Doodle Watt (oz14538)

About this Plan

Doodle Watt. Radio control sport model for electric power, using a Speed 400 motor with 'remote drive' using a flexible piano wire drive shaft, back to the tail-mounted prop.

Quote: "Doodle Watt. A sport aerobatic electric model, by Peter Holland.

Try this novel layout for your Speed 400 motor and mini R/C gear. Peter has just developed it from his 'Doodle Bug', a rear-motored little machine of the late 1970s and incorporated some of wing structure used in his successful 'Flapdoodle' aerobatic electric of that era.

Doodle Watt has several features, which over the years, have led to improved performance in my electric models.

1) The payload is all concentrated at the centre of gravity (the Doodle Bug had the smallest Astro motor on the fin LE, which made it prone to pitch inertia, this used with flaperons that were coupled to the all moving tailplane gave it sensitivity. Fine for fooling around, but uncomfortable in gusty weather for level flight.

2) Powerful pitch authority produced by having the prop near
the tail plane LE is ok for the type of thrust we have with Speed 400 type motors.

3) A simple remote drive was already proven in my 'Camberwell', a variable camber pusher model with a central motor and prop aft of the tail. (The coupled flaps of Flapdoodle superseded this design in terms of lift and pitch performance).

4) The flight pack is external, for ease of changing and lessens stress on the fuselage on touchdown if the ground is uneven (or higher than you anticipated !)

Other features: Rather than using a higher angle of attack of the whole model for gaining height, I have chosen a lifting flat-bottomed aerofoil to get it up there on less amps, and agreed to live with the lower inverted efficiency, offset by those reverse coupled flaps. This geodetic wing is easier to build too.

To save space and weight, the elevator pushrod is a bamboo skewer and the three bellcranks and horns are 0.8 mm ply reinforced with cyano at the holes and bushed with brass tube to run on supporting wire brackets which you cyano in place.

Wing Building: Make the leading edge ribs in a stack, W2-W11, sandwich fashion. Cut the two root whole ribs W1 from med hard 3/32. All the rear parts of the ribs are strips. Cut the top parts of these from med 3/32 sheet using a template, like those for indoor models. The wing tapers, but wait until assembly before trimming them to fit.

Make the spar from med hard 3/32 sheet and fit the ribs and LE over the plan. Now add tips and TE. Put 1/32 packing pieces under the spar and cut each 3/32 sq lower rib to length and pack them up 1/32 to match, at the spar.

Tailplane: Use light 1/8 X 1/4 strip for the outlines of tailplane and elevators. The bracing is 3/16 x 1/16, or 1/8 x 1/16, depending on weight and rigidity of your balsa. This type of bracing should result in a fairly rigid structure, but cover it carefully with Litespan and keep it flat while you tighten it. A single self tap screw allows it to swivel if it gets a clout. Note the geometry of the elevator horn, to match the pushrod angle.

Fuselage: The prototype was designed by taping all the internal payload together and drawing round it. If your gear is non standard mini shape, make the width to suit. The sides are full length 1/32 ply..."

Doodle Watt from Silent Flight, February/March 1996.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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