Re: [PSUBS-MAILIST] Sonar

["Captain Nemo" <vulcania@interpac.net>]

Dan,

My first tests in the NAUTILUS MINISUB were conducted in zero visibility
water, and a fishfinder with an LCD screen provided information about the
boat's height above the bottom, a visual representation of objects in the
water column and on the bottom, and so forth.  The unit was inexpensive,
accurate, and handy to have aboard.  I'm still using it, in fact.

The transducer came with the unit.  Mounting was easy: the receiver screen
required a bracket inside the pressure hull; the "fin shaped" transducer was
mounted outside the P-hull: partially concealed with the business end
sticking through a hole in the free-flooding bow of the ornamental outer
fairing.  The only real design concern that came up when placing the
transducer was making sure the downward projected sonar "cone" was clear of
the structure of the hull.   Easy, really.

For the "through hull", I cut and trimmed a hole in the P-hull nose cone;
welded in a slip-fit female-threaded steel coupler; put a male-threaded
reducer the inside; routed the receiver-end of the cable in through it, and
filled the coupler with high-strength hard-drying epoxy.  Inexpensive,
strong, watertight, and the coupler/reducer assembly gives solid steel
support that keeps the water pressure from pushing the epoxy plug into the
P-hull.

Before installation, I also ground off one of the coupler's end-flanges so
the inside end would be small enough to pass in through the hole in the
P-hull, while the shoulders of the outer flange would be larger than the
hole and abut the outer surface of the hull.  This way, instead of a simple
(and relatively weak) "tube in a hole", I've got a metal-on-metal support
that is better able to resist the depth-pressure's tendency to drive the
gland into the hull from the outside.   This self-supported structure,
backed up by a generous amount of welding, provides great strength.  Within
my operating depth limitations, I don't sweat the gland's pressure resistant
integrity at all.  Something else on my boat will implode long before this
does, I'm sure.

If I'd wanted to take the time to make it removable, I could have either
filled the coupler with something like firm-setting silicone (to make it
easier to remove than epoxy, and minimize the chances of damaging the cable
during extraction); or made it in the form of a "packing gland" (put a
reducer on both ends; route the cable; fill the coupler with a suitable
shaft-packing material, rubber grommets, or the like, and torque the
reducers down on the packing until the gland is watertight.)  But I've had
this "epoxy gland" in my boat for ten years now, and it's been maintenance
free.

I also used an epoxy gland for the wires going out to my motor.  When it
came time to replace the old 24-volt MK-4HP with the new 36-volt MK Riptide
101, all I had to do was heat the coupler with my "blue tip wrench".   One
tug and the old plug popped right out the uncapped end, harness and all.  It
cost me was a few pennies worth of copper wire, but I'd planned to replace
that with new stuff anyway.

However, for things like coaxial cables that are integral parts of
commercially made transducer units, and might be hard or expensive to
replace; the removable systems (a packing gland or the like) have some
advantages at maintenance or replacement time.

On-going renovations to my boat include 18 exterior lights; a submersible
speaker for the Public Address system; and a HELLEPHONE underwater
communication unit so I can talk with my dive support crew (thanks, Phil!).
All these electronic goodies will require through-hulls for wiring, co-ax
cables, and such.   Where simple wire is utilized, I'm installing the same
epoxy glands I used with the fishy-finder.  For the expensive co-ax cables,
I'm using the more maintenance-friendly means.

Of course, there's probably better and worse ways of doing it, but this is
what works for me.

Hope this helps.

Pat



  From: "Dan H." <machine@epix.net>
To: "PSUBS" <personal_submersibles@psubs.org>
Sent: Wednesday, April 25, 2001 2:33 AM
Subject: [PSUBS-MAILIST] Sonar


>
> A while back, I was talking with a small sub owner about sonar, and he
> told me that he uses a modified fish finder and it worked pretty good.
> I plan to be spending some time in lakes with poor visibility.  Sonar
> could save a lot of headaches caused by bouncing my head off the
> viewport after striking submerged objects, or worse!  Looking through
> some marine catalogues, I see there are quite a variety of sounders
> available.  Some with CRT and some LCD displays.  Some with a lot of
> bells and whistles, some quite plain.
>
> My sub, a K-350, isn't ready for the water yet, but I need to consider
> through hulls for the transducer, and choose the proper transducer for
> the unit I will be buying.
>
> Is anyone out there using a device like this?  Some input
> please.........
>
> Thanks, Dan H.
>
>
>
>