Final Setup/Weight and Balance
Great Planes 33% Pitts
by Bob Pastorello
Final setup of the GP Pitts. Here's the GOOD news. With my ZDZ 50 (COOLING the Motor) in the nose, and tail servos in the rear, four ailerons, THEIR spinner, the CG is exactly 5 1/4" from the leading edge of the top wing. This is the center of the recommended range, so we should be good to go.
Bad News - have to replace my extensions with amplified/buffered extensions, cause I'm getting some pretty bad jitter on the lower wing servos and the rudder (engine OFF). Had one on hand, plugged into a lower aileron - problem gone! Of course, this could just be characteristic of the JR FM receiver I'm using, so I'm going to run some tests with my Hitec, see if the outputs are better.
UPDATE 3/31 - For the sake of accuracy, I have to say that the extensions did NOT correct the jitter, but = the jitter was due to my workshop fluorescent lighting. Outside, engine running, everything was FINE, even on the FM, so my trading to the 649 PCM **AND** buffered extensions ended up being an unnecessary exercise. Maybe...this is a much safer configuration, all around, so it should be fine!
I set all control travels per their instructions; they seem reasonable for this kind of biplane, so I'll find out about those on first flight day.
A Word of Caution - if you are using a lighter glow motor, you will be in BIG trouble for CG, unless you mount the battery and throttle up on the firewall. That's what Great Planes recommends, so I'm guessing they knew, and DID test various glow motors.
My final weights -
| PART | OUNCES | POUNDS |
| Fuse - RTF | 183.9 | 11.49 |
| Upper Wing | 31.1 | 1.94 |
| Lower Wing | 26.6 | 1.66 |
| TOTAL | 241.6 | 15.09 |
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| Front Left Engine | Front Right Engine | Interior/Aft |
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| Bottom/Plug Cap | Note Switch/Batt | Forward Interior - EMPTY! |
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| Front Bottom View | Close Up of Plug | Hanson "Chris" in White Cockpit !! |
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| Close up of Cowl Air Slits | Cowl Front View |
COOLING -Photos above show slots I made, and openings I cut out for cooling on the Pitts/ZDZ...later in the summer, I may need to baffle it, but I'll use a CHT and monitor temps to know what's going on.. The slots DO let some air around the cylinder fins.