Cambria 'Scimitar'

Written for 'RCM&E' July 1981.

Picture of 'Scimitar'

The kit - Covering - Installation - Flying - Conclusions

Until the opportunity arose to build a Cambria 'Scimitar' for a kit review, I had never built an aerobatic slope soarer. This now seems rather odd since I had built other types of slope soarer and had always wanted to build something more aerobatic. Somehow, there were always more important things to build and, anyway; few of the aerobatic slopers I had seen appealed to me.

The "Scimitar" became available at just the right moment, and I immediately liked the looks of the model and, on opening the box, the. kit too.

The Kit

A very high degree of prefabrication is immediately apparent. Indeed, it would be difficult to imagine a kit with a higher number of preshaped parts, whilst still leaving you anything to build. Despite this. it is by no means an ARTF model.

The fuselage structure consists of preshaped 3/16" sheet sides with 1/32" ply doublers and just four formers. To this is added top and bottom decking in the form of five preshaped foam blocks. Four of these - the front arid rear top decking, the rear bottom decking arid the wing fairing - are supplied covered with obechi veneer. For extra. strength, the front bottom decking is covered with 1/64" ply. All of these decks are intentionally made slightly narrower than the main structure to.assist final shaping, although a slightly greater difference would be beneficial and the formers could be made some 1/32 - 1/16" wider.

A slot is ready made in the top decking to accommodate the fin which is assembled from four pieces of sheet balsa. The tailplane fits between the bottom decking and the fuselage sides and is from a single piece of balsa sheet with no provision for anti-warp bracirig. A single piece of sheet is also used for each elevator although the rudder does incorporate a stiffening piece along its lower edge. Small blocks are fitted to each side of the fin to round off the rear of the fuselage, while a single block finishes off the nose. After fitting the 1/8" sheet cockpit floor, the nicely moulded clear canopy and the rudder and elevator hinges, your fuselage and tail is complete!

Provision is made in the foam top decking for a weight box.. This is rather on the small side and a quick.calculation showed that this would take abouf 1 lb. of lead. For a model that is quoted in. the instructions as weighing 3.75 lb. this would be a mere drop in the ocean and the box was, therefore, left unfinished until the model could be test flown.

One oddity of the kit is that while the fuselage deckings are formed from beautiful, high density, blue toam, the wings are of ordinary white foam! Nonetheless, they are nicely cut and veneered and feature a 1/8" ply dihedral brace which would do credit to a '60' powered aerobatic model. This does not quite extend the full thickness of the wing and it is necessary to do some fiIling. There is the usual advice to cover the wing centre with gIassfibre tape (supplied) and resin. At this point, I invariably have visions of future archaeologists digging up wing centre sections and wondering what on earth ancient man used them for! Needless to say, I adopted my usual method of using one layer of 1 in wide nylon tape applied with balsa cement (after joining the wings with epoxy of course).

The leading and trailing edges and block tips have to be added to the wing cores and the ailerons have the now conventional arrangement of torque rods driving strip ailerons - which looked awfully small for an aerobatic glider. When hinging this type of aileron, it is best to make the hinge slots before doing any shaping. If you then make small pieces of ply (1/64" thick if using Mylar strip hinges) to temporarily replace the hinges and then tack glue the ailerons to the wing and then do your shaping and sanding you will finish up with perfectly aligned ailerons and hinges. When attaching thel Mylar hinges themselves, I use cocktail sticks and cyanoacrylateglue. At the risk of starting a huge correspondence, I must state that this is one of only two uses I know of where this type of glue is superior to anything else!

Wing attachment to the fuselage is by means of a dowel at the leading edge and two nylon bolts at about 80% of the chord which screw into nylon saddles on the fuselage sides. The iristructions suggest the afore-mentioned instant glue for attaching these saddles, I suggest Evostik - see later.

