[PSUBS-MAILIST] Terminating a conical transition
Joe Perkel via Personal_Submersibles
personal_submersibles at psubs.org
Sun May 4 15:07:16 EDT 2014
I've incorporated some of the suggestions in the attached drawing. Still, I've got a lot to think about here but I am also excited about the possibilities and the potential outcome. This image should give some idea of what's on my mind. What you see is the water ballast arrangement on the original Seehund, and how my proposed pressure boundary fits into this scaled down version. The following is a list of concerns and or design considerations.
1) Clearly, I have no need to compensate for the loss of torpedoes
2) New pressure boundary provides for massive MBT volumes (Low pressure compressor to blow down volumes)
3) Torpedo battery pods may need to incorporate some free flooding spaces to reduce weight, or perhaps reduce battery capacity to a single pod in lieu of the former forward water ballast tank, then completely free flood both torpedoes completely??. (Boat will incorporate a gen-set)
4) Questionable reliability of external motor pod assembly.
5) Stability considerations
Thanks for the input gents, It really helps me to take a step back on occasion!
Joe
On Sunday, May 4, 2014 10:19 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Joe,
When I mounted the tanks back on Gamma, I changed the mounting location to give a greater angle also I did what Vance is saying on a small scale. I then poured a gallon of paint in each tank and rolled the sub slowly to ensure there was complete paint coverage. If I was operating in salt water I would mount some nipples to the tanks with plugs. After a dive in salt water, remove the plug and you have access to spray fresh water inside and rinse the salt water out. A large panel is a good idea also because you
can open it up after each dive and let it dry out.
If I had a K350, I would not copy the Nekton tanks exactly. I would change the shape so they have more volume at the top reducing the rolling effect. Also I would consider making them from SS. Also SS heads solves the problems entirely. Start watching ebay for ss heads. I once saw a ss tank exactly the same as a 500gal propane tank for 1,500 dollars on ebay.
Hank
--------------------------------------------
On Sun, 5/4/14, via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Subject: Re: [PSUBS-MAILIST] Terminating a conical transition
To: personal_submersibles at psubs.org
Received: Sunday, May 4, 2014, 8:32 AM
Joe,
Consider using an elliptical head back there, for
starters. You aren't building for much depth here, so
the K-350 size will be fine (.375" ish). The ellipses
are cheaper, do the same job, and give you a touch more
inside room. Then I would have a cone rolled
with a short flange on the major diameter, maybe a couple of
inches, to match the hull OD.
The Nekton cone-to-dome caused a
pinch point that was always a hassle to clean and paint, and
ultimately left some pitting in the pressure hull that had
to be weld-repaired. A short cylinder on the sheet metal
would give you a little more room under there to sandblast
and paint during assembly and later for overhauls. I would
say for maintenance a couple of flush-mount, gasketed panels
in the tank would serve you well. Don't make them too
ornery to remove or you won't do it as often as you will
wish you had.
I'm wondering now about my own
boat and using tanks like that. Is there anyone in the group
who can plug and chug a metacentric height on Nekton tanks
installed on a K-350? Assembly would be so simple that way.
And it would tow better, which is always a good thing. The
Nektons roll a bit, but are reasonably stable. A K with the
pods should have plenty of weight down low. Hmm. Would it
work? I'm thinking yes. Anybody else have an opinion on
that?
Vance
-----Original
Message-----
From: Joe Perkel via Personal_Submersibles
<personal_submersibles at psubs.org>
To: personal_submersibles
<personal_submersibles at psubs.org>
Sent: Sun, May 4, 2014 12:28 am
Subject: Re: [PSUBS-MAILIST] Terminating a conical
transition
Vance,
Rethinking that aft assembly to make it all soft tanks aft
of a hemi head ala Nekton.
If I go weld-on to the head ala Nekton, how best to attach
to the head to allow for periodic access and maintenance?
