Pelle Gris

Hi all...

This last week I had my first go at towing gliders.
The club I belong to each year holds an R/C summercamp, and this year I had got my hands on an old towplane. Weighing in at 20Lbs dry and powered by a G-62 I had no problem towing any of the gliders present, from an 98in Plilatus to an 196in 20Lbs homegrown full glass ship.

During the week I crunched the original APC 22x10 prop and changed to an APC 24x8 and noticed an increase in "towing power". After the first struggeling seconds towing a 20Lbs glider of the ground without a wheel installed, I found that I could easily throttle back to 50% power and still gain altitude quickly. That got me thinking that maybe I could move up to an even bigger prop like an APC 26x8 and thereby lower the noise generated by the prop and maybe even get more pulling power?

At the present I get 7400rpm on the 22x10 and 7100rpm on the 24x8 (new engine...about 2gal). The 10in pitch provides more than enough speed as does the 8in.
Soooo.... anyone got any ideas about the performance of an 26x8 compared to the other props? Maybe even expected rpmīs?

The prize of a prop that large makes me quite reluctant to just go out and buy one, in the event that it will decrease the tow performance...

TIA & Best Regards
Tinus Nielsen
Denmark

Ben Diss

My Feedback: (23)

If you have the ground clearance to run a 26x8, I would say that would be the way to go. Yes, it will slow the motor down and it will bring it back into it's maximum torque RPM. 7,000 is a little high (even though it's still safe). It will pull much stronger with a 26x8.

-Ben

nIgHthAwK17

It seems that with the 22x10, the engine was over-revving, aka "on the backside of the power curve." You said that you noticed a significant power increase by increasing the diameter of the prop and decreasing the pitch. This is also concurrent with being on the backside of the power curve of any piston engine. My past (and brief) experience with a G-62 was that the prime RPM was not near that high. As Ben said, if you've got the clearance, go with the bigger prop and stay at the 8 pitch.

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Pelle Gris

Thanks to you both for replying... I have asked the same question in the "giant engines" forum, to get some more opinions. But based on your posts I guess I will have to dig up the cash and get that 26x8....

Safe landings to you all...

Tinus Nielsen
Denmark