|
Hi George.
I really like your idea. It even reminds me of a
PVC flight simulator named "Joyrider" found at this link..... http://www.acesim.com/main.html
Your design and my wetsub have much in common
except yours is more of an open framework. There are some pictures
of my wetsub on moki and also a lot of them on the
frapper site. It has a rudder operated with pedals, a joystick that
inclines
and declines the dive planes. I have a single 78lb
thrust minnkota mouted on the stern. It has a 5 ft long 12" pvc pipe for
its
keel weight and battery pod. The 4 deep cycle
marine batteries will work in series to supply one primary and one reserve
power to the minnkota. I have a few tips for you
that might be helpful. You said...."It would be powered descent and ascent
only... I would probably ballast it slightly
bouyant in case your batteries go out then it would slowly rise to the surface
on it's own."
Being a diver I don't want something that will take
me to the surface because it's batteries gave out. That's not a good
idea.
That's fine for a 1 atm boat where you're not under
pressure and no need for deco or worries about rising too fast, but not for a
DPV
that is basically taking a diver to the surface
before his time to surface or at a speed that could injure the diver. It will be
very hard
for you to get that built in slightly over buoyancy
just right so it rises ever so slightly and never speeds up as it rises. Very
difficult.
My wetsub was originally built for a movie where it
did just what you describe. I have that movie and have watched the sub rise
slightly
and try to go up and was held down by another
diver when the two divers got out of it. It was designed to be slightly
buoyant just like you
are contemplating doing. That means you can never
get out of it to look at or pick up somthing without it rising to the surface.
Not good.
So there are two reasons in my opinion not to
make a WETSUB slighly buoyant. What you
want is to have control of your buoyancy so
you can be completely neutrally buoyant, negative
or postivie and have instant control over that at all times. Once you get to the
depth you
want to be, you will want to become neutrally
buoyant so you can literally float in one spot neither rising nor falling. Just
floating in place.
Then you click on the motor and go and use your
dive planes to control your depth. Remember, you are still scuba
diving. Do not rise faster
than your bubbles go up, the standard is 1 ft per
second. You have to observe the same rules as scuba divers to stay alive,
so this influences
how and what you build into your boat. Actually
with my wetsub and your design we both have basically a jumbo large size motor
powered
BCD, so think of it that way. Operate it like a
normal BCD. Make your boat where when you have flooded all ballast tanks she
sits right on the bottom and won't move
very easily by current action. Then you can use
your ballast tanks to get her back to neutral and start flying again. Then when
it is time to surface
you can keep her neutral and use her dive
planes to ride her up to your 15 ft safety stop on the anchor or dive line. Your
personal diver BCD should
be enough to hold you and your wetsub in place
while you hang on the anchor line for 3 minutes. Then after your 3 minute safety stop at 15 ft, you
could either slowly power the sub up and then fill
your ballast tanks, or you could slowly fill your ballast tanks and slowly rise
your last 15 ft.
I have two stainless steel coca cola water tight
tanks. One of them fits perfectly in the stern but the other will not fit in the
bow because of the
joystick bar and rudder pedals not allowing enough
room for its installation. So I might use the one in the stern, but I
would have to have a flexible
bladder for the bow. The best source of a
cheap bladder with it's already built in valves and fill tubing, is cheap, non
weight integrated BCD's off of
E bay. As long as the bladder is strong and the
tubing is in good shape, you just bought your ballast tank. It has generally two
bladders on each
side if it is a vest style BCD. A wing type BCD has
a horse shoe shaped bladder and you can even buy those individual wing bladders
with the
inflator tube seperately from the harness of the
BCD on e bay as well. I intend to strap one bladder inside the upper bow and it
will clear the joystick and
rudder pedals. Then I may install one in the stern.
Then run tubing from my side mounted scuba tanks to the inflator hose of the two
bcd bladders
seperately so I can fill whichever one I need for
trim or surfacing. By installing a longer inflator hose to each bcd (I can have
long ones made up at
a hose shop) I can have the inflator valves right
there mounted on the dash or side of my cockpit. The bladder tanks I described
could be all you need
and you may not need two tanks at both stern and
bow. The way I see your design you have them at the same heights and the other
one does not
help increase your freeboard on the surface, so why
have two on each end? My wetsub will also have large pvc pipe attached to the
side of the sub
and lower than the bladder tanks so after I surface
I can fill up those tanks either with my mounted scuba tanks (which are mounted
over the pvc pipe
soft ballast tanks) or as suggested by some of the
members here...I could install a waterproof blower fan and just blow them dry at
the surface. I
wouldn't mind building in both ways. These same
soft ballast pvc tanks which raise me higher at the surface than my bladder
tanks would, also can be used
for surfacing in case the bladders malfunctioned.
One of these days I'll post some pictures of the interior of my cockpit and show
how its joystick and rudder
pedals are positioned and how I would install a
bladder and hook it all up. I don't know why you think you would need to replace
your frame and ballast
with something sturdier if you are just diving to
scuba depths. I see no need fot that. Someone here recently sent us all a link
to a site where they have trolling motors for sale
that are good up to
100 ft. I saved that e mail but can't easily find it right now. I will look
later. You can also do what I am going to do with my minnkota.
All minnkotas are only guaranteed to 1 bar, 1 atm
in depth or 33 and 1/3 ft. I know. I called the minnkota corporationa and they
told me. So you have
two choices. You can completely oil fill your
minnkota motor. You have to make sure you got every smidgen of air out of
the housing and tubing and will
probably have to install a fitting into it
somewhere either in the motor housing shaft or the motor housing itself and
pressure bleed out any air just like you
would do with the brakeline in your car and
eliminate all the air. Then your motor will be equalized to any depth since the
oil in noncompressable the water
will not seek to enter the motor housing shaft or
the motor housing. Your motor will run slower because you lose some of its rpm
because of the friction of the
oil on the motor rotator but you buy a stronger
unit than you need and account for that beforehand. That's one way. Another way
is to send off your motor to vendors
that will fit a ceramic and graphite seal for your
prop shaft that will be stronger and go to deeper depths than the factory one
will go before leaking. But to me the easiest
and best choice I have chosen is to air equalize
the motor housing to prevent inward leaks for a
scuba depths sub.
I intend to attach the factory motor housing shaft
to the motor housing and bring that shaft up into the sub body
interior.
Then that shaft will be cut shorter and plugged
except for having a scuba regulator attached to it. Simple. Job done. The scuba
regulator will automatically pressurize the motor housing
shaft and the motor housing as you dive deeper and
exhaust excess air from it on surfacing. One last thing. Stay away from
foam. It will compress and become useless
because it will not decompress very well and will
stay pretty much compressed forever once it gets compressed by
water pressure. It might work for some depths ok, but
a 60 ft dive would probably compress damage it. Why
take the chance? Don't use it. I hope this has been helpful to
you.
Bill Akins.
|
