Tracer 200 (oz11809)

About this Plan

Tracer 200. Radio control pylon racer model.

Quote: "Tracer 200 by Bill Burkinshaw - A 'Club 10' pylon racer, is a scaled down version of famous 70's design for Club 20 (Tracer). The other side of the Skeeter plan from January 1994 Radio Modeller, but with such a small model there was room for the wing too! All the best,"

Direct submission to Outerzone.

Quote: "Tracer 200. Bill Burkinshaw took the famous Cotswold Kits 'Tracer' pylon racer and shrunk it to produce this spritely Club 20 contender.

Nearly all who have seen the Tracer 200 ask me if the model is my own design. In a sense it is, but it would be absolutely churlish to deny the origins of the model even if the name doesn't give it away in any case. It is, of course, a reduced size version of the incredibly successful Cotswold Kits 'Tracer', a Club 20 pylon racer of impeccable pedigree originally designed by Sid King in the mid 1970s. The Tracer must have won more pylon race events world-wide than any other design in pylon racing history and continues to be a very competitive design for racing and a smooth flying sports model as well.

My local model club, Aylesbury Model Flying Club, decided to try something a little different this year for a club event and, inspired by member Philip Alderman, Club 10 pylon racing was devised. The specification is absolute simplicity, only O.S. FP-10 engines with the muffler extension and standard R/C carburettor may be used in standard form, three servos on elevator, aileron and throttle have to be fitted and then the rest is up to the builder and designer. Racing is done three up round 10 laps of a triangular course totalling 1.5 miles. All the procedural rules closely follow established pylon racing practice.

So far at least a dozen original designs have been produced by
club members to this formula and two rounds of the four round competition series have been run very successfully.

Tracer 200 is my second design for the class; the first, 'Hurri-Hurri' was published in the Model Pilots' Association magazine as a free plan. The
original Tracer is constructed with a GRP fuselage and foam cored wings and is a particularly sleek and curvaceous model. The only methods that could properly reproduce the shape of the Tracer fuselage would be either fully planked or carved from block balsa; neither methods appealed to me so I adopted a simpler structure which faithfully follows the profiles but misses out a little on the cross sections.

The secret of a fast model which handles well lies in aerodynamic design but selection of materials, well judged use of glues and adequate sanding to the shapes shown are vitally important. My 'Hurri-Hurri' design finished up at 18.75 ounces ready to fly. Overweight, I felt, because of dual aileron control systems in the wing (my original tube and cable linkage was too imprecise) and consequent redesign of the servo layout. I attempted to at least equal this target with the Tracer 200 and very nearly did so but I think the bolt-on wing model loses out to the one piece variety in this aspect.

There are no doublers. Formers are either laminated or Lite-Ply and spars are balsa. As designed, the structure is more than strong enough to take the stress of sports flying or racing, there is no need to strengthen it up at all. If you do modify the design and your model ends up too heavy it will not fly very well. I used cyanoacrylate almost entirely for the construction while Deluxe Materials aliphatic glue was used for skinning the wings.

Construction: Cut a set of wing ribs out from light quarter grain balsa and prepare medium soft straight grain balsa sheets by edge jointing for the wing skins. Sand the outer surface of the wing skins prior to adding them to the structure. Prepare the jigging strip cut from scrap 3/16 or 1/4 balsa and the leading edge. Pin down the lower 3/16in sq balsa spar and jigging strip and add all the ribs, the top spar and the basic lin x 1/16in trailing edge and the leading edge. Angle the root rib W1 using the template. Check and trim the upper wing skin and glue in place whilst the framework is still pinned to the board.

Lift the half sheeted wings from the board and fill in the spaces between ribs W2 to W6 with scrap 1/4 balsa; this in-fill should be positioned so that, when the ailerons are cut out, the gap between the sheeting will be filled and there is something for the hinges to be fitted into. Similarly, fill in at the centre section to reinforce the area where the wing bolt hole will be drilled. Fit 1/16in balsa webbing behind the wing spars for four rib bays making sure that it is a really good fit between the ribs. Trim the spars and LE/TE ready for joining.

Now check that the two wing halves match perfectly at the roots and sand carefully to make any adjustment needed. Glue the two wing halves together upside down on the board. When the joint is set, use a razor saw or similar to cut away a thin slot in front of the spars to fit a 1mm plywood brace. Trial fit a piece of ply and mark a line onto it using the spar as a guide so that it can be trimmed to a perfect fit. Once the ply brace is fitted and the in-fill pieces sanded down, carefully mark on the outside of the upper wing sheeting the place where the cuts will be made to release the ailerons once the top sheet is fitted.

Now fit the underside wing skins. Be very careful; until these skins are fitted the wing is not very rigid and a permanent warp can be built in very easily. Trim all sheeting and fit the tip blocks, carve and sand to shape and then cut out the ailerons to the lines already marked, Trim a generous 1/8in from the ailerons to allow addition of 1/16 facings and a little clearance. The next step appears brutal. Cut a 1/8in wide strip out of the underside of the centre sheeting exactly along the line of the aileron torque rods removing small sections of the ribs at the same time. Put the piece of sheet removed carefully to one side. Bend up aileron horns from threaded end bicycle spokes remembering to slide on the nylon bearing tubes before making the final bend. Fit the horns and replace the strip of wood you put to one side..."

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