Re: [PSUBS-MAILIST] Re: high speed subs

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

----- Original Message -----
From: <VBra676539@aol.com>
To: <personal_submersibles@psubs.org>
Sent: Monday, February 28, 2000 2:50 PM
Subject: Re: [PSUBS-MAILIST] Re: high speed subs


"Hmmm. Don't know exactly unless you are using tankage aft to help fore and
aft trim. Even then, what difference would that make? The sub is either
trimmed or it isn't. If so, it doesn't make any difference whether the hull
is doing the deed or a seperate tank. Okay, now that I have that brain cramp
worked out, I'll wait with some curiosity to see if'n she do or if'n she
don't squat in the stern on the next Ops.  Vance"


I just went over my test video footage, looking for this kind of thing.  The
neat thing about the NAUTILUS is that dorsal fin and tail fin (especially
the long flat section leading back to it from the aft deck)  make excellent
gauges of pitch angle variation in the stern.

I selected scenes where the boat was ballasted tail high; tail low; backing
up and then moving forward; and starting from a dead stop while ballasted
both level and tail low.  I looked at these again and again; regular speed;
stop motion; and frame by frame.  She's just not doing it in any
configuration.  During some of these runs, the dorsal fin and that flat
section leading back to the tail fin were just barely visible above the
waterline.  If she was experiencing a negative aft pitch destabilization
under load and prior to actual acceleration, I'd have seen it.  I looked for
it.  I mean I REALLY REALLY LOOKED for it.  It's just not happening, as far
as I can tell.  (Did I mention I really looked?)

In a way, I wish I HAD found it happening; I'd feel "normal" about all this.
But there's a good side to this: if we compare the differences in the
NAUTILUS to other designs, maybe the possible reasons why mine doesn't do it
will help us eliminate factors and better define why others do.

There's another guy on the boards I've been talking to who is an authority
in this kind of thing; he calls the problem "squat", says it is very simple,
and has promised to enlighten us in a future post.  I'm really looking
forward to having him explain why we don't understand squat.

Anyway, you can bet the next time I put her into the water we'll spend some
time experimenting with this.  It's not going to be for a while, though; I
want to get that corrosion protection done first, and right now I'm weighing
input I'm getting from you guys about whether or not to paint underneath the
resin.  On that score, I painted her black and then painted resin over the
welds and some inaccessible outer surfaces of the ballast tanks, and there
isn't any apparent crazing, corrosion, "intergranular exfoliation", or
anything like that (visible anyway).  I think I'm going to go ahead and to
it.  Better to have some protection between the steel and the salt water
than none at all.  If it crazes or cracks, I could always strip it or
sandblast it.  I just want to keep the corrosion from eating my boat, at
this point.  And I really can't think of any other way to do it right now.
But as of this morning, I'm still thinking, haven't actually started, and
still welcome input.

Thanks!

Pat