Great Planes Super Sportster 90/120 Kit - GPMA0214 - Manual (Page 45)

GREAT PLANES PRODUCT IMPROVEMENT SHEET
INSTRUCTIONS FOR BALANCING YOUR SUPER SPORTSTER
The recommended balance point for the Super Sportsters is
shown on the plan, and is located approximately 29% back from the
lead ing edge. However, all Sportsters have been thoroughly test flown as
far back as 36%, and found to be completely stable throughout the entire
range from 29% to 36%. (These numbers represent a percentage of the
total wing chord, as shown in the sketch).
Total Wing Chord-
Balance
Points
If, when balancing your Super Sportster, you find it necessary to
add several ounces of nose weight to balance it at the location shown on
Ihe plan, it is preferable to balance farther aft, up to 36% (the aft limit),
rather than adding a lot of weight As you balance farther aft, however,
the airplane will become more responsive to elevator control; therefore,
you should reduce the maximum elevator throw in accordance with the
table of "Recommended Maximum Elevator Throws." The elevator throw
is measured at the widest part of the elevator, as shown in the sketch.
The best way to balance your Super Sportster is to make a
Balancing Stand from a square of 1/4" plywood and two 3/8" dowels.
Mark the fore and aft limits of the balance range on the top of the wing (on
both sides of the fuselage), and place the airplane upside down on the
balancing stand as shown in the sketch (empty fuel tank). Move the
airplane forward or aft on the stand until it balances with the stab level.
If it balances outside the 29% to 36'% range, you must either shift the
location of radio components or add weight to the nose or tail until it
balances within the range.
Take note of where the airplane balances. If it balances near the
front of the recommended range, then adjust the linkages to your elevator
to provide the maximum throw listed in the 29% -30% column in the table
below. If it balances near the middle of the range, set your elevator for the
maximum throw listed in the 33% column. If it balances near the aft limit
of the range, set your elevator for the maximum throw listed in the 36%
column.
Measure Throw
Here
RECOMMENDED MAXIMUM ELEVATOR THROWS
FOR VARIOUS BALANCE POINTS
(29-30X)
LE to CC MAX ELEV.
(33X)
LE lo CG
(36X)
LE to CC MOOEL MAX ELEV MAX ELEV.
SPORTSTER 20 2-15/16" 3-3/16" [9/32-] IV--]
SPORTSTER 40 [11/32-] (5/16-] 3-3/8' 3-5/6' [V6-]
SPORTSTER 60 [13/32-] 3-5/16' [7/16-] 3-3/4- (3/B-) 4-1/16'
SPORTSTER 90 3-15/16' 4-13/16" t'V'6-] 4-3/6- [5/6-]
1-7/6'. (11/32'] | 2-1/16'- [5/16-] SPORTSTER BIPE 1-1/2'- [3/8"]
(MESAURED BACK FROM LE OF BOTTOM WING)
WARNING! If you balance your Super Sportster aft of the plan
location but fail to reduce the maximum elevator throw, the
elevator may over control the pitch of the airplane, and may result
in unwanted stalls and "snap rolls"!
SSADDOl