Mike, I completely agree with you about having a bigger, coarser pitched prop in order to take bigger chunks out of the air. I originally started out with a Culver 54” x 48” (diameter x pitch) propeller, and while it climbed terrific, it’s cruise speed left much to be desired. I now run a Sterba 54” x 54” and it doesn’t climb out quite as good (however I’m talking about maybe a 100-200 fpm loss, not very much at all) but it’s cruise speed is terrific, and was well worth the slight loss in climb performance. I went from nearly 104-105 Knots TAS at 3200-3300 RPM with the culver, to approximately 110+ KTAS (sometimes in the 111-112 range) at 3100-3200 RPM with the Sterba. The 100 RPM may not seem like much, but over the course of an hour flight, that’s a lot less revolutions, and hence wear that the engine experiences.
The lower speed of the engine, combined with the additional thrust of the propeller and the increase in cruise speed, means that there is also a lot more airflow for cooling, going over the cylinder heads, and also through the oil cooler. With the Culver propeller, my oil temperatures were always right at/slightly over the 220F “green” limit on my engine. With the higher pitched Sterba, my oil temperatures have almost never experienced anything over 200F, and that was on an extremely hot 90+F ambient temperature day in Mississippi. Up here in WA, they’re usually in the 140F-160F range, almost too cool. I considered re-sending my propeller back to Ed Sterba to try to have it re-pitched slightly higher to off-set the increase in power, however after re-considering I’m just going to keep the 54”x54” as is, and (hopefully) enjoy the increase in climb performance. In 50-60F ambient temperatures, I currently can get about 700-800 FPM with just myself and half fuel, and about 400-500 FPM with a passenger and full fuel. I’m hoping after these upgrades it can be closer to the 1000 FPM solo, and 600-700 FPM with a passenger. Will post those results once my engine is back on the plane and running. Those pictures are impressive, by the way! V/R Sam Spanovich N6399U 74S, Anacortes WA Sent from Mail for Windows 10 _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. 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 krnet-le...@list.krnet.org
