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Hi, Ian,
Yes, even with extensive test data, an accurate Water Speed
Indicator (WSI) is highly valuable (somebody help me with the proper
terminology). And a good WSI is going to be the best method for
securing the test data for base performance charts to begin with. My point
is that in any circumstance other than in proximity to a fixed point
with good visibility, the WSI is only going to tell half the story or
less.
If you can visually establish your position in relation to a
fixed point and then maintain your position by adjusting
heading and power, the WSI should accurately read the velocity of the current
at that point and at that depth.
Jim
In a message dated 11/1/2010 4:10:12 A.M. Central Daylight Time,
irox@ix.netcom.com writes:
Hi,
I think there would be quite a bit of value in
knowing
the vessels water speed, regardless of how well you know
you
throttle positions. Move the throttle for 0 to 50%
and you will be
accelerating for while (until you hit
terminal velocity), i.e. not
traveling at a constant speed,
so knowing the your water speed will know
when you've
finished accelerating. I recall not having a
good
sense of acceleration when in a sub, so just going on
throttle
position alone won't give you much sense of
speed or
position.
And don't forget the coriolis effect if you are
trying
to determine position! :)
Cheers,
Ian.
-----Original Message-----
From: Alan James
Sent:
Oct 31, 2010 9:32 PM
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST]
speedo
Hi Jim,
No you're not missing anything, I think I'm having
trouble thinking this
through.
Yes, If you knew your boat speed at
various increments of your throttle
then there
wouldn't be much more of
an advantage having a speed indicator, other than
it would indicate
your
speed as you got up to speed. Because of current speeds relative to
the
Psub norm of 3 knots,
any accuracy with reguard to real speed or
tracking of distance travelled
would go out the window.
I think this
has something to do with the theory of relativity.
Alan
-----
Original Message -----
From:
JimToddPsub@aol.com
To: personal_submersibles@psubs.org
Sent:
Monday, November 01, 2010 2:50
PM
Subject: Re:
[PSUBS-MAILIST] speedo
Alan, doesn't the equipment
you described measure the sub's
water speed so that it would
indicate the same at a given power
setting regardless of no
current, head current, or tail current? Only
the ground speed
would be different. Or did I miss something
completely?
Wouldn't be the first time or the last.
Thanks,
Jim
In a message dated
10/31/2010 8:43:23 P.M. Central Daylight Time,
alanjames@xtra.co.nz
writes:
David,
In hindsight
ignore the bit about a current indicator.
If you were being
carried along in a
10 knot current you would be flowing with
the water
& the indicator would
hardly
indicate.
Alan
----- Original Message -----
From:
Alan James
To: personal_submersibles@psubs.org
Sent: Monday, November 01,
2010 2:26
PM
Subject: Re:
[PSUBS-MAILIST]
speedo
Hi David,
I'll keep the
idea percolating. I have some ideas;
it could be used
with the rotary pot.
The beauty of the position sensor
circuit (wich I
didn't design) is that the circuit
can
be tuned by two pots to light the full range of
LEDs
even though the magnetic potentiometer
might be used only through a small degree
of it's range. So it can be easily adapted.
It
might be a good water current indicator. If you
were
mid ocean with no visual reference &
you knew what
your boat speed should be by
experience, & found
that you were going faster or
slower according to the
speedometer, then you could
calculate the current.
That's providing the
current isn't coming from the
side.You would
probably need another one for
that.
I believe another Psubber was working on
an expensive system involving a computer &
using
all sorts of data input to log their
progress.
Regards Alan
Original Message -----
From:
David Bartsch
To:
personal_submersibles@psubs.org
Sent: Monday, November 01, 2010
1:07 PM
Subject: RE: [PSUBS-MAILIST]
speedo
Alan,
Being able to determine
the speed at which you are traveling while submerged when no visual
aids
are there to help you would be of great
importance to me. This idea you
mentioned
would be a much desired device. I would like to encourage
you to undertake its development as the end product would be
worth the
while.
I had
considered a paddle that would be forced
against a spring to give a mechanical indication of speed but your idea
looks much better.
David
Bartsch
From: alanjames@xtra.co.nz
To:
personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST]
speedo
Date: Mon, 1 Nov 2010 08:55:54
+1300
Hi David,
You've got me thinking on this speed indicator
idea.
On my projects page is the "Position
sensor". I'm
using a rotary magnetic
potentiometer,
but there is a linear magnetic
potentiometer shown
also.
You could have a slider over the top of the linear
potentiometer, with a vane that is pushed
by water movement against a spring. The vain
portion has the magnet & as it slides
further
along the potentiometer it changes the
voltage
wich is registered on the circuitry
also on
my projects page. You could have the
speed
indicated by the LEDs as is, or output
to a
panel meter. This could be calibrated in
a
swimming pool by either adjusting the spring
size
or tension, the size of the vain, or by
adjusting
the display range with the pots on
the circuit board.
Regards Alan
----- Original
Message -----
From:
David Bartsch
To:
personal_submersibles@psubs.org
Sent: Sunday, October 31, 2010
10:10 PM
Subject: [PSUBS-MAILIST]
speedo
Can anyone describe how a
speedo speed indicator system
works and
would such a system be suitable for small submarines? Is'nt
such a system deployed on the R-300 Cliff?
David
Bartsch
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