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RE: [PSUBS-MAILIST] Acrylic end of life

Its in PVHO and depends on the geometry of the window. For example, for a dome with a square edge its 10 years, but for a dome with a conical edge its 20. Let me know what geometry you're interested in and I can look it up.

rgds,

Alec

-----Original Message-----
From:	Laurent ROUFFIGNAC [mailto:laurent_rouffignac@yahoo.com]
Sent:	Thu 11/21/2002 5:42 PM
To:	personal_submersibles@psubs.org
Cc:	
Subject:	[PSUBS-MAILIST] Acrylic end of life

This conversation is quite interresting but I have a
question for you all...
Does anyone knows or have data about acrylic end of
life? Due to the mechanical constraint, uv, salt
water, how often should you change a viewport to keep
a safe margin?
Thanks,
Laurent

--- Mark Steed <plutomark@mail.astate.edu> wrote:
> Hey, I had me a bad case of credentials once. Don't
> know whether I  got them cleaning out a pool or
> siphoning gas with a hose. Somebody needs to come up
> with a salve or something. This bunch is the
> greatest! Mark Steed
> 
> 
> ---------- Original Message
> ----------------------------------
> From: "Herve" <caribsub@coqui.net>
> Reply-To: personal_submersibles@psubs.org
> Date:  Thu, 21 Nov 2002 17:43:22 -0400
> 
> >Credentials, credentials.....so what?
> >those who have "true"credentials dont need to
> justify themselves, re the
> >endless list of vessels and subs built by
> "credential" people that lay on
> >the bottom of the sea, and what about creations and
> machines built by non
> >credential individuals.
> >Real credentials are referrals, not only piece of
> papers in a nice frame on
> >a wall.
> >I dont think this forum is for anyone to talk about
> his credentials, unless
> >others talk about it.
> >Herve
> >----- Original Message -----
> >From: "Ray Keefer" <Ray.Keefer@Sun.COM>
> >To: <personal_submersibles@psubs.org>
> >Sent: Thursday, November 21, 2002 1:28 PM
> >Subject: Re: [PSUBS-MAILIST] Hydraulic Drive Unit
> >
> >
> >> Hi Carl,
> >>
> >> I am one of the ignorant ones also. That is why I
> host this site. To
> >> learn from others, whether they are credentialed
> by experience or
> >schooling,
> >> I don't care.
> >>
> >> But every tid bit I hear about I weigh and judge
> for usefulness in my
> >> projects. I am responsible for my final design. I
> like hearing about
> >> other's concepts however the designs I will come
> up with will have
> >> elements that fit my need, and mine only.
> >>
> >> Regards,
> >> Ray
> >>
> >> > Date: Thu, 21 Nov 2002 00:31:50 -0700
> >> > From: Coalbunny <coalbunny@vcn.com>
> >> > X-Accept-Language: en
> >> > To: personal_submersibles@psubs.org
> >> > Subject: Re: [PSUBS-MAILIST] Hydraulic Drive
> Unit
> >> > Content-Transfer-Encoding: 7bit
> >> >
> >> > I come here because I like the idea of mini
> subs.  I guess us
> >> > non-credentialed folk ain't got no business
> here then.
> >> > Carl
> >> >
> >> >
> >> > Walter Starck wrote:
> >> > >
> >> > > Gary,
> >> > >
> >> > > I don't have the time nor inclination to get
> into a pissing contest
> >over
> >> > > credentials.  I understood this thread to be
> about the putative merits
> >> > > hydraulic driven propulsion for PSubs.  I
> offered the opinion this
> >> > > approach offered no real advantage and
> considerable disadvantage as to
> >> > > cost, total system bulk, complexity and
> efficiency.  I also said they
> >> > > will work and work well but in view of the
> disadvantages they are not
> >> > > the best solution.
> >> > >
> >> > > Thus far your arguments for hydraulic
> propulsion are all hypotheticals
> >> > > addressing non-problems while your objections
> to straight motor drives
> >> > > are in regard to problems that in actual
> practice have been solved for
> >> > > many years.  Literally thousands of 
> successful PSubs, ROVs, DPVs,
> >> > > research submersibles and larger military and
> commercial submarines
> >have
> >> > > been built.  Only a tiny minority employ
> hydraulics for propulsion.
> >> > > Propulsion system leakage and  reliability
> are rarely problems and in
> >> > > those rare events are neither disasterous nor
> difficult to fix.
> >> > >
> >> > > I am not familiar with your particular
> application and have no opinion
> >> > > in that regard but as a general solution for
> PSubs which is what the
> >> > > discussion seemed to be about, hydraulic
> propulsion would be a poor
> >> > > choice.
> >> > >
> >> > > Walter Starck
> >> > > Golden Dolphin Video CD Magazine
> >> > > The premiere publication of diving and the
> ocean world.
> >> > > www.goldendolphin.com
> >> > >
> >> > > ----- Original Message -----
> >> > > From: "Gary R. Boucher"
> <engineer@sport.rr.com>
> >> > > To: <personal_submersibles@psubs.org>
> >> > > Sent: Thursday, November 21, 2002 10:28 AM
> >> > > Subject: Re: [PSUBS-MAILIST] Hydraulic Drive
> Unit
> >> > >
> >> > > > Walter Starck wrote:
> >> > > >
> >> > > > >Gary Boucher wrote: " I get somewhat
> irritated when people that
> >have
> >> > > not
> >> > > > >gone through this process sit back like
> armchair quarterbacks and
> >> > > make
> >> > > > >broad reaching
> >> > > > >technical statements."
> >> > > > >
> >> > > > >I do too but with over 40 years experience
> in designing, building,
> >> > > > >operating and maintaining a wide variety
> of underwater and marine
> >> > > > >equipment I have gone through the process.
> >> > > >
