Re: Trolling Motors

[Rick Lucertini <empiricus@sprint.ca>]

Ray Keefer wrote:

> Hi,
>
> I know this is a "dead horse" by now but the concern over the shaft seals is a
> safety concern.

Hey, a dead horse will feed a family of twelve for a month!  Don't knock it!   ;-)

One of the techniques the US Navy practicies for casualty drills (holed hull,

> you just sprung a leak) is to go to full power and point the sub upward. The
> hope is that you can make it to the surface before you take on so much water
> that you never will make it. As a side benefit of heading for shallower water,
> the water pressure is less thus there is less water being forced into your
> hull.

Not to mention that Boyle's giving us an extra hand.

> The option of powering to the surface requires a good shaft seal on your
> trolling motors because it is your motors that provide the motive force. They
> conk out you don't go.

Well, I agree somewhat.  It would depend on what you mean by "go".  Upward progress using motors would
result from vectored movement.  Decreasing depth would be a function of forward movement, hence, a
secondary consideration of motor thrust.  Not a direct input.

> Of course there are other techniques in case of casulty. Like blowing main
> ballast tanks or dropping ballast. [snip]

These would be my first choices.  I would ditch my hard ballast first IF I COULD DUMP IT A FEW POUNDS
AT A TIME!!!  Dry suit divers out there know what I mean.  Dump, say, 10 lb. past neutral from your
hard tank, and the sub will surface CONSISTENTLY (no acceleration) all the way to the surface.  Given,
of course, that there's no air in the other tanks that are open to ambient pressure (ref.: Boyle's
Law).

Admitting air had better be to a hard tank.  In a 1 atm. boat, you can prepare for a broach, in
extremis, if you blow ambient tanks.  Got seatbelts installed?  (think I'm kidding?)  In an ambient
boat, wet or dry, prepare not only for a nasty broach, but, also, for the usual physiological mishaps
that accompany a too rapid ascent.  Lack of a canopy could result in a facemask being ripped off, as
well.

>  If you
> get a leak  at 120 feet. How fast can you bail? You might be 150+ before you
> get clear of the sub.

Agreed.  Things happen fast, especially in low vis without the usual visual cues we use to orient
ourselves with regard to depth.  Certainly I would opt for a controlled release of lead before
admitting air to a soft tank.

--
Rick Lucertini
empiricus@sprint.ca
(Vancouver, Canada)

"You have a very interesting face, but, you should drain it once in a while."