The performance of a model is directly dependent on how well it is balanced. It is difficult at best to balance a model without a means of supporting the model at the precise center of gravity. The use of the old method of supporting the model with a finger under each wing may be suitable for some of todays trainers but is not adequate for balancing a precision aerobatic model. Every modeler should have a fixture which will support a wide variety of models while allowing for hands free operation during balancing.

The "Tinker Toy" balance jig is easy to build from readily available materials using common tools. The skills required to construct this balance jig are well within those of many beginners. It is easy to assemble simply by slipping the shafts into the holes, hence the name "Tinker Toy". It is easy to set up for any model and accurately locates the center of gravity. It can be taken apart for storage.

Construction begins with obtaining the materials required. There is nothing critical about the items listed. These just seem to be the ones which work the best. A 1 x 6 board can be ripped to make the bases. A 1/4" hardwood dowel can be used in place of the arrow shaft but the assembly will not be as stiff. The dimensions of the assembly can be increased to accommodate larger models.

The bases are first cut from the selected material. The 1/4" holes for the support shaft are drilled at a 75 degree angle from horizontal. The bases should be stacked for drilling the 1/4" holes for the slide shafts to ensure proper alignment. The shafts should be a snug fit in the holes but should slide in the holes with little effort.

The pivot head is made by locating a point 1/4" from one end and on the center of the side. This is the center of the 1/4" radius. A line should be permanently marked at a 15 degree angle from this point to the end of the block. This is done on one side of one block and on the opposite side of the other so there is a right and a left pivot head. Next, the 1/4" hole is drilled in the center of the block on the opposite end from the reference line. The 3/32" hole for the locator wire is drilled at a 15 degree angle at the location shown centered in the block. Finally, the 1/4" radius is cut and sanded on the top end of the block.

The locator wire is made simply by bending the 3/32" music wire according to the detail. The inside radius of the bend should not less than the diameter of the wire. The bend should be at a near perfect 90 degree angle. The wire should be a snug fit in the hole in the pivot head.

To use the jig, the distance from the leading edge of wing to the center of gravity is measured from the plans of the model. This distance is set by moving the locator wire so that the distance from the indicator line to the back side of the locator wire is set to the required dimension. The distance between the pivot heads should be set to clear the fuselage by sliding the bases on the slide shafts. Finally, the model is set on the pivot heads with the locator wire just touching the leading edge of the wing. Balancing the model can commence.

That is all that is required to produce a balance jig for trouble free operation. It is inexpensive, easy to build, easy to use, and easy to store. Put simply, building and using the "Tinker Toy" balance jig is child's play.