Pierre,
Very interesting! I didn't realize that would work at all. I thought
the
metal would conduct the magnetism and sort of blur it equally all
around you
when in the hull. I'll play with that next time I have Persistence
out.
I found a liquid filled auto dash board compass that I'm going to
mount on
the fiberglass MBT, out in front of the viewport and try that. Even
if it
works, it will be tough to read it without a light when deep in the
water
around here.
I got a quote for an electronic compass with a sensor outside and a
digital
readout to mount inside. I told them that I'd take care of all the
water
tight stuff and they only need quote on the electronics. The price
was 750
Pounds English. Way out of my league! I probably shouldn't have
mentioned what I was using it in.
Thanks Pierre, and everyone else that contributed to help me find my
way.
Dan H.
----- Original Message -----
From: "Pierre Poulin" <pipo305@hotmail.com>
To: <personal_submersibles@psubs.org>
Sent: Saturday, November 06, 2004 7:41 AM
Subject: RE: [PSUBS-MAILIST] Last Launch and Trials
Hi Dan,
Not sure if it's pertinent but...
When I was in the army, We used a regular compass to orient ourselfs
while
inside a tank (APC). If I stand inside the crew commender hatch,
witch was
"magnetic center" of tank, no problem.
You could try it while the sub is on the trailer. Go far of anything
metal,
take a reading and spot a far object. Then climb inside persistence
and
spot
again the same object. While moving the compass inside the sub you
should
be
able to find the "magnetic center" of your sub.
Hope this help!
Pierre Poulin
Building a dry ambient
Québec Canada
From: "Dan H." <jmachine@adelphia.net>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: [PSUBS-MAILIST] Last Launch and Trials Date: Wed, 3 Nov 2004
22:15:49 -0500
Hi All,
I apologize for not posting sooner. I was hoping to have more to
post.
I took my sub, Persistence, to the lake where I first launched it
for a
day
of diving. Although not a great dive location, it's close to home
and
has
a nice launch ramp. There are also two docks on it, about 800 feet
apart,
where I planned to do timed runs to determine it's speed.
Since the lake is located within a state park, it's patrolled by park
rangers. The part time "rent a ranger" that was there on Sunday had
some
issues with my safety. Like HE was going to save me from my own
demise by
not letting me in the water that day. He insisted that I would need
a
"surface boat and a scuba diver in the water to be safe to go in that
thing." After discussing the situation for twenty minuets, I could
see
that his mind was made up.
I did launch that day in another lake about an hour away but the
location
didn't lend itself to testing the subs speed and we already spent a
lot
of
daylight.
I got to test my fish finder / sonar more and found it pretty
difficult
to
tell much with. Maybe with more practice I'll learn how to find more
information in the squiggly lines. It's great for determining depth
and
watching as I'm approaching the bottom. It counts down until I touch
down.
I turned the pickup facing upward but it won't read the distance to
the
surface when sitting on the bottom. I guess it can't detect the
boundary
between the water and the air.
Another thing I tried out was a mirror I located on the top of my
hatch
cover on the outside of the up looking viewport. When the sub is on
the
surface, but still at neutral buoyancy, none of it actually sticks
above
the surface. I can only glimpse out of the up looking viewport.
Seeing
the
sky isn't much of a help when trying to get a fix on a direction or
proximity to an object. It takes time and air to inflate the MBT's
enough
to get the conning tower viewports out of the water. With a small
mirror,
fixed at 45 degrees, located above half of the hatch viewport, I can
look
up and see forward just enough to scan the surface. I know it's no
periscope, but it's simple and doesn't have the hazards of a
periscope in
a
small sub.
I recently posted a request for help in choosing a method of keep on
course
under water. I thank each of you who posted suggestions. After
reading
your postings and considering my options, I've decided to try to
find a
liquid filled dash board compass to mount outside the pressure hull
as a
first try. They're hard to find now with electronic ones on the
market.
My second choice would be an electronic compass made in two parts.
If I
can find such a unit, I'd encapsulate the sensor in epoxy and mount
it
under my fiberglass MBT, pass the wires through a thruhull and mount
the
readout inside. I've found some one piece electronic units and some
sensors but I don't have the electronic skills to separate the one
piece
units or marry together a sensor and readout. I don't want a whole
computer in the sub.
If anyone knows of an off the shelf unit or could give me explicit
instructions, I'd like to try an electronic compass with remote
located
sensor.
My last choice, probably the most expensive, is to install a 28 volt
aviation gyro compass. The biggest draw backs are it needs to be set
each
time, it's noisy and an electronic gyro is expensive. They are a
nice,
easy to install and use, one piece unit that will work well in a sub.
That's it from Persistence! If I get a chance to test speed or a
guidance
system before the lakes freeze over, I'll post my progress.
Cheers to all, Dan H
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