Great information. Thanks for the feedback and keep it coming. Brian Kraut Engineering Alternatives, Inc. www.engalt.com
-----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of jscott.pi...@juno.com Sent: Sunday, September 25, 2005 12:16 AM To: kr...@mylist.net Subject: Re: KR> Jeff Scott's Modifications - Early Flight test results Here's my analysis of the changes I have implemented on my KR over the last 4 months following the FAA's mandated 5 hours of test flying. Clearly I'm still a long ways from being done testing, and I'm not done modifying, although I am a bit burned out on it for now. The modifications to the horozontal stab and elevator turned out to have very positive results. The challenge is how to best quantify the results into something that makes sense. I'll start with the new horizontal stab and elevator. Incidence: In building the new stab, I attempted to correct the incidence. I need some in flight photos to know how close I got it, but from the test flight results, I would say it is very close, although a touch more nose down would probably have resolved my trim problems. More on that later. Stability: The larger 8 foot span horizontal stab is absolutely fabulous. The best example I can give is a comparison that was easy to make. As I was flying home from the SWRFI in May, after about 3 hours in the seat my butt was numb, so I let lose of the stick and used my hands to scootch up in the seat a bit. That movement with me at 270# caused a quick 1/2G negative on the G-meter before all the stuff from my right seat and lap came raining back down on me from the canopy. I have done the same thing several times in the last few hours of test flying. The plane simply doesn't change in pitch in any noticeable way. The stability hands off is abloslutely rock solid. Feel: There have been comments in the past that by building a larger stab to change the stability, the plane would lose it's sporty feel. I can easily put that rumor to rest. The elevator is every bit as quick as it ever was, although it does have a bit more aerodynamic load on it, so gives a bit more feedback through the stick. Credit Mark Langford for the stab/elevator design and for posting it to his web page. My recommendation is to use it. It works... very well. I think I can truthfully say that mine is the only KR to have flown with both tails and I think my preference is clear. Wing Root Fairings: The wing root fairings were created for two purposes. #1 was to reduce drag by cleaning up the air flow at the wing root junction with the fuselage. #2 was to hide the actuator linkage to the new flaps. Despite having added a significant amount of weight to the plane with all the mods, it has picked up some speed as well. Not a lot. The small amount of testing I have done so far has shown a 4 - 7 mph increase in indicated airspeed at 9000'. Density altitude was roughly 11,000' during testing. Full throttle straight and level at 9000' used to yield a top indicated airspeed of 143 mph. This week I have seen it top out from 147 - 150 mph IAS at 9000' in various configurations. Flaps: The flaps are an absolutely fabulous addition to the plane. My wing stub flaps are 11 1/2 x 25" per side and deploy to 37 degrees. All I can say is WOW! I can turn final at 160 indicated, pull the nose up, reduce power and drop the flaps and this plane will drop out of the sky like a Cessna. No more planning the approach from 10 miles out to try to get down. I can either reduce flaps or add power to have complete control of the descent. No more gliding half the runway in ground effect while the plane slowly bleeds off speed. With this much deployable drag, I can drop the plane on a spot. A performance requirement that I placed on the flaps was that the plane had to be able to climb with full flaps. I took off with the Density Altitude at 9300' and sluggishly climbed from 7200' (airport altitude) through 8000'. Rudder: In my opinion, the larger rudder has also enhanced the controlability of the plane. Between the larger rudder and the drag generated by the flaps, crosswind landings have changed from a real wrestling match to a non-event. Elevator Trim: I designed my own elevator trim control using biasing springs and the original MAC trim servo out of the old tail. This piece is unique to the geometry of my elevator control system. (see the last two entries under http://www.vla.com/jscott/kr/index.htm) I have spent the bulk of my test flying time tuning the trim. I do have it to a functional level, but not optimal. The issue seems to be that at speed the aerodynamic loads on the elevator is sufficient enough that the biasing spring is unable to keep the nose down past roughly 145 mph indicated. This works OK for cruise at 9000', but may not work so well when I get the plane to a low altitude (which is rare for me!). I'm going to be tuning on the trim control for a while yet. The challenge is to get enough spring pressure to trim the elevator while keeping the springs light enough to not ruin the light feel of the plane. Since the required test time is already flown off the plane, in all likelyhood I will have it at Copperstate again this year despite it's unfinished state. Jeff Scott N1213W _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