There is really only one tricky part of the assembly, and that is fitting the wing fairing. I originally used the fairirig to align the front and rear lower fuselage decking and then made it fit the wing by trial and error and careful trimming. One notable point is that the ends of both fairing and deckings are face dwith plywood. However, the holes in the fairing for access to the wing bolts are not reinforced and soon become ragged.


For convenience the entire model was covered with iron-on film (Ouickcote in this case), all upper surfaces being in white and lower surfaces in yellow. The same material tne same material was used for the red, orange and yellow trim. All lettering was formed by drawing the required shape directly onto red film with a felt pen and cutting around the edge with a sharp scalpal blade. These were then stuck down to orange film and the outline design similarly drawn and cut out. This double layer was then ironed onto the model.

The hinges were sealed by taking the film over the hinge line and pushing it down into the gap on both sides.


This is made very easy by the fact that all the necessary bits and pieces are supplied (except the radio) and the plan clearly shows where everything should go. On theassumption that you cannot criticise some that you haven't tried, I installed everything as instructed, with the rudder and elevator mounted in the fuselage adjacentto the wing leading edge (the pushrods therefore crossIng the weight box area) and the aileron servo in the wing cut-out. There is plenty of room in the forward fuselage area for receiver and battery pack and, with these as forward as possible, 1 oz. of lead was needed behind the noseblock to achieve the CG position specified on the plan. All control movements were set up as advised in the instructions. Total weight came to 2 lb. 14 oz., which is surprising as the instructions give the typical weight as 3.75 lb.


With a press deadline fast approaching, it became urgently necessary to fly the model and obtain some photographs so, as it was a baautiful fine sunny day (this was in early April - about a fortnight before the snowl), a trip jo Ivinghoe Beacon was arranged. Yes, you guessed - not a breath of wind. The model was flung into the air as hard as possible on three occasions and amazed everyone present by being able to stay up on whatever wind was available - while being flown in a straight line. Any attempt to turn produced an immediate loss of height, shortly followed by a hasty landing. All that we managed to discover was that the stall was very gentle with aileron control maintained throughout.

On the third landing the wing parted company with the fuselage due to the failure of the joints between the wing bolt saddles and the fuselage sides. Cyanoacrylate is not renowned for its gap filling properties and nylon mouldings are seldom flat, hence my recommendation for a more substantial adhesive.

A subsequent visit to the slope in a fairly stiff breeze proved that the model was a safe and stable flyer as set up but not fully aerobatic. Despite the solid aileron response at slow speeds, the roll rate at speed was very slow and made rolls difficult. This was made somewhat worse by the fact that the model was very nose heavy and needed full down to maintain inverted flight. To be fair, however, the instructions do state that the movements and CG position given are a safe starting point - which they are.

The piece of lead in the nose was removed and the receiver packed further back to move the CG about 1/4" further aft and all the control linkages were adjusted to give the maximum amount of movement possible.

This proved to be much batter, the CG position being about right with only a small trim change between upright and inverted. Loops were fine but outside loops were marginal and more down elevator than up is required.

It was also very apparent that the model was far too light. The design is very clean and has plenty of penetration yet a long steep dive does not build up any great speed. The amount of space available in the fuselage around the CG is somewhat limited. There is plenty of room ahead of the wing leading edge for ballasting, but this, due to the wing sweep. is far too far forward and would need a corresponding amount in the inaccessible rear fuselage to compensete. Possibly the answer would be to install weight tubes sirhilar to those normally fitted in thermal soarer wings.

Control surface movements - Ailerons 3/8" up, 5/16" down. Elevators 5/16" up, 3/8" down.


A very well thought out and presented kit which makes up into a very striking model, which will stay up in a very light breeze and has exemplary handling characteristics. If you require out and out aerobatics, you will probably be the type who would change everything, anyway, so this model would be a good starting point. With a towhook fitted, it just might make a good F3B model too.

Coloured divider

Top Home C/L Heli Articles Links What's New