About the ZAGI

A ZAGI is a radio-controlled aircraft made of expanded polystyrene (EPS) and/or expanded polypropylene (EPP) foam, with balsa or Coroplast elevons and winglets, with or without electric motor, in the shape of a flying wing, with a wingspan of around 4' (120cm). It is usually covered in polythene tape. It usually comes in kit form, consisting of a few large pieces to be glued together. Kit building can be completed in a day or afternoon.

The glider variant, "Zagi-Si" in the UK, costs £35 or thereabouts.

The kit includes the EPS wings, EPP leading edges, Coroplast winglets and elevons, control rods, clevises and control surface horn things, as well as a roll of coloured tape. The radio gear (I use Hitec Focus single stick, standard servos, Sanwa receiver - avoid the Hitec Feather receiver if possible, it is very poor) costs about £80; when bought as a deal, you should be able to get some money off. I advise against going to Dunstable Model Centre as the fellows in there are among the grumpiest people I have ever had the displeasure of meeting. They even refused to swap the white tape that my ZIG came with for the colour of my choice. Bastards.

The ZAGI is the ideal beginner's radio controlled aircraft, because it's virtually indestructible. For this reason, it can also fight other Zagis in mid-air. These dogfights are great fun!

The ZIG

My Zagi-Si is called the 'ZIG', and has had three different "tape-jobs":

The ZIG before its first flight. Notice how immaculate the tape-job appears to be. Click to enlarge.

1. Yellow (above) with two black stripes, front-to-back, across one wing, and 'ZIG' underneath the opposite wing. Black winglets.
   This scheme lasted a long time. Eventually, the fictional sponsor "eberspatula" was drawn on the top.
   
   I used a lot of fibreglass tape on this job, with strips of it along the leading edges as well as down each trailing edge, top and bottom, crossing over to meet the opposite leading edge. The elevons were attached using "hinges" made from interlocking strips of fibre tape. Because of all this heavy fibre tape behind the centre of gravity, quite a hefty piece of lead ballast had to be used in the nose to balance the aircraft, and the ZIG ended up weighing more than the upper guideline weight in the instructions. When the ZIG was crashed, this lead ballast moved around a lot, helping to pummel the polystyrene into a useless mess, prompting the Nose Job (below).
   
2. Clear tape all over. Following a conflict between the ZIG and an innocent gentleman watching the proceedings (and a near-miss between the ZIG and the gentleman's expensive model gliders on the ground), and having become fed up with how heavy the damn thing was, I decided to re-tape it using a slightly different quality clear tape. This scheme only lasted a couple of weeks, because the clear tape was thicker than the coloured tape, and didn't stick very well.
   
3. (current colour scheme) Black and white stripes all over, solid black under half right wing, one elevon black, one white, white winglets, shiny "ZIG" under right wing in aluminium tape. This is its current colour scheme. The central "tail" is a strip of fibreglass tape that can be trodden on while taking up slack on the winch (more about that later) to hold the ZIG in position.

(click images to enlarge in new windows)

This is the lightest colour scheme yet: I have only used as much fibre tape as necessary and the elevons are attached with standard tape. It therefore is more suited to light winds. However, it can handle stronger winds of around 25-30 knots, thanks to a lead ballast weight that I have made for it, which is 3/4 the size of a CD case, and can be stuck to the underside of the ZIG with fibre-tape for strong wind penetration ability. There is a winch-hook underneath, made from the wire hook of a clothes hanger, bent into shape with pliers. The nose job EPP is visible in the picture on the right.

Nose Job:

Halfway through the first colour scheme, the ZIG had been crashed nose-first so many times that the EPS (white) at the front had compressed and separated from the EPP (grey/black). This is because EPS tends to hold its shape more when compressed than EPP does. I decided to give it a nose-job, by using some EPP that "Al the Man" (thanks, Al) kindly donated.

