On 9/22/2020 1:08 PM, Mark Langford via KRnet wrote:
I'm not sure there's any real reduction in error possibiliy here, and
the main problem I see is that you're trying to measure with accuracy
to a point that you can't hang a tape measure on.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Let's see if this makes sense. I put my airplane on scales and level.
I use a square from the floor to the axles center line of the main gear
and mark the floor. I draw a line between these two marks. I hang a
plumb bob from the lead edge of the stub wing on each side and mark the
floor. I draw a line between these two marks. I then pick a point
ahead of the axle line and measure out (lets just pick 60 inches) to the
datum I pick. I now take my scale readings, arm X weight = moment for
all scales, add all the moments and divide by total weight. That gives
me the CG location. The answer should be in the area of the wing for
recommended CG location and is the sum of the 60" + the distance behind
the lead edge of the stub wing for the required CG location.
I think a plumb bob is more accurate than some other method if the
hangar doors are closed to eliminate air movement. I've never seen
gravity fail. If the fuselage is not perfectly level (nose to tail) a
piece of angle to the floor could be off several inches. Also, is the
part my angle is attached to exactly perpendicular to the center line of
the airplane? Another possible error. I can easily measure from my
two reference lines to my datum with a tape measure and the length to
the datum will never change, regardless of changes made to the aircraft,
with the exception of relocating the wing or landing gear in relation to
the airplane. The example below ( if it comes through) shows how the
big guys do it. Fuselage station "0" is not even located on the fuselage.
Larry Flesner
Weight and Balance Principles - AviationChief.Com
_______________________________________________
Search the KRnet Archives at https://www.mail-archive.com/[email protected]/.
Please see LIST RULES and KRnet info at http://www.krnet.org/info.html.
see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change
options.
To UNsubscribe from KRnet, send a message to [email protected]
