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Re: [PSUBS-MAILIST] Posted my design too!
Erik,
Turd polishing...eh? I'll have to file that one for future reference.
Is there a turd polishers union in PR?
I suppose it won't be going that fast to create a low pressure pocket
or turbulence. And if it's hovering or turning it probably has no effect.
It seems though with forward motion even at low speed that it would
direct flow over the V-tail rudder giving you better control.
A wind tunnel would be great. There are some computational fluid dynamics
programs [links] that I have filed and will post to the group later.
This might help
diagnosing parasitic drag and dynamics between the duct and v-tail.
--Steve
On Sun, 07 Mar 2004 10:09:04 -0400 Erik Muller <emuller@naic.edu> writes:
> Steve,
> To answer your question, I have no clue why I put it there, but it
> looks
> snappy.
> (too young to have alzeihmers... grr)
> I think I did so to improve the flow through the back, and not
> create
> zillions of pesky vortices. You will notice that the fairing extends
> out
> past the hull, (i.e. it has a diameter larger than the frontal cross
>
> section of the hull) which looks as though it scoops up flow and
> re-directs it into the turbulent part in the back. I am concerned
> about
> dragging a lot of water around after the boat, so I suppose that is
> what
> it is for, although such a thing could simply exacerbate the problem
> by
> piling up more water into the turbulent part I suppose. On the other
>
> hand, I might be turd-polishing..
>
> Aren't we meant to be building a wind tunnel for this or something?
> Wind
> tunnels... Im very much a fan (insert other unfunny and poorly
> contrived puns here).
>
> As for email: the PR network has been cactus all weekend.. I havent
> had
> a look yet.
> EM.
>
>
> Steven Mills wrote:
>
> >Erik,
> >
> >I noticed a fairing or duct aft of the cockpit. Is this designed
> to
> >smooth out laminar flow and reduce vortices? Have you done
> >any calculations to this effect? Or "will" there be a rear thruster
> ?
> >
> >BTW, I don't know if that url helped or not, but I noticed [ in my
> >browser ]
> >the illustrations were poor. There is a pdf file for this, too.
> The
> >figures
> >are much clearer, but in BW.
> >
> >PDF] ME 415 Group #5 Design of an Autonomous Underwater Vehicle
> Advisor
> >...
>
>http://golem.math.stevens-tech.edu/auv/ME/DesignReport/meDesignReport.pd
f
> >
> >
> >Did any of the computation formulas help?
> >
> >--Steve
> >
> >
> >
> >On Sun, 7 Mar 2004 01:51:56 EST DJACKSON99@aol.com writes:
> >
> >
> >>EM
> >>
> >>What is the displacement? So the tubes on the side are the
> batteries
> >>and soft
> >>ballast, right? Where is the weight? Also in the side tubes? If
> >>the weight
> >>is not in the keel, I'd think it might list too easy to when your
> >>existing the
> >>hatch in the top, envy if your not Santa :) Calculate your
> center
> >>of
> >>gravity for when your sitting on the hatch and make sure you not
> >>going to tip over,
> >>flood and sink. Have you considered a bottom hatch and a wet
> entry?
> >>
> >>Do I count 4 thrusters? If the tail does not turn then do any of
> >>the
> >>thrusters? Or are you planing on steering only buy thruster speed
>
> >>and direction? I
> >>guess that can be done, but the control circuit will complex.
> >>
> >>No doubt it will be a lot cheaper to build than a 1 ATM, but
> >>certainly no
> >>less fun. What materials are you thinking of using in addition to
>
> >>the acrylic?
> >>
> >>Puerto Rico sounds like a great place to be building a sub. Are
> the
> >>walls
> >>close to shore?
> >>
> >>With greetings from Oklahoma
> >>Doug J
> >>
> >>
> >>
> >>
> >>In a message dated 3/3/2004 2:48:51 PM Central Standard Time,
> >>emuller@naic.edu writes:
> >>Thanks Doug for your comments, I can address a few of them right
> >>away:
> >>I was actually planning to have separated ballast, i.e. a fore and
>
> >>aft
> >>separation in the middle of the big ballast tanks.
> >>
> >>The tanks on either side will be linked, so that rolling is not
> >>generated by an offset boyant force, although pitch trim can be
> >>fine-tuned depending on depleation of air tanks etc. Of course, I
>
> >>might
> >>end up adding forward planes anyhow.
