Since I finished my Legacy, I’ve been running 1 prop and only 1 prop. At our club stunt contest last month it took 3rd place. I’m on about flight number 35 as of this afternoon.
This prop works fairly well, so I left it alone until I could get other minor adjustments out of the way first. I also didn’t want to over load the engine, since it only had minimal break in time, the prop has been a “stock” Zinger 12x5 wood, or as some people say, a prop kit. The plane flies fine with this prop, if not a little fast, but great line tension every where. I also noticed a small tendency to wind up in the wind and hit its own wake a lot, even with a light breeze. Another oddity is the way the engine shut off, with several laps of at least a dozen false stops and restarts, more on this later. The engine is really running like a clock now, and fuel economy has come way up, needing only about 4 ounces to do the pattern with time to spare.
So, time to play with props...
I’ve ordered a Bolly 13x4.5 as it is noted elsewhere as a winning combo. But while waiting for the prop to arrive I had decided to try re-working a larger wood Zinger 13x5 prop to a reasonable and less clunky prop, using an old Rev-Up as a model for cleaning it up. I thinned down the trailing edge and took off the blunt square leading edge, plus took off the square tips and swept them back in a clean radius while thinning down the prop as much as I dared with wood to the tips.
After one flight on the 12x5 today, I then flew the reworked 13x5 Zinger. It loaded up the motor noticeably at the same needle setting on the ground. I turned the needle in to see if it had any more to give, but nope, the needle had to be backed off a ¼ turn instead so there was some “reserve” rpm left in the motor. I also noticed the motor became less responsive to the needle on the ground, more flat response. In the air, the plane flew great, the prop acting as a regulator on down legs of maneuvers. No wind up at all but maybe a hair too slow. I may do up another one of these 13x5 Zingers and trim ¼” off it, then compare results. Hitting it's wake was gone as well. Is this really due to the change I made in the prop tips or am I imagining it? I always though wing tip vorteces were the worst offender?
Oh, and the “more on this later” part… The engine shut down MUCH cleaner, with only 2 false stops, and no major speed up in lap times at the end. I guess this is attributed to the motor being run closer to peak and the way in which it draws fuel when loaded????
Any and all input will be appreciated on all aspects of this subject. I find all of this fascinating, and really dig learning what this combo is capable of. Also, any help on how to run the Bolly, or how it will compare to my current experiences? I actually have the Bolly now, but didn’t have a spinner nut/adapter to mount the setup today, dang it! (I'm not hand starting no 4-stroke with a Bolly triple razor!) Will pick one up this week to try next time.
Eric Viglione