[PSUBS-MAILIST] Terminating a conical transition

Sun May 4 21:06:59 EDT 2014

Joe,

Per ABS, the CB must be at least 2" above the CG when  submerged.  It must 
still be at least 1" above in the event the drop weight  is released.

When I was considering auxiliary saddle tanks I planned to  position them 
so the tops were even with the water line when all tanks were  blown.  My 
thinking was to gain the maximum freeboard available since any  portion of the 
tanks above the water line contributes nothing to buoyancy.   However Alec 
very correctly pointed out that the portion above the water line  functions 
as reserve buoyancy to counteract roll when that side of the boat is  
depressed such as when someone steps on that tank.

The CG/CB spreadsheet that Cliff developed is on the Psubs  website.  It's 
an excellent design tool.  If you aren't already using  it:  
Psubs/org>Resources & Reference>Design  Tools.  "Ballast & Buoyancy Control" is on the menu 
at  the left side.  Once you open the spreadsheet, choose the tab at the 
bottom  labeled "Instructions."

Best regards,
Jim

In a message dated 5/4/2014 4:54:05 P.M. Central Daylight Time,  
personal_submersibles at psubs.org writes:

Hank,

Most  boats see about 100 hours use a year. I expect this to be no 
different. I want  a neat little toy to play with in the garage on the occasions 
when my wife  turns me loose! :)

This  is why I want to section the hull,...and I just convinced myself to 
shorten  the thing a bit!

Joe

On Sunday, May 4, 2014 5:45 PM, hank  pronk via Personal_Submersibles 
<personal_submersibles at psubs.org>  wrote:

Joe,
Sounds like you need to have the longest  cones possible at each end to 
reduce the size of the free flooded areas.   Another option is to change the 
design, decide what your priorities are.   What is most important? if long 
transits are the plan then you may need to  change things.  If fuel cost is a 
consideration, another change.   Looking very cool dock side, you nailed it. 
It just wouldn't be fun if it was  easy.
Hank
--------------------------------------------
On Sun,  5/4/14, Joe Perkel via Personal_Submersibles 
<_personal_submersibles at psubs.org_ (mailto:personal_submersibles at psubs.org) >  wrote:

Subject: Re: [PSUBS-MAILIST] Terminating a conical  transition
To: "Personal Submersibles General Discussion" 
<_personal_submersibles at psubs.org_ (mailto:personal_submersibles at psubs.org) >
Received:  Sunday, May 4, 2014, 5:30 PM

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_ (mailto: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_ (mailto: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_ (mailto:personal_submersibles at psubs.org) >
wrote:

Subject: Re:
[PSUBS-MAILIST] Terminating a conical transition
To:  "Personal Submersibles General
Discussion" <_personal_submersibles at psubs.org_ 
(mailto: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_ (mailto: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_ (mailto:personal_submersibles at psubs.org) 
>
wrote:

Subject: Re: [PSUBS-MAILIST] Terminating a conical
transition
To: _personal_submersibles at psubs.org_ 
(mailto: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_ (mailto:personal_submersibles at psubs.org) 
>

To:
personal_submersibles
<_personal_submersibles at psubs.org_ (mailto: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_ 
(mailto:personal_submersibles at psubs.org) >;

To:

<_personal_submersibles at psubs.org_ (mailto: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_ 
(mailto:personal_submersibles at psubs.org) >

To: Personal Submersibles General
Discussion <_personal_submersibles at psubs.org_ 
(mailto: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_ (mailto: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_ 
(mailto: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_ 
(mailto:personal_submersibles at psubs.org) >; 

To:

Personal
Submersibles General

Discussion <_personal_submersibles at psubs.org_ 
(mailto: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_ 
(mailto: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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