Hi all
Which prop should I use for a Zenoah G45 pulling a Top Flite 1/5 Mustang around. I am new to gas and I am aware that there are several combiations availabe. I have a Menz 20x10 at the moment.
Thanks for you input. May you take offs equal your landings

A menz is a little big for a G45. I used a 19/10 Menz Ultra and 20/8 Zinger on mine. The 19/10 Menz Ultra was loud but pulled nicely. I had this on a Midwest Extra.
http://www.geistware.com/rcmodeling/...textra300s.htm

A 22x10 would be a good start.
Use my [link=http://mvvs.nl/prop-power-calculator.xls]calculator to try out different rpm/prop combinations[/link]
In there are options to choose your flight field elevation, and prop type. If you have noise restrictions, check out the max rpm for noise.

@ Bob Atkins:
If your son needs the calculations to update his code for ThrustHP, he is welcome to it.

19 x 10 3 blader Menz on my Sist 1/5th scale 190. Nearly the same size and weight plane as yours. Flies it beautifully. Similar results with a Menz 21 x 10 2 blader. Both turn over 6 grand.
video here:

http://media.putfile.com/15th-scale-SisT-Focke-Wulf-190

and here:

http://media.putfile.com/15th-scale-FW190A-8-video-2

If you like the way this plane flies, these are the props that work on it--yours should be very similar. Just get all the cooling to the motor you can.

Pe,

After having heard much about your calculator and seeing it for the first time I had to give it a try, and used my RCIGN1 cnverted G23 engine as the test sample. Using an APC 17 x 6 at 8,900 rpm gave a calculated thrust reading of 13 lbs.

This seems fairly accurate based on the strong flying performance of my 10.3 lb. CG Extra powered by this engine.

You can compare engines, adjust prop specific data, adjust height of your flight field, and it hands out a suggested max rpm for the prop

Thanks for the feedback, because that is what mainly drove the correction factors in the calculations.

You might want to consider the Lowly plastic Master Airscrew. It looks "Scale" on a Mustang, and is much more resistant to surviving mishaps on the field than a wood prop. The 20X10 is perfect @ 7200rpm on the ground. It flew my 20lb P-47 around nicely. I would not suggest the 22x10 in any style prop, it will lug the engine.

I used 6000 rpm static to guestimate the prop size. At these rpm, about 20 lbs thrust is generated by the Zenoah, which would be very fine for that warbird. For 3D I would have used a more free-spinning setup like large, low-pitch prop at 7500 rpm
Gas engines are not lugged down at 6000 rpm, but operate in their best torque range, depending on muffler system used; In addition, the low rpm growl of the gas engine suits a war bird much better. In a dive, the engine will spin up, and the prop may even produce sonic slap, but only if the pilot wants it to.
Maybe an example will illustrate my point of view, and experience which led to it:

As my first gas engine, I used to fly a Quadra for towing. Set up around 8000 rpm, it was very disappointing, and would hardly fly the tow plane. Once propped for 6000 rpm, it was ready to go and do it's thing.
Over the past two decades, rpm at our flying field continued to drop in order to meet noise limits. Amazingly, performance was not impaired, and remained at the same level, or even improved. That could be judged, when an old-style pilot reappeared with his screaming plane. He was not able to mingle with the new generation anymore, and did not pass noise measurements, so the guy was in double trouble.
Conclusion: RPM by itself are a dream, not nesessarily leading to real world performance.

flyrc100 is correct........the 22x10 is best suited for a G-62 or similar

Thanks for the feedback. I seem to have over-estimated the Zenoah power curve.
The 22x10 is a perfect choice for the MVVS 43cc

I loved the menz ultra 20-10 on my G45. Pulled REAL good!~).

HTH

Joe

I have used a Check carbon fiber ( I can't spell the name- stars with an M) 22 10 for years on my G45. It turns it about 6500 and flies my 72" Weeks Special with authority