OS 50sx prop size
05-11-2005, 09:46 PM
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OS 50sx prop size
I was advised that an APC 12.25x3.75 prop would be appropriate on my Katana GS 40 powered by an OS 50sx. The engine tacks at 11500 rpm, but the engine itself has less than half a gallon through it. Is 11500 rpm enough for this prop? thx. Jim
05-12-2005, 05:05 PM
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RE: OS 50sx prop size
That's way too low. With stock muffler, you should get at least 13000 rpm with this prop. With tuned muffler, like Tower 46 muffler or Rossi 46 black tuned muffler, people are getting 14k.
05-22-2005, 03:27 PM
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RE: OS 50sx prop size
I have a 40 size MOJO which is VERY close to your katana. They should weigh about the same and are intended for no holds-bared 3D. On my mojo I run 3 props depending on what I can get.
I prefer APC prop because I hit the ground a lot and even when the get shorter I just keep flying for the day.
My favorite APC's are
1. 12 x 4
2. 12.25 x 3.75
3. 11 x 4
If they spool up a little slower than you would like try a master airsrew or preferably a wood prop like a 12 x 4. The wood props spin up MUCH faster although they give a little less thrust in the end I think, from flexing.
Hope it helps,
Dave
Hey try the tower hobbies .46 muffler, its a gem for 15.00 bucks
I prefer APC prop because I hit the ground a lot and even when the get shorter I just keep flying for the day.
My favorite APC's are
1. 12 x 4
2. 12.25 x 3.75
3. 11 x 4
If they spool up a little slower than you would like try a master airsrew or preferably a wood prop like a 12 x 4. The wood props spin up MUCH faster although they give a little less thrust in the end I think, from flexing.
Hope it helps,
Dave
Hey try the tower hobbies .46 muffler, its a gem for 15.00 bucks
05-26-2006, 11:54 PM
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RE: OS 50sx prop size
ORIGINAL: kf6gub
I was advised that an APC 12.25x3.75 prop would be appropriate on my Katana GS 40 powered by an OS 50sx. The engine tacks at 11500 rpm, but the engine itself has less than half a gallon through it. Is 11500 rpm enough for this prop? thx. Jim
I was advised that an APC 12.25x3.75 prop would be appropriate on my Katana GS 40 powered by an OS 50sx. The engine tacks at 11500 rpm, but the engine itself has less than half a gallon through it. Is 11500 rpm enough for this prop? thx. Jim
Jim, that's a little lower than it should be. Like the guys are saying, 13k+ is more the norm for that engine/prop combo. Does the muffler still have the baffle installed? Install a Tower muffler - this should be worth at least 500 rpm on its own. The .50 SX also responds well to a little nitro, with good gains in power up to about 15%.
Good luck and report back on progress.
05-28-2006, 05:30 PM
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RE: OS 50sx prop size
I build a moosecan for a friend of mine for his OS.50SX he was getting 15,000 with a 12x4. It would pull a 5lb profile out of sight. It has so much power the whole fuselage would flutter on full power uplines. and yes the prop was balanced.
05-28-2006, 05:48 PM
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RE: OS 50sx prop size
If the engine has less then a half gallon through it I would give it some time most engines need a couple gallons before the really wake up
05-28-2006, 06:32 PM
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RE: OS 50sx prop size
As some have pointed out, this is a ringed engine. It's just not broken in yet. Less than 1/2gal is not even half way through the break-in process for ringed engines. Run it slightly rich for no less than a full gallon of fuel. Don't try and get max rpm until you do that. Then, very gradually lean it during your second gallon of fuel. It will get there.
05-28-2006, 08:06 PM
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RE: OS 50sx prop size
Oh, my 13,100 tach reading is still within the first gallon of fuel. I am still running it rich, about 1.8 - 1.9 revolutions on the needle.
