xray328

My Feedback: (1)

Is a 10x6 too much for an OS .40 FP?

I couldn't get it much past 10K rpm on 10%. It was pulling like crazy at WOT, but 10K just seems a little low. I got it close to 11K but it was too lean.

Another thing, it gets really rough around idle, which I could only get down to 3500 rpm. The whole thing started shaking and vibrating alot and seemd like it was on the verge of quiting, although it didn't. Is that normal? I was thinking it should idle in the 22-2500 range. Whats the deal with the shake? It sounded really rough at idle. Does it have something to do with the low end needle (which I don't know alot about)? The transition seems fine, no hesitation.

iaclmac

I am not sure of your application .... but ... I have used OS 35's, 40's and 46's with 10-6 props for years. They worked well on even the the best stunt controlline planes that use only needle valves for speed adjustments. If it is speed you want ... maybe a better choice of prop would be a 9-7.

broke_n_bummin

10x6 is the break in prop for that engine. 11x5 is what I use on my 40's. 10K with a 10x6 sounds about right with a stock muffler and a spinner.

bigchap

i use an apc 10x6 on my 40 fp and it revs its head off!i am getting 14k on this prop and 10% fuel,they do seem to be fussy on crank end float and mine seems best with 5 thou end float.

red head

10X5, 10 X 6, 10 X 7 all should be fine on a 40 FP. I'm not so sure I'd use an 11 anything on an FP. ENJOY !!! RED

jaka

Hi!
A 10x6 is nearly too small for the OS FP (or LA .40) if you intend to use it in a trainer aircraft.
A much better prop size is a 11x5 or 11x6 APC. Do not use a MA prop...at least not the black ones with white tips ...they don't provide as much speed and pulling power as the APC and they are very noisy.
Use an Enya 3 or a OS 8 glow plug.

Regards!
Jan K
Sweden

sigrun

At risk of pointing out the painfully obvious, check your carb rotor is opening fully allowing maximum effective throat diameter at the choke point. If it is, then consider that all blade shapes aren't equal. If you were using a Master Airscrew square tip or classic, tacho test RPM will be considerably lower than if you are using a curved blade like an APC or Bolly Clubman. If that figure was already using one of them and you can't get past 10k, you've got a problem.

The 40FP will throw a 10 x 6 OK, but it isn't a one size fits all prop for this engine, and flight performance will suffer unless the model is small and light. 5" pitch props work much better with this engine, 10 x 5 or 11 x 5 depending upon application, or a smaller diameter blade with more pitch for speed.

Fresh fuel, 10% nitro and 20% oil should have you peaking better than 10k. How's your glow plug? Right heat range? Quality element? Changed it recently? Try fitting a new O.S. #8 or Enya # 3 or 4 and see how you go. Head gasket/shim in place?

Idle setting won't effect top end. The two are unrelated. The FP has an air bleed carb, but as you mention both the top end performance is lacking and bottom end is lumpy, you might want to give your carb a cleanout 'n overhaul (strip, clean, inspect and reassemble) in case you've got lint, coagulated castor or some other grunge causing an intermittent or partial blockage in there which might be restricting fuel flow.

If it's shaking and firing with a bang, could be pre-igniting or detonating instead of firing. ie: possibly modified port timing, too hot a plug, or carbon incandescence in conjunction with your idle mixture setting.

For quick fix, you could try to just give the spraybar (carb) a cursory clean by reverse flow under pressure and blowing air though it plus fitting a new glow plug and see how you go with one of those recommended props. If that didn't improve things, here's what I'do.

1. Remove, strip, inspect clean the carb and spraybar. Fit new 'o' rings if necessary. Refit.
2. Remove the head and inspect (a) for carbon buildup and (b) gasket in place. Decoke if required, fit gasket if required. Refit and retenshion head.
3. Fit new glow plug. If using with 10% nitro, Id use an O.S. #8, Enya # 4 or equivalent.
4. Loosen and retenshion the backplate bolts (air leak).
5. Fit an APC 10 x 6, get some fresh 10%, fire her up, set the HS needle at full throttle, reduce to sustainable idle, set the low speed IB screw, and see how you go.

PS: FTR I have a 40FP, so I'm not speaking purely hypothetically. They are a reliable PB engine in class. Process of elimination of the above will sort out your problems unless the engine is just plain worn out or damaged. You don't give enough info to ascertain that. If the liner is damaged (chrome chipped off), that'll cause it to run like a dog. So when you dissassemble, you might like to take out the liner and inspect to eliminate that as a probable cause. But I'd try an easy quick carby backflow clean, new plug and prop change and see if that improves thing first.
Good luck.

sigrun

11 x 5 is the perfect prop on an FP for a big draggy trainer like the SIG LT-40.

Gary496

I have a 11x5 on a 40 FP in a Avistar, the FP loves it!


gar