RE: [PSUBS-MAILIST] new to the list

[Alec Smyth <Asmyth@changepoint.com>]

Just some more thoughts on the dome viewport. From a design perspective, a
180 degree dome is the most structurally efficient geometry, and also offers
great visibility, so one gravitates towards it easily with CAD mouse in
hand. But fabrication is another matter altogether. On professionally built
subs these domes are cast, and that costs a bloody fortune. For example,
Phil's Deep Worker domes cost $11,000 each -- and that's using a mold
they've already got on hand. Blowing a dome (the method for garage builders)
is way cheaper but you end up with a much reduced thickness at the apex,
which affects the depth rating. My approach to getting around this has been
to reduce the included angle of the dome from 180 to 120 degrees, which
preserves most of the apex material. This is fully PVHO compliant. On the
other hand if the dome is vertically oriented and you are trying to stick
your head in it to look forward, the 120 degrees does not leave you much
room. So its probably only an approach that works for forward-looking domes.


Another fabrication issue not apparent in the CAD world is the dome seat.
PVHO allows a choice of conical or square edge. Conical is better, but
there's a practical problem; you need an enormous lathe or mill, plus how
the hell d'you secure a dome in it for machining a conical edge? I believe
the answer is with a custom fabricated vacuum cup, but that again sounds
expensive, especially when outsourced due to the size of the machinery.
So... the suboptimal yet good enough method was better for me as a garage
builder, and I put a square edge on the viewport for zero cost. 

As far as the hydrodynamics of PVHO viewports go, you might want to fair
them with a second, free-flooding canopy that is better shaped. In fact, you
can even formulate the acryllic in that second layer with UV protection, to
help preserve the expensive viewport.

Now for a wilder idea... with the sort of horsepower you're planning, and
the good hydrodynamics, we're obviously talking a fast sub. Your methods of
control (primarily surfaces as opposed to statically oriented thrusters)
also indicate your vision is of a sub thats moving fast rather than
hovering. So what if you articulated those pods for vertical movement? You
can have your CG-CB separation per ABS for a surfaced condition, but once
submerged you could make it go to zero and truly fly.

Hey, considering I'm half way through building my first sub and have never
even been submerged in one, I would hardly call myself an expert. But I'll
definitely be at the convention, so we can chat about this sort of stuff to
our hearts content.

Got to get back to the official job now!

rgds,

Alec



-----Original Message-----
From: Cliff Redus [mailto:dr_redus@devtex.net]
Sent: Wednesday, March 13, 2002 5:45 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] new to the list


