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Wing Rigging

Wing rigging a Pitts Special that I used to fly was done at the factory. The left lower wing had much twist via washers underneath the rear of a rigid interplane strut. After that, flying and landing wires were tightened to predetermined value using a flying wire tensiometer . . . great for such a rigid aircraft.

Rigging on the less rigid Taperwing (even the interplane struts have wires between them) is different. After ensuring that the center section wire lengths are equal, rig it the way you want . . . usually so that it flies level at cruise with rudder holding heading.

Dihedral was a personal choice back then . . . operators set dihedral to their tastes. I found a document which advised no dihedral in either top or bottom wings. Others in the field advise 1 degree in the bottom wing.

I use some dihedral but still have little roll coupling (rudder causing roll) at cruise speed. There is plenty of roll coupling at slow speed.

The WACO Factory exported Wacos so they wrote preliminary rigging instructions for remote assembly of the aircraft.

The following WACO Factory wing rigging information is from Ray Brandly's Taperwing WACO book.

WING RIGGING - PRELIMINARY

Remove all streamline wire ends and screw them back on five complete turns to insure an equal amount of adjustment on each thread end.

Fasten inter-plane struts on upper wings.

Cut inspection hole on underside of fuselage. This will be rectangular opening cut inside of line of tacks.

Cut out the cloth inside the patches on both sides of inspection hole. (For aileron control rods).

Cut slot in small adjacent patches. (For lower wing tie wire).

Front wing root fittings for lower wing should be bolted to fuselage. Rear fittings bolted to wing.

Wires are marked with brass sleeve tags.

Hand landing wires FL5-9475 and RL4-10250 on the center section fittings. (Do not tighten).

Place lower wing between fittings on fuselage, drive long 5/16” bolts through front wing root fittings and front spar.

Fasten the landing wires to wing fittings. Having both wings thus hung. fasten rear wing root fitting to fuselage.

Place root end of upper wings with interplane struts attached as before mentioned between fittings on center section. Line up entering edge of wings with entering edge of center section. Line up holes in spars. Drive long 5/16” bolts in front spars first. follow with rears.

Fasten interplane struts on lower wing.

Now tighten center section wires. These must be adjusted until the dimensions are the same on each side. This can best be accomplished with trammels.

Fasten both ends of flying wires (do not tighten).

Draw front landing wires to 8’ 1” center to center of pins.

Tighten rear right landing wire to length of 8’ 8-1/8”.

The left rear landing wire RL4-10250 should be about 1/4” longer than the right landing wire. This permits the rear spar on this side to droop slightly (wash in) to take care of motor torque.

Tighten front flying wires W-OT19 and drift flying wires DF4-13625 and readjust them until the leading edge of upper wings is parallel with the leading edge of lowers. This is generally noted by lying on your back under the lower wing and sighting along both edges.

Tighten rear flying RF5-12825 and anti-drift flying (A.D.F.) until snug.

Tighten the incidence wires SI4-6025 and LI4-7250 bringing tension on both these wires at the same time. Have them snug.

Tighten lock nuts on all streamline wires.

Push bottom wing tie wire (short stranded) through slots in fuselage cover and fasten both ends with clevis pins. Tighten snug and safety wire.

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