Glad my explanations were readable!! A lot of
writing, simple concepts.
Regarding snorkel designs, just last week I was
perusing the Gato/Balao schematics online. Did I link to the site?
Of course not!
However, there for the world to see was a schematic
of the fleet boat snorkel design. You'll have to Google it but it is out
there.
Rick
Vancouver
----- Original Message -----
Sent: Saturday, November 26, 2005 6:49
AM
Subject: Re: [PSUBS-MAILIST] Re: Working
Schematic, specifications
Rick,
I concur with Paul, great stuff thanks a lot. Things are progressing nicely
on the learning curve and my design is showing it, thanks to all.
That term "total floodable interior space" came from the NAVPERS manual and
I assumed that it is used in part to help determine soft tank volume
during the design process.
I am discovering the specific gravity problem you mentioned. At this point
it is becoming necessary to determine the total mass of all structures
external to the crew compartment. Less is better, more density is better but
you still need to maintain shape and structural integrity. This is like trying
to design a submarine out of styrofoam dixie cups, it's a problem....lead
is what now, 708 lbs per cubic foot?
The issue of trim aside from dynamic stability of the planes in my
particular design, still needs work, this boat is going to be limited by
design, to 33' by the limited air supply but she will be able to travel at
periscope depth on the diesel for 10 hours. (Any leads on snorkel system
designs from anybody is greatly appreciated).
Ah yes the appearance of the lines affliction! It sure would be easier to
dispense with the lower free flooding spaces on my design altogether but she
just wouldn't look right!
Thanks
Joe
From: Paul Kreemer
<paulkreemer@gmail.com> Reply-To: personal_submersibles@psubs.org To: personal_submersibles@psubs.org Subject: Re:
[PSUBS-MAILIST] Re: Working Schematic,
specifications Date: Fri, 25 Nov 2005 09:59:08
-0800
great note Rick. thanks for the explanations and news
on your project.
> wrote:
Hi, Joe . . .
If I am understanding what I have
learned so far "floodable interior space" is the total displacement
of the air volume that
you are trying to submerge.
I've never heard that particular term before.
It seems contradictory. Rather than complicate things by
establishing
nomenclature [just for the moment] I'll refer to the
interior dry volume
(cabin) as the bubble I have to force underwater.
A dry cockpit volume of 4 x 4 x 4 will yield 64
cubic ft. or 4100 lb. of buoyancy. Weight includes two
occupants at 150 lb.
ea. Also include the seats, instruments, dash
panels, batteries,
controls, a good book [Busby - at least 35 lb.], a packed lunch
with thermos and
a sleeping bag and misc. other items. Obviously, if you
have 4100 lb. of
keel ballast in the form of, say, lead, you're going to the
bottom fast.
Let's put less lead in the amount of all that cargo we
mentioned above.
Lead + cargo = cockpit bubble. That's
it.
All other materials, say, ply hull,
fibreglass/resin, motors, deck fittings, anchor/chain/rope, skeg,
etc. that will
be fully immersed will have an amount of buoyancy depending on
their particular
specific gravit
This is the difference between dry
weight and what would be required to submerge to neutral buoyancy.
Quite frankly, I am
having trouble determining how to look at it, whether soft
water ballast is
"increasing" weight or "decreasing" displacement or perhaps
both?
"Soft tanks" are upside down glasses that you fill
with air at the surface to lift the boat higher out of the
water. Open at the
bottom like a glass. Very little inherent pressure
internally. No
reason to have much pressure. They still have to be
sturdy.
That figure above is roughly the 30%
ratio to interior volume for a seagoing boat as Carsten had pointed
out. He had also
pointed out that high volume soft ballast ratios are not
unheard of as in this
example so I am still playing with the idea.
Take a look at your own boat. Everything other
than your dry cockpit/cabin will be wet. Those areas will be
flooded
100%. No mystery. Your hull is for streamlining and
lifting your
boat out of the water while surface running.
Where the confusion may be arising is in the hard
tank[s]. At the surface, having lots of hull space to force
air into will
lift your boat up high. Those are the soft tanks.
The hard tank [as in "hard-walled" to resist water
pressure] is used to fine-tune your neutral buoyancy. It is
NOT open at
the bottom - it's sealed against pressure. Ideally, if
this sealed box is
full of air, the sub will not dive - it's too light. Your
cockpit canopy
will be awash. If this box is filled 100% with seawater,
your boat will be
too heavy - it will sink.
