Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Prop size

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Old 07-04-2007, 01:26 AM
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indoorff
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Default 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
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Old 07-04-2007, 02:43 AM
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Default RE: Prop size

need to know the plane....
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Old 07-04-2007, 07:52 AM
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Default 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.
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Old 07-04-2007, 08:17 AM
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FBD

What mufflers are on the 500's?
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Old 07-04-2007, 08:33 AM
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Default 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.
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Old 07-04-2007, 11:43 AM
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Default 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.
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Old 07-04-2007, 01:41 PM
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Default 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
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Old 07-04-2007, 07:10 PM
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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.
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