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

WHats the best prop for a OS.40MAXFP Engine?

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Old 11-25-2008, 01:01 PM
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blhollo2
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Default WHats the best prop for a OS.40MAXFP Engine?

If im trying to get fast speeds/Rpms out of a .40 engine what prop size do I need?
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Old 11-25-2008, 01:24 PM
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Default RE: WHats the best prop for a OS.40MAXFP Engine?

Hi blhollo2 ,

As a plain bearing engine, the 40FP is not the greatest powerhouse but is a great, lightweight, sport engine. I have used it in a control-line racing class and on low nitro fuel (5%) and 20% oil, it liked a 9x6.5 APC or a 9.5x6 Bolly. A 9x7 may work fine too. As a matter of interest I now have a Davis Diesel head on it (but unrun due to lack of ether where I live/work), that according to adverts, jacks up the torque well and could probably run 9x7 or 9x8.

Good luck!
P
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Old 11-25-2008, 02:30 PM
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Default RE: WHats the best prop for a OS.40MAXFP Engine?

Hi partner. The FP is a great sport engine, but not a very fast motor (also is a plain bearing one). To obtain the maximum power from it try a scimitar prop design like APC or similar props ballanced carefully. Try one that give you some 13.000/13.500 rpm in the air because this engine dont have the power curve in the high rpm. For speed purpose i would try from 9X6 to 9X8, testing each in the model. For normal sport i would try a 10X6 or 11X5 for trainer duties, the same for scale models. This engine haves great torque at lower rpm and will serve you better as a sport engine. You could also try hotter fuels with more nitro in search for more speed, and in general OS engines run fine with nitrated fuels up to 20%, as we see in our flying field.. (reduce compression ratio if you note detonation or plug blowing, also reduce the prop load in this case)
enclosed a pic from my 40 FP
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Old 11-25-2008, 05:44 PM
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Default RE: WHats the best prop for a OS.40MAXFP Engine?


ORIGINAL: stg61abc
For speed purpose i would try from 9X6 to 9X8, testing each in the model. For normal sport i would try a 10X6 or 11X5 for trainer duties, the same for scale models.
I'd ditto that. I would start with the 9-6, but that's just me. I've flown 9-6 APC's on a couple of different models and middle of the road .40's and the performance was decent. You should try the range as suggested above.

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Old 11-25-2008, 08:29 PM
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Default RE: WHats the best prop for a OS.40MAXFP Engine?

Take advantage of the light weight and put this engine on a small plane. I've seen this engine and the LA .40 go pretty good on sub 400 square inch flying wings with 8x7 props.
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