Sam, thanks for your lessons. Very helpful to understand more the storys about speed and climb performance. My question to you is...wat was your takeoff weight with the test?
Thanks Stef > Op 23 oktober 2020 om 9:13 schreef Samuel Spanovich via KRnet > <[email protected]>: > > > 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] Steph and his dad are building the KR-2S see [http://www.masttotaalconcept.nl/kr2](http://www.masttotaalconcept.nl/kr2) _______________________________________________ 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]
