Bright idea or not?

Boats run in water so why not use water to drive your boat. Environment friendly no gears, or oil and use water lubricated brgs.

 

There have been a lot of guys try this for helicopter blades. I haven't seen any that went into production, but I'm not a copter guy.

If you go to this site you can see one set of plans for a helicopter blade tip powered jet. Not what you were talking about but it is a similar idea.
http://www.rqriley.com/gluharef.html

Good luck.

I think it may be difficult to get the propeller speed you need for much push.

 

Thank`s for reply and I am aware of that idea used in helicopter rotors and they have seemed to be successful. There is advantages with tip driven rotors.It would be great to have just one moving part in a stern leg drive and being able to fit motor and pump any where. I have had fun trying it out.

 

Can we see your attempt?
I never argue against success.

 

I had many old outboards given to me over the years and many parts.
Image shows one of them which like many other old outboards had no water pumps and relied on the low pressure on the leading face of the propeller to siphon the water up to the cylinders.

Red arrows show where I detached a feed line and connected a high water pressure hose ( I tried air too) thus pushing water down to the prop which had channels cast in. The water went every where just like a garden rotary water sprinkler.

 

A water jet is mechanically simple but think of the weight of the water taken on by the jet unit to propel the boat.
The friction of all of that water and the drag on the impellers etc.,
The drag changing the water flow direction and the permanent installation alterations.
The wide open throttle to take advantage of water jet design. To name a few.

A cheap clip-on Hydro Pulse unit made in China in plastic`s giving 360 degrees of turning,tilt-able and jack-able tractor or pusher with no problem maintenance would be great for the handyman so he can put his water blaster (or similar) in his boat connect up and go of "hunting shooting or camping anytime". There are many variations of this "bright idea".

 

What RPM would the propeller rotate and how thick would it have to be to have these water channels cast into it?

 

That`s a very leading question and not easily answered, deciding on such things would need a lot of research and deciding if high volume of water (probably) through the system or high pressure would be best is unclear.
The RPM of the propeller can be controlled by dumping some water flow before entering the stern leg. There are many questions with no answers. The thickness of the prop in my trials were the same as ordinary cast aluminum props. I had no choice as to where the exit of the water flow was but that would be very important. Do you have any ideas?
I have had maintenance experience on some very big (two ton) high pressure pumps that could cut your arm off if some thing went wrong.

There is an alternative approach by building in a ( Google ) a water motor into the stern leg.

 

A tip mounted jet is likely to be very noisy even under water. That killed the Fairy Autodyne.

https://www.youtube.com/watch?v=y9633v6U0wo

http://en.wikipedia.org/wiki/Fairey_Rotodyne

 

Rim drive thrusters exist in the commercial world ( and on one megayacht)

 

Rim drive thrusters exist in the commercial world.

powerabout,

Give us links please. We do not doubt the veracity of your claims, we'd like to see how they work. Do they utilise water pump powered blade tip jets as proposed by Tom Kane?

Thanks.

 

just google it ( rim drive thrusters) Pericles, they work on magic as you will see when looking at the photos.
They are made up to about 1.5 mw now.
As Tom points out pumping water has massive losses associated with it.

 

powerabout,

Google delivers different results in different countries. Google is even banned in certain parts. Vetus units the only make I have found & are electrically powered. Such rim drive thrusters are unlikely have the endurance for main propulsion. I'd be grateful if you would please post your Google results as magic is a source of motive power unknown to me.

OTOH, why not bring back a golden oldie answer for high speed navigation?

http://en.wikipedia.org/wiki/Turbinia#mediaviewer/File:TWAMWIR_first_group_dl_110.jpg

Now, that's an array of screws.