Wattsname (oz5475)

About this Plan

Wattsname. Electric RTP model. This plan appeared in part 1 of the 2 part article 'Electric RTP Flying'. Part 2 of the article also (see supplement file) includes detailed instructions to build the RTP pylon using Meccano.

Quote: "Part One. With full size plans of Vic Smeed's Wattsname.

ELECTRIC ROUND-THE-POLE FLYING dates back a few years - possibly the first large-scale demonstrations were at the Dorland Hall exhibitions in London twenty-five years ago. However, these models required specially built motors, and despite occasional attempts by individuals, and one kit model in about 1947, interest languished until in 1968 various of MAP staff experimented with slot car motors and an assortment of prototype models to see if a simple combination could be found for demonstration at the Model Engineer Exhibition.

It took about a dozen models by four or five different people before success was achieved, but once the path to follow was found, few succeeding models had much difficulty. Since that time, several clubs have taken electric flying up, as a result a fair amount of development has taken place. Our original aim was to fly on 12 ft lines, but one club now flies on lines up to 46 ft long and finds that the longer the lines, the less exacting is the model required.

We will come on to the lines and the pylon head in the second half of these notes, next month, but for those who have heard little of this type of flying, we can perhaps mention that the pylon head is mostly simple Meccano and that besides aircraft, lines, and pylon the only requirement is a controlled power source, which can either be a 12v car battery and model slot car hand controller, or a model railway transformer/rectifier able to deliver 1-1/2 amps. Also needed is a space large enough to fly in, and we recommend a minimum circle diameter of 20 ft, so unless your house has very big rooms, flying must take place in a church or school hall, Scout hut, or similar, or in the open air - provided there is very little breeze and a smooth surface on which to land and take-off.

Now to the model. This was the fifth design by the writer, based on experience with the previous four (and some from many years ago) and also observation of a number of other models, The original was built and heavily used at the 1969 Model Engineer Exhibition, where it was easily the fastest model of the twenty or so flown. It survived rough handling by novice pilots and flew again in 1970, when it became so battered that it was retired. A second model was built for this year's show, and again proved the fastest of a large number of models, even when re-engined by a 'cheap' motor. It therefore seems that the design is responsible for the performance, rather than a good motor in the first model. The two points contributing most are light weight - just under 2-1/4 oz complete - and the tapered nose, which allows all the propeller area to be effective. A fat-nosed model blankets much of the prop, and though larger props can be used, it is then better to use a gear reduction which makes the model a little more complex.

Initially, we used Rikowhip motors, costing close to £2 each and, we understand, no longer made. Actually, any good 16D size slot car motor should be suitable but we would suggest that a figure of about 60p should be the minimum you should expect to pay. Anything costing less than this is unlikely to have a high enough performance. The inexpensive motor we found very successful was the Rikochet, available at the time at about 65p.

What you need then, is the motor, two sheets of 1/16 x 3 in balsa (one very soft, one medium to soft), a Cox .010 3 inch propellor, a stub of 12g brass tube, a pair of wheels, a few inches of 20g piano wire, a small piece (about 12 x 1 or 6 x 2 in) of very soft 1/4 in balsa, two press studs, a couple of feet of fine hook-up wire, washers (to hold the wheels on), cement, sanding sealer, colour dope, and just a dab of epoxy glue.

Construction starts with the wing, which requires the sheet of very soft 1/16 balsa. Trace or pin-prick the outline and cut out; the bottom panel should be just a shade under the full width of the sheet. Use this panel to mark out the second, which is the full width. The slight difference in width allows for the curve of the top panel. Trace and cut out the six ribs and cement them to the bottom panel, pinning it down on a flat surface. Nick the ribs to allow the two wires to pass, and cement them in place, poking the ends out through two small holes so that they can later be soldered to the press studs which will be cemented on the outside. Make sure you put them in the right wing! The wing will have to be pinned down with its tip projecting over the edge of the board once the wires are through. Leave a couple of inches spare on each wire at each end. Also fit the wire tethering eye, which needs to be firmly cemented in place.

Now sand the bottom panel to a chamfer all the way along the leading and trailing edges, sanding the ribs as well if they happen to be a little long. Run cement right round the outline and across each rib, then place the top panel in position and pin down with either weights or pins pushed through at a slight angle, every inch or so. Make sure that the two panels are in smooth contact all round, and leave to dry. Note, incidentally, that the wing has no dihedral, ie it is flat from tip to tip.

Trace and cut out the fuselage sides from medium to soft 1/16 sheet; be careful to get the wing and tailplane seats accurate to the drawing..."

Supplementary file notes

Article, in 2 parts. Includes RTP pylon design.

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