Cue Dot (oz2835)

About this Plan

Cue Dot. A1 competition glider model.

Quote: "Your Full-Size Free Plan. A 51 inch wingspan A/1 specification glider. Cue Dot, by Martin Dilly.

THIS model was constructed because a similar structure and aerodynamic set-up worked reasonably well in A/2 size and the author was interested to see how the Benedek 6456-f airfoil performed with smaller chord sizes.

A sheet upper surface is used for the wing as, with the thin airfoil employed, there isn't enough rib depth at the rib to trailing edge joint to provide adequate strength; by using a strong but light grade of 1/16 sheet, lightly sanded before use and weighing 0.55 to 0.65 ounces for a 4 in wide yard, the structural weight can be kept within acceptable limits.

It is advisable to start construction with the boom. Commence by selecting. two yards of the lightest and most rollable 1/32 tangent cut balsa you can find. Cut so they taper from about 2.4 down to 1.4 in, the exact size depending on your particular mandrel; a billiard cue was used for the originals but anything else straight and of about the right taper will do. Note that the dimensions at this stage do not have to be very precise, as final seam cutting will take place when the blanks are laid up on the mandrel.

Now look to see if there's any natural curve in the sheets and, if there is, dope the concave side, or any side in the case of a flat sheet, with a couple of coats of unthinned clear dope. This will both curve the wood and waterproof one side; when the sheets are dry, immerse them in a bath of warm water to curve them even more.

The next stage is to roll one of the wet blanks round the mandrel; this requires a little patience and 'sympathy for the wood'. Starting at the large diameter hold the blank tightly to the mandrel using Sellotape and gauze bandage strip or rubber, but do be careful if you do use rubber, as it's easy to dent the wet wood if the rubber strip is wound too tightly.

When the first blank is dry unwrap the rubber but try to leave the Sellotape intact; now use a steel straight-edge and cut the seam accurately along the length of the overlapping edges, cementing the joint with PVA glue, after having first waxed the mandrel to prevent the whole lot sticking together.

Using a strip of paper as a flexible rule, measure the outside diameters of the ends of the balsa tube, remove the tube, and mark the mandrel where these diameters occur; use these marks for the ends of the second layer, which is made in the same way as the first, direct onto the mandrel, but slid along a little way to give a larger diameter. However, do not cement the seam. When this layer is dry remove it, replace the first tube, coat it thoroughly with Cascamite or a similar cold water resin glue, slide on the outer layer and tape up tightly; surplus glue will be forced out of the seam and will bond both layers together. Wipe off any surplus glue, and fill any gaps with slivers of balsa while the glue is still wet. Also while the glue is still wet, make sure that the mandrel will move, pulling it out slightly if necessary.

All right, so you've got a boom. Now cut the keel from plywood and the soft balsa side pieces, carving the rear of these to a circular cross section to fit into the boom, but do not cement anything yet. When you're happy that everything fits snugly together, lash the wing, fin and stabiliser into place (these will have been made while the boom has been drying) and hold the skid and timer in place with Sellotape..."

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