Joe
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From:
via Personal_Submersibles <personal_submersibles at psubs.org>;
To:
<personal_submersibles at psubs.org>;
Subject:
Re: [PSUBS-MAILIST] Terminating
a conical transition
Sent:
Sat, May 3, 2014 2:03:36 PM
Joe,
It
seems like an expensive and complex assembly for what you
get. Why not close the aft segment in a simpler way and fair
the stern to the shape you prefer? A hemisphere with an
extended shaft housing to put the prop where you want it,
for instance.
Vance
-----Original
Message-----
From: Joe Perkel via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Sat, May 3, 2014 8:17 am
Subject: Re: [PSUBS-MAILIST] Terminating a conical
transition
Sean,
Yes,
a bolted flange with O ring.
I've
attached an image of what's on my mind. This hull is
36" OD, cylinder length is 120". Anything bigger
in diameter, simply gets way to big and bulky for
handling.
I'm
thinking at this size, I must bolt at least two hull
sections together for outfitting and maintenance, and the
cones can be un-stiffened or perhaps only at the
joints.
Joe
On Friday, May
2, 2014 9:50 PM, Sean T. Stevenson via Personal_Submersibles
<personal_submersibles at psubs.org>
wrote:
Each cone section in that case is considered
alone, so if you were using stiffeners, you would need a
heavy stiffener at every joint. Depending on the size, it
may be simpler to use unstiffened geometry for such an
assembly.
The rules do not address bolting pressure
hull sections together, but I don't see why you
couldn't, provided you meet the requirements in terms of
the stress analysis under the maximum combined loading
conditions, which are prescribed in the ABS rules. Might
require some FEA to be sure. You're thinking an O-ring
groove seal? Or other arrangement? I think an ASME
code compliant flange would be a good place to start, but I
would make sure that the cross-sectional area of each half
of the flange considered individually met the requirements
of a heavy stiffener per ABS, at a minimum material location
(bolt hole). I would also be inclined to use SuperBolts for
the connection.
http://www.nord-lock.com/superbolt/multi-jackbolt-tensioners/
Sean
On May 2, 2014 6:03:21
PM MDT, Joe Perkel via Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
Sean,
Would the heavy stiffener rule apply equally to several cone
segments stepping down at different angles?
Also, do ASME pipe flange specifications translate equally
to bolted pressure hull sections? Have I missed a section
somewhere on bolted cylindrical sections?
Very helpful Sean thank you!
Joe
Sent from Yahoo Mail for iPad
From:
Sean T. Stevenson via
Personal_Submersibles <personal_submersibles at psubs.org>;
To:
Personal Submersibles General
Discussion <personal_submersibles at psubs.org>;
Subject:
Re: [PSUBS-MAILIST] Terminating
a conical transition
Sent:
Fri, May 2, 2014 11:45:11 PM
2:1 semi-elliptical heads are usually
fabricated with some length of straight flange (tangential
cylindrical section) beyond the axis of the ellipse.
Hemispherical heads may or may not have a straight flange
section, but in either case are permissible to use adjacent
to conical sections, provided all other requirements are
met. For stiffened cones, you must have stiffeners meeting
the "heavy stiffener" criteria at both ends, as
close as practicable to the cone-to-cylinder and
cone-to-head transitions. For unstiffened cones, the length
L_c used in overall buckling calculations must be the total
length between the next heavy stiffener to either side of
the entire compartment length, or between the 40% of head
depth points if otherwise unbounded. Cone to head
welds are done in the same manner as cone to cylinder welds,
and if your
head is supplied w!
ith a
flange, it is the same
thing.
Sean
On May 2, 2014 2:48:52
PM MDT, Joe Perkel via Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
I have
spotted the ABS diagrams and specifications for
re-enforcement and butt welds at conical to cylinder
transitions. I am somewhat unclear however as to terminating
at the head.
For
example, the diagrams in the 2014 ABS underwater vehicles
and hyperbaric chamber publication shows conical transitions
either bordered by a cylinder at either end, or simply open
at the small end???
I want to terminate the small end of a conical transition
directly to a small diameter hemi-head without another
straight section, but I am unclear as to whether or not
that is acceptable
in practice.
Joe
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