Dan Heath wrote: > This got me wondering, so I went to my W&B Spread sheet to check. From full > to 45 min reserve, mine moves .856" aft. Header tank only, 12 gallons. Now > that does not jive with Marks numbers, but that is what my spread sheet says > from 12 to 3 gallons.
Dan, you made me drag out my spreadsheet as well. I was wrong about two things. I said my shift from full to empty was a little over an inch at gross weight. It's actually exactly an inch from full fuel to totally empty, and it moves aft. I was also wrong about header tanks. I said they shifted 2-3 times what my wing tanks did, and the real answer is 1.5" further aft, but still in the wrong direction. This is what happens if you move my 15 gallons of wing tank fuel to the same location my header tank would have been. So if the CGs are at the same location at takeoff, I land 1" forward with empty wing tanks, or 1.5" aft with an empty header tank, for a difference of 2.5" in CG shift between the two scenarios. Maybe that's not significant to some, but it is almost half of the allowable 6" range, so I think it is important, especially when carrying passengers. Obviously, there are a lot of variables here, such as the fact that my KR2S would put my header tank 2" further forward than your KR2 tank, and there's some variablity in tank design and location. Even airfoil is a consideration, since the ASxx airfoil shape helps concentrate the weight closer to the front spar (another bonus!). This reminds me that I've been thinking about redoing my weight and balance, so when I put the new 3100cc engine in I'll update it. Mark Langford, Huntsville, Alabama see KR2S project N56ML at http://home.hiwaay.net/~langford email to N56ML "at" hiwaay.net --------------------------------------------------------------
