The two main
factors which seem to govern whether or not we can go flying is the available time and, of
course, the weather. The latter we can do nothing about, with in my case, the former being
restricted by my employment and the "head honcho" at home. Occasionally I find that I have a one
or two hour window twixt domestic chores and work, but it's hardly worth loading up and making
the trip across town to Calder Park or nipping out to Brimmond. So, even before the two recent
indoor events at Inverurie, I'd been toying with the idea of building a park-fly/indoor model
that I could take to the nearby University playing fields at Balgownie on just such
occasions.
But what to go for? I fancied something with a scale look, that would take the inexpen-sive sub-minature gear and wasn't too difficult for someone with "club hands" to build. Obvious candidates were the attractive range of biplanes produced by GWS, Simprop or Robbe, but at £50 upwards for the basic foam kit (OK, you get the motor too!), this seemed like suitable grounds for divorce. Whilst browsing through a back issue of Model World, out jumped those two magic words... "FREE PLAN"! In this case for an attractive looking fully built up 26 inch wingspan WW1 Bristol Scout that required only a few additional sheets of the correct grade of balsa to be purchased, so construction could more or less start right away. (If you want to keep the weight down, see Mike Pirie's article on the importance of balsa selection or go on a low-fat diet.)
No need to bore you with an in-depth account of the construction because it was all pretty basic stuff. a bit like putting together a rubber model! However, I did "kit" all the parts before reaching for the cyano, using the sandwich method to produce all of the wing ribs. This sandwich thing was a first for me, and a lovely job it made too!
All the major components were constructed using cyano, then carefully covered in Litespan, with the upper surfaces getting a lick of Humbrol paint and the waterslide roundrels applied before final assembly. Joy of joy, no warps! ...another first for me! Whilst on the subject of painting, brushing the Humbrol onto the Litespan covering straight out of the tin produced a very streaky result. By thinning 30% with white spirit, slapping the paint on was now a doddle without so much as a run in sight, but a second coat of the same was required to build up the colour. Finally, a vac. formed pilot and WW1 wheels finished it off. It was only at this stage I became aware that the red, white and blue flashes on the rudder were the wrong way round ...one glass of plonk too many, I guess!
Now came the fiddly bit. The plan was a bit sketchy on positions for the radio gear, but after a bit of trial and error, I finally got the CG about right (my batteries and servos were a lot further forward than the designers photos indicated??). Shoe horned into the tiny airframe was a GWS 150 geared motor, a 7 cell x 300Nimh battery pack, Jeti Rex 5 receiver and two Hitec 55 servos (rudder / elevator) for an AUW of just under 7.5 ozs. Wow, I was impressed ...and it was actually within the target weight. Considering that my models generally carry that sort of figure in epoxy alone, a celebration was called for ...what difference will another glass make, eh?
A word of two on these light-weight battery packs. Mine were supplied by Overlander early on in the build. Sometime later I contacted Walter Wilkinson of Hillcott Electronics, who specialise in the park-fly/ indoor market, to order the motor/ gearbox and speed controller for the Scout. He told me that they now stocked a Lithium-Ion 800mah pack which was lighter than the Nimh pack that I'd be using. These new batteries, he assured me, were typically producing flight times of around 1 hour and could be field charged in 15 minutes or so. Bugger, if only I'd phoned him first! On the downside, they're a bit more expensive, with one pack and dedi-cated charger (as I recall) costing in the region of £40. Worth looking into if you fancy building small though!
Maiden flight took place on a calm, warm March morning at Calder Park. All the usual precautions were taken... double check the CG, range test and, of course, no sex the night before. I wanted to remain very focussed!
Mike Pirie was on launching duties and with full throttle applied away it went, straight into an uncomfortably steep climb and gentle stall. This was repeated a couple of times before enough down trim had been fed in to produce level flight. Phew! Once settled down (me, not the model) it flew quite happily on half throttle and at slightly more than what would be considered a scale speed. Neverthe-less I was fairly chuffed, and after 7 minutes of cautious circuits pulled off a successful landing ...a gentle noseover in actual fact, because long grass and little wheels don't mix! For the following two flights a 7 gram lead weight was stuck into the cowl to make it slightly less sensitive to control inputs. This seemed to bring an improvement, but a light breeze had picked up which tended to throw the Scout around a little, so final trimming flights would have to wait for another day.
Several weeks on and half a dozen sorties in the uncommonly calm, settled spell of weather. With no room to move any of the gear further forward, I was disappointed at having to add 14 grams of lead to the nose (half an ounce to us oldies!), so my "rear" must be a little overweight despite having used the recommended grades of balsa.
But the Scout still purrs away happily for a full 10 minutes of circuits and bumps. Aerobat-ics are out of the question, with even a basic loop proving tricky ...diving on full throttle only results in a marginal increase in air speed, so it tends to run out of puff before reaching the top of the loop. Perhaps a change of prop would help here? So, am I disappointed by the Scout's limited performance and the restricted conditions that it can operate in? Not a bit of it! A wonderful ten minutes of gentle, stress- free stick time out of earshot of the wife! What more could a guy ask for?