Mike's answer here is the first to really hint at the solution for speed. Horsepower is great for climb, but if you want to go fast, work on drag reduction. If you want to go even faster, work on weight reduction. When I first finished my KR, I was pretty disappointed in the performance. I couldn't even keep up with a Cherokee 235, and had to struggle to outrun a Cherokee 180. I've put a lot study, time, and effort into drag reduction on my KR. Today, my KR is 80# heavier and roughly 40 mph faster than it was when I first flew it 22 years ago, and I find that I can usually outrun the Mooneys and SR-20 Cirrus guys. A 40 mph improvement is not an insignificant number. Additionally, reduced drag also requires less HP for level flight resulting in more excess HP, which equals better climb performance.
Drag reduction takes work. What I found over the years is that every little bit helps. Keep at it and pretty soon all those little things that make you 2 or 3 mph start adding up and you suddenly find your plane is will exceed your expectations. With every round of drag reduction I have done on my plane, I come away with more ideas for how to continue to improve it. I have more ideas in mind now. I'm just not sure I still have the ambition to execute them. Longer wings won't necessarily make the plane fly slower. Flat plate drag will go up marginally, but the induced drag of the airfoil may drop off significantly. In fact, the longer wing may significantly increase the cruise speed depending on the altitude and load. However, when you start lengthening the wings, now you need to re-evaluate the wing structure for the additional leverage caused by the longer wing. The KR you guys are remembering from Red Oak was a KR-360, which had a 180 HP IO-360 mounted to the nose. But the only real resemblance that plane had to a KR is that it also had a wooden airframe and spars. The fabrication was creative and the workmanship was really nice. But we haven't heard from him since. I can only think of one KR that had an O-320 mounted up front. It was destroyed on it's second flight with the larger engine, even though the pilot was an experienced builder and KR Pilot. I know the problem was not CG related as his O-320 weighed in exactly the same as the O-235 he was replacing. I can't opin whether the structural capabilities have reached the end of it's capabilities or not, or that an O-320 won't be a fine engine on a KR as I don't have the engineering background to do the calculations. But do keep in mind the intended VNE of the plane, which can be easily exceeded with an O-200 or Corvair, and how much weight we are putting on these airframes that were originally designed to fly with VWs. At some point in time, we will start to push the margins of safety if we haven't already done so. 22 years ago when I showed up at the KR Gathering with my new Continental powered, "stretched" KR, the old guard was convinced that my plane already exceeded what the plane was intended to be, and were pretty unanimous in that they didn't like it. My how things have changed in the last 22 years. And are likely to continue to change in the future. -Jeff Scott Cherokee Village, AR > Sent: Thursday, April 11, 2019 at 8:45 PM > From: "Mike Sylvester via KRnet" <[email protected]> > To: "Craig Williams" <[email protected]>, KRnet <[email protected]> > Cc: "Mike Sylvester" <[email protected]> > Subject: Re: KR> Roger Baalmans plane > > I put the wheel pants back on N236MS and found some clear sky a few days ago. > WOT at 3000 level she pulls up to 175 mph indicated. That's with a fresh > O-200 with a Sterba 60x68. Your results may vary. > > Mike Sylvester > kr2s builder > Birmingham,AL. > > Cell no.205-966-3854 > > ________________________________ > From: KRnet <[email protected]> on behalf of Craig Williams via > KRnet <[email protected]> > Sent: Thursday, April 11, 2019 8:20 PM > To: KRnet > Cc: Craig Williams; Chris Matheny > Subject: Re: KR> Roger Baalmans plane > > I can give you an opinion from a guy who has been looking for the best of the > best options and what I am seeing with N886MJ. > > First, Larry is right. In my opinion this design has been pushed to its > limit. At this point most everything has been tried and the best options are > being used. If you build light and go as big as safely possible on the > engine (which I believe is ~125hp), you can achieve a 1300MGW and 150mph > cruise airplane(in a Tailwheel (TW) configuration). As soon as you try to > increase the MGW with more wing area your gonna slow the airplane because of > weight and drag and then your gonna need that 150hp to go 150. I have > actually changed engines on my build 4 times. First a Corvair, then an > O-200, then and O-235 and now I am back to a Corvair. Luckily I pretty much > broke even on all those engines. I am now headed twords the 120hp Corvair > with my TW build. My current 2S is a trigear and I am close to hitting that > brick wall with the 100hp Corvair in it. My top IAS is 150 at 1200lbs GW. I > have a few more mods to complete but I suspect I wont see much more speed. > Maybe 10 more if I am really, really lucky. I settled on the KR many, many > years ago because I wanted a 150mph cruise. It's looking now like I might > just get there with the 120hp and the TW configuration on my build plane. > Here is a video from a test I did a few days ago after I put the wheel > fairings on. Best I saw was 145 IAS @ WOT and about 134 in cruise so I am a > bit disappointed as I don't see this airplane getting to 150 cruise without > me and the plane each loosing 100 lbs. > > https://youtu.be/759DgW50A7U > > Craig > N886MJ > N232WJ under construction. > > > and the o-235 engine in it. Anything you would do different or > > change? I'll be starting a build this summer an want to do a 26' wing with > > the longer fuselage and wider tail and use a 150hp engine I'm developing > > now. Thinking 1300 max load. I'm curious of the performance you're getting > > with the 125hp engine??? Thanks > _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/[email protected]/. 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 [email protected]
