27 - Section 2
Weight & Balance
I went to Marc
Zeitlen's site and downloaded his Weight & Balance Excel spread sheet to perform
by weight and balance calculations. Before any calculations can be done, I need
to take a few dimensions (on the place) such that the W&B calculations are
specific to my plane.
Determining Moment Arm Lengths
I followed Nat's
Pilot Operating Handbook Section 6.1.6. Here's what I did:
1) I leveled the plane and placed chokes
on all three wheels. With the help of plumb lines and lasers, I establish my
plane center line onto masking tapes on the floow;
2) I started with the wing root position
with plumb lines and assume they are at 113.9"
3) With laser triangulation, nose tip
position is determined to be -6.9";
4) Nose wheel axle at 18.95"
5) Canard leading edge at 18.50"
6) IP front face at 41.25"
7) Main gear axle at 109.90"
8) Fire wall (including fiberax & sheet
metal thickness) at 124.4"
9) Propeller flange at 124.4" + 40.25" =
10) Nose ballast compartment at -2.5"
11) Second ballast compartment (behind nose) at 6".
I fed these numbers (as appropriate) into Marc's spread
sheet for the moment arm dimensions. My numbers differ slightly from Marc's,
generally no more than 0.1". I considered them good to go.
Weighing The Plane
is one of those moments that give Cozy builders anxiety attacks. We all
worry that our plane may be too heavy and will end up with a slow airplane.
Well, my turn has arrived... Clark
Canady was gracious enough to loan me his weight and balance scales and a nicely
build ramp for rolling my plane onto the scales. Nicely done Clark - Thank You!
I set up all the
scales, follow its calibration instructions
and line up the ramps to the wheels. Susann and I pushed the plane up to the
scales and made the measurements. I have 25 lbs inside the nose compartment, 26
lbs at the front compartment, no fuel & 7 quart oil.
My weight came in
as follows :
Total (plane, 7qts
oil, 51 ballast) = 1,237 lbs
1,237 - 51 = 1,186
lbs...I am happy...