EXTERIOR JIGGING - by Hube Start

There are many types of building jigs used to keep the wing from warping during construction. However, by the time you cover and paint, the jig has been removed, and warps can creep in just as easily during these operations too. The following method not only immobilizes the wing during leading edge sheeting, but allows you to further use the jig to hold the wing straight while applying, shrinking, and doping silkspan.

Drill a 1/16" hole on the centre-line of each corner of the wingtip where you can slip in a 1/16" nail inert that's held securely in a block of wood at the same height as the wing root. Measure carefully so that all inserts are at the same height and the wing is warp free, and weight everything down so it doesn't move. This exterior jigging does not really get in the way. It's easiest to do halfway through construction, with the top block not yet on, and the plane upside down on the table so that it's all flat and level.

When the bottom is papered, turn the plane over, block it up level fore and aft, reinsert the blocks on the corners of the wingtip, and do the top. You can just keep on going like this turning the plane over until at least the base coats of clear are on, and most of the risk of warp is gone. Continue on, then, with the rest of the construction.