Prop modification ?
 

I run a APC 8X8 on a OS.32SX with tune pipe.
I want more pitch and less diameter, like a 7.5X9 or 7.75X9.

What is the better match. Buy a 8X9 prop and cut it to 7.75 or 7.5 or buy a 9X9 and cut it to 7.5 or 7.75?
Do I need to keep the same shape (thin tips) or just cut it straight and sand a bit?

If you have pictures of your custum prop.
Thanks

RE: Prop modification ?
 

nexxa Hi. Your plane looks nice. I don't think you will like the smaller dia. props. With the combination you have I would suggest the apc 8.5x7 with spinner for best all around performance.

RE: Prop modification ?
 

Thanks. Yep, your right for the spinner, I broke it on the first Take off, I replace it temporally with this one.
I will try many props on it, 8X7, 8X8 and like you suggest 8.5X7. I'm sure, the 8.5X7 will give me unlimited vertical, very easy and strait take off, but I need to make some test.

To make a 8.5 X 7 . Do I need to cut a 9X7 or 10X7 prop to the right diameter? (APC prop).

I’m not sure for the prop tips. They are thin, do I need to shape my tips, or just cut square or with a small angle?

RE: Prop modification ?
 

nexxa, The apc 8.5x7 is an off the shelf pylon prop. No mods required. Have fun with your testing.

RE: Prop modification ?
 

Apc has a large selection of Pylon props available.

RE: Prop modification ?
 

Thanks, I will order a couple of APC 8.5X7.

But for my personnal information... to make me a better guy!!! Somebody have pics of there modified prop, I prefer to saw a APC prop picture. Just want to know how to cut it. I never had trouble with Master Airscrew or others ordinary shape prop. But with APC it not the same story.

Thanks.

RE: Prop modification ?
 

You can cut them off straight (easiest way to get both sides even) and then lightly sand and balance.

RE: Prop modification ?
 

I cut down an APC 7x8 to about 5.45 inches for my Nova Rossi .21 that is mounted a Diamond Dust, I need to get the rpm up to about 28,000 for this engine to perform. I had one inflight propeller failure where one of the blades departed, ruined the throttle servo and loosened the engine mounts. This plane is slow to get started but is almost as fast as my Diamond Dust with a JETT FIRE 60LX and tumed pipe.

RE: Prop modification ?
 

I thought the standard APC props were only good to 20K.. The pylon ones are a little more and then the CF Q40 are more yet but I would be careful spinning a sport prop that fast..

RE: Prop modification ?
 

nexxa try this prop.

http://www2.towerhobbies.com/cgi-bin...?&I=LXHCG3&P=7

RE: Prop modification ?
 

try the 7.8x7.8 APC QM40 prop :)

RE: Prop modification ?
 

Too late! :D
I got my pylon APC 8.5 X7 yesterday and I tried it. I don't want anything else now. Very impressive acceleration, I have less pitch than the previous one (8X8) but I go faster in straight line, and when I turned, wow it doesn't loss speed...
I tried also a modified APC 8X9 to 7.5 X 9. Very fast out of big dive, but loose too much speed on level flight, and it too slushy in curve.
My Shrike is a bit heavy with its 2.8 pounds, and the wing are not so thin. I need thrust!

But its good to know it, the winter comes fast; I want to build something really fast this winter, who can run a 7X9-10-11 at 20 000 rpm and more.
I want to break my 145mph barrier and go like 170 mph...

RE: Prop modification ?
 

nexxa. Two engines that pop into mind, Jett 35 or Webra 36. Either one with a tuned pipe will rip the wings off your plane with a 8.5x7.25. As far as planes go, LR-1 or Ashley 2 which is hard to find. Have fun and let us know how 7" props work.