Mark,
You didn't provide the measurement to the fuel tank, but using the leading
edge to tank measurement for my KR2 with wing tanks installed aft of the
spar, here is the result. I've also calculated the CG for your oops flight
and you with full fuel for a normal test flight. Provided these weights
and measurements are accurate and on these calculations, your incident
flight CG should have been slightly forward of the forward limit and should
not have resulted in the experience you had with not being able to lower
the nose. If anything it should have felt very nose heavy. It would
possibly indicate that there is something else wrong outside of CG or you
data is incorrect. Let me know if you have any questions.
Sincerely,
Adam Deem
Date: 5/20/2026
A/C Type: KR2S Serial #:
Registration #: N771MJ
Owner Name: Mark Jones
Address:
Datum: Front edge of prop crush plate
Allowable CG: 54.5"-60.5" Max Weight:
EMPTY WEIGHT & CG
Description Station Weight Moment
Left Wheel 67.5 319.0 21532.5
Right Wheel 67.5 325.0 21937.5
Nosewheel 21.5 259.0 5568.5
Empty Wt/CG 54.31 903.0 49038.5
ADJUSTMENTS
Description Station Weight Moment
Full Fuel 75.5 -145.2 -10962.6
0.0
0.0
0.0
0.0
Adjusted Weight/CG 50.25 757.8 38075.9
OOPS FLIGHT CG 1/4 TANKS
Description Station Weight Moment
Empty Wt 50.2 757.8 38075.9
Pilot 65.0 178.0 11570.0
Passenger 65.0 0.0 0.0
Fuel 75.5 36.0 2718.0
Baggage 100.0 0.0 0.0
Loaded Wt/CG 53.9 971.8 52363.9
CG WITH PILOT & FULL TANKS
Description Station Weight Moment
Empty Wt 50.2 757.8 38075.9
Pilot 65.0 178.0 11570.0
Passenger 65.0 0.0 0.0
Fuel 75.5 145.2 10962.6
Baggage 100.0 0.0 0.0
Loaded Wt/CG 56.1 1081.0 60608.5
NOTES:
CG range is listed as 8-16" aft of stub wing leading edge by Rand Robinson
build manual, however flight testing has shown operation in the aft 2" is
undesirable due to insufficient stability. The range listed on this sheet
excludes the aft 2" as recommended.
On Wed, May 20, 2026 at 2:19 PM Jerry Pryce via KRnet <[email protected]>
wrote:
> I don't know if it got through but I calculated 56.07"... Assuming his
> station measurements and weights are correct.
>
> Jerry Pryce
>
> On May 20, 2026 10:11, Chris Pryce via KRnet <[email protected]> wrote:
>
> What are you getting for a calculated CG for the aircraft in flying
> configuration? I would hope that it is 54.5 to 60.5 based on your Datum for
> your leading edge.
>
> On Wed, May 20, 2026, 10:05 mark jones via KRnet <[email protected]>
> wrote:
>
> HELP......I am so confused. My new KR WunderBird is ready to fly except
> for the weight and balance. I have made many runs down the runway and on
> one run I lifted the nose and she shot straight up to about 100' and I
> could not push the nose down and she stalled on me. I was fortunate enough
> to cut power and get her flat before she contacted the ground very hard.
> Bent the main landing gear brackets and had to make more. I did some w&b
> adjustments, repaired the gear and tried again. Still tail heavy. I am very
> lucky I did not destroy the plane on that first flight attempt. So, here is
> my challenge to anyone who wishes to figure a weight and balance on this
> bird. I just want to compare others with my calculations. Here are the
> parameters.
>
> Weighed with FULL FUEL: 12 gallons each wing.
> Left Main 319 lbs
> Right Main 325 lbs
> Nose wheel 259 lbs
> Datum measuring point: Front side prop Crush plate
> Datum to nose wheel: 21.5"
> Datum to Mains: 67.5
> Datum to leading edge stub wing: 46.5
> Datum to Pilot: 65" with pilot weight 178l lbs
>
> Thanks for any help.
>
> Mark Jones
> KR2S (N771MJ)
> Cessna 140 (N1856C)
> Tampa, FL
>
> [email protected]
> www.flykr2s.com
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>
>
>
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