I'm trying to figure out whats the best way to make the most effect prop tip design ....

The setup is in F3D, I'm using home made FAI fuel.
The plane that is used is the new Evo from BigBruceRacing.com, using the MB Profi, using his new pipe and prop design.
The prop size is 7.1x7.75

What is hard is finding the length and tip design... What I'm told is for this setup is 6.65-6.75.''
The issue is you can spin a 6.8'' at 28,000rpm with the tips square, and the shape them more around and gain more rpm.
you can also spin a 7.1'' prop at 28,000rpm if you shape the tips just right, or sweep the tips back more for more rpm.....

You may gain rpm but you won't always gain effective part on the prop.

Well I'm spinning a 6.501'' at 29,500rpm on the ground but its not biting the air and taking off like it should when its on the air.


Any help?

thanks in advance,
Kevin

There Are as many tip designs as there is props. All engine/aircraft setups will work differently with the same prop, so it is a matter of trial and error. If you want one for flat out speed you will lose some on acceleration. It is a matter of balance and the only real way to get this is trial and error, and will be slightly different for each engine that you use due to slight inconsistitys in the engines. You will go through a lot (LOT!!!) of props to find the right one.

Cheers

Hi Kevin, G'Day Ghost,

Trial and error as ghost said. You may find the Bolly site of help. http://www.bolly.com.au/

Cheers,

Colin

Thanks for the help.... I pretty much got the same answer I was expecting to get so....
Well thank you,

Kevin

Gentlemen,
I would like to know how to built a device / contraption to measure the thrust an engine / prop produces. would the higher thrust number be the only factor to consider or is the rpm of equal importance. Im not interested in speed but rather flying slow but with the tork there to pull it out should I get in trouble. The engine is a Brillelli GT26 installed in a Stinger 120. I thank you in advance.

Hi!
In racing we don't measure thrust! We fly the plane and observe! If it looks to go faster than before we are satiesfied.If not we modify the prop or make a new one and try again.
Static thrust is only worth anything if you want to hoover.