> >>
> >>Getting in and out will be through a hatch in the top (not for
> >>santas).
> >>There is enough ballast to give a freeboard of around 30-40 cm
> when
> >>loaded up (I estimate). I envisage that the frame extending out
> that
> >>
> >>back can also be used to attach boyant modules to fine tune
> ballast.
> >>The V tail is simply a cop-out to try to get some stability mostly
>
> >>against roll, since the projected resistive area against pitch and
>
> >>yaw
> >>is minimised for a 45 degree angle in the V and is maximised
> against
> >>
> >>roll. Since that part of the machine will be (probably) in more
> >>turbulent flow a small x-section is preferable. Furthermore, It
> will
> >>be
> >>entirely passive. Steering (yaw and pitch) is achieved by motors
> >>only. I
> >>wanted to get away from dive planes because I live in puerto
> rico...
> >>
> >>there are big walls that I want to be near and be agile at low
> >>speeds.
> >>
> >>Since I am not using many heavy materials, that require much
> >>machining,
> >>I hope that it will be cheaper than the typical 1 atm sub. I think
> I
> >>am
> >>at more liberty to get things wrong and make a second attempt
> later
> >>on.
> >>I expect that it will be quite iterative.
> >>
> >>Thanks again for your comments! Please let me know if I am
> proposing
> >>
> >>anything which cause your eyebrows to jump in
> >>confusion/hysteria/contempt/disbelief!
> >>EM.
> >>
> >>DJACKSON99@aol.com wrote:
> >>
> >>
> >>
> >>>Greetings EM
> >>>
> >>>Slick looking design. Not the metal can I'm building :) You
> >>>
> >>>
> >>might
> >>
> >>
> >>>consider reducing the displacement of the cabin in order to
> >>>
> >>>
> >>decrease
> >>
> >>
> >>>the amount of ballast required when you convert to dry? Maybe you
>
> >>>
> >>>
> >>can
> >>
> >>
> >>>use 2 canopies, one for hydrodynamics and the second for the air
> >>>seal. Since you're going to operate shallow you may want to
> >>>
> >>>
> >>consider
> >>
> >>
> >>>that light entering the top of the canopy will reduce downward
> >>>visibility due to reflection. You'll need a forward ballast
> >>>compartment too, or you'll have to add dive planes and be more
> >>>
> >>>
> >>like
> >>
> >>
> >>>the Bionic Dolphin (www.bionicdolphin.com
> >>><http://www.bionicdolphin.com>) And you need some way of getting
>
> >>>
> >>>
> >>in
> >>
> >>
> >>>and out without sinking once you strap on the ballast needed to
> be
> >>>
> >>>
> >>>dry, because your canopy opening will likely be below the water
> >>>
> >>>
> >>line.
> >>
> >>
> >>>Maybe inflatable pontoons or a small top hatch? The v-tail is
> >>>
> >>>
> >>cool
> >>
> >>
> >>>and low drag but they require a mixer that will complicate the
> >>>
> >>>
> >>build some.
> >>
> >>
> >>>
> >>>Thanks for showing your design. I look forward to seeing more.
> >>>
> >>>Doug Jackson
> >>>www.jackson.parcabul.com/sub
> <http://www.jackson.parcabul.com/sub>
> >>>
> >>>In a message dated 3/3/2004 8:10:40 AM Central Standard Time,
> >>>emuller@naic.edu writes:
> >>>
> >>> Hello folks,
> >>> Due to pressure from un-named folks here (i.e. gauge
> >>>
> >>>
> >>pressure),
> >>
> >>
> >>> and the
> >>> upcoming threat of competition by scubatron (i.e. absolute
> >>> pressure), I
> >>> have also posted some images of design plans for an ambient,
> >>>
> >>>
> >>dry
> >>
> >>
> >>> machine
> >>> on moki.
> >>>
> >>> I suspect I will take the construction in a two-step process,
> >>> firstly by
> >>> building a wet torpedo-like thing and checking how it all
> >>>
> >>>
> >>works,
> >>
> >>
> >>> construction methods etc. Then I will cover it over and blow
> >>>
> >>>
> >>all the
> >>
> >>
> >>> water out to turn it into a dry machine.
> >>> Comments please??
> >>>
> >>> EM.
> >>>
> >>>
> >>>
> >
> >
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>
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