Zippy (oz7664)

About this Plan

Zippy. Slope soarer. Folding wing for easy transport. Use 2 function R/C.

Quote: "Zippy is a rather unusual slope soarer, for a start, it's a flying wing and that means it can be bundled in and out of the car with the least delay whenever the urge to go flying becomes too strong to resist. And secondly, to make storage and transportation even more convenient, the wing itself folds in half by means of an ingenious new application for the humble zip-fastener.

Have you ever wanted a little model that can be easily transported and easily 'hidden away' for holidays, etc? I have, and knowing roughly what was wanted thought I would have a go at rolling, my own. Hence Zippy was born.

I picked a wing span of 36 inches which seemed a good starting point: The wing would be two-piece giving a broken down size of 18 inches by about 6 inches. To try and keep to this overall storage size, the fuselage would have to be about the same size, that is, about 18 inches long - a bit shorter - how about a flying wing? That's the answer. I had never built a flying wing design before so, in the interest of experimentation, blindly onwards.

To keep things simple I went for a flat bottomed, constant chord wing with a small amount of sweep-back to get rid of the ugly 'plank' look. The fuselage would be a typical box section with formers and triangular fillets in the corners so that a degree of roundness could be achieved. Building materials would be balsa wood mainly with 1/32 plywood in strategic areas for strength.

Obviously, with a flying wing it necessary to mix the roll and pitch controls. This caused a bit of a problem because I didn't want the complication of sliding servos. Then I thought of using a rocking servo box which is nice and simple.

The method of wing joining was another problem as I didn't want. piano wire wing joiners because of the weight penalty. Then I remembered seeing, ages ago, a zip-up wing; that was the answer! Wing band dowels would be internal to keep the outside of the fuselage clean.

I didn't do the drawing first, I sort of drew the outline on the balsa and cut it out. As a result, the end product just evolved. Building was very straightforward and only took a week or so of evenings to build and didn't cost much either! The final specifidation of Zippy is as follows:

Span: 38in
Wing area: 2.3 sq ft
Section: Clark Y
Weight: 18 oz /sq ft

So, with everything installed and ready to go we set off for the first flights. Would it? Wouldn't it?

It did! First flights were with the surface movements set to the minimum shown, ie 1/4 in up and down. On launching, everything was fine until I touched the down elevator. The nose dropped and the model dived vertically, sometimes into the ground. This repeated crashing broke former F4 which had the rear wing band dowel fixed to it. This former was subsequently replaced with a beefed-up version of 1/8 balsa and 1/32 ply as per the plan. This solved that weakness and no other serious damage has occured.

The pitch problem was rectified by moving the CG back to about 30% root chord. This gave a much better behaved performance, very docile, if little fast.."

Direct submission to Outerzone.

Update 02/05/2016: article pages, text & pics added, thanks to RFJ.

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