|
Hi all,
A quick reply to several people. Have had relatives
here all day & one is staying
in my computer room. (She's in bed while I
type)
DAN--- I have a sketch of a K250 that I'm
putting horizontal lines through at various
points to illustrate what happens when you flood a
hull. I'd like to see a white paper
on sub escape written, maybe a group
effort.
GREG--- It surprised me how quickly the hull
flooded but more importantly as the last
section flooded the rate of pressure change really
went up.
Thanks for those figures on recommended descent
speed. We would be definitely violating
them. I think there would be a median fill speed
that would both keep your ear drums in tact
& avoid getting
you the bends. As you say the valve would need to be in reach of the
conning
tower.
FRANK---- I think if this was planned well & as
you say take a pony bottle, you & your
passenger could get out 100 out of 100 times. If
you filled the sub too fast & blew both your
& his / her ear drums & were in
excruciating pain from freezing water entering them, then
your chances would go down. Re the cold-- I used to
trout fish in rivers & fell over in them a
couple of times also had to jump in to get someone
out. This was when there was ice in
pools on the river
banks. You are definitely operational after a small initial shock
period.
JIM--- I hadn't thought of the sub being on an
angle, but it would probably be an advantage
as it would minimize the air pocket in the conning
tower / hatch area & you wouldn't get the
explosive effect of the air rushing out. The down
side is you'd have to dive down to see if the
hatch could be opened.
HUGH & VANCE--- When I was going through these
figures I was very much impressed with
the fact that you really want to do everything else
you can to avoid the flooding option & I
thought these figures would probably encourage
others to the same conclusion. I had the
thought of getting a
list of local technical divers ph. numbers & leaving them with my
boat
person.
However you go to the trouble of putting a flood
valve in your hull so you may as well
learn how to use it properly. I will re-calculate
based on your flood calculator Hugh, when
Jon puts it up.
ALL---- Someone mentioned Narcosis. At 200ft they
say it's the same as having 6 Martinis.
Maybe someone could do some research on this &
tell us how easy it is to get out of there
sub (on dry land). Vance you've got a couple of
subs haven't you.???
I liked the suggestion someone made of having a
small bottle of mixed gas on board to avoid
bends & Narcosis.
Alan
----- Original Message -----
Sent: Wednesday, August 25, 2010 1:13
AM
Subject: Re: [PSUBS-MAILIST] Escape from
a K250 at 200 ft
Alan,
Very interesting what your reporting here.
I suggest you make your finding up in a chart then post it on the
website. A chart that showed flooding at a few different
depths. for both K-250 and K-350 would be great information for the
community.
A K-350 is the same diameter but two feet longer
in the straight portion of the hull. A K-250 has an internal VBT
and batteries that aren't inside a K-350. There is probably a few
extra liters in a K-350 conning tower also. The results will
probably be close to adding an extra 40% to your times.
In a situation where a person was actually
flooding for escape, a second or two either way wouldn't make any
matter.
I had no idea of the actual flooding time and
never thought about calculating it. I knew it would flood really fast at
first through a 2" valve but that's about it. It's great to see
numbers.
Interesting, very interesting,
Dan H.
----- Original Message -----
Sent: Tuesday, August 24, 2010 4:06
AM
Subject: [PSUBS-MAILIST] Escape from a
K250 at 200 ft
Hi all,
I've put some facts & figures together re
flooding a K250 at 200 ft.
Firstly, sorry I move between metric &
imperial. I was brought up on
imperial then N.Z. moved to metric. The metric
system is great for these
soughts of calculations.
The first assumption is that the hull &
hatch area displaces 1,100 liters.
The hatch 100 liters & the hull 1000
liters.
The flow figures through a 2" pipe come from
table 2 on this link. It was the best I could find.
These figures are approximations as the flow
rate changes all the time. Also I'm not
taking into account how many or how fat the
occupants are.
To fill to half way with the 2" valve at 100
psi the water will be coming in at 384 gallons per minute.
It will fill the 550 liters (132 gallons) in
about 20 seconds. The air in the hull will be compressed
to half its size & will be an equivalent
pressure (14.7 psi) as at 33 ft.
To fill the hull from 1/2 to 2/3 the
flow pressure will be between 85 psi & 70 psi. About 340
gpm.
The volume to be filled is 183 liters ( 48
gallons ).This will take 8 &1/2 seconds. In terms of
internal
pressure you have just gone from 14.7 to 29.2
psi wich is the same as diving from 33 ft to 66 ft in
8&1/2 seconds.
To fill the hull to 3/4 the pressure will be
from 70 to 55 psi about 300 gpm.
The volume to be filled is 92 liters ( 24
gallons ). This will take about 5 seconds. Again this is
equivalent to going down another 33 ft. to 99
ft.
Am being kicked off the computer for the night
so will leave it there.
But that is flooding so fast, I'd want to have
my hand on the valve as at that rate you'd blow
your ear drums for sure. It's best to equalize
your ears before they start feeling pain & in this
instance you can't reverse the
pressure like while diving, by ascending.
These figures are open for
correction.
Regards Alan
|