Ken Rand was an engineer who worked, I believe, for Northrup. His design. His numbers. The rule of thumb is "common practice" in the aviation community, which is conservative. However, how much risk do you want to take 2 miles above the ground?
KR built his VFR KR2 to plans with a 2100 VW engine to have an empty weight of 485 lbs. It can be done, but not if you put any goodies on it. Use a handheld radio and no electrical system. Plan on starting by proping and gravity feed the fuel from the header tank. No alternator, starter, or fuel pump and the Revmaster engine is only 141 lbs (included in the 485 lbs). This means that you can have a 200lb pilot, a 150lb passenger, and 65lbs of fuel (about 2.5 hours) and still be no more than 900 lbs. That leaves 100 lbs of extra fuel, passenger, and/or cargo with you still not exceeding 1000 lbs and a gray out 6 G capability. Put in extras and expect to end up like the typical military hot rod that is turned into a dog. At 485 lbs, the plane can be basically full aerobatic. At 600 lbs, the plane is useful, but not quite the tiger unless the pilot and fuel are light and there is no passenger. At 800 lbs basic, struggle and groan. A bigger engine will boost the plane up, but it will not change the structural limits at all. Of course, if you can guarantee smooth air at all times and never exceed 30 degrees of bank, you can go to the higher weights - but then why a KR2? >how and who came up with this rule? Is there any science behind it? > >Wolfgang >The KR2 is rated at +7/-7 G at a gross of 900lbs. A loose rule of thumb is >to lose 1G per 100 lb thus at 1300lb your're looking at only +3/-3. Larry Severson Fountain Valley, CA 92708 (714) 968-9852 lar...@socal.rr.com
