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Re: [PSUBS-MAILIST] Working on a new DBP design.
Just a note to those concerned. Syntactic foam is great if you learn
how to use it. That is if you mix your own. I have some tips if anyone is
interested. This foam has a tendency to form air pockets inside that you
can not easily get rid of. This may not be a factor at low depths but when
you go deeper, they may collapse. SF should be mixed in a vacuum in such
cases. Flotech does sell the kits, but they DO NOT like to sell those kits
to people to do subs. They would rather know that they go to use in ROVs.
Also, the techspheres are no longer sold (As of last summer this was
the case) as a stand-alone product. They still use them as filler inside
syntactic foam. Some had a tendency to leak.
Gary Boucher
At 07:09 AM 3/12/01, you wrote:
>Soren,
>
>Here is my input, for what it's worth...
>
>1. Differential thrust works well and is effective.
>Trolling motors are designed for optimum trolling
>speed and I haven't found them to be the most
>responsive - I can stop and back my sub in half a
>length using a single MinnKota 35T, but the
>accelerations seem painfully slow. That may cause
>problems when going for differential thrust.
>
>2. Syntactic foam is readily available - check out
>flotec.com. They also have "techspeheres" which are
>plastic spheres capable of withstanding the depths you
>are interested in. Last time I checked, a huge box of
>these was just over $100. Blocks of foam are also
>available and can be machined to shape, either by them
>or by you. Alternatively, you could check out
>high-density styrofoam. It comes in sheets and is
>normally used for insulating homes, but it serves as a
>dandy float.
>
>3. Using plywood as a pressure vessel is a really bad
>idea in my opinion. Plywood is really flexible, hard
>to join effectively, and is somewhat porous. To build
>something to withstand even 30 feet of depth out of
>plywood would be an engineering feat. Once submarine
>I saw had two square pressure vessels built for its
>onboard computer system - these were maybe 18 inches
>square and about 6 inches high, custom designed and
>built out of carbon fibre about an inch thick. They
>experienced severe distortion at 50 feet. Be wary -
>having water flow into your exposed battery
>compartment could possibly kill you.
>
>4. The depth rating of the motor depends entirely on
>its design. There are underwater thrusters out there
>with a lot of power and torque, rated to 6000 feet of
>depth, but they also carry a huge price tag. I am
>working on a set of low cost, high power,
>oil-compensated, full-ocean depth thrusters with
>intelligent motor systems because I am not happy with
>anything else available.
>
>5. Underwater connectors are pretty easy to come by -
>I get mine from a guy in Halifax - DASCO Equipment
>(Dave Stewart is the guy). He reps Subconn Underwater
>Connectors, and they are by far the best quality ones
>I have used. Dave overnights me connectors when I
>need them, and his prices are lower than anywhere else
>I have tried. His email is dastewa@ibm.net, or you
>can find him if you search under DASCO Equipment on
>the net. They have big fancy catalogs that he can send
>with all the info in them - a typical 4 pin bulkhead
>connector and pigtailed in line connector will run you
>$120-$150 or so. They are pricey, but work really
>well and are easy to use - also wet-pluggable.
>
>6. No help here, sorry!
>
> -Tim
>
>
>
>Hi Everybody,
>
>I'm new to the list, but have done some research, incl
>searching the psubs archives, and I'm impressed with
>what people are doing.
>I got here after deciding to enhance my diving
>experience by building a long range / long endurance
>DPV.
>I have some ideas, and would love to get some feedback
>by all the experienced people here.
>First, a quick overview of my ideas so far. I like the
>principles of KISS, so my plan is the use painted
>plywood sheets as frame construction material, and, as
>I'm an electronics engineer, use electronic controls
>as much as possible.
>My target deep is abs max 200', usefull deep 130', air
>for 3-4 hours (using 4 80cf tanks), topspeed whatever
>I can get from std trolling motors and range 4-8 miles
>roundtrip.
>The basic design is when viewed from the rear:
>o o|
>I Diver I|
>O |I I| O
> ----|-------------|----
>O | Batteries | O
>-------------|
>
>
>And viewed from the side:
>
> /----------------------------\
> / |
> / [ ] |
> < --------------------- |
> \ [ ] |
> \ |
> \----------------------------/
>
>It's basically a H, with four electric engines 'O',
>fixed lift on top 'o', thin variable lift tanks 'I',
>battery box below, about where the engines are
>located, and 4 std scuba tanks in front of the
>batteries. The side sheets would be a 2x7' sheet, but
>with big pieces cut out to reduce weight and improve
>view. The 'H' mid sheet is 3' wide, where the diver
>would lay on, would be solid from the rear and 5'
>forward, leaving room for the diver to look down. All
>weights will be at the bottom, and it will have wings
>for stability during "flight". I would be designed to
>be modular assemblies for easy transport.
>So here comes the questions:
>1) I'm trying to avoid mechanics, so is it possible to
>get good results by using only the four engines for
>left/right and up/down control by controlling power to
>each engine, assuming the DPV has been set for neutal
>balance and buoyancy using the variable lift tanks ?
>2) I like those syntactic floats for the fixed lift,
>are they easy to get in the shape I need (long square
>blocks or pipes), or can I get some standard blocks I
>can cut to shape ? And sources for normal people ?
>3) I would like to avoid pressure compensation, would
>a battery box of plywood be able to withstand the
>pressure, assuming it has internal support brackets
>between each battery and the sealings holds ?
>4) Again for the engines without pressure
>compensation, would they be able to withstand the
>pressure if the shaft is sealed with t.ex silicone ?
>There has been some discussion of that in the
>archieves, but not any conclusive if no pressure
>compensation is used. Somebody talked about that the
>Evinrude can go deep, but I would like to use Minn
>Kota's, as they seem to have plenty of choices at good
>prices.
>5) Anybody know a good sources for the underwater
>connectors in small quantities and low prices ?
>6) Sources for valves to fill and empty the variable
>lift tanks ?
>And any good ideas and/or sources for the tanks ?
>
>Regards,
>
>
>Soren Kristensen
>
>
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