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Re: [PSUBS-MAILIST] Ambient pressure design considerations
Hi Dave!
I'm also building a dry-ambient sub. Me and Jon Wallace made a presentation
for the last psubs convention. It's a power-point presentation explaining
some principle and building process of my project.
Let me know if you would like to have it. I can e-mail it to you directly.
Also, I'm very interested in your project. Do you have a drawing of your sub
that you could post on the moki exchange files? That would be great. Always
easyer to talk about something we can see...
Talk to you soon!
Pierre Poulin
----- Original Message -----
From: "Dave Altis" <dabe@fidnet.com>
To: <personal_submersibles@psubs.org>
Sent: Sunday, November 02, 2003 11:54 PM
Subject: Re: [PSUBS-MAILIST] Ambient pressure design considerations
> Hi Jorge,
>
> Thanks for responding. I could not agree more about having little use for
a
> semi-dry sub (I've seen no sharks in the lakes around here), which is why
I
> wouldn't bother! ( There are some rather large catfish though! ) I
> understand the engineering challenges involved in ballasting and boyancy
> control of an ambient sub and I understand Boyle's law, but I also
believe
> I'm quite capable of overcoming these challenges and I believe I will. If
I
> find I cannot, I'll build a 1 atm before I go with a wet sub. I know
> condensation will happen anyway, but I still feel like it will help if I'm
> not breathing on the window I'm trying to look out of. Thanks for
pointing
> me to the SportSub site, I found answers to a couple of questions there.
>
> I fear I've given the wrong impression to several of the group by refering
> to my "ignorance". Please don't confuse this with a lack of intelligence.
> I've accomplished a lot of difficult things that a lot of well-meaning
> scoffers have said "can't be done". The sub has been an ambition of mine
> for many years, long before I knew of this group's existence. One of my
> greatest areas of caution underwater is entrapment, a friend of mine
watched
> his son die that way, the least thing I want to do is become entraped in
my
> own devices. I'm just trying to cover all my bases here, learn from the
> mistakes and experience of others, not become another statistic. No, I
> don't know it all. That's where the "ignorance" comes in, but I intend to
> learn all I can to make this as safe as it can be. That's how I found
this
> group.
>
> Thanks again, (it did help!)
>
> Dave Altis
>
> ----- Original Message -----
> From: "Jorge Lourenço Jr." <jorloujr@uol.com.br>
> To: <personal_submersibles@psubs.org>
> Sent: Sunday, November 02, 2003 2:56 AM
> Subject: RES: [PSUBS-MAILIST] Ambient pressure design considerations
>
>
> >
> > Hi, Dave !
> >
> > Being a hard-core full time lurker myself I'll dare this time to
disclose
> MY
> > deep ignorance, following your (good !) example:
> >
> > I think that there is no point building a sub where you are wet and
> wearing
> > a mask (yeah, I recall your saying DRY, but I'd bet it's gonna be a
> semi-dry
> > vehicle due to ballasting issues...). The only justifiable thing I can
see
> > in this approach is the protection against some environmental hazards
> > (sharks ?). We'd be better off diving donning the regular diving gear
and
> > being pulled by a scuba tow. That means a lot of speed, greatly extended
> > bottom time and unsurpassable freedom of movement. And a lot cheaper,
> let's
> > not forget ...
> >
> > If I ever build an ambient dry submersible I'll mimic the SportSub [
> > http://www.ivccorp.com/ssinfo.html ] and the Markham Wing [
> > http://www.psubs.org/pic/wet.html ] designs, for instance.
> >
> > The SportSub features a continous flow air feeding device that sweeps
away
> > the stale air and besides that has the advantage of providing a
> rebreathing
> > effect that circumvents the oxygen waste of a scuba (open circuit) gear
> > extending bottom time about four times. This is not to be despised. By
the
> > way, CO2 buildup is not a concern, if you are not diving for hours, even
> in
> > the K-250, where the breathing air is what is entrapped inside the hull
> when
> > the hatch is closed, and moisture condensation will happen anyway,
> requiring
> > more than fresh air to be avoided.
> >
> > The Markham Wing has a simple pipe pivoting around its elbow to set the
> > water level inside the "cabin" thus controling the buoyancy.
> >
> > Both devices are very simple, easy to build and operate, reliable and
> cheap,
> > fully adhering to the K.I.S.S. principle, leaving little to be desired.
> >
> > That's it for now, hope it helps...
> >
> > Jorge L.
> >
> >
> > >
> > > Okay, I've silently observed this list for some time now and I'm ready
> > > to disclose some of my ignorance to the group in the hope of gaining
> > > some valuable input.
> > >
> > > My intent is to build a small ambient pressure dry sub for
> > > recreational use in the fresh water lakes of my area. The conceptual
> > > design would be limited (by pressure switch) to a depth of 33 feet
> > > (aproximately). I need to keep the sub as small and hydrodynamic as
> > > possible to minimize power requirements. The sub will remain slightly
> > > positive in boyancy and will power-dive using dive planes which will
> > > be linked via a mechanical mixer to provide both pitch and roll
> > > control. A control stick and rudder pedals would be incorporated as
> > > in an airplane (like flying under water). If the craft exceeds the
> > > depth of 33 feet the pressure switch will deactivate the motor thereby
> > > forcing it to ascend back into its window of operation. An emergency
> > > override switch will allow the use of power beyond the 33 ft. limit.
> > > My plan is to breathe compressed air through a two-stage regulator
> > > (scuba) with an exhaust duct to carry exhaled gasses to the outside of
> > > the sub.
> > >
> > > Any red flags yet?
> > >
> > > By exhausting the exhaled air to the outside I hope to minimize
> > > moisture condensate and CO2 buildup inside the sub, however, I realize
> > > in order for this to work it is absolutely essential that the air
> > > pressure inside the sub remain ambient to the pressure outside the
> > > sub.
> > >
> > > I have to go for now, but I have more questions relative to ambient
> > > pressure and boyancy to come in another post. I'm not looking for
> > > ridicule, but if you have some constructive criticism or see cause for
> > > concern with my plans thus far, I would value your input.
> > >
> > > Thanks,
> > >
> > > Dave Altis
>