Hi Barry, the sizes on the Jabiru-Sides is for the "normal" airplanes... ;-) The diameter is limited by the "mach-speed"! Generaly is: if the diameter is bigger, the result of the prop is better... but if the tipps of the prop is "cruising" on Mach1 , the prop will be broken! So Jabiru take the diameter of the prop to the max by the 3300rpm. For this informations show the side from Ed Sherpa : www.greatplainsas.com/edrules.html On this side you can see all informations about propconfiguration. If you want to take the optimal prop for your plane, do this: 1. calculate the pitch for your max. speed 2. cut the tips of the prop (beginning from the max diameter), to have the optimal static run for your engine and form the tips. Don't forget the weights of the plates must be equal! 3. check this configuration in fly (for cruise-rpm/max-rpm), and if it will not be the optimum, do it once more... ;-) with best regards Juergen PS: My english is not the best, but I hope you understand, what I mean...
Am Donnerstag, 19. August 2004 03:50 schrieb Barry Kruyssen: > Hi All, > > Well the decision has been made (I can sleep tonight, though much poorer > now). I'm scrapping the Hirth and replacing it with a 85hp Jabiru engine > (the 120hp engine is expensive and too heavy which would require a major > rework) > > At the same time I'm replacing the retractable under carriage with the > Jabiru tail dragger gear, wheels, brakes and wheel spats, all for $2500 > Australian. There are 2 reasons to upgrade: 1. My retractable gear is fixed > down and looks like two barn doors in the slip stream, 2. I need the extra > height and bigger wheels as I'm operating from a grass strip and Jabiru > recommends a 60" diameter prop, which brings me to my next question. > (remember I know nothing about propping an aircraft) > > The engine and prop should perform as follows: > static run up 2700 to 2900 (2800rpm 74hp 150ft lbs torque) > cruise 2750 to 3000 (3000rpm 81hp 140ft lbs torque) any lower rpm and it > really sucks fuel max 3300 (85hp 138ft lbs torque) > > Jabiru props come in the following sizes for their Jabiru aircraft (see > http://www.jabiru.net.au ) dia x pitch > 60" x 42" recommended for fast climb > 60" x 44" recommended for slower climb but 5kts + speed > 60" x 48" for their 6 cylinder aircraft > 60" x 53" for their 6 cylinder aircraft > > Which of the above would be best for a standard KR2? > > Thanks > Barry > > > ----- Original Message ----- > > So I'm thinking of scrapping the Hirth and putting in a Jabiru 85hp @ > 60kg or 120hp @ 81kg. My Hirth is/was 92hp @ 52kg. The smaller engine is > preferable as the weight will be easier to deal with, But we all want > HORSEPOWER. > > _______________________________________ > to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net > please see other KRnet info at http://www.krnet.org/info.html
