Again I recommend taking a look at the downloadable spreadsheet here http://www.aircraftdesign.com/sadfh.html. It allows you to put in all the parameters of the plane and then do tweaking to see what the performance improvements will be. I have a KR set up in the spreadsheet and I was going to do a plot of performance figures for a KR with a constant drag with different engines installed, but life keeps getting in the way.
The book is also excellent for anyone doing aircraft design or just looking at tweaking an existing design. I have dozens of aircraft design books and this one is by far the most usefull. Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Colin Rainey Sent: Friday, March 16, 2007 1:15 AM To: KRnet Subject: KR> Speed vs. HP "You will probably see 250 mph with pants and 200 hp" It doesn't work like that in the air, like adding HP to a car and expecting speed increases. Mark's climb rate will definitely get a BIG jump, possibly the best in the bunch so far, if he can match a prop to it. But increasing HP does little to increase cruise or top speed after a point, especially for planes flying at or near 200 mph and up. Back a few months ago we discussed this at length, and all who have studied on this have agreed; more is gained by drag reduction than HP increase. To double the speed, drag is increased by 4 times. To get 250 mph from a KR2S, one needs to lose the front wheel, or work very hard on a completely aerodynamically faired leg, not just a cover, and the same holds true for the mains, and their legs. Now anything sticking out in the breeze becomes important; so that round strobe Mark has will have an impact at these speeds; any antennae should have a fairing, not just be left round; wing root fairings need special attention due to this area relating heavily to the highest lift area on the wing so also potentially the highest drag area; cowl flap(s) become a consideration to reduce drag; greater rake to the vertical stab, etc... "Speed with Economy" is definitely the bible here... There are a lot of pluses to using the Mazda 13B in aircraft with firewalls designed for their weight. But without alot of reinforcing, similar to the refit rebuild that the KR360 got, I think the Mazda is too heavy, and high output. Better to use a different engine with slightly less HP but just as much torque after the re-drive and stay with what your firewall/airframe can handle... JMHO... Colin Rainey brokerpi...@bellsouth.net N96TA _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net Post photos, introductions, and For Sale items to http://www.kr2forum.com/phpBB2/index.php please see other KRnet info at http://www.krnet.org/info.html
