Chaka III (oz14448)

About this Plan

Chaka III. Radio control intermediate aerobatic slope soarer.

Quote: "Chaka III, by Mike White. There were five models fairly close together in good lift just west of Slieau Maggle in the Isle of Man on that fine breezy day. Down through the valley one could see the sea and further out, the Irish coast around Ardglass. Glorious!!

High enough now and time to come back in a whistling dive towards the slope face followed by a swooping loop. Bring it round.... Bring it round.... Nothing happens. Battery dead? Try again, but still the darn thing doesn't respond. What the...! Now, here it comes. Hey! That's not my model!! What's more it isn't in the gaggle at all. Everyone is doing their thing except me!! Yes, I had been flying someone else's model, Chaka was nowhere to be seen. It was as if God had plucked it from the sky and taken it home with him. Never saw the going of it. Never did find it, never saw it again. Two Futaba micro servos gone too! Still, there were some problems with the design so back to the drawing board.

I changed the airfoil section as the original would only fly well in a really good blow. It was also reluctant to loop if started into wind, so the weight was increased by using a ply sided fuselage and providing a facility for ballast. I had recently purchased a Futaba Skysport transmitter (not clever enough for a true computer type!), so I could play with aileron and elevator coupling, lifting flap and breaking flap. Two aileron servos now go into the fuselage driving through the sides. It is almost a new design although nose and tail moments remain the same as do the wing and tail planforms.

The model may now be flown gently in light winds of about 10 mph and when ballasted to the maximum (get in as much as the fuselage volume will allow, typically 20-25 oz) 20-30 mph and more, if you like that sort of thing. Me? I'd rather sit in the freezer thanks!

Wing construction: The cores are usual EPS (foam) hot wire cut by your favourite operator and covered with obechi veneer. Fit the LE and sand to shape followed by the balsa TE and wing tips. Join the panels using epoxy and then give the wing a coat of PVA glue, slightly thinned with water, on the top and bottom two inches each side of the join.

When dry put another coat of PVA unthinned one inch each side and lay on a piece of two inch cotton cloth well stippled on. An old sheet will do fine. Then put on another coat of glue and a piece of cotton four inches wide and again stipple well into the cloth. Neat job. Instead of cotton you could also use medical bandage of good quality.

Ailerons are fitted using the film method or all weather tape. Some sanding will have to be done to get the ailerons to follow the changing thickness of the false trailing edge... "

Chaka III, Silent Flight, December 1996.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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