Prop size
 

Hello all,

I have a OS MAX FX .46, and I just got the Macs tuned pipe outfit for it. I understand this is not really a purpose built speed engine, but should still be able to produce a descent turn of speed. My question is, what size of prop would anyone recommend? I have some 9x12's (too big I expect) and some 7x9.5's (too small?). I have a feeling I may need to get something in between.

Chris

RE: Prop size
 

need to know the plane....

RE: Prop size
 

....a 9-7 is a good place to start....;)

Viper....OS 40FX, !6,200 rpm, Master Airscrew 9-7 prop.
Sonic....GMS .47, 16,000 rpm, Master Airscrew 9-7 prop.
Mach Racer, OS .45 FSR, rpm unknown, Master Airscrew 9-7 prop.

FBD. :D

RE: Prop size
 

FBD

What mufflers are on the 500's?

RE: Prop size
 

The muffler on the OS 40FX is off a Magnum .52XLS....it works great.

The muffler on the GMS is the tuned muffler, the same as the Tower .46 tuned muffler.

FBD. :D

RE: Prop size
 

The 9x7 is a great place to start...Depending how slick your airframe is would make a difference here- 9x8 might be good and there are a lot of pylon porps to choose from in between.

Let us know the airplane and maybe we can offer some better info.

RE: Prop size
 

Thanks guys

I am building an airframe around the engine. It is similar to the F3S Speedcup airframes in appearance - the engine and pipe will be cowled so it will be very sleek.

Chris

RE: Prop size
 

I ran the same engine with a UltraThrust tuned muffler and a 9 x 7 worked great. An 8.5 x 9 would have the same load and may be faster on your plane if it is slippery enough.