Ford Tri-Motor (oz8706)

About this Plan

Ford Tri-Motor. Scale model airliner for RC and electric power using Mabuchi RS 54, Astro Flight 05, Ripmax Cyclone, or similar motors.

Quote: "Build a Tin Goose! Ford AT5 Tri-Motor. Here's Dennis Tapsfield's 59 in span version for electric power.

HAVE YOU EVER had that feeling of nostalgia - you know, the vision of that vintage type aircraft just breaking ground, and flying out straight and level at its hair-raising 100 mph? Me too, and here is the result, a third-in-the-line of electric-powered multi-motored models.

Fifty years ago, in the July of 1926, in the Ford factory at Dearborn Michigan, the first all-metal tri-motor was completed and the fact that there are some of these big (in their day) all-metal aircraft still flying is a glowing tribute to their designers and builders.

It was the first to fly a scheduled airline service, the first to carry two uniformed pilots and a flight steward. The model is finished in the red white and blue livery of one of the planes still flying at the time of writing.

It was decided in the interest of weight-saving not to attempt to simulate the corrugated skin of the full-size aircraft but only the well informed purist is likely to comment! Before you get too enthusiastic, let me say that if you only enjoy screaming round the sky with a 61 powered bomb, this model is not for you since like its full-size counterpart, it has to be flown with feeling and consideration. It is not very aerobatic; the odd loop and roll are about the limit - but do gain some speed by a shallow dive first! Anyway, who's heard of a vintage aerobatic airliner!

It will take off from a smooth surface and properly handled will fly in a sedate scale-like manner and evoke some oo's and ah's from appreciative spectators. The flight times are in the 5-6 minute bracket, using the series-parallel switching system for the motors. This makes use of the servo to operate a slider system with micro-switches which gives two power levels; the first position applies full voltage to the middle motor and connects the two outers in series; the second position connects the two outers in parallel, ie full power. The power output in the first position is enough to maintain altitude with a considerable saving in battery consumption. Landings can be made by cutting the power completely and, handled in the right way, very realistic smooth, soft arrivals are the rule.

If you are still keen to build a 'Tin Goose' this is the way: keep it light! Aim for a maximum bare airframe weight of 30 oz - this means complete, covered trimmed, with landing-gear and wheels! To this weight you must add 3 motors (about 16 oz), power pack (about 24 oz), general wiring and switches (say 4 oz), plus the radio at around 14 oz. A grand total of 88 oz! Try very hard not to exceed this. The lighter it is, the better it will perform - so it's up to you.

CONSTRUCTION: Wing Cut out all the ribs; do not make the spar cut-outs too tight a fit as this will cause distortion. Since the wing is flat on the top - ie no dihedral - it is made upside-down. Pin the joined spar in place on the plan, (you must have the complete wing drawing as it is in one piece). Pin the 1/4 x 1/2 in packing piece in place at each end; this supports the tail-end of each rib in the correct position. Glue the ribs in place upside-down, add the bottom spar and the leading edge and allow to dry. Cover the bottom of the leading edge and the trailing edge, being careful not to cause any warps.

When set, remove it from the plan, and complete the structure; do not web the spars yet. Fit the aileron control system now. I used Bowden cable in nylon tube. Cut out the nacelle frames from 1/8 ply, slit the leading edge sheet to take them, and glue them to the 1/8 ribs. Thread the motor wires through the ribs, and pull them out by the nacelle frames. Make sure the wing is true before you add the spar webs. Make the ailerons, hinge on with film..."

Ford Tri-Motor, Radio Modeller, February 1978.

Direct submission to Outerzone.

Supplementary file notes

Article, thanks to RFJ.

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