Sid brings up a good point here, especially for builders that are early on in their projects. I think sometimes we forget that the original KR design tended to be a tail heavy design that was balanced by a large header tank in the nose. That didn't work out so great as it left the pilot landing in an aft CG configuration when low on fuel. 20 years ago, there were lots of stories about guys taking a friend for a ride and experiencing an exciting landing with low fuel and an aft CG at the end of the flight.
With the advent of the -2S design nearly 20 years ago, many of those lessons have been forgotten. But as Sid points out, the wings were essentially moved forward in the -2S to help balance the plane. Additionally, most builders are putting their fuel in the wings to avoid the large CG shift, as well as for other safety reasons. My KR has the extended tail, but was not stretched in the nose (started before the release of the -2S plans). I knew when I was building it that this plane wanted to be tail heavy, so made a concerted effort throughout the build process to move weight forward. I used the Rand Robinson designed O-200 motor mount and a C-85, then eventually an O-200 with the heavy accessories to help keep that weight forward. I also mounted my battery on the front of the firewall. When completed, my CG came out where I wanted it without the need to move more things around or the need for ballast. However, as I said, I made an effort through out the build to move weight forward. As for Sid's checklist of modifications to move the CD forward, I did them all to get the plane right: 1) Move the engine forward (used a longer mount than what was normally used). 2) Hung Battery on the firewall. 3) Installed a heavier engine. That's what it took to get a nicely balanced plane with the shorter KR-2 firewall placement. -Jeff Scott Los Alamos, NM > > John, > If I knew the actual answer to why so tail heavy, I would have fixed that > long ago and would not be having all this discussion. The only plausible > explanation I have is: The designer, Stu Robinson, set the RAF-48 wing > 2-inches farther forward in the stock plans than it should have been. That > is a moot point with the advent of the KR-2S. > I know there are hundreds of KR-2 aircraft flying. It seems they either > have moved the engine forward, hung batteries on the the firewalls, > installed heavier engines and/or fly them onto the runway at 70+ knots and > never ever stall them. That or the builders are not around to tell about > their last flight. > > Sid Wood > Tri-gear KR-2 N6242 N6242 > Mechanicsville, MD, USA > -----------------------------------------------------------------------------
