Re: [PSUBS-MAILIST] 2 person submersible design for feedback/review.

Ian

The web site is very nice for being able to see the design drawings and pertinent design data (PDD).

I agree with Alec on the use of flanges for sail. If the goal is to make this easy to fabricate then you would have to go with standard off the shelf pipe flanges which would be larger diameter and thicker than what you have shown on the drawing. Also these would add significant weight above the CG of the boat. Also they add potential leak paths. The PDD shows the design for 1-2 persons. The VBT displacement of 55 lbs this is inconsistent with a two persons. You would need more displacement for two people. This looks correct for one person. If you sized this VBT for two, i.e., could compensate for with or without one 170 lbs person, then the VBT envelope would be obtrusive in its current location. Therefore, this kind of limits you to one person for current design.

I note you are using a ducted prop for the horizontal thrusters. The duct shape does not look right to me. Typically, the width of the duct is half the diameter and also you need to pick the duct shape depending on your design objectives. According to Kuiper , The Wageningen Propeller Series, when the bollard pull is of up most importance not only in ahead but also in astern direction, a more symmetrical nozzle has to be use like a Wageningen series Nozzle 37. If you want more Ballard pull ahead and to a lessor degree astern, then a Nozzle 19A would be more appropriate. Using Kort nozzles are more efficient than the symmetrical cylindrical ring shown around these thrusters.

I know you are tyring to simply fabrication by not having conventional "T" stiffening frames but I worry about the structural integrity around the sail/hull interface without these frames. At 500 ft, in fresh water assuming a 24 inch diameter sail, the downward force on the hull is 100,000 lbf. This represents a very non uniform loading of this unstiffended cylindrical shell. The ABS spreadsheet would not be a good analysis of the stress in this hull shape. Make sure you do some FEA work on this. My guess this will force you to add some heavy frames to counter this load.

Just looking at the weight distribution in the boat, it looks like there would be a good spread between the CG and CB of the boat while submerged which is good for submerged stability. If this is so, then I don't think the bow and stern 25Kg thruster will be able to generate any significant pitching motion if that is one of their functions. They then would only be useful in generating heave movement after the boat is neutral. If this is so, then they could just a well be located at the longitudinal CG of the boat and wired in parallel. If you do want to generate pitch, you would need stronger bow and stern thrusters.

Also with the orientation of the bow and stern thruster, they generate no sway movement of the boat. You might want to consider adopting the design of the Deepworker 2000 which has the vertical thrusters near the longitudinal CG of the boat and have them tilted but offsetting angles so that in addition to heave movement, they can generate sway movement.

Cliff

From: irox <irox@ix.netcom.com>
To: personal_submersibles@psubs.org
Sent: Thu, February 10, 2011 2:35:54 AM
Subject: [PSUBS-MAILIST] 2 person submersible design for feedback/review.

Hi,

I while ago I started designing a small 2 person 1-ATM sub. The aim of
the design was to be simple to construct, but once constructed easy to
reconfigure and play about with. I guess one goal of this design is to
counter the lack of proven (i.e. K-*50s) used small subs on the market.

I've code named the project SSP for "Small Submersible Platform". It's
borrowing heavily from the K subs, but a slight large diameter pressure
vessel with no ribbing.

There is still a lot of design work to be done before it's ready for
the construction phase, but I'd like to get some feedback from people,
particularly submersible owners, before I invest more effort into finishing
the design. Missing parts include a clear idea of the MBT design (I want
to add some "stove pipes" on the bottom, and "top-hat" style vents on the
top), VBT plumbing/placement, HP air plumbing, electrics, drop weight
release (I am think K-350, but maybe something better could be done) and a
bunch of other things (feel free to suggest things for the TODO list)...

I am trying out the subdb.info site for communicating information about the
sub.
Main ssp page on subdb.info, not much info here yet:
http://www.subdb.info/database/showvessel/index.cgi?ID=1296535743&VN=SSP-001&VT=1

The design doc and drawings (work in progress):
http://www.subdb.info/database/vessels/1296535743/vdocs/manuals/design-outline-preview.pdf

Thanks in advance for any comments and feedback.

Cheers!
Ian.

************************************************************************
************************************************************************
************************************************************************
The personal submersibles mailing list complies with the US Federal
CAN-SPAM Act of 2003. Your email address appears in our database
because either you, or someone you know, requested you receive messages
from our organization.

If you want to be removed from this mailing list simply click on the
link below or send a blank email message to:
removeme-personal_submersibles@psubs.org

Removal of your email address from this mailing list occurs by an
automated process and should be complete within five minutes of
our server receiving your request.

PSUBS.ORG
PO Box 53
Weare, NH 03281
603-529-1100
************************************************************************
************************************************************************
************************************************************************