Alec, my goal was to design a two-manned submersible following ABS
regulations as much as possible that would be streamlined to reduce drag and
have adequate power for maneuverability via control surfaces.  The rudder
and hydroplanes are mounted to a jet ski nozzle which gives me yaw and pitch
articulation.  The jet ski impellor itself is shafted to both a 20 HP DC
series wound motor and 110 hp engine located in the pressure hull which is
0.25 inch ASME 516, Gr 70 pressure vessel steel.  The jet ski nozzle yaw and
pitch articulation is achieved via small hydraulic cylinders that enable me
to make easy and bullet proof hull penetrations.  The drive shaft penetrates
the hull through a stern tube that has a cutlass bearing for radial support
and a double mechanical cartridge seal for sealing the shaft.  The double
mechanical seal is pressurized to 225 psig via a bladder type hydraulic
accumulator.  Any seal fluid leakage would be out the stern tube not into
the cabin. Roll control is achieved by two ailerons that are also
hydraulically controlled.  Main ballast tanks are soft and oriented fore and
aft.  These are controlled by a pneumatic control valve that is connected to
four externally mounted standard scuba tanks located aft.  There are two
soft trim and compensation tanks that are located inside the pressure hull
for and aft. These are operated by a PD pump that is driven by a hydraulic
motor.  The T&C tanks are vented to the inside of the cabin when trimming is
underway and then isolated with solenoid valves.  There are two exteranl
pods that are oriented to give good CG-CB separation.  They contain O2
bottles for emergency life support and 10 marine deep draft batteries in a
watertight battery box. The pods also contain the drop weight mechanism and
saddle oriented fuel tanks.  The battery boxes are on slides and are
connected to a hydraulic cylinder that can articulate the boxes.  This give
longitudinal balance control for condtion of one ore two man crew.  Both the
pods and shell around the pressure hull are made of 0.25 inch FRP and are
free flooding.  The location and types of the viewports were a major problem
due to ASME PVHO-1-1997 rules.  I was trying to achieve a NASA minimum drag
profile as a basis for both the main hydranimic shell and the pods.  As you
know, there are no minimum drag shape viewports that meet this profile.
Hemispherical is about the best you can do following ASME PVHO-1-1997 rules
for a bow viewport.  I opted to give the pilot two viewports, a 24 inch
hemshircal acrylic dome for forward and above visablity and a 20 x 3 inch
cylinderical viewport that is rotated about 20 degress from horizontal for
viewing below and forward. I should have sent a jpg rendoring of from the
bottom. The passenger also has a similair lower viewport and 5. 10 inch
cylinderical viewports for side, forward and above visablilty.  My biggest
headace was in achieving the ABS 2.5 ft freeboard clearance contraint whiile
not totally destroying overall drag peformance.  To do this I have
incorported a teardrop crossection to the sail.  The sail however still
pressents a significant cross sectional area to drag. This may give me a
pitching up moment at high speed.  I toyed with using a hydraulcially
retractiable sail but this rapiudly got to complecated and heavy. Sorry to
be so long winded. I have come to the conculsion that it it hard to give a
short answer when it come to Psubs.  Are you planning on going to the
convention?  I love to sit down and discuss boats.  It would be great if
those of you that have actually designed and built projects could serve on
design review teams that folks like me could come to at the end of the
design phase of a project for a detailed technical review.  This would
probably save a lot of $'s

Good luck on the "flyer".


Cheers!

----- Original Message -----
From: "Alec Smyth" <Asmyth@changepoint.com>
To: <personal_submersibles@psubs.org>
Sent: Wednesday, March 13, 2002 2:59 PM
Subject: RE: [PSUBS-MAILIST] new to the list


> Oh my, that's one heck on an interesting design. Hats off Cliff, you've
got
> a whole bagful of innovations. I can't make out the mechanism just ahead
of
> the tail... is it some sort of actuated universal joint? Also, I couldn't
> see the propulsion, although you described it in the write-up.
>
> One suggestion; can the dome be put on the bow? I think you'll spend most
of
> your time looking forward and down, as opposed to forward and up and your
> current dome placement suggests.
>
> I think this will be one to watch. Go for it!
>
>
> rgds,
>
> Alec
>
> -----Original Message-----
> From: Ray Keefer [mailto:Ray.Keefer@Sun.COM]
> Sent: Wednesday, March 13, 2002 3:37 PM
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] new to the list
>
>
> Hi,
>
> These pictures are on the web site. See Whats New.
>
> Regards,
> Ray
>
> > From: "dr_redus" <dr_redus@devtex.net>
> > To: <personal_submersibles@psubs.org>
> > Subject: Re: [PSUBS-MAILIST] new to the list
> > Date: Sun, 3 Mar 2002 14:59:08 -0600
> > X-Priority: 3
> > X-MSMail-Priority: Normal
> > X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2600.0000
> >
> > Thijs, I have email to Ray four jpg files representing top, side, front
> and
> ISO views of the project.  I am hoping he can post to the list.
> >
> > -Cliff
> >   ----- Original Message -----
> >   From: Thijs Struijs
> >   To: PSUBS
> >   Sent: Sunday, March 03, 2002 9:11 AM
> >   Subject: [PSUBS-MAILIST] new to the list
> >
> >
> >   Welcome to the list Cliff,
> >
> >   It looks like a real serious project you are working on. I would like
to
> see
> the picture, please mail it to us. It is probable to big for the list so
you
> can
> sent it at MOKI.
> >   Look at http://www.prismnet.com/~moki/subfiles.html for more details.
> >
> >   Greetings,
> >
> >   Thijs Struijs