- This article was first published in April 2000.
- Although a brushed motor power set is described, builders would be advised to look at a modern brusheless electric power system for their model.
- The Hindsight plan is available from the RCM&E Plans Service.
Hindsight is the second version of this model that I’ve built, the first being a 56” span version powered by an Enya 60 four-stroke. Having now swung entirely towards electric power, I toyed with the idea of converting my original design, but it soon became obvious that it was going to be rather expensive. Thus, Hindsight came into being.
Why Hindsight, you may ask? There again you may not, but I’m going to tell you anyway! Actually, the name is double edged. The model was designed as it is because I wanted to use an economy power set-up, running on seven / eight cells. So, in ‘hindsight’ I was going to require something smaller than the 56” version. Not only that – it also looks very much like the Hawker aircraft of a similar name. The outcome of all this was a handy sized, scale-like biplane that not only flies well, but looks great too. My fellow club members, here at King’s Lynn, were so impressed tthat she won the sport section of our main annual competition. With the day being quite breezy, Hindsight was one of only a few models able to manage the flight required, confirming her static judged position – even though the five foot take-off run was far from scale-like.
BASH THAT BALSA!
I always design my models with a simple-to-build policy in mind. Yes, I know, I’m idle! Just remember though that the more complicated a model is, the heavier it often turns out to be. Lightweight models are the key to success at this end of the electric flight spectrum, so don’t use five bits of wood when one will do (they work out cheaper that way too). The things to remember are that light models fly better than heavy ones, and simple models are easier to repair should you have a mishap. With the above in mind, don’t be tempted to ‘beef’ up your model; it works well as it is, having been designed to fly rather than bounce!
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I like to start with the wings, while I’m still keen. I find them pretty boring, and once they’re built, I’m far less likely to get side-tracked before the model is finished. We’ll begin with the top wings, since they’re the easiest.
The first two jobs here involve notching the trailing edge for some ribs, and trimming the lower edge of the four root ribs to allow for your centre section sheet. Now, pin down the trailing edge, lower spars, and 1/16” centre section sheet, before gluing the ribs in position. Ensure that all ribs are vertical. Also, glue in place the leading edge, wing tips, and tip gussets, followed by the strut plates (centre section and interplane), before allowing to dry thoroughly. The top spars and spar webs may now be added, and once dry, the capping strips. We’re now ready to join the wings.
Slot your root ribs to take the 1/16” ply braces; glue the braces to one wing panel and, once dry, glue the other wing panel in position. Don’t worry about the sweep; your braces can always be soaked and pre-bent if you’re having trouble – try a ‘dry’ run before gluing, to make sure. The wing has no dihedral, and so is pinned down flat while the glue dries. You now only have the upper 1/16” centre section sheet, and wing cut-out facing, to add before trimming and sanding overall.
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The lower wing is built in three simple sections, as shown on the plan, and is very similar in construction to the top wing. Build the centre panel first, adding dihedral braces before fitting the undercarriage plate and wing dowels. Don’t, however, fit the upper sheeting at this stage. Note that ailerons are built into the wing panels during construction, and are separated after the panels have been trimmed and sanded. See the wing section shown on the plan for details of the aileron leading edge.
Having joined your outer panels to the centre, install the servo extension leads, and only then, the upper sheeting. You now have the most complicated parts of the entire model ready to cover!
By this time, you probably think you deserve a rest, so we’ll do the tail surfaces now because they’re very straightforward. Simply build them over the plan from a combination of 3/16” balsa sheet and strip, as indicated. Once the glue is completely dry, remove the components from your board, trim / sand to shape, and join the elevators with your wire joiner. Easy, wasn’t it?
This assembly follows my usual method, i.e. it’s built in two separate sections – a front sheet, and the rear, built-up, one. Both are made until I reach the basic box stage, and then joined over the plan. A word of warning here: on the prototype, I used 3/16” sheet for the front section, and had a devil of a job trying to pull it in around former ‘N’. If you use two layers of 3/32” sheet, with the grain of the inner one vertical, it will make this task much, much easier. The rear box section is totally conventional and should cause you no problems, so I’ll concentrate on the more complicated front bit.
Pin down the strut and motor plates over your plan, and glue in place the sheet sides, F2, F3, and the undercarriage plate. Only glue your sides to the uncurved part of the ply plates at this stage, and allow the assembly to dry thoroughly before proceeding. Once ready, pull in your sides onto the lower half of former N, fitting F1 at the same time. Follow this by gluing the lower nose block in position. Having ensured that the assembly is all perfectly square and evenly curved, leave it to one side for full curing.
Things will now really begin to come together. Join the two sections of fuselage over your plan, and fit the 3/32” balsa infill and tail skid plate, once again checking that it’s all square. Remove the assembly from your board, and shape / hollow the nose block; bolt on the struts, and securely glue in place the rolled ply motor tube, complete with motor. Use a few pieces of balsa block glued in place, one either side of the gearbox, to ensure that the motor will not be able to rotate in your tube. Once all the formers, sheeting and stringers are in place, fit a scrap spinner as a guide, and trim / sand your fuselage to shape. The ply cooling scoop is optional, but helpful if you want to hide the cooling air-hole under your nose.
