Since there has been some discussion recently on propellers, I figured I would post the results from my test flight yesterday using John Bouyea's old 56"x56" Sterba propeller, and compare it with my two previous propellers.
Quick Background: Since my engine rebuild this past summer, I have tried three different propellers on my engine. Stock Tricycle KR2S RAF48 airfoil ~650 lbs empty weight Revmaster 2100D (upgraded) - approximately 75-80 HP Prop spinner used (except in Prop #3) Prop #1 Culver 54"x48" (diameter x pitch) Static RPM - 3000 at first, but increases to 3200-3300 by 80 mph Takeoff Roll to 80 mph- 800-900' Climb Rate - 1100-1200 fpm at 100 mph on a 60F-70F day Cruise Speed - 110 knots at 3200-3300 RPM Description: Worked great when I first bought the plane two years ago when the Revmaster only produced 65 HP, however now that I am pulling at least 10 HP more, it is simply not enough prop. However it is a great starting propeller, and if you really want to rev. your engine up and make your engine as sporty as possible, this is a good choice. Prop #2 Sterba 54"x54" Static RPM - 3200-3300 Takeoff Roll to 80 mph - ~1000' Climb Rate - 1000-1100 fpm at 100 mph on a 60F-70F day Cruise Speed - 120 knots at 3200 RPM. Description: Not quite as good of climb as the Culver, but the increase in cruise speed more than makes up for it in my opinion. Still pretty sporty for the most part, and the oil temperatures were much cooler than with the Culver since there is more airflow going into the cowling. Prop #3 - Most recent test Sterba 56"x56", 3" width at the hub; one beast of a propeller. Static RPM: 2800, much lower than I expected. Takeoff Roll to 80 mph - 1000-1100' Climb Rate - Still around 1000 fpm at 100 mph, but at a 50F day vice 60F-70F. Cruise Speed - 122 knots at 2900 RPM (without a spinner). Description - Very unusual performance. At the first run up, I thought "oh wow, this is anemic performance, how is this going to go down?". However I was pleasantly surprised to find that the Takeoff Roll was almost identical as my 54" Sterba, and only about 200' more takeoff roll than the Culver. I still managed to get about 1000 fpm initially, and actually closer to 1100 fpm when I was lighter and lower on fuel. Cruise speed, there was no contest to the other two props; I managed 122 knots at only 2900 RPM WITHOUT a spinner. I figure a spinner would add 1-2, and actually cleaning the airplane would add another 2-3 (yes, my plane is filthy again). That is a potential 125-127 knots, while only sacrificing a small bit of climb rate and takeoff roll! I especially love this propeller because the cruise RPM is much lower at 2900 RPM at 3/4 power (I could only get 3000 RPM with wide open throttle) which saves a lot of wear on the engine internals, and also gives much, MUCH quieter engine operation when compared to the other two propellers. It actually gives a false sense of engine performance, because the engine noise is very minimal (especially if you're used to higher RPM ranges), and it really does make the engine sound weak and anemic, however my airspeed indicator showed otherwise. Bottom Line: If you aren't a sucker for cruise speed and want the most powerful, loudest, sportiest, adrenaline filled airplane you can get, the Culver 54"x48" offers the most RPMs, best acceleration (and takeoff roll), and climb rate. The Sterba 54"x54" offers fairly similar performance to the Culver, while also giving about 10 more knots in cruise and about 10F lower oil temperatures. However if you're like me, and are truly a speed junkie and want the fastest cruising airplane you can get, something bigger and beefier like the 56"x56" might be a decent option IF you are in the 75HP-80HP range. I would not recommend using such a large propeller on a stock 65HP Revmaster (it wouldn't be able to handle it), however it would likely work okay on the Great Plains 2180. Ultimately though, there is only one way to find out..... Funny though, that I prefer this propeller over the Culver, because not too long ago I believe I made a post claiming that I was an adrenaline junkie (which I am), so it would make sense to prefer the Culver over the higher pitched Sterba, but after running the 56"x56", I'll take the cruise speed over the small increase in climb rate.. As usual, feel free to reach out to me with questions. Thank you to John Bouyea for the propeller. And to John Shaffer, if you read this, I am shipping out YOUR propeller today (Friday). V/R Sam Spanovich N6399U 74S, Anacortes WA _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/[email protected]/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to [email protected]
