Steve Goosic wrote: >>Since my wings are already built (RAF48), do I extend both wing spars or is it possible to add additional foam to the existing wing end and shape to form? Also, how much further do the wings need to be extended?<<
See http://www.n56ml.com/900hour/ for how I extended my KR2S wings 14". Also, below is something I posted to KRnet at about the same timeregarding the same question. I fished this out of the archive, at http://tugantek.com/archmailv2-kr/search. There's plenty more on this subject there as well, but below is a pretty good summary. Bottom line is that the plane has to be very light (like same KR2 gross weight) to get away with adding only a few inches to each wing. Subject: Re: KR> longer wing panels, etc. From: Mark Langford <n56ml at hiwaay.net> List-Post: krnet@list.krnet.org Date: Sat Jul 10 19:37:54 MDT 2010 Tom Garner wrote: > My hope is that some young bright engineer will come up with a wing design > to make KR2-s comply with LSA requirements. Outer wing panels of > course, not a total rebuild. That's not as difficult as it sounds. You almost don't need any math to get there. If you believe the stall speed numbers published for the KR2, about all you have to do is increase wing area by the same percentage you want to drop the stall speed to get under LSA requirements. Of course your gross weight may be higher, so you've got to do that twice. And if the published numbers are optimistic, you might build in another fudge factor. And then there's just spending an evening doing homework by reading stuff like John Roncz's ""Designing Your Homebuilt" from Feb 1990 Sport Aviation magazine or "Sizing Your Wings", or something similar. His spreadsheets are floating around on the web also, which make it even easier. Coefficient of lift is given in info on one of the links from the AS504x webpage at http://www.krnet.org/as504x/ . There are several variables involved in upsizing the wings for YOUR airplane, so rather than have somebody do the work for you, I'd recommend doing it yourself for your airplane. There's a basic equation the FAA might use to give your design a "reasonable test" for stall speed, and all you have to do is meet that (you'll find it in the Roncz works). And I'd name the airplane something other than a KR also, because the KR2 and KR2S already have "hard" stall speed numbers published by the manufacturer, so to keep from muddying the water, call your plane something other than a KR. But the bottom line is that you could almost guess that an extra few inches longer than the Diehl wing would get you into LSA territory. You just need to be able to whip out that calculation when the FAA guy asks for it. But you might want to use the 18% AS5048 airfoil to get deeper and therefore stronger spars in the deal. And if the plane's already been registered as an experimental, it's too late to call it an LSA, although I believe it can still be flown as an LSA. The other part of that is the max speed, so you'd need a small engine or a fine-pitched prop to keep from exceeding it. Gotta get back to the hangar for another round with the vinyl ester fuel tank... _________________________ Mark Langford ML at N56ML.com http://www.n56ml.com
