I agree with Mark that you can only move the firewall forward a couple of inches. I did exactly that as I wanted a little more leg room. When I built the boat and added the 2" forward for legroom, I was dedicated to installing a 2180 VW but then in 1999 at the Lake Barkely Gathering, William Wynne showed up with a Corvair engine mounted on a trailer and after listening to him for most of the day on Saturday, I became a Corvair convert. Then as time went on and I began to learn more and more about how to build an airplane I began to worry about the extra weight of the Corvair sitting 2 inches further out from the CG. Well to make a long story short, I finished the plane and did a W&B with the battery sitting against the forward side of the main spar. The engine it self was as close to the firewall as possible as the nose of my starter is 1/8" off the firewall. The CG calculated in this configuration to be 2.7 inches aft of the forward CG limit fully loaded with pilot and passenger. Not too shabby!!! Then I moved the battery to the firewall and the CG moved forward to 2.3 inches aft of the forward CG limit. Great!!!!!! I left the battery on the firewall and have been flying that way ever since. She is a very stable craft that when trimmed will fly hands off for several minutes. As a matter of fact I HAVE flown 4 minutes and thirty seconds without touching the stick but I was having rudder inputs toward the last couple of minutes to help keep her straight & level. Remember, every KR will be different. Factors such as your turtle deck weight, tail feathers weight, etc.... all make a huge difference whether you will need ballast in the tail or not.
Mark Jones (N886MJ) Wales, WI USA E-mail me at [email protected] Visit my NEW KR-2S CorvAIRCRAFT web site at www.flykr2s.com ----- Original Message ----- From: "Mark Langford" <[email protected]> To: "KRnet" <[email protected]> Sent: Saturday, December 31, 2005 7:54 AM Subject: Re: KR> CG and the KR2S > >> I do not believe that the CG limits were changed for the KR2S from those > already designed for the KR2. They are still the same, which is why the > standard modification is to add one bay forward and one bay rear for the > total stretch.<< > > There's only 2" added to the front of the S as opposed to the KR2, if you > built them both by the RR plans. If you add a whole 'nuther bay to the > front of a KR, you better have a really light engine up there! I know Ed > Blocher added 4" to the front of his KR2S, and I'm not sure how he was > planning on hanging a Corvair up there. > > You can modify a KR in many ways, but adding legroom has its limitations! > Mine is "stock KR" in front of the main spar, and with the Corvair hanging > up there a half an inch from the firewall (and no header tank), my CG is at > the forward end of the range. Not that there's anything wrong with that (it > sure makes it stable), but if I added 2", 4", or another bay, I'd have to > have 30 pounds of lead in the tail (and my backup battery is already back > there). > > Mark Langford, Huntsville, Alabama > see KR2S project N56ML at http://home.hiwaay.net/~langford > email to N56ML "at" hiwaay.net > -------------------------------------------------------------- > > > _______________________________________ > Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp > to UNsubscribe from KRnet, send a message to [email protected] > please see other KRnet info at http://www.krnet.org/info.html
