Tube Type Wing Jigs

For what its worth, I originated the tube type jig, making the first one forty years ago in 1966, and publishing photos of it in the Mustang article in 1968. Needless to say, this jig has also evolved a bit over the years, improving its practicality, and finally becoming part of an integrated jig system for complete alignment of the airplane. In 1966, the only jig that I was aware of was the Adjusto-Jig which I didn’t consider very practical. It used two center supports and ¼” solid rods. The center supports were in the way of bottom wing structure. The rods would sag from their own weight and were too thin to hold ribs upright. Also, it was much more expensive than my aluminum tubes and scrap wood base.

My jig vertical supports are all cut to 8" tall to give me enough clearance for mounting the landing gear while the wing is in the jig. When the wing is finished, the gear is removed and the vertical supports are cut to whatever height required to mate the wing with the fuselage in its jig, usually about 3 1/2", but depends upon the height of the fuselage jig.

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When you lay out the wing for construction on a tube type jig, you must take into consideration the location of the bellcrank, leadouts, gear mounts and flap pushrod. It sometimes requires a bit of ingenuity to locate the front jig tube where it doesn’t interfere with these components.

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My center supports are notched to clear the wing structure during construction and sheeting. It supports the wing center at the same height as the tip supports. When sheeting, these vertical projections from the center support extend upward through the lower wing skin through two small holes which are later patched. This is necessary to hold the wing center in alignment while the wing is completely sheeted. The shape of the center vertical support, actually, the spacing of the two upward projections which hold the center of the full span jig tubes, is determined by the necessary spacing of that particular rib set. These photos show a center support before and after it has been cut down to mate the fuselage. All three supports are initially 8” tall but only the center support need be notched. There is no need to cut out the tip vertical supports as they are always located outside the wing tips and out of the way of structure.

Since I have to replace the vertical supports anyway, and the wooden parts of the jig tube are so cheap, I like to start with all new supports and base. This costs about $10 and takes only about a 1/2 hour to make.

One addition to the jig was the use of the plywood wing cradles attached to the top of the vertical jig supports. These cradles locate the jig tubes so well that it is usually unnecessary to tie the wing down until starting sheeting. This freedom really facilitates the building of the initial wing structure as the wing with its tubes can be simply picked up flipped front to back or tip to tip. This makes it easy to position the wing for work on the front, back, top or bottom.