Ian Beckett's Duster

Extract from S&G December to January 1984/5

IAN BECKETT writes about a project which has taken much of his free time over the last five years - building a Duster.

The first of May arrived bright and blue. A moderate easterly breeze was forecast and as everything was ready I could think of no reason why this should not be the day. After several telephone calls had secured the help of the CFI, a tug pilot and some friends, I set out for the airfield.

The "moderate breeze" turned out to be distinctly fresh, but as the take-off would be directly into it I decided to carry on, consoling myself with the thought that at least the machine would (hopefully) become airborne at a relatively low groundspeed.

We assembled the glider and having double-checked everything, towed it to the far end of the airfield. This gave me a breathing space in which to collect my thoughts and try to calm my stomach. I strapped myself into the cockpit and with the wind shut off by the canopy and the tug taxying forwards, I began to feel very lonely.

The subsequent flight was, thankfully, an anticlimax, although it wasn't until I judged I was high enough to jump out that I really began to relax. The little Duster behaved just like all the other gliders I have flown and I was able to complete a reasonably confident, if somewhat cautious, approach and landing. Corks popped and we all drank a windswept toast to the successful completion of a project which had begun in earnest almost five years earlier.

The concept of building my own glider first occurred to me about twelve years ago when the Neukom Elfe was available in semi-finished form for amateur completion. For reasons which mainly involved the strength of the Swiss Franc and my own lack of Sterling I did not pursue the idea very far, but the seed had been sown.

Two years later a short item in S&G, December 1974, p265, caught my eye. It described a small American glider which had been designed specifically for home construction and gave a Box' No. in California. I wrote off for more information and so began a chain of events which led to the creation of BGA 2938.

The Duster is a single-seat wooden sailplane with a wingspan of 13 metres. Its construction is conventional, using spruce together with Douglas Fir and Gaboon plywoods, and just a smattering of glass reinforced plastic.

Duster

My original intention had been to build the airframe from scratch and import prefabricated metal fittings, but even a rough costing showed that in the long run it would be much cheaper to obtain all the materials from America.

To give an example of this, shortly before the kit was shipped the manufacturers wrote to advise me that they were currently importing their Gaboon plywood from England. They were prepared to allow me a discount amounting to the value of the plywood so that I could obtain it locally.

"That was nice of them" I thought and reached for my materials catalogue which was already two years out of date. I was amazed to discover that it was significantly more expensive to buy the plywood from British sources than to re-import it from America. The same applied to the necessary nuts and bolts and I estimate that scratch building would have added at least 50% to the cost of the materials.

An order for the kit was placed in November 1978 and I sat back and waited. The importation process was lengthy but uneventful and in May of the following year I was advised that my "Aeroplane Hobby Kit" would be arriving at Felixstowe aboard the container ship Liberty.

As soon as it had cleared Customs I borrowed a glider trailer and rushed up to Ipswich where, after paying what to me seemed totally unreasonable sums of money to HM Government, I was directed to a cavernous warehouse. A massive forklift truck appeared loaded to the hilt with a box which hardly seemed large enough to contain a set of garden furniture let alone an aeroplane. Two small cardboard boxes and a crate containing the plywood soon followed.

"Are you sure that's all there is?" I asked the driver. "Yes - sign 'ere". It was his lunch hour. We drove back to Dunkeswell, where Brian Weare had offered me some workshop space, and on the afternoon of Saturday, May 26, 1979 I broke open the crates. Four years, eleven months and six days were to pass before the Duster became a reality.

Anyone who is interested in what happened during that period is welcome to get in touch with me and I shall be happy to discuss the more technical aspects of building an aeroplane. All I will say here is that 1918 man-hours and well over 150 gallons of tea and coffee were consumed in the course of the project. There were certainly times when I wondered why I had ever started, but for the most part the work was enjoyable and very satisfying. The Duster's airframe was specifically designed for amateur construction and no complicated jigging is required. The aeroplane is built on a single 12in x 2in plank, 18ft long, which must be solidly mounted to form a long, level trestle table. Simple hand tools, an electric drill and jigsaw, are sufficient for most of the construction work, together with as many G clamps as can be acquired. I had access to over forty and there were occasions when I could have used a few more.

A certain amount of more specialist equipment for operations such as line-reaming and spraying was needed and this was hired, begged or borrowed for the relatively short periods for which they were required.

The plans for the Duster are proper engineering drawings of excellent quality and certainly instil a lot more confidence than the sheets of sketches which are provided with some home-built aeroplanes. The glider was built as designed with only two significant alterations. The wing of the Duster is made up of two outer panels 18ft long and a small centre section of 7ft span which is supposed to be bolted permanently to the fuselage. It seemed to me rather silly to have a glider which would fit into a trailer only 20ft long but which would need to be over 7ft wide to accommodate the centre-section, and I decided at an early stage that it would have to go. There were two options, either to redesign a two-piece wing or modify the centre-section in order to make it removable. The former was beyond my ability and so I now have a three-piece wing which is a bit fiddly to rig but much more convenient for towing than the original arrangement.

The other modification was to substitute an Ottfur cable release mechanism for the pieces of bent metal shown on the drawings.

When people ask about the Duster the two inevitable questions are "How Long?" and "How Much?” While I kept a reasonably accurate account of the time involved in the project, I tended to ignore the costs in the hope that they would go away. Suffice to say that the total cost of the Duster and trailer is comparable to that of a second-hand K-6CR and so one's motives need to be other than financial. These answers usually result in the third question "Why?” which I find difficult to answer in a manner which sounds convincing to myself, let alone anyone else.

Well, how does it fly? For the past eleven years most of my flying has been at the controls of a Slingsby Eagle after which any single-seater seems delightful, but I shall try to be as objective as possible. In flight the Duster is very manoeuvrable. As one would expect, its rate of roll is very rapid and the rudder seems powerful enough to cope with most of the demands made on it. Although the empty weight is only some 4001bs, the small wing area results in a loading of 5.71bs/sq ft with me in it, which gives the glider quite a solid feel and it is not thrown about unduly in turbulence. This wing loading also results in a Min sinking speed of about 1.5kt which is a bit on the high side by modern standards. Stalling and spinning characteristics are normal and recovery is positive and rapid.

Launching by both winch and aerotow in crosswind components of up to 10kt have presented no difficulties so far, although she does have a tendency to pitch towards the top of a winch launch.

As far as its glide performance is concerned, after 40hrs flying my best guess is that it lies somewhere between the K-8 and the K-6CR. The designer claims 1:27, the manufacturer of the kit enthusiastically claims 1:30.2, and I find that 4 miles/I 000ft seems to give a reasonable safety margin so that's what I use.

On the debit side the trailing edge airbrakes are not very effective, and I made a mistake in not fitting a wheelbrake - the ground run goes on forever. Generally I find it a very pleasant glider to fly, although it requires a bit of care when landing - but don't they all!

Reflecting over the past five years, I realise that I underestimated the commitment of time, effort and expenditure that building the Duster would demand. I had a fair amount of experience of working on wooden airframes before I started but even so there were times when help and advice was welcome and I was very fortunate to be able to lean on Brian Weare when I was not sure what to do next.

It is certainly not the kind of project which should be undertaken lightly, and I don't think I would do it again. Although having said that, if I were to increase the span to 15 metres, perhaps ……..

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