Rule for calculation of material dimensions for hull
>>
opening reinforcement.
>>
>> 2. Introduction.
>>
Reinforcement of hull openings (for example the conning tower) is
>> required to ensure vessel integrity while submerged.
Current ABS rules
>> appear to be overly conservative and result
in dimensional material that
>> exceeds known configurations which
have performed safely for many years
>> (K250, K350). While
PSUBS encourages use of ABS standards in home-built
>> vessel
design and fabrication, this particular design area utilizes ABS
>> rules which conflict with both existing home-built vessels and
many
>> currently under fabrication.
>>
>> 3.
Proposal.
>> Adopt the 100% rule for reinforcement of large hull
openings in
>> home-built manned submarines as the official PSUBS
standard and
>> guideline, and amend Design Guidelines for
Personal Submersibles
>> appropriately.
>>
>>
4. Justification.
>> ABS rules are in most cases the definitive
guideline for home-built
>> submersibles. However, hull
reinforcement is an area in which the ABS
>> rules appear to be
overly conservative resulting in dimensional
>> requirements for
large openings (conning tower) that vastly exceed
>> dimensions of
known configurations which have operated safely for years
>>
(K250, K350). A chart is available for review at
>>
http://www.psubs.org/design/pvho/ which illustrates the dimensional
>> requirements for reinforcement of three different sized large
hull
>> openings (22, 23, 24 inches) based upon three different
methods of
>> calculation; ABS rules, 100% rule, and Bildy
rules.
>>
>> ABS RULES are calculations based upon 2010
Steel Vessel Rules, Part 4,
>> Chapter 4, Section 7 Openings and
Reinforcements. ASME essentially
>> publishes the same
rules.
>>
>> 100% RULE calculates reinforcement by
ensuring that all of the metal
>> taken out of the hull when the
opening is created, is replaced within
>> the nozzle. Years
ago the reinforcement could also be included in a
>>
circumferential pad attached to the hull but this is no longer allowed
>> for externally pressurized PVHO by ABS rules. In almost
all cases this
>> results in the nozzle (CT) being thicker than
the hull. For example,
>> the K250 and K350 both use a .75
inch thick nozzle in a .25 thick hull.
>>
>> BILDY RULES
are calculations based upon FEA analysis performed by Les
>> Bildy
( see http://www.codeware.com/support/papers/bildy.pdf ). Bildy
>> proposed that the standard ASME calculations were too
conservative and
>> in fact potentially caused stresses that could
weaken the pressure
>> vessel service due to the weight of the
very thick material calculated
>> by those ASME formula.
Bildy's rules were adopted by ASME as an
>> alternative method for
reinforcement calculation in their Boiler &
>> Pressure Vessel
Code (BPVC) Mandatory Appendix 1, Supplementary Design
>>
Formulas, Section 1-10. While Bildy's rules were adopted by ASME only
>> for internal pressurized vessels, they are included for
reference
>> because external pressurized vessels require only 1/2
the reinforcement
>> as internal pressurized vessels, and Bildy
was the only other source
>> available as an alternative design
that could found, to offer some other
>> comparison.
>>
>> Using the K350 as an example of a vessel that has a long
history of safe
>> diving behind it, the chart compares the
thickness (.75 inches) of the
>> "Conning Tower Insert" (the
nozzle) designed with the 100% formula by
>> George Kittredge and
approved by Lloyd's (also approved by ABS for the
>> K250), to the
required thickness ( 1.169 inches ) which is currently
>> required
by existing ABS formula. Rounding up to the next most commonly
>> available steel thickness, the minimum thickness for a K350
conning
>> tower insert would reach 1.25 inches or possibly 1.5
inches depending
>> upon availability of material in a
home-builders local area.
>>
>> This presents a problem
for PSUBS safety message since maintaining
>> adherence to ABS
rules in this case is clearly at odds with existing
>> K350
vessels built with a .75 inch conning tower insert, and a
>>
preponderance of diving evidence (experience) showing that the (or lack
>> of accident evidence). PSUBS cannot suggest adherence to,
and build
>> operating procedures around, ABS rules on the one
hand; and
>> accept/welcome vessels into PSUBS operations that do
not comply with
>> those rules on the other hand. Such a
policy would legitimately be
>> criticized as hypocritical and
lower the effectiveness of PSUBS to
>> influence safe design,
fabrication, and operation of small submersibles.
>>
>>
The concept of "grandfathering" has been suggested as a potential
>> resolution in which existing vessels that did not meet current
ABS
>> requirements would be not be required to retrofit their
conning tower to
>> thicker material, but any new fabrication
would be required to adhere to
>> the ABS rules. There are
potential problems with this concept however
>> that need to be
considered. First, while grandfathering is often
>> applied
to non-safety related situations such as zoning (land
>>
development) it is not applicable in all cases. An individual could
>> legitimately suggest that this issue could be reduced to a
"black or
>> white" interpretation. In other words, a .75
inch thick conning tower
>> in a K350 is either safe, or not
safe. If we continue to use ABS as the
>> standard of
safety, then we must assume that anything less than the
>> large
opening reinforcement thickness required by ABS rules is not
>>
safe. Consequently, if the K350 design is not safe, we cannot let
those
>> owners dive with us. Second, we need to consider
real world
>> experience. The concept of "grandfathering"
was applied to automobiles
>> manufactured in the 60s which did
not have seat-belts. In the US, even
>> though seat belts
are now required equipment and most states require
>> their use, a
person is not arrested or fined if they are driving a 1960
>>
Chevy that did not have seat belts installed as standard equipment when
>> that car was manufactured. However, automobiles and seat
belts are
>> different in that there is substantial scientific
data that shows seat
>> belts reduce injuries. In the
examples used for this RFC (K350 sub), we
>> have no data that the
.75 inch thick conning tower is unsafe. In fact,
>> the K350
has no safety mishaps recorded due to hull opening
reinforcement.
>>
>> The 100% rule is documented in
"Manned Submersibles" by Frank Busby, and
>> also incorporated
into all of sub designs created by George Kittredge.
>> In
addition, a limited review of other non-kittredge submersibles has
>> yet to show a single submersible complying with the ABS rules
for large
>> opening hull reinforcement, including vessels
certified by ABS. The
>> effect of ABS rules for opening
reinforcement on small home-built
>> submersibles is enough to
warrant PSUBS investigating continued adoption
>> of those
rules.
>>
>> Beginning reference for discussion:
http://www.psubs.org/design/pvho/
>>
>>
>> 5.
Requirements.
>> None.
>>
>> 6.
Dependencies.
>> None.
>>
>> 7.
Enforcement.
>> This is a minimum standard. Members will be
expected to meet or exceed
>> this standard in order to
participate in PSUBS sponsored diving events.
>> Nothing
shall prevent a member from using a more conservative formula to
>> calculate reinforcement.
>>
>> 8. Comment
Deadline.
>> 11/15/2010 (may be extended upon majority vote of
members)
>>
>> 9. Comment Evaluation.
>> All
comments will be evaluated for potential modification of the
>>
proposed standard.
>>
>>
>>
>>
>>
>>
************************************************************************
>>
************************************************************************
>>
************************************************************************
>>
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>> If you want to be removed from this mailing
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>> membership account and uncheck
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>> list.
Problems? Contact support@psubs.org
>>
>>
>> PSUBS.ORG
>> PO Box 311
>> Weare, NH
03281
>> 603-529-1100
>>
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>>
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>>
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>>
>
>
>
>
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personal submersibles Member-Forum mailing list complies with the
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