[PSUBS-MAILIST] Dive report: Snoopy at Seneca

Tue Jun 9 19:54:40 EDT 2015

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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