[PSUBS-MAILIST] Terminating a conical transition

Joe Perkel via Personal_Submersibles personal_submersibles at psubs.org
Sun May 4 17:30:19 EDT 2014


Sean,

Have you ever notice how the Civil War design of the USS Alligator stabilized the boat submerged? A couple of crazy little tethered floats, but the rationale has never escaped me.

I will reduce free flood space wherever I can. Trapped inertia being on my mind, but I needed someone to remind me of the waste in efficiency / power requirements, thanks! Also, your comments bring home some compelling reasons to shorten the design with a "Just enough but no more" design mindset.

I've given thought to the conical section in the front, I can reduce this down to a 30" head with forward viewing ala Kraka, but quite the tight fit! Not sure, I have to give it some more thought.

If I reduce the aft end with a cone, then I would bring the motor inside and do a standard marine hybrid installation. Expensive, but certainly a more reliable answer. If I do that, I would dispense with the notion of propulsion units in the aft end of the pods, truly no need then. This boat requires a  massive ventilation / climate control scheme for surface operations, that's why I've been overly generous with the machinery space in these early drafts.

I'm still concerned about stability because I have to contend with what to do with all of that centerline space. The VBT would take up some, but I would have to flood the rest.

Thanks again Sean!

Joe
On Sunday, May 4, 2014 4:56 PM, Joe Perkel via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
  
Hank,

What you see there is the original Seehund arrangement, my intention is as you say, up higher. The aft cone on mine essentially now an MBT. Those lower volumes will be flooded in practice, but I am wondering if they could be blown down dry to help with trailer launching and recovery??

Plenty, and I mean plenty of room along the centerline for keel ballast.

I keep thinking about what you've told me regarding Gammas attachment, always in the back of my mind!

Thanks Hank!

Joe
On Sunday, May 4, 2014 4:34 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
  
Joe,
Your dive tanks are to low, they should be at the top of the sub.  The way you have it will be less stable.
The motor pod should be okay, just like the K subs. You do not want your torpedo's to be buoyant, they should be as heavy as possible for stability.
Hank
--------------------------------------------
On Sun, 5/4/14, Joe Perkel via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Subject: Re: [PSUBS-MAILIST] Terminating a conical transition
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Received: Sunday, May 4, 2014, 3:07 PM

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
  
  
  
  Sent from Yahoo Mail for iPad 
           
  
       
           
  
     
          
     
  
  
               
     
  
               
         
  
               
             
               
             
               
                
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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