New Toroidal props

[Alan de Enfield]

9 minutes ago, howardang said:

Crab and lobster pot buoy ropes and long line fishing gear can wreak havok  and they are all common around UK waters.

 

Howard

 

 

So someone else has had the same problem.

I am not alone !

[howardang]

22 hours ago, Goliath said:

Looks a beautiful piece of engineering. I wonder how more difficult they are to cast.
 

And ain’t all lobster pots all marked with flags?

 

 

No, they're not all lit and flags in any case they  are extremely difficult/impossible  to see in the dark , even in a flat calm and if there is any kind of sea running they are virtually invisible.

 

Howard 

[Bee]

General purpose props have hardly changed much over the years so there must be room for new thinking. As Goliath said, difficult to cast. I can't see me having much success with a box of sand and some scrap metal.

[ditchcrawler]

[magnetman]

A russian screw tank would be good for non dredged canals. You could just go round the locks. 

 

 

 

https://www.military.com/video/logistics-and-supplies/russian-equipment/cold-war-era-russian-screw-tank/

 

 

[TheBiscuits]

On 28/01/2023 at 15:25, magnetman said:

crowthers anyone ?

 

Not since they closed in July 2020, no ...

 

 

[MtB]

On 28/01/2023 at 16:15, IanD said:

If you go and read the articles there are actual test results; IIRC at the same engine power, they deliver something like 20% more thrust.

 

How does that work then? Does a 'normal' prop waste more than 20% of the shaft power absorbed doing things that don't result in thrust?

 

I suppose its entirely possible that turbine effect and centrifugal throwing of the water outwards instead of backwards wastes quite a lot of power, and this new design reduces those losses. 

[IanD]

2 hours ago, MtB said:

 

How does that work then? Does a 'normal' prop waste more than 20% of the shaft power absorbed doing things that don't result in thrust?

 

I suppose its entirely possible that turbine effect and centrifugal throwing of the water outwards instead of backwards wastes quite a lot of power, and this new design reduces those losses. 

Yes. IIRC a normal prop is about 50% efficient at converting shaft power into thrust , the Sharrow is about 60% efficient -- the reason is that less energy is wasted in tip vortices.

[Hudds Lad]

20 hours ago, Bee said:

General purpose props have hardly changed much over the years so there must be room for new thinking. As Goliath said, difficult to cast. I can't see me having much success with a box of sand and some scrap metal.

3D printing? They can print in several alloys, must be something good for marine use?

[IanD]

11 hours ago, Hudds Lad said:

3D printing? They can print in several alloys, must be something good for marine use?

If you think casting or CNC machining a prop like the Scarrow is expensive, try 3D printing it in one of the large-scale sintered metal 3D printers... 😉