Re: [PSUBS-MAILIST] New comer w/ROV Question

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

----- Original Message -----
From: "Jonathan Grant" <scuba4fun97321@yahoo.com>
To: <personal_submersibles@psubs.org>
Sent: Thursday, July 19, 2001 12:14 AM
Subject: [PSUBS-MAILIST] New comer w/ROV Question


> I am working on a ROV for my first project.

Hi Jonathan,
I'm mostly into subs, but there is some ROV interest at here, so you'll
probably get the answers you need.  If not...
I haven't visited the site lately, but I remember a place called ROVTECH
that had a lot of info and parts for people into this sort of submersible.
Try:

www.rovtech.com



I have
> been doing some victim recovery diving in the pacific
> north west.

My ol' splashin' grounds.  Whereabouts?

 The fresh water recovery can be tricky due
> to the 12 to 18 knot currents in some of the rivers I
> have been dealing with.As a diver being 10 lbs over
> weighted and carrying a 35 lb lead anchor it is still
> difficult to fight the currents. I would also like to
> use this for deep ocean use.

I'm thinkin' 18 knots in a river?  With a ROV?  Hmmmmm.   Ocean sounds
better to me.

>    I am working on a submarine shaped (approx 8" X
> 30") ROV. I believe with the bow planes, and making
> the sail so I can adjust (pitch side to side) for
> control at the front of the sub. Combining this with
> the rudder control on the aft end, I will be able to
> control the ROV using the currents to my advantage.

Wait a minute, yer confusing me here.  Let's establish some terms: Pitch is,
say, moving the nose up and down; yaw is moving the nose right and left, and
roll is rotating the hull; OK?  Now, I see you pitching the nose up and down
with your bow planes; and yawing the boat left and right with the aft
rudder; but what are you doing with that adjustable sail: making her roll?
Sounds like you're after three axis control.  Hmmm.  R/C model subs do
sometimes have a tendency to roll in response to tendencies generated by the
sail when they are yawed vigorously.  You probably could roll her with a
maneuverable sail at a high enough speed or in a good current flow.  Then
again, you might get by without it.  Keeping her bottom heavy and controling
two axis (pitch and yaw) might be enough.  You might want to think about
vectored thrust for maneuvering, too.


> A strong motor to push against the currents.
> Transparent nose cone for camera, sonar,...
>   If anyone has any suggestions they would be greatly
> appreciated.

Well, you're going to need some thrust to overcome 18 knots with enough left
over to go driving around.  With the size of the hull you've mentioned,
you're limited for space.  Are you thinking internal battery pack or power
supply umbillical cord?  Maybe batteries inside, motors out?

Camera?  That shouldn't be a problem; all types and sizes around these days.
Think they used to have some at ROVTECH; if not, I know you'll find one
somewhere.

Sonar?  Again, the size of the hull is going to be a factor.  Are you
thinking about the towed array from one of those high-dollar sidescan jobs
like they drag from boats?
>
> Also can anyone share the formula for pressure at
> depth of sea water?

Same like they told you in class when you quallified for your C-card: one
additional atmosphere for every 33 feet of depth.  (When this comes up, we
usually get a lot of people with different ideas of what one atmosphere is:
some ballpark it at 15 PSI; others say 14.8, 14.75, etc.  Divide 1500 by 33
and multiply by, say 14.8 and you'll get the pressure of about 672.73 PSI.
Or if all you want is an easy, rough estimate you can do in your head, just
divide depth in half minus 10 percent of the result: that'll get you pretty
close.)

 For example, how many pounds per
> square inch would be applied at 1500 of sea water.

See above.  About 673 PSI uncompensated pressure, in excess of that 14.8#
surface pressure you had inside the hull when you capped it shut at sea
level.


> What is the best material to use, aluminum (1 piece
> machined) or welded steal?

I like steel, but I think in your application, aluminum has advantages.  You
don't have a very big hull, so you want enough strength with minimal weight,
so you'll be able to put all your goodies inside and still float the boat;
and if you machine the cylinder out of a single piece, you won't have a seam
to worry about; and even better, you can get it really, really round; and
that's pretty important in, as Phil says, "keeping it from turning into a
Halibut".  I'd go with aluminum.

How thick should this
> material be to resist the 1500 fsw?

Need a little more information about the type of material, the shape of the
hull, etc.  Don't have the specs in front of me, but someone here probably
will.  Let us know more about the shape of the thing, and what kind of
material you decide on.

> The transparent nose cone acrilic or polycarbonate?

I've used both; I'd go with acrylic.

> And how thick?

I don't have the specs for that either; but how about a hemisphere?  I'm
just guessing, but one measuring  8" by 4", made out of acrylic, and
properly mounted, wouldn't need walls any more than , say,  3/4 inch thick
to do the job.  Maybe less.  Anybody wanna do the math on this?

> I hope this is not below anyone to help on something
> so small but as I said I'm just getting started

Nope!
>
> Thank so much
> Jonathan

Yup!

Pat