RCM Wing Jig (oz6254)

About this Plan

RCM Wing Jig. Note this is not a full-size plan. This is not a plan at all. This is an article describing in detail how to build a simple wing jig - as requested in the Wanted page.

Quote: "Thoroughly tested by RCM, this ultra simple wing jig is completely versatile, built in thirty minutes for under two dollars. By Major Frank Jepson.

HERE is a wing jig that you can make in 30 minutes at a cost of under $2.00, and which will allow you to build perfect wings in half the time of conventional construction.

Like everyone else that builds model aircraft, I enjoy it to a point but have always dreaded building wings, particularly the elliptical airfoil types. A couple of years ago, I set out to devise a system of wing construction that would be inexpensive, provide accurate assembly, and allow the builder to work on either surface without disturbing the alignment.

Several butchered wings later, the system shown evolved and has produced many wings, each straight as an arrow. What's more, I don't dread building wings any more but, rather, enjoy it. Admittedly, only wings of the constant chord variety have been built but I can see no reason why the jig would not work equally as well on tapered wings, swept wings, delta wings, stabilizers, or what have you.

To make this jig you will need one (1) six-foot length of 3/8 inch Reynolds aluminum rod, available from any good hardware store for about $1.40, a couple of pieces of square 1-1/2 x 1-1/2 x 12 in hard wood for the rod supports and some scrap hardwood for the rod hold downs and front rod butts.

Cut your aluminum rod into two (2) three-foot lengths, round the ends with a file and polish them lightly with steel wool. The hard-wood rod hold downs should be cut to approximately 1/2 x 1-1/2 x 10 in. Dimensions are not at all critical. A scrap of wood approximately 1/4 in thick and an inch long should be glued to the top front edge of each rod support. This will serve as an alignment key later. Jig construction is now complete.

Build your wing a panel at a time. Secure the jig rod supports to a flat surface about 34 in apart; sufficient for even the largest wings. I screw mine right to my work bench. Be sure the blocks are parallel to each other. Center your wing plan between the blocks and tape or tack it down. Fore and aft location of the plan is unimportant. We are interested only in the spacing of the ribs and parallelism between them.

Prepare your ribs for installation on the jig. I make my ribs in a stack and sand them to shape from an aluminum template which insures uniformity. All spar notches and gear block cutouts should be made at this time.

Next drill two 3/8 holes squarely through the entire stack. One hole should be on the rib center line about an inch behind the leading edge, the other on the center line about an inch in front of the trailing edge. The location of the holes may be adjusted for easy assembly with the type rib you are using, but all holes should be in the identical place on each rib. A drill press is recommended for this job as inaccurately drilled holes could cause you to build a twist into the wing.

Number your ribs in the order in which they come off the stack, and keep them in sequence when installing them on the jig. The effect of drilling errors will be minimized if this procedure is followed.

Slide the rib stack onto the aluminum rods. If you are going to install gear blocks, start with the ribs upside down. Position the rods on the support block and butt the leading edge rod up against the stop block on each side. Position the rod hold downs over the rods and screw them down tight. This clamps the rods in position and prevents any tendency for the rods to sag. Slide each rib to its respective position over the plan.

Stand back and take a last check. Your ribs should be properly spaced, parallel to the support blocks, square to the rods, and square to the bench. You can now glue in all spars, leading and trailing edges, spar webbing (don't skip the webbing, it adds tremendous strength) and bellcrank hardware if notched ailerons are to be used. Notice how nice everything fits..."

Direct submission to Outerzone.

Note for the companion article on the RCM Fuselage Jig from Feb 1972, see RCM Fuselage Jig (oz11465).

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