Submarines, Car Engines, and Displacement
 

"Gould 0738" wrote in message
...
Fascinating. What does the depth indicator say when the sub is surfaced?
Obviously it would not be zero.

That would depend on how far it surfaced. Did it blow all ballast or is
it just barely surfaced?

Steve


It can't blow enough ballast to put the keel on the surface. My point is
merely
that if the depth is measured between the surface and the keel, (and I
have no
reason to doubt that it is) there could never be a "zero" reading.

There is never a "Zero" reading, when on the surface it
is mid to high 30's depending on the type of sub. Also
for safety sake we never surface a little bit, when we
surface all ballast is blown.

Terry

Submarines, Car Engines, and Displacement
 

There is never a "Zero" reading, when on the surface it
is mid to high 30's depending on the type of sub. Also
for safety sake we never surface a little bit, when we
surface all ballast is blown.

Terry

Thanks!

Submarines, Car Engines, and Displacement
 

"del cecchi" wrote

Ahhh yes, there are the creative ideas I was thinking
must be out there.

Thanks to everyone that responded to these questions.

Submarines, Car Engines, and Displacemen
 

"K Smith"

From your thread title I think you want the "volume" of the hull below
the water line??? not the area??? Also your question seems to suggest
"while it's in the water"?? you want to work this out without pulling
the boat out??


Sorry, not worded clearly on my part.

I'm looking for the area. Reason is just for curiosity. Reason I want the
area
is to calculate the pressure per square inch. Example: Boat is 4000 lbs,
area
where it touches the water is X. So approximate pounds/square inch is Y.

No, I don't need to do this IN the water. What I was trying to say is that
I only want the area that TOUCHES the water. The remaining area of the
hull would not be "supporting" the boat while in the water.

It's just a winter month curiosity exercise.

Thanks.

Submarines, Car Engines, and Displacement
 

Again, thanks for all the answers.

Submarines, Car Engines, and Displacement
 

Gould 0738 wrote:

I don't dispute that- ergo the disclaimer.
But if the depth is measured from the keel and there is a depth indicator on
the sub it will never read zero. Is that somehow incorrect? That was why I
postulated *if* a depth guage read zero at the surface the reading would have
to be from the normally ballasted waterline. Since it apparently does not read
zero, that theory doesn't fly. Freely admitted.

It has never been part of submarine law that it must read zero on the
surface. Why should it?

The depth to keel is also an indication of freeboard. A submarine, after
surfacing, will use a low pressure blower to push the last bit of water
from the ballast tanks in order to increase the freeboard. The depth
gauge shows when it is as high as it will go.

Rick

Submarines, Car Engines, and Displacement
 

"Rick" wrote:


On modern gas car engines and when it's cold
outside, is it still better to let them warm up a
bit and how warm (how long) is necessary?

RTFM

I read the f'ing manual. It explains how
to start it in the cold but not a word
about warming it up or idling.

Submarines, Car Engines, and Displacemen
 

"Gary Warner" wrote in message
...
Sorry, not worded clearly on my part.

I'm looking for the area. Reason is just for curiosity. Reason I want
the
area
is to calculate the pressure per square inch. Example: Boat is 4000 lbs,
area
where it touches the water is X. So approximate pounds/square inch is Y.

No, I don't need to do this IN the water. What I was trying to say is
that
I only want the area that TOUCHES the water. The remaining area of the
hull would not be "supporting" the boat while in the water.

It's just a winter month curiosity exercise.

Thanks.



Do not need the wetted area of the boat for those calculations. Just how
far under water is the square inch. And take the average depth of the
location and multiply by the pressure at depth. And the pressure is a
little under 1/2 psi per inch of depth.
Bill

Submarines, Car Engines, and Displacemen
 

K Smith wrote:



This is a mea culpa.

I've made a mistake!! (yes, yes I know; again!!)

If there is anything I can say in mitigation, it's that I did realise
it on my own, get it checked this time:-) & have now tried to belatedly
correct it.


