Re: [PSUBS-MAILIST] new to the list

[Michael Holt <mholt@richmond.edu>]

Cliff Redus wrote:
> 
> Mike, for propulsion, I am using the drive train and impellor and nozzle
> from a Sea Doo XP jet ski.  The screw is a three blade axial flow single
> stage pump that is bolted in a frame in the aft of the boat. 

What I didn't see was the jet drive; all I saw was the four-bladed 
scimitar at the stern.  How much control will you get from those 
narrow blades?

> For yaw
> control, this gives me +/- 26 degrees of rotation and +/- 8 degrees for
> pitch control. 

Why, then, do you have the blades abaft the jet?  

> For submerged operation, I am driving the unit with 20 HP dc
> motor connected to 120 VDC controlled by a Curtise PMC model 1221C-7401
> Transistor Motor Controller.  With a POT this enables me to vary the speed
> of the motor and jet pump from 0 to max rmp or even reverse the motor though
> in my case, I am not planning on doing this.  The speed range on this motor
> matches the rather high shaft rpms needed by the jet pump.

What rpm does the pump expect?

>  On the surface,
> I am driving the jet ski impellor with a Rotax 787, two-stroke engine that
> puts up 110 hp.  I know that using a two-stroke engine is a bit
> controversial for psubers but I could not find a marine diesel with the
> power to weight ratio I was looking for. 

I'd not argue about it.  One uses what works!  

Have you asked the Coast Gaurd what they want you to change on
the Rotax?  I recall getting some official flak when I asked
about using a lawnmower motor to drive a generator.

> I could not stand the weight  of a
> marine diesel for this boat size. It would have caused me to increase the
> overall size of the boat which in turn would cause more drag.  

How much does the Rotax weigh?  

>  To address
> the safety issue (gas fumes), I am connecting exhaust and intake manifolds
> directly to hull penetrations on either side of the sail and I am also
> planning on using a carbon monoxide sensor that will shut in the engine if
> readings go abnormal.  

I'd given some thought to putting a gasoline engine in a separate
pressure hull.  It's be expensive, and once I'd given it some *more*
thought, I realized a big problem was that I'd not be able to 
get to the engine while in the water.

> At normal speeds this combination of engine and motor
> give a calculated 98 mile surface range and a 63 mile submerged range using
> 18 gals of fuel and a full charge on the batteries.  The batteries are
> charged overnight with a BYCAN model BY-120/132/144-25A onboard battery
> charger (for 120-144 volt battery packs).

That's a good range.  Take photos of the first trip!

By the way, your side view shows the sail with an angle
forward.  What advantage do you gain?

I want to see this one operating.  It's beautiful.



Mike