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My model is covered almost entirely with silver and chrome Solarfilm, the latter being used for those polished metal nose panels. All markings are commercial items, and available from any good model shop. The strut and undercarriage paintwork is Humbrol gloss enamel.
Just how much detail you add to your model is up to you, but I would suggest at least a pilot, Lewis gun, and exhaust stubs. Should you wish to add panel lines and rivet detail, to break up the nose areas, I’d further recommend the use of a fineline, all-surface, permanent marker. These work well on film, and will add some realism.
MAKE IT A MINI
If at all possible, try to avoid using standard sized servos. The model will cope with them, but they’ll add a lot of weight that you could well do without. Hitec HS101 minis are ideal for a model of this type being light, cheap, and very reliable.
The servos, receiver, and speed controller in my model are all retained with servo tape. Smear a little epoxy onto the wood in an appropriate position, and allow to go tacky before fitting the tape. I’ve never had a servo come adrift using this method: similarly, I’ve never lost a NiCad pack, these being retained with either silicone sealer or a cable tie.
Anyone who has flown electric models of this type will sympathise with my dislike for having to dismantle a model in order to recharge the NiCad – especially when you’re flying a biplane! Anyway, I got around the problem like so: add an extra lead to the -ve terminal of your pack and a longer, +ve wire to the speed controller. Join the -ve speed controller lead to a -ve wire from the NiCads. The extended controller +ve, NiCad +ve, and second NiCad -ve leads are fitted with plugs and sockets – plugs for +ve, socket for -ve. All run into the rear cockpit floor, where they are epoxy glued in place. There are no connection between the +ve leads for charging purposes; once your pack is charged, you simply run a jumper lead between the two positives – and then your’e ready to run.
Since this system uses BEC, and no receiver NiCad, as soon as the jumper lead is fitted, power is supplied to both receiver and motor: so, make sure the Tx is switched on. As for the on-board equipment, I’d recommend using a Kontronic Easy 3000 speed controller, and Hitec mini four-function Rx. Both are reliable, and very reasonably priced. Do, however, only use good quality NiCads for your flight pack. Mine are 1700SCR cells, but RC2000s would provide a longer flight duration, with only a minimal weight increase. Don’t even attempt to fly this model on cheap cells; they’re just not up to the task.
Position the fuselage over your top wing, with both inverted, and once totally satisfied with the alignment, mark and drill some screw holes in the ply wing plates. Screw the top wing in position. Fit the lower wing bolt bracket to F3, and mark it’s centre onto the fuselage. Temporarily fit your lower wing to the fuselage, align it with the top wing, and mark the centre section rear-edge onto your fuselage. In addition, mark the wing bolt centreline onto your wing. Remove the wing, fit your wing bolt into its bracket, and measure the trailing edge mark – bolt centre distance. Transfer this measurement to the wing, and drill your bolt hole.
I know this sounds a long and complicated process, but it does ensure that your bolt aligns with its bracket, and that the wings will still align. The interplane struts are simply sprung into place, and work in compression only.
Use the wing / fuselage assembly as a guide for aligning your tail surfaces, and epoxy them in place. The ailerons on my model are top-hinged with film, whilst all other hinges are from Mylar strip. Linkages are as shown for the ailerons; use snakes for both rudder and elevator.
HINDSIGHT IN HEAVEN
Make sure the model balances slightly nose down at the point indicated, and set up your control throws as follows: rudder, 1” each way; elevator, 1/2” each way; ailerons, 3/8” each way. These are only initial settings, and will prevent your model being too sensitive during initial flights. Obviously, you can always increase the throws to suit your individual flying style at a later date.
So, you’ve carried out all your checks, faffed and fiddled about for as long as possible – now, you just have to try her in the air. Head her into wind, open the throttle, and hold in some up elevator until she’s moving. Let her pick up some speed, then ease her off with another dose of ‘up’. All very basic stuff, in fact. The climb-out will be steady, with very little need for trim changes. She will, with increased throws, loop easily, do a ‘barrelly’ roll, and a very passable Cuban eight. You’ll need to hold in some down elevator during inverted flight, but not too much. She is a very pleasant little model to fly, and great fun too.
My model is, I’m afraid, now dead. I misjudged a low inverted pass by about 6”; the wing stopped instantly, the fuselage went a bit further – and the NiCad further still. Looking on the bright side, at least it liberated some radio gear for another model! I may yet build another Hindsight though; she looks good, flies well, and is inexpensive to build. Quiet, too! What more could you ask? Build one yourself; you won’t regret it.
Model type: Electric biplane
Designed by: Peter Rake
All-up weight: 3.3/4 lb.
Wing area: 383 sq. in. (top)
306 sq. in. (bottom)
Rec'd motor: Speed 600
Rec'd battery: 7/8 cell 1700 – 2000 mAh (BEC)
Control functions: Aileron, elevator, throttle, rudder