To measure surface area accurately you'll need to measure 1/2 the
bottom of the boat & that part of the sides (if a chine boat) below the
waterline, where ever possible reduce it to oblongs or squares, then
various right triangles when you run out of easy oblongs etc. Add them
all together, double it & that's the total surface area.

In boat design they use a planimeter to run over the lines.

To calculate the "displacement" (volume of the boat below the
waterline) you can actually get a pretty accurate measurement by using
"simpson's formula" even as your question seems to suggest, with the
boat still in the water by;

(i) Boats are usually designed on 10 "sections" i.e. notionally the
boat has 11 transverse stations/bulkheads across it equal distance apart
from the waterline bow. Say a 30 ft WL boat they'd be 3ft apart?? These
stations/bulkheads are not "real", although usually bulkheads are at a
station point, but whatever but you can easily measure with a tape what
the below waterline areas would be, even on a bigger boat.

(ii) You need to measure the "area" of each of those notional
stations/bulkheads, but just that area which is below the waterline.

This is WRONG it's not the "area" it's the perimeter length or
circumference!! Having made this error I carried it on through the rest
of the description.

(again designers with plans drawings etc run around the 1/2 shape X3 div
by 3 to average with a planimeter)

Damn!!! I even correctly described how designers measure the perimeter
length of irregular shapes, but once I had a mindset of "area", well
there ya go, I'm sorry again.

(iii) Once you know the below the waterline only area in sq ft

This should read "Once you know the below the waterline only perimeter
length in inches"

of
each of the boat's 10 notional stations, you multiple each by simpson's
multipliers 1,4,2,4,2,4,2,4,2,4,1 (11 notional below waterline
stations/bulkheads gives 10 equal length sections of the boat)

(iv) Add all the answers together so you now have the sum of functions.

(v) Use simpson's formula to work out the boat or ship's current
displacement per;

2 X 1/3 X sum of functions of 1/2 areas X (inverted scale)sq X the
common interval X 64 = displacement in ponds of salt water, or for fresh
water use 62.2 as the last figure.

This is the formula as used in boat design, so it is a bit more yuk
than you need, all you need is;

(a) 2 is to account for only using 1/2 the below waterline
station/bulkhead area, you can leave it out if you measured the full sq
ft of each area before using his multipliers.

(b) 1/3 is just part of the formula.

(c) Sum of the functions is explained in (iv) above. (but
designers tend to just use 1/2 then multiply by 2 see (a))

(d) Inverted scale squared doesn't bother you because you
can use feet as a direct measure, whereas a designer might be using say
1/2"
to the foot in their drawings. So make sure your notional below the
waterline areas or 1/2 areas if you choose, are in sq ft.

This whole paragraph needs correction because clearly if you have the
sum of functions in inches then you don't need to adjust for scale. So
you just use you answer from (iv)

(e) Common interval is the length in feet of each section,
again say it's waterline length of 30 ft the "common interval" is 3.

(f) At this point the formula should have delivered you the
boat's below the waterline volume in cubic feet, the 64 is just the
weight in pounds of a cubic ft of salt water, or 62.2 for fresh water;
to give you the displacement in lbs (weight of the boat).

The rest looks pretty much OK, so I hope not too many of you have been
working in vain on this:-) Of course I know I know I know nobody even
read it:-) but so what?? it was wrong:-) I can't help but correct it for
the record.

Sincere apologies again.

K


K




Gary

Submarines, Car Engines, and Displacement
 

On 07 Jan 2004 08:04:48 GMT, (Gould 0738) wrote:

Fascinating. What does the depth indicator say when the sub is surfaced?
Obviously it would not be zero.

That would depend on how far it surfaced. Did it blow all ballast or is
it just barely surfaced?

Steve

If you do an emergency blow from test depth, the forward third of the boat will
come completely out of the water when the boat reaches the surface. For those
few seconds I think that would be a 'zero' reading.

JJ


It can't blow enough ballast to put the keel on the surface. My point is merely
that if the depth is measured between the surface and the keel, (and I have no
reason to doubt that it is) there could never be a "zero" reading.

James Johnson
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