[PSUBS-MAILIST] Dive report: Snoopy at Seneca

Tue Jun 9 20:13:22 EDT 2015

Alan,
My gut feeling is the hose will flatten quite easily as is because it has no support to keep it round. Just a feeling, can't argue with specs though.
Hank 
--------------------------------------------
On Tue, 6/9/15, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
 To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
 Received: Tuesday, June 9, 2015, 7:54 PM

 Do
 you mean if it is crimped Hank?Or
 are you saying that just as is it will flatten
 easily?Alan

   From: hank pronk via
 Personal_Submersibles
 <personal_submersibles at psubs.org>

 To: Personal
 Submersibles General Discussion
 <personal_submersibles at psubs.org> 

 Sent:
 Wednesday, June 10, 2015 11:27 AM
  Subject: Re:
 [PSUBS-MAILIST] Dive report: Snoopy at Seneca

 Alan,
 I think
 it will flatten under water right away because it is not
 round and has little strength to keep it round.
 Hank--------------------------------------------
 On Tue, 6/9/15, Alan James via
 Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:

  Subject: Re:
 [PSUBS-MAILIST] Dive report: Snoopy at Seneca
  To: "Personal Submersibles General
 Discussion" <personal_submersibles at psubs.org>
  Received: Tuesday, June 9, 2015, 7:15 PM

  Hi

 Alec,that one
  is also showing 40psi.This is
 a
  Sean type problem.I guess
  it's a bit like snapping a match stick.
 Anyone can do
  it, but try breaking it
 bycrushing
  it from end to end. In this case
 you can squeeze the tube
  & bend it but
 try crushing
  it cross sectionally with
 even pressure all
  around.A

 solution may be to just squeeze up a section of the hose
  with a hose crimpso that a

 point of weakness is created for the water pressure to
  continue crushing thetube from
  there along it's length.Alan

    From: Alec Smyth
 via
  Personal_Submersibles

 <personal_submersibles at psubs.org>

  To: Personal
  Submersibles General Discussion
  <personal_submersibles at psubs.org>

  Sent:

 Wednesday, June 10, 2015 10:55 AM

 Subject: Re:
  [PSUBS-MAILIST] Dive report:
 Snoopy at Seneca

 Wow. If
  there is no mistake that is really
 counter intuitive,
  because the hose feels
 super pliable in your fingers -
  almost like
 those yellowish rubber lab hoses if you know
  what I mean. The size I'm using is half
 the wall
  thickness of what you calculated
 with, if that makes a
  difference. It's
 1/4" ID X 3/8" OD X
  1/16"
 thickness.
  Alec
  On Tue,
  Jun 9, 2015 at 6:46 PM, Alan James via
 Personal_Submersibles
  <personal_submersibles at psubs.org>
  wrote:

  Alec,I had a
  look at the
 specs on that link. Thanks.The
  3/8" ID
 x 5/8" OD X 1/8" tube is rated for
  40psi internal pressure.As this
  is for fuel there could be a safety margin of
 4x, so 160 psi
  burst pressure.I ran a
  couple of plastics I have in my pressure
 program through
  internal and
 thenexternal
  pressure, & the maximum
 external pressure was 2/3rds the
  internal
 in both cases.This
  could mean that it would
 take 106 psi before the hose would
  equalize
 significantly.The
  diameter would maybe
 shrink a bit before
  collapsing.Cheers
  Alan

    From: Alec Smyth via
  Personal_Submersibles <personal_submersibles at psubs.org>
   To: Personal
  Submersibles
 General Discussion <personal_submersibles at psubs.org>

   Sent: Wednesday, June
  10, 2015 10:11 AM
   Subject:
 Re:
  [PSUBS-MAILIST] Dive report: Snoopy at
 Seneca

  The stuff
  I'm using is really flexible, and has a
 wall thickness
  of only 1/16". I'm
 having trouble imagining that
  the seal
 could offer less resistance than this, it's
  very soft. See McMaster item #5552K25.
  Best,
  Alec

 On Tue, Jun 9, 2015 at 5:29 PM, Alan James

 via Personal_Submersibles <personal_submersibles at psubs.org>
  wrote:

  Does anyone (Sean)
  have the
 material specifications in theirpressure programs for the
 soft pvc that we
  would be using inour
  flexible compensation hoses?The nearest I had
 was nylon, & that had
  a crush depth of
 8,000ftfor a 1 meter long tube, 10mm diameter &
  2mm wall thickness.I was

 thinking of using oil filled light housings with the
  wiringrunning through

 flexible hose as compensation, but are having second
  thoughts.Alan

  From: Sean T.
  Stevenson via
 Personal_Submersibles <personal_submersibles at psubs.org>
   To: Personal
  Submersibles
 General Discussion <personal_submersibles at psubs.org>

   Sent: Wednesday, June
  10, 2015 6:11 AM
   Subject:
 Re:
  [PSUBS-MAILIST] Dive report: Snoopy at
 Seneca

  I have
 always
  been a fan of oil compensation at
 higher than ambient
  pressure, for a variety
 of reasons. The only real downside
  is the
 environmental impact of potentially losing oil to the
  surrounding water in the event of a leak, but
 that impact
  can be mitigated with oil
 selection. Positive pressure
  allows you to
 compensate for volumetric changes in your

 compensated volumes due to the exterior pressure, as well
 as
  for thermal expansion of the oil, and if
 you have any
  leakage at all, you leak oil
 out, rather than water in,
  which can be an
 expensive lesson. Additionally, if you

 provide the bias with something like a spring loaded
  cylinder or elastomeric bladder, you can
 instrument its
  displacement for accurate
 monitoring of demanded
  compensation volume,
 and potentially detect leaks well in

 advance of when they actually become a problem. 
  Ambient-only compensation has the disadvantage
 of not
  compensating for boundary-layer
 viscosity effects on
  rotating shafts,!
    density
  differences
 (gravity induced exchange and/or centripetally
  accelerated fluid) and other small but
 cumulative effects
  that can contribute to
 water ingress.  

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