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[PSUBS-MAILIST] Working on a new DBP design.
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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