gary van dyke

My Feedback: (9)

I have been running a YS140L in an aerobatic biplane with an APC 18-10. I am assembling a fun-fly/3D type plane. I am considering an APC 18-8W or 18-6W prop. Does anyone know which prop is the better choice and/or will turn comparible rpms to the 18-10. I have no experience with the wide props so any input would be greatly appreciated. Thanks in advance.

Dean Wise

what kind of RPM are you getting with those props?

JohnW

My Feedback: (6)

18x10 seems a bit stiff for the L. What RPM do you see with that prop?

For funfly types, I'd put on a high diameter low pitch prop, low mass and probably with a wide blade. The diameter will increase thrust, pitch must go down to compensate for the extra load of a large diameter. You will probably want the maximum diameter possible and still have enough pitch to safely fly the plane. Depending upon the stall speed of the plane, I'd say you probably don't want to go below a 6 pitch with that engine, assuming ~8500 rpm, which would be ~50MPH. The wide blade should be more efficient, especially at lower RPMs because it will operate at a higher Reynolds number compared to a slimmer prop at the same RPM... at least that's the theory. I'd also try for a low mass prop to increase engine response, less mass = quicker spool up. The APC 18" props tend to be quite heavy. I don't know for sure in that size range, but I'd think a Mejzlik prop would be lighter.

Big Mike

Gary

I have a 140DZ on a Sig Cap 231ex. From what the Pattern guys at our field say the 140L has about the same top end power as the DZ but the DZ has more midrange torque and spools up faster. Anyway, with the Cap weighing somewhere around 11lbs. and running CP 30% heli fuel I would have to say my personal preference for performance (especially vertical) is the APC 18x6W. It gives incredible acceleration and responce. I haven't put a tach on it yet (after 2 gal of fuel) but I think that it might be over revvving if I just go WOT on the straight and level but I rarely do that anyway. At 3/4 throttle the plane is moving right along (I'm guessing somewhere around 80 mph).

I have used an APC 18x8W also and feel it is easier on the engine but is lacking a little in the acceleration department. Not slow by any means, it's still accelerates really well but it's not the beast it is with the 18x6W. It's like a '66 427 Corvette with 3.36 gears vs the same car with 4.11 gears.

So there you have my opinion. If you want a beast go with the 18x6W. If you want something more manageable and easier on the engine go with the bigger pitch. I'd say try them both and see which one suits your style. I don't think you'll be unhappy with either one.

Good Luck

Boss248

I have kind of the same question but the 140 I have was the first model 140 YS produced, problem for me is ground clearence. Can I swing something in the 16" size and if so what pitch and rpm would be recommended?? I am also burning 30% chopper fuel. The plane is the W.M. Zen 90...I know...I know..that's to much motor but I was surprized to find that even with the 140 in the nose I had to mount an 1800 mah battery under the fuel tank location. The plane handles the 140 real well but it is real hard on 17" props.

seanychen

My Feedback: (4)

If you have the ground clearance and the extra cash, you may try the Bolly 19x6 from Desert Aircraft.

JohnW

My Feedback: (6)

Boss248: I you are having ground clearance issues, you might try a 3 bladed prop. If you are using a 16" 2-blade now, I'd try either a 15" or 14" 3-blade at the same pitch. I'm not for sure on the early 140's, but my guess is you want to be in the 8K-9K range for RPM, reguardless of which prop you select.

BigMike: I have both the L's and Dingos... FYI, the Dingo has a LOT more power at the high end than the L's.

gary van dyke

My Feedback: (9)

John and Dean:
If I remember correctly I was turning about 8300 on the 18-10 running a little rich on 20% nitro.
Thanks everyone for your advice!

JohnW

My Feedback: (6)

Gary: I think you may find that a wide blade 18x6 will load the engine about the same as that narrow blade 18x10. I'd let the engine wrap up a bit more, say to 8600-8800 RPM. Try a 18x6W and let us know how you like it.

gary van dyke

My Feedback: (9)

John:
Thanks for your input. I was leaning toward the idea of trying the 18-6w first. After rereading all the replies I have decided to go that route. It may be awhile before I get this plane plane ready to go but I'll let you know the results. Thanks again.

Frankenthumb

My Feedback: (2)

John, sorry to dig up such an old post, but it seems like you're a YS guy and I'm wondering if you have any experience with the 140 Sport? I'm looking to do some freestyle/IMAC with an 11 pound plane and I want a decent prop for it.

Thanks!

OldRookie

My Feedback: (13)

What type of motor mount is best for the 140L?
I thought that all the 140's are to be run on soft mounts.

Greg