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RE: [PSUBS-MAILIST] Minn Kota - Thrust
Jon,
I read the hull form article and I have a couple of comments. First, it
seems to me that with a center of volume and most likely a center of gravity
aft, the hull would be dynamically unstable. I beleive that that was an
oversight in the procedure that the hull was tested under. The article
states that sensors were included to determine the stability of the hull
while it rose to the surface but with a chunk of aluminum at the back and
foam up front the thing would be as stable as a pyramid when it was rising.
However, as soon as you remove that condition and try to apply the shape to
something practical it is no longer stable. It may be possible to increase
the size of the control surfaces to compensate for the loss in stability but
then who knows if it is still worth the effort. Of course I could be wrong
about that which brings me to my second point.
The idea of the hull is to move the transition from laminar to turbulent
flow further back on the hull because laminar flow creates less resistance
due to skin friction than turbulent flow would. For an AUV that would be
fine provided you could get the hull smooth enough but a manned sub must
have a hatch and a hatch will create a discontinuity in the hull. Even the
smallest discontinuity can trip a laminar turbulent transition and ruin the
benefits that the hull form provides. In addition, without careful
analysis, you might discover that a laminar boundary layer will separate
after the apex and then you're really hooped.
Wade
-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Jon Hylands
Sent: Saturday, March 11, 2000 10:53 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Minn Kota - Thrust
On Sat, 11 Mar 2000 07:47:05 -0000, "Captain Nemo" <vulcania@interpac.net>
wrote:
> You gotta scanner? Let me know when you find the reference. We could
swap
> graph paper drawings to compare.
Okay, I found the reference. Turns out my memory was a little bit porous,
the paper was from England, but anyway...
http://www.soc.soton.ac.uk/OTD/asub/doc87.html
Later,
Jon
--------------------------------------------------------------
Jon Hylands Jon@huv.com http://www.huv.com/jon
Project: Micro Seeker (Micro Autonomous Underwater Vehicle)
http://www.huv.com