During normal use, if the usual occupants' weight is
known, the weight of Busby's book is known, your cell phone, note
pad, video
camera, box lunch and pina colada thermos are all known
weights, THEN you can
remove lead to the point where your hard tank will be filled
about half way to
achieve neutral buoyancy.
Until then, using these known weights, your canopy
will forever more be doomed to be awash until that hard tank is
filled half way with
sea water.
So why is it hard? To keep Boyle's Law out of
your hair. An open [soft] tank will accomplish the same thing
as a hard tank -
for the first few feet of depth. Once the air starts to
compress, you'll
face every diver's dilemma - keeping neutral buoyancy.
A hard tank will isolate the ocean pressure from the
contents and the air in this hard tanks will not contract.
A company called Dacor designed a hard tank scuba
pack [back in the eighties, I believe] to get around Boyle. It
wasn't a
success. Apparently the pack wasn't strong enough to last
through to
full scuba depths and you had to release pressure
mid-dive. Not easy
to control. Now, if you build one out of Al2.
There's
thought.
If you want to maintain some degree of
scale in a replica you run into these volume and length problems.
What have you worked
out for your Typhoon replica "Magical Child?"
Hardy-har. Finally someone else with the same
dilemma!!! These subs were designed around using the entire
interior as
dry volume.
Your particular affliction - and mine - is to
maintain the same degree of "look" or authenticity as the
original. It wouldn't look
cool if the lines weren't right. You, I suspect,
have an artsy streak
running through you. I'd be willing to bet you'd never be
happy with
anything but an Italian motorcycle [damn the
electrics]. http://www.motoguzzi-us.com/bikes/v11lemans/index.html
Soo-weet.
]
For Magical Child, I've had to compromise between authenticity
[the cool factor]
and the length of my workshop. I truncated Magical Child
until I could
squeeze it into my 18 foot shop. A 15 X 2.5 ft. [NOT the
original Typhoon
L/B ratio] hull allows tandem seating [not my first choice] and
a 6:1
ratio. Not bad. It'll flow smoothly on the surface,
offer a large
deck area for movement, lounging, etc., will be fairly kind
in a seaway [no
thanks to its bows], will be hydrodynamic underwater, and will
keep the props in
the water during heavy seas.
It'll also be aesthetically
pleasing.
Dans words keep ringing in my ears
though and I believe it was you who suggested a "proof of concept"
boat. I am seriously
looking at downsizing even further to a two man craft or
smaller.
I'd like to share the u/w world with
my kids, hence the two seater. Think "kayak" around a
cockpit. See
this link. http://www.psubs.org/pic/wet.html#sleepingbeauty
It's a wet boat - pic contributed by someone back in the
'90's.
;-)
Put a canopy on it, compensate the cabin and Bob's
your uncle. Proof-of-concept still has to be fun. I have
not the
resources to do this solely as an intellectual exercise
(hmmm . . . that
didn't come out right). It HAS to be fun as soon as
the thing hits
the water.
The S-boats at 219' by 20.6' could be
scaled to roughly 1/10 and come to about 22' x 3'. A single
cylinder
diesel/electric would be damn cute!
A different L/B ratio would simply make a fatter
boat. Decent lines could still be
maintained. I enjoy inserting a jpg of a sub drawing into
Word, then using
the image markers to expand or contract the image as I see
fit. Hold a
ruler up to the screen or use Word's built in rulers and you
can get INSTANT
visual results with ratio changes.
Do it with both the elevation and plan views.
It's a scream. BTW, if the technique appeals to you, mess with
the sectional
views, too. Print out a copy of the proportions you like,
white-out the
yucky parts, draw in your own canopy design, scan it back in to
the puter, then
play with THAT jpg in Word.
A word on modeling: I've bought several well
proportioned human figures so I could work with them during the
modeling
sessions.
This link shows one of my human figures. Obviously, the
gentleman in the
picture is not in proportion to the hull he's sitting in.
It was for
roughing out. I've since bought three more Typhoon
hulls of different
scales to play with as well as several other human
figurines/dolls.
The Magical Child model I'll be building
will be thirty inches long because the figure I've chosen is twelve
inches
tall. His arms, legs and torso all bend at the right
place and
are anatomically well proportioned (my smart-ass 13
year old daughter,
looking over my shoulder, wants to know if he has a
penis) Same boat
building techniques as the final build: glass-over-ply.
Warm regards,
Rick
Vancouver
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