[PSUBS-MAILIST] Water jets
hank pronk via Personal_Submersibles
personal_submersibles at psubs.org
Sun Oct 26 16:25:48 EDT 2014
Alan,
Not much roll when you have a couple thousand pounds of ballast. I light low volume sub might get some roll.
It would be a bugger to get into at the surface though. Maybe leave the rolling for airplanes.
Hank--------------------------------------------
On Sun, 10/26/14, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Subject: Re: [PSUBS-MAILIST] Water jets
To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Received: Sunday, October 26, 2014, 4:14 PM
Hi
Hank,Graham
wanted to rotate his jets separately so he
couldget a roll / flying
type motion. So he would need to havetwo
separate intakes that rotated identically to the vertical
outletsto
acheive that without getting the forward motion &
addedinefficiencies.
I wonder what sort of roll you could get with
aconventional
set up.You
must have tried that Hank / Alec. Do you get much of a
tiltwhen you
have your vertical thrusters working in
differentdirections?Alan
From: hank pronk via
Personal_Submersibles
<personal_submersibles at psubs.org>
To: Personal
Submersibles General Discussion
<personal_submersibles at psubs.org>
Sent: Monday,
October 27, 2014 8:57 AM
Subject: Re:
[PSUBS-MAILIST] Water jets
Alan,
I did
not think of that, but your right. You could put a shroud
over the inlet that is inline with the discharge so then the
pump is pulling and pushing.
Hank--------------------------------------------
On Sun, 10/26/14, Alan James via
Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
Subject: Re:
[PSUBS-MAILIST] Water jets
To:
"Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
Received: Sunday, October 26, 2014, 3:50 PM
One
problem
I can see is that if you have your Jet
suckingwater in
from the front & you
pivot your outlets to get
verticalmotion,
then you will get forward
movement from the suction
ofthe inlet
at a similar rate.Also I
did
a bit of research on jet propulsion a couple of
weeks back&
what I read
said it was inefficient compared to conventional
propulsion.Alan
From: Alec Smyth via
Personal_Submersibles
<personal_submersibles at psubs.org>
To: Personal
Submersibles
General Discussion
<personal_submersibles at psubs.org>
Sent: Monday, October
27, 2014 8:11 AM
Subject: Re:
[PSUBS-MAILIST] Water jets
I
don't think water jets are necessarily inefficient,
but
if there is considerable piping around
of the water before
it exits through the
jets, that's what I was referring
to.
However, even that was not meant as criticism, it is
just a normal trade-off. It is surely less
efficient than a
conventional
direct-coupled prop, but you also get
entanglement-resistance and maneuverability.
On Sun,
Oct 26, 2014 at
10:11 AM, Marc de Piolenc
via Personal_Submersibles <personal_submersibles at psubs.org>
wrote:
There is
nothing inherently inefficient about
waterjets. There are
commercial fast
ferries using them and getting very good
thrust per horsepower - better than any supercavitating
propeller could do at the same speed,
certainly.
Lousy design will of course
produce poor results, and jets
are much
less amenable to rule-of-thumb construction than
open propellers. But whether it is "well
known" or
not, good design will
produce good results.
Marc de Piolenc
On 10/26/2014 8:41 PM, hank pronk via
Personal_Submersibles
wrote:
Graham,
In the world of marine jet drive it is well
known that jet
drive takes two times the
horse power to do the same job.
Jet drive
is well suited to a craft that needs a shallow
draft. I think you will find it very
complicated to
control and it will be very
inefficient. I have been down
this road, I
love the concept but abandoned it. If you go
forward may I suggest you start with a jet
drive. It is
not a simple part to
replicate. The impeller tolerances
are
critical. I have a jet unit on the shelf I could
donate to your project. The jet is from a
jet ski. I would
consider a single rear
motor on a full gimbal.
Hank --------------------------------------------
On Sun, 10/26/14, Graham
Bayliss via Personal_Submersibles
<personal_submersibles at psubs.org>
wrote:
Subject: [PSUBS-MAILIST]
(no subject)
To:
"'Personal Submersibles General
Discussion'" <personal_submersibles at psubs.org>
Received: Sunday, October
26, 2014, 7:39 AM
#yiv9417249292
#yiv9417249292 --
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#yiv9417249292 Hi I
am near the end of my build
of my k350 and have started to look at new
designs I
am
interested in building a flyer sub and have
come up with
a
design which will include a vectored motor
drive this
will
enable my flyer to hover and stop where
ever I want. I
have
designed a motor unit which will drive a
fan type
propeller
as an intake this will force water to the
rear of the
unit
where it is compressed then it is
forced into
ducting
which will take the water to four nozzles
on the side
of
the craft. The nozzles are able to turn
three hundred
and
sixty degrees both side are independent
of one another
so
rolls will be achievable. The reason for a
vectored motor
is
you only need one motor source and one
power pack this
will
ease the maintenance and increase the
enjoyment of
using
your sub. I am interested in the clubs
thought of this
kind
of design. Graham
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