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Hi David,
I was waiting for Brent to say something about syntactic
foam as he mentioned previously he was going to use it.
There are different materials used in the various types of
syntactic foam & as Brent says some have been used to avoid sonar
detection.
Its advertised as having good thermoforming properties, so
you may be able to heat , bend & glue it. With a bit of luck you could get a
small sample
sent to you as they have a cutting service & would
have plenty of throw-aways.
Regards Alan
----- Original Message -----
Sent: Thursday, July 09, 2009 3:15
PM
Subject: RE: [PSUBS-MAILIST] Sonar
Baffling Material
David,
I wonder
what the acoustic properties of syntactic foam or lead is? I know some
military subs have over a inch of rubber type coating on the exterior of there
hull for a number of reasons. Including I believe absorbing active
sonar. Perhaps for a channeling device you could use a large capped at
one end FRP, PVC or ABS plastic tube coated with a thick layer of rubber,
or Rhino type coating on the exterior of the tube, would absorb noise on the
outside of the tube, but allow in noise coming from the direction the tube is
pointed. My 2 pennies worth.
My grandpa
always told me I could build just about any thing if I had two pennies to rub
together. I've just about rubbed those pennies to half there
original thickness. ;}
Regards,
Szybowski
From: dbartsch2236@hotmail.com
To:
personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] DSV 3 Turtle,
Styrofoam Shot Glass
Date: Wed, 8 Jul 2009 01:39:00 -0400
Brent,
The reason for my quest for finding
or using foam is this:
I need a substance that has
a drastic difference in medium than that of water (salt or
otherwise) the reason being I need this barrier to reflect sound rather than
absorb it. The piezo elements we use are actually omni-dirrectional and I need
this barrier to channel the sound from a set direction into this
element.
If this barrier is not seen by sound, (as
cork was suggested) but is simply passed thru it, this will be of little use
to me. sound will be heard by hydrophones on the opposite side of a
circular array farthest from the sound source.
From the earlier discussion, I have chosen plastic juice cups at least for
initial array testing. (Other channeling devices made from differing materials
could be used in later sessions.) This I will further explain as this testing
array becomes presentable and should should also generate great
discussions.
I should point out again that I am not
all knowing about this field of passive sonar or hydrophones and welcome any
suggestions or things discovered thru testing and experimentation. By
combining the sum of all of our know how, we can derive at better sound
reception for our use aboard these submarines. This is a road to learning
that is best when shared with
all.
David
Bartsch
From: brenthartwig@hotmail.com
To:
personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] DSV 3 Turtle,
Styrofoam Shot Glass
Date: Tue, 7 Jul 2009 01:07:55 -0700
Hi David and Vance,
It's
interesting that just before you guys started to talk about the styrofoam
going deep, I was sizing and uploading pictures I very recently took when I
got to spend a fun day with a friend of mine by the name of Joe Hurst.
The pictures I took were of a signed styrofoam cup for Joe that went down
10,000 fsw with the DSV 3 Turtle in 1987. Joe is a composites expert,
and worked extensively on the Turtle and Sea Cliff DSV's. I've got a
pile of interesting data from Joe for you guys.
http://cid-5085d10eb6afe47c.skydrive.live.com/browse.aspx/Turtle%20DSV%203%20%20Pictures
Regards,
Szybowski
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] Re:
[PSUBS-MAILIST
Date: Sat, 4 Jul 2009 10:34:45 -0400
From:
vbra676539@aol.com
One other thing to do is have everyone involved sign
a cup, write info on the dive (location, depth, dive number, etc). The cup
will squash, and the writing will squash at exactly the same rate. It
will still be neat and legible after the dive and your passengers will
have a neat little souvenier of their dive. It only works partially in shallow
water, but after a couple of hundred feet, you get a shot glass for the
bookshelf that will not reexpand or change. I've still got a few from
memorable dives. The ABS certification dive on PC-8 in Norway for instance,
plus my first time over a thousand feet, over two thousand and then at nearly
five thousand (Pisces VI in Canada).
Vance
-----Original
Message-----
From: Juergen Guerrero Kommritz
<groplias2@yahoo.com>
To: personal_submersibles@psubs.org
Sent:
Sat, Jul 4, 2009 8:11 am
Subject: Re: [PSUBS-MAILIST]
Hello David and Vance
the Styrofoam cups are
allways a nice joke in deep sea expeditions, we put then in a bag
attached to the epibenthic sledge or Box corer or Multicorer and let
them go down to the bottom and when the device comes again on board with
the sample we also have tyni cups and are allways a nice suvenir from
the expedition. Other nice joke in holydays like easter is to put some
boiled eggs in a bag and send them down. If they go to 400020m
deept the presure push saltwater inside the egg so when you get it on
board again with the sample you have a salted egg. :-)). Crazy
things people do after some weeks on open ocean. Well part of the
scientific study of effect of pressure.
Best
wishes
Jürgen
--- vbra676539@aol.com <vbra676539@aol.com> schrieb
am Sa, 4.7.2009:
Von: vbra676539@aol.com <vbra676539@aol.com>
Betreff:
Re: [PSUBS-MAILIST]
An: personal_submersibles@psubs.org
Datum:
Samstag, 4. Juli 2009, 13:13
David,
Styrofoam is a closed cell
styrene foam and will compress almost immediately. Cups will go from
coffee size to shot glass size at just a couple of hundred feet. Wig
stands (the head you spoke of) will be slower on the inside at shallow
depths, but will distort almost immediately, just like the cups. The
issue is not really about crushing the air out--it is the physical
collapse of the foam chambers (the bubbles). They do on come back,
once crushed.
Vance
-----Original Message-----
From:
David Bartsch <dbartsch2236@hotmail.com>
To:
personal_submersibles@psubs.org
Sent:
Sat, Jul 4, 2009 5 :49 am
Subject: [PSUBS-MAILIST]
I remember years ago seeing an article in a
National Geographic showing Alvin in which a styrofoam head was shown
after the submarine had come back up from very deep. This head was
stored in an external retrieval basket and was thus subjected to the
pressure of this deep dive. It was shown compared to what the head
looked like prior to the dive and was quite small having most of the
air within it crushed out.
How much pressure or
rather how deep must styrofoam go down to expel the air within it? If
it were perhaps just cups and not thicker, would it go down to say 500
feet without being crushed smaller?
Anyone have
any idea? I was concidering using simple styrofoam as an inexpensive
sonar baffling for reletively shallow operations. How far down should
this be good for without changing shape upon returning
topside?
&n
bsp;
David Bartsch
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