On 7/21/2022 12:34 AM, Gary Sack via KRnet wrote:
When I read "When I left Alaska for Russia, laden with 220 litres of
fuel on board, or 55 US gallons. I could hardly lift the tail wheel
off the floor and knew already, without scales or maths or charts,
that the C of G was beyond the aft limit, in the divergent range."
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
When telling our story we need to be careful of the words we use and
their interpretation. When he stated that the KR was beyond the aft CG
limit what he should possibility have said was with the weight of the
tail he assumed it was beyond the "published aft limit". If it was
beyond the "mechanical / aerodynamic aft limit" he wouldn't have been
around to tell us about it. Readers could come away with several
interpretations. First. Maybe the flyable CG range is greater than
published, second, without scale and tape the actual CG on that flight
was merely at the rear most published limit, third, who with common
sense would make a flight when assuming the aircraft is beyond the aft
CG limit even before takeoff. You can only be wrong once. Anyone
suggesting you can play fast and loose with aft CG loading is being
irresponsible.
On another point:
*/[[[[["95% of my flights are made at 1150 pounds with the CG at the
center of the range. "/*
Is this the CG range specified in the original plans or have you
established the CG range for your particular aeroplane? Perhaps you
could share the method by which you established sensible forward and aft
limits so that other KR-2 builders/flyers can apply a similar
methodology? ]]]]]]]]]
There is only one rule when playing in the "experimental sandbox" in the
U.S. Wash your hands before you eat. If I were a betting man I'd bet
that Rand and Robinson established the CG range using commonly accepted
numbers, the same as I'd find in a Tony Bingalis book. The KR was in
fact based primarily on the Taylor Titch and I'm not aware of any flight
testing being done to verify any numbers. Ken's airplane empty weight
was under 500 pounds and Ken weighted in at 130 pounds, give or take a
meal or two. It was after a number were built and flying that pilots
started to advise other pilots not to use the aft 2"s of the CG range. I
used the CG range numbers stated in the plans and worked up slowly to
the rear limit using an ever increasing number of 25 pound sand bags
secured in the right seat. Not scientific but acceptable.
With Ken's unfortunate and early death and Stu not taking an active roll
in the company, all mod's / improvements made to the KR have been the
result of builder input and testing to whatever extent that took place.
The only design calculations after the original plans that I ever heard
Jeanette Rand mention was the "firewall analysis" rated its strength a
22G's and the longer wing on the 2S "lowered it's G rating a bit". Even
the new wing was the result of members of the KR net and to my
recollection the only early testing was done by Troy Petteway after he
damaged his RAF48 wing, installing the new wing, then giving us his
"impression" of the flight qualities. I also don't recall a new /
different CG range ever established for the new wing. We're just
"winging it" so to speak.
The large "EXPERIMENTAL" placard and the "experimental" placard on the
panel are required for a reason. Place your A** in this airplane and
take it to altitude and you might well be leaving your soul in the hands
of the devil. Don't expect more from the KR than you can verify.
Larry Flesner
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