New zealand new inventer boat propulsion

[durban]

I found this in nz forums

[url]http://www.3news.co.nz/Southland-inventors-revolutionise-boat-propeller-system/tabid/421/articleID/268643/Default.aspx#ixzz26DEXR1Mz

[/URL]http://www.contrapel.com/index.html

 

[halfmoa]

Re: New zealand new inventer boat propulsion

Interesting!

Good looking boat too!

 

[Another retired guy]

Re: New zealand new inventer boat propulsion

I don't see anywhere that this has actually been tested in real life boating applications. It's mainly theory with controlled lab-type tests. Another "snake oil" claim of better/faster/cheaper???

 

[H20Rat]

Re: New zealand new inventer boat propulsion

Scratching the head trying to figure out how this is better... So its 2 counter-rotating props in a conventional jet drive. Two propellers spinning is an automatic efficiency hit, and the advantages of a conventional dual prop outdrive aren't really relevant to a jet pump.

*** edit **
did some more reading... It isn't a jet pump by definition, its far more of a ducted dual prop system, or a very low pressure jet. Basically its a jet that is happy with slow speed operation, and probably a little more efficient at less than top speed.

 

[Slide]

Re: New zealand new inventer boat propulsion

Scratching the head trying to figure out how this is better... So its 2 counter-rotating props in a conventional jet drive. Two propellers spinning is an automatic efficiency hit, and the advantages of a conventional dual prop outdrive aren't really relevant to a jet pump.

It's not a conventional jet drive - there are no losses from a convergent nozzle or stator section. You are right that it is a traditional propeller setup inside a jet. If you assume negligible losses to the function of the propellers themselves by being encased in a jet, you are essentially getting "free" thrust - since thrust is the product of mass flow rate and exhaust velocity, both of which are byproducts of propeller operation.

The ingenious part of this idea is (as they say), they go right in the face of traditional jet theory by maximizing mass flow rate (Mdot) at the expense of exhaust velocity (Ve). Ve is a parameter that is relatively easy to control through nozzle geometry (especially with fancy variable geometry nozzles), whereas Mdot is more or less constant for a given propeller speed.

It's sort of analogous to a turbofan engine, where the relatively minor power required to run the fan equates to a significant increase in thrust.

 

[JEBar]

Re: New zealand new inventer boat propulsion

It's sort of analogous to a turbofan engine, where the relatively minor power required to run the fan equates to a significant increase in thrust.

thanks for the analysis .... thinking about it that way makes sense to me .... sooner or later technology/research/dumb luck seems to kick in and improvements happen

Jim

 

[LippCJ7]

Re: New zealand new inventer boat propulsion

Simply put its a Bravo III in a Jet Housing...

Interesting, sort of...

 

[phillnjack2]

Re: New zealand new inventer boat propulsion

Well i cant see what all the fuss is about.

its not new and has been around a long time, its just duo prop.

duo prop is not as efficient as many would like us to believe.
duo does not double the efficiency it helps a bit, but also takes more engine power as well.

the contra rotaing props encase in a jet housing !!!!!! no different to contra rotating props in kort nozzles.

so i cant see its such a revolution.
get any normal single prop and put it in a nozzle and it will create a touch more velocity of the escaping water.


ill stick to single prop for now and be happy with what ive already got.
Lets see if the major boat industry thinks its a good idea,
coz if it is then mercury,Brp,honda , etc will all be using it very soon.

to be honest i dont think it will catch on, and price will be crazy as well.



phill

 

[Scottish]

Re: New zealand new inventer boat propulsion

I presume Slide is correct in his summation, therefore can I ask him what he thinks would happen when oscillation is applied to the propellers?