03-03-2011, 04:55 PM
Gday Gazz
I remember doing a prac in Engineering that dealt with this matter.
Wish I could remember more than the fact that I remember doing it!
However
I have to date converted 3 aircraft from 2 to 3 blade operation. Fiirst was the ST Cessna, then the Twinstar and more recently my HK Pitts.
I used a rule of thumb that looked at how efficient the prop was. If you treat a spinning prop as a "propellor disc" you could argue that by adding a third blade to a prop will increase it's efficiency by 1/3, going to a 4 blade prop from a 3 will increase efficiency by 1/4. get the drift?
Wattmeter tests have sort of backed me up in regards to validating the above. If you convert say a 2 blade 13/8 prop to a 3 blade 13/8 prop you will notice a 1/3 increase in the amps drawn(that's solid), and performance increases by what I perceive to be about 1/3 more.
For my 2c worth the 3 (or more) bladed props look good, sound good and are worth the effort.
Cheers
Rob B
I remember doing a prac in Engineering that dealt with this matter.
Wish I could remember more than the fact that I remember doing it!
However
I have to date converted 3 aircraft from 2 to 3 blade operation. Fiirst was the ST Cessna, then the Twinstar and more recently my HK Pitts.
I used a rule of thumb that looked at how efficient the prop was. If you treat a spinning prop as a "propellor disc" you could argue that by adding a third blade to a prop will increase it's efficiency by 1/3, going to a 4 blade prop from a 3 will increase efficiency by 1/4. get the drift?
Wattmeter tests have sort of backed me up in regards to validating the above. If you convert say a 2 blade 13/8 prop to a 3 blade 13/8 prop you will notice a 1/3 increase in the amps drawn(that's solid), and performance increases by what I perceive to be about 1/3 more.
For my 2c worth the 3 (or more) bladed props look good, sound good and are worth the effort.
Cheers
Rob B