> >> > > > I have no idea what your credentials are. 
> Forty years of
> >"experience"
> >> > > is
> >> > > > pretty vague, but lets say that you have
> experience in actual design
> >> > > and
> >> > > > construction of manned submersible
> propulsion systems.  The issue
> >that
> >> > > I
> >> > > > raised stands.  You are making a blanket
> condemnation of hydraulic
> >> > > > propulsion and this is an uninformed
> declaration.
> >> > > >
> >> > > > >Alec Smythe Wrote: "In an earlier post
> Gary pointed out that in
> >> > > > >hindsight, he recommends compensated
> trolling motors for their
> >> > > > >simplicity."
> >> > > >
> >> > > > Lets set the record straight here.  I do
> recommend pressure
> >> > > compensated
> >> > > > trolling motors for most applications where
> people are designing
> >> > > > PSUBS.  There is a simple reason for this. 
> It is the easiest
> >approach
> >> > > for
> >> > > > the PSUBer who has limited knowledge of
> other approaches.  A
> >thru-hull
> >> > > > shaft is probably the very last thing I
> would recommend for these
> >> > > > people.  I don't recommend hydraulics for
> every application.  I
> >don't
> >> > > > recommend hydraulic propulsion for most
> subs.
> >> > > >
> >> > > > You probably have no idea what the design
> philosophy of my sub is.
> >> > > You
> >> > > > have no idea what the intended purpose of
> my design was, or is.  You
> >> > > are
> >> > > > placing yourself in the position of an
> expert and basically saying
> >> > > that all
> >> > > > hydraulic propulsion is a bad idea.  I
> strongly disagree.
> >> > > >
> >> > > > If hydraulic propulsion is such a bad idea,
> why don't you take this
> >> > > > campaign to the manufactures of thrusters
> that are driven by
> >hydraulic
> >> > > > fluid.  They are on the market.  They must
> sell because they still
> >> > > make them.
> >> > > >
> >> > > > >This seems to agree completely with what I
> have said although Gary
> >> > > now
> >> > > > >seems to disagree.
> >> > > >
> >> > > > No, no change in my opinion.  The main
> reason that I would rethink
> >my
> >> > > > design if I had it to do again is weight. 
> I am marginal on my
> >weight
> >> > > and
> >> > > > would for that reason like to have some
> extra buoyancy provided by
> >> > > motor pods.
> >> > > >
> >> > > > >Sean Stevenson wrote: "For the
> homebuilder, overcoming the
> >efficiency
> >> > > > >issue is the only real hurdle for emplying
> a hydraulic system."
> >> > > > >This like saying overcoming gravity is the
> only real hurdle to
> >> > > building
> >> > > > >a flying saucer.  High friction losses are
> inherent in hydraulics.
> >> > > For
> >> > > > >brief or intermittent operation or
> anywhere power is not limited
> >this
> >> > > > >loss may not be important.  In small
> submersibles however,
> >available
> >> > > > >power is a limiting factor and taking a
> 30% or more efficiency hit
> >on
> >> > > > >usage is an important consideration.
> >> > > >
> >> > > > I will quickly admit that efficiency can be
> an issue.  Whether this
> >is
> >> > > a
> >> > > > deciding issue or not cannot be judged by
> anyone without first fully
> >> > > > understanding what the design emphasis is. 
> Engineers learn very
> >> > > quickly
> >> > > > that nobody can build the perfect car,
> airplane, boat, submarine,
> >> > > > etc.  Compare a Jaguar  to a Lincoln.  Each
> is an excellent car in
> >its
> >> > > own
> >> > > > right.  Each has a totally different
> functional design, a totally
> >> > > different
> >> > > > purpose.  If fuel efficiency is your issue,
> buy a Taurus.
> >> > > >
> >> > > > Each design is an optimization of purpose
> based on a very extensive
> >> > > set of
> >> > > > tradeoffs.  The engineer's main purpose is
> to make judgements as to
> >> > > what is
> >> > > > important and what is not, what is going to
> promote the design
> >> > > philosophy
> >> > > > and what is not.  Good engineers are going
> to weigh the merits and
> >> > > balance
> >> > > > the pros and cons.
> >> > > >
> >> > > > I hear a lot of talk about propulsion on
> PSUBS.  I hear some really
> >> > > > outlandish proposals.  Most are not
> feasible, but I seldom discard
> >> > > these
> >> > > > ideas, in that I put many of them on the
> shelf for later
> >> > > consideration.
> >> > > >
> >> > > > >Carsten Standfuss obviously understands
> the issues.
> >> > > >
> >> > > > Carsten apparently is a good engineer and
> builder.  But, just
> >because
> >> > > he
> >> > > > elected to not use hydraulics for his
> controls does not make, in
> >> > > itself,
> >> > > > hydraulic controls a poor decision.
> >> > > >
> >> > > >
> >> > > > Gary Boucher
> >> > > >
> >> > > >
> >> >
> >> > --
> >> > "You delight not in a city's seven or seventy
> wonders, but in an answer
> >> > it gives to a question of yours, or the
> question it asks you, forcing
> >> > you to answer, like Thebes through the mouth of
> the Sphinx." -- Kublai
> >> > Khan
> >>
> >>
> >>
> >
> >
>  
> 
>                    


=====
-----------------------------------------------------------
From:       Laurent ROUFFIGNAC
            444 Saratoga Avenue, Apt 8G
            Santa Clara, CA 95050 USA
            Home: (408) 244-1285  Business: (408) 546-4704
            Email: laurent_rouffignac@yahoo.com
-----------------------------------------------------------

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