Avro 641 Commodore (oz15712)

About this Plan

Avro 641 Commodore. Radio control scale model, for electric power. Wingspan 18 in.

Direct submission to Outerzone.

Hi Steve,

As promised here are the photos to accompany the Avro 641 Commodore plan that I sent you. I'll send you a few shots of the model uncovered and unpainted in a second email and you can choose which you'd like to use to illustrate the plan page.

Background

The project was sparked when my friend up in the far north of Scotland, one-man-aircraft factory and pioneer of micro-RC conversions, Barry Scollay, suggested building an Avro Commodore to fit the UMX RC board from a Volantex 400mm span micro warbird. These are versatile little boards, being equipped with a 1S speed controller for brushed motors and a very clever 6-axis gyro system. The problem was that only one plan existed for an Avro Commodore, an Aeromodeller design from 1940 for a very much simplified, almost 'cartoon scale' rendition, see Avro Commodore (oz5426). Fine if you like a lot of vintage charm but not really a scale model.

Before I knew it, I'd volunteered my services to knock up a 'quick n' nasty' plan for Barry to build from. I was vaguely familiar with the Avro Commodore and downloaded some three view drawings. I was also sent lots of original references that another aspiring Avro Commodore designer had collected, (thanks George!) but as I started drawing and correcting and comparing with grainy photographs, the plan developed and started to look nice. Before long, I realised that my 'quick n' nasty' plan was worth getting right, annotating fully and inking, in case other modellers fancied having a go at this rare but charming 'British Waco'. I leaned heavily on Barry's extensive experience in converting small rubber models to micro RC models and designed the Commodore to be RC from the outset, with control surfaces designed in and incidence angles set up to make a smooth flying RC model, as opposed to a free flight design with excessive positive incidence on the mainplanes. It was also designed to be rugged and handle the often-gusty winter conditions that Barry flies in, being perched up in the Northern Highlands.

After Barry did such a great job enlarging and modifying my Caudron Goeland (oz14732) design, I had no doubts that he'd do an equally great job at building the Commodore, thus it's been proven as I'm sure the attached photos attest.

Model Specifications

Technical specs are as follows: RC board, aileron servo and motor, all bought from AliExpress as Volantex spares. The motor is a 1020 coreless brushed motor running through a gearbox. Barry suggests that an 0820 motor would also fly the model, he chose the 1020 for a bit of extra weight and a bit more punch to get through the winter gusts.

The battery is a 300mAh 1S LiPo. Covering is 30 micron soft-touch Doculam, painted with alloy wheel spray paint, decals are homemade using clear decal paper and the model depicts the prototype in its handsome and understated all over silver colour scheme.

All up weight, ready to fly, is 88g (3.1oz).

Modifications to prototype

Barry made a few changes to the construction shown on the plan, namely he sheeted the cowl with 1/32" balsa, eliminated the use of paper for fairings, making the upper wing root fairings from carved balsa. He also increased the stringer cross section to 2mm square, as opposed to the 1/16" square shown on the plan and a little more infill planking was added behind the upper wing trailing edge to smooth the lines. The fin outline was made slightly thicker than shown on the plan and sanded out to scallops between the ribs and spars after construction, all sensible precautions when using 30 micron Doculam on a relatively small model.

Known deviations from scale were an increased fin and tailplane area and a slight simplification of the fuselage cross section at the lower wing trailing edge to ease building.

Onto the part that everybody's interested in - The flight report!

Barry and I consulted on where we thought the centre of gravity should sit, and I suggested that the leading edge of the lower wing might be a conservative estimate. Barry concurred and we both agreed that the best answer to the question would be to fling it! December on a rocky, windswept promontory, jutting out into the North Atlantic is not generally known as an ideal time or place to test fly little scale biplanes but Barry, being of Viking stock, wasn't perturbed and declared that an 18mph gusting to 20+mph would be just fine. The cockpit windows and screen weren't yet fitted either but similarly to the unholy gale, this didn't bother our plucky test pilot!

I've learned by now that Barry always proves my doubts and fears groundless, so I kept them to myself.

It proved to be the right decision again, because the Commodore not only flew, but it also flew flawlessly, not requiring a single click of trim! Barry and his son both took turns in testing the model, looped and spun it, and flew slow, high-alpha flight and normal circuits. One thing that I, as the designer, wanted to know was that the model could be flown without any gyro stabilisation, Barry confirmed that he switched all the the gyros off, expecting a sudden trim change and the need to switch them on again, but the model continued on smoothly and flew without any correction in trim being required. This means that the model could easily be built using any of the commercially available micro-RC equipment and doesn't need the 6-axis stabilisation of the Volantex equipment. It also suggests that, with a little positive incidence (2 degrees) built into the mainplanes, it would make a stable free flight design too.

Conclusions

Both Barry and I are delighted with the outcome of this joint project, I'm certainly very grateful to him for building another prototype from my plans and providing such superb photographs to illustrate this page, we hope that many others out there have a go at making a Commodore of their own! Special thanks are owed to George Gilbert for kindly providing us with so much reference material.

Pete Theobald 07.12.24

Corrections?

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