---------------------------------------------------------- Kitfox-List Digest Archive --- Total Messages Posted Wed 02/24/16: 5 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:56 AM - 912 Prop (jareds) 2. 09:54 AM - Re: 912 Prop (Pete Christensen) 3. 12:40 PM - Re: 912 Prop (Guy Buchanan) 4. 06:18 PM - 912 fuel return line () 5. 06:58 PM - Re: 912 fuel return line (Guy Buchanan) ________________________________ Message 1 _____________________________________ Time: 05:56:47 AM PST US From: jareds Subject: Kitfox-List: 912 Prop Have my choice between props. Just wondering which prop is best for a 912 and prefer speed over climb. Is there some place to call that would know? ________________________________ Message 2 _____________________________________ Time: 09:54:30 AM PST US Subject: Re: Kitfox-List: 912 Prop From: Pete Christensen I use an IVO ground adjustable. Pete On 2/24/2016 7:55 AM, jareds wrote: > Have my choice between props. > Just wondering which prop is best for a 912 and prefer speed over climb. > Is there some place to call that would know? ________________________________ Message 3 _____________________________________ Time: 12:40:42 PM PST US Subject: Re: Kitfox-List: 912 Prop From: Guy Buchanan Jared, You're showing some weird props there. The square tips look like they might have come off a drone. I'll say, in general, that the longer a prop is the more "efficient" it is because of lower induced drag. (Think: glider wings.) The limitation on length is: 1) dragging it on the ground; and 2) running the tips supersonic. In general, with a 912, the prop RPM is so low you don't have to worry about #2 because #1 limits. Big /however /for the 912 is the mass inertia limitation. Since inertia varies as the mass times distance from the hub squared you might hit it with a really long 2-blade. Second consideration is number of blades. In general, the fewer the blades the more efficient the prop. (Less dirty air.) However, many say that shorter, multi-blade props climb better, whereas longer, fewer blade props cruise faster. Not sure why, but I suspect it's because people over-prop with multi-blade props and subsequently run them flatter, giving better climb performance. (Prop thrust varies as the RPM squared, diameter ^3.5, and square root of pitch. Citation ) As to brand, I've seen several prop comparisons on 912s and have never seen an appreciable performance difference between any. (Prop design was very nearly standardized by the time of the Wright brothers.) This excludes the radical trans-sonic stuff more recently designed, none of which applies to our vehicles. On 2/24/2016 5:55 AM, jareds wrote: > Have my choice between props. > Just wondering which prop is best for a 912 and prefer speed over climb. > Is there some place to call that would know? ________________________________ Message 4 _____________________________________ Time: 06:18:43 PM PST US From: Subject: Kitfox-List: 912 fuel return line In finishing up my KFIV after 24 years of building, I noticed that the more recent Rotax 912 installation manuals call for a fuel line running from the fuel manifold or "Y" on the engine, through a restrictor then back to the fuel tank. I've been told this is to help prevent vapor lock. 1. Is that the way you guys have set up your fuel system? 2. Should this return line go to the wing tanks or to the header tank? thanks for your help, Clem Wehner KFIV- 912, # 1461 (24 years building and almost done) Lawton, OK ________________________________ Message 5 _____________________________________ Time: 06:58:58 PM PST US Subject: Re: Kitfox-List: 912 fuel return line From: Guy Buchanan On 2/24/2016 6:17 PM, clemwehner@sbcglobal.net wrote: > 1. Is that the way you guys have set up your fuel system? No. I ignored it. Most Kitfoxes do. > 2. Should this return line go to the wing tanks or to the header tank? I think it's supposed to go to a place with minimal back pressure, thus the wing tank. Guy Buchanan Ramona, CA Kitfox IV-1200 / 912-S / Warp 3cs / 500 hrs. flying again. 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