Kestrel (oz11675)

About this Plan

Kestrel. Radio control scale model sailplane. Wingspan 2840 mm. Scale is 1/6.

Quote: "High Performance R/C sailplane designed by W Klinger from original drawings supplied by Glasflugel of Schlattstall. Scale 1/6.

The Kestrel is a crown prince among gliders. With a glide angle of 43 and a minimum sink of 56 cm/sec it is at present one of the very best sailplanes in the world. Its aerodynamic qualities are exceptional, and this induced us to choose the Kestrel for our model.

We have taken great trouble to see that this model is the crown prince among R/C gliders. The model is designed for Re numbers of 100,000 at a speed of 7 m/sec. We chose the Eppler 385 section as this gives a wide usable speed range. The zero lift angel of this section is - 6.6°. The relatively thin aerofoil demands careful wing design and here we have been highly successful. The trailing edge is notched, ensuring connection positioning of wing ribs. The great strength of the wing permits flying in strong winds, as well as ordinary bungee launching and simple aerobatics. Ailerons are fitted as standard.

The T tail provides excellent stability on the bungee and protects the tailplane when landing on rough terrain. The tailplane is not affected by the airflow over the wing. The tailplane is all moving, and the model is consequently very responsive in pitch. The rudder too is very positive, and for this reason ailerons are not absolutely essential.

The model's high aspect ratio and close adherance to scale make it easy to mistake it for the full size. The Kestrel is especially suited to aerotowing.

Mr Raymond Brogley, from Orthoz, France, used his Kestrel to set up a new World Record for closed circuit distance, flying 322.2 km in 6 hours 51 minutes.

Another 'Kestrel' success: Mr JF Duda won 1st place in scale at the US Soaring Nationals in 1974.

TECHNICAL SPECIFICATIONS
Span 2840 mm
Length 1175 mm
Area 44 dm2
Tailplane area 6.9 dm2
Loading at 1400 gm 27.5 gm/dm2
Wing aerofoil E 385 (Go 829), lifting tailplane, aspect ratio 18.35."

Direct submission to Outerzone.

Note photo of completed Kestrel 2.8m model was found online at http://www.coogan.de/wik_kestrel_2800.htm

Update 18/11/2021: Added kit review from RCM&E, May 1975, thanks to RFJ.

Quote: "Kit Review: Wik Kestrel, by John Elliott.

THE Kestrel is a scale model sailplane with a wingspan of 112 in and a fuselage length of 46 in. One thing must be said for the German kits which I have handled - all are very attractively presented in boxes giving a large colour plate of what the finished product should look like, its colour scheme, and other markings.

On opening the fairly large box, the main eye-catcher is the absolutely superb glass-fibre fuselage, weighing 11 oz, this being almost opaque as it is not pigmented like some, and, after rubbing down with fine wet and dry paper (used wet) and any small air holes filled, will either require spraying or painting with a suitable polyurethane paint.

Putting the fuselage to one side, one becomes aware of the rest of the kit. The plan is very clearly printed on thick, good quality paper, it being necessary to join an extra continuation strip to one side of the main plan, there being line up marks to ensure positioning. An excellent piece of German efficiency is that every part of the plane is drawn full size, including both left and right wing panels, which obviates the tiresome job of Sellotaping the plan to a large window so one can trace the reverse panel. (Plan also shows position of radio gear).

There are four type-written pages of building instructions in fairly good English and these should be carefully followed and also a separate sheet containing seven building sequence photographs, six of which are concerned with building the wing structures. A help in building this type of plane is the continental method of numbering all parts and these are built in sequence, ie number 2 is built on to number 1, number 3 built on to number 2 and so on into the hundreds.

The wings and elevator are straightforward traditional balsa constructions, the wing section is almost as undercambered as an A/2, F/F glider and therefore one may feel more suited to thermal soaring, but if its performance is anything like Hegi's ASW.15, which also has a very similar wing section, then it will be able to cope with a wine range of slope soaring conditions and as soon as the weather improves I'll find out!

The plan shows controls on rudder, elevator and ailerons. It could be flown perfectly well without ailerons as the wings have 3° dihedral, but in my case 1Iave fitted the ailerons which will enable me to make more realistic turns, plus the ability to pick up a wing if necessary when flying near the ground.

The rest of the kit consists of a selection of superior grade balsa, each piece having been carefully selected for its particular role - the spindle moulded trailing edge being a perfect example, having an accurate rebated slot for the location of the wing ribs, which, along with the jigging strip, ensures that the wing is built free of warps as it has a remarkably thin section. The ribs are die stamped on selected sheets and come out so cleanly that it would be possible to use what remains as a stencil to draw out further sets of ribs, should the occasion arise.

Also included is a bag containing a good selection of metal Kwik-links, horns, wing rods and tubes, plus a few water slide transfers (here I feel that for the price paid, the manufacturers could have included a set of identification numbers which other scale glider kits do contain).

All control surfaces are controlled by cable. The kit contains two kinds: wire Bowden cable running in PTFE which 1 used for the ailerons, and nylon inner running in PTFE tubes, which I promptly discarded as they tend to bind, these latter being replaced by two more wire cable Bowden "snakes" for use of rudder and elevator.

It is possibly usual, when reviewing a kit, to build and finish as per makers' instructions. For this model however, I decided on certain modifications from the start as the glider will only be flown as a slope soarer - but more of this anon.

The wings should be built first, as they are required later to accurately position the wing retaining tubes in the fuselage. Before starting the wing construction, the leading edge, the spruce spare and the top and bottom wing sheeting all have to be spliced. The spruce spars are ready tapered for splicing and the only point to watch here is the short outer end of the spar which is stepped to cope with the very thin rib depth. The sheeting is spliced by laying the 36 x 3 x 1/16 in sheet on the building board up against a long straight edge, placing the smaller sheet up to the straight edge and overlapping the larger sheet by 3 in.

Next, pin down and cut diagonally across the overlap using a steel rule, remove the offcut corners, cover splice with Sellotape, unpin, turn over, fold back the short end, run in some PVA as it will sand and pin down to building board. From here on, the construction of the wing is relatively basic and using the two jig strips supplied (not mentioned in the instructions) under the trailing edge position, you will finish up with two perfect wing panels, including the 6mm washout at the trailing edge tips. When it comes to webbing between the ribs, the kit contains accurately cut 1/16 balsa sheet, but for the first six bays from the root I used 1/16 ply. Other than this, the wings were built as per makers' instructions.

As I have said, the ailerons are worked by wire Bowden cables, the outers being laid along the leading edge after first filing grooves in the underside front tip of the ribs, making sure the cables are level or slightly below the leading edge, and not above as per instructions. After pinning, secure in place with 5 minute epoxy.

When both wings are completed and lightly sanded, and, if using ailerons, this then is the time to cut them from the finished wing. If care is taken in following the makers' instructions no problems should arise..."

Supplementary file notes

Review.

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