[Member-Forum] [PSUBS-MAILIST] Terminating a conical transition

Mon May 5 08:09:09 EDT 2014

Joe,
I was once talking with an engineer for a  defense contractor and admitted 
that sometimes I did things backwards  by making something in the shop first 
and then drawing it up.  He  grinned and said, "Yeah, you'd be surprised 
how often we do that,  too."
Jim

In a message dated 5/5/2014 6:23:37 A.M. Central Daylight Time,  
personal_submersibles at psubs.org writes:

Jim,

I  had not seen that particular spreadsheet, thank you!

I  do have the advantage of software that will accurately calculate weights 
and  balances based on materials and position within the model. But, I have 
to get  the broad strokes done first to do some fine tweaking later. In the 
past, all  this was done on paper and then trial and error in practice.

Joe

On Sunday, May 4, 2014 9:09 PM, via  Personal_Submersibles 
<personal_submersibles at psubs.org>  wrote:

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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