I cut a pentagon of EPS out from the nose, behind the EPP leading edges, using a hacksaw blade, and inserted a replacement pentagon of EPP into the hole, glued in place with Araldite (2-part epoxy glue). I then cut the excess EPP off with the saw blade, cut new recesses for the battery, receiver and ballast, and replaced the covering tape. Here's what happened:

Crash damage to polystyrene (top)	Crash damage (bottom)	Cutting out damaged area of polystyrene
Polystyrene cut, ready for EPP.	EPP cut, ready to be inserted.	EPP inserted, glued with Araldite Rapid and held in place with tape while glue dries.
Retaped, good as new, bottom	Retaped, good as new, top

Pictures of the ZIG in flight (with original yellow colour scheme):

ZIG with aerial of transmitter in shot	ZIG approaching - duck!	Turning right	Dive, dive, dive
Flying along	The ZIG is quite high here	Turning left	Flypast
Prof. Vugel flies the ZIG into a thermal - look how high it is!!	Fighting gravity	Turning	Flypast
Crashed in a tree	Vugel locates the ZIG in the tree

Super Wench 91SE Pro

This is not a medieval strumpet, but merely a single-cylinder Suffolk Punch engine powered winch for the ZIG. It utilises 500ft of braided nylon kite line, has a ripstop nylon parachute (fabricated from a kite, indeed), and a length of elasticated shock cord. It has a throttle, brake, wheels and a detachable handle to ease transportation.

The Super Wench is the evolution of a winch concept started by Team Grecet a number of years ago with the Fishslice.

Fishslice fact sheet and photos

Name	Team Grecet "Cordless Fishslice" Winch
Powerplant	1x Suffolk Punch single cyl. 75cc engine
Chassis	Wooden skateboard
Drive	Centrifugal clutch, no reduction
Drum	Plastic spool; subsequently, plywood/metal drum
Line	50lb monofilament fishing line
Brake	Broom handle, rubber brake pad, "parking brake" drum-stop
Parachute	Handkerchief
Total Cost	about £5
Front view	Rear view (driver's view)	Drum stop open	Drum stop closed

The Fishslice, despite looking like a load of rubbish bolted togther (which, in many respects, it was) worked remarkably well. It was possible to launch the ZIG, into a very slight wind (too windy = no ZIG winching) to around 150ft high. This was only ever properly achieved once. It was difficult for the driver (Vugel) to regulate the speed of the winch, thanks to the unpredictable clutch with its high engagement speed, which often caused the ZIG to spin. The monofilament line was strong enough, but liked to tangle up, and didn't like to stay on the drum. Tangles were frequent and annoying, thanks to the low sides of the spool.

Eventually, once the plastic drum was eventually crushed by the line, we made a new spool with plywood sides and a steel centre, stuck together with Araldite. It had high sides and a smaller centre, so that the winch speed would be easier to regulate and the line wouldn't tangle so much.

The new spool worked well, and only broke after we started hitting it with a hammer (I can't remember why - I suggest not to hit these things with hammers if it can be avoided). However, we took the engine off the winch to use it for something else, and a year passed with no winch.

The "Wenchmaster", as we don't call it, was created with relative patience and love. At over £50, it cost more than the Fishslice did. We originally tried to TIG weld it together from aluminium, which failed and was a waste of time and money. The main feature of this winch is its belt drive, giving a reduction of about 2:1 and further regulating the winch speed. It utilises the wood/metal drum from the Fishslice, running on bearings that cost £10 each, and is painted with real paint.

The line on both winches is guided onto the drum by a pair of aluminium runners. A complicated paying-in gear would just be too complicated for this crude level of technology.

When viewed from ground level, it looks like some sort of robot from Robot Wars ("Shunt", perhaps).

We have yet to test it in low wind, and hence we have yet to get a decent launch from it. More pics and video when that occurs. I certainly wouldn't use the winch with any kind of delicate or expensive model (unless it was a calm day when consistently good launches were being attained with the ZIG!).

Super Wench Photos

Closeup of carburettor	Winch from ground level, from right	How to apply the brake (modelled by Chelle, the Super Wench herself)	Ready to launch (short launch distance)
Ready to launch (long launch distance)	Winch from ground level, from left	Winch from right	Stack pipe with flap (modelled by Chelle)
Winch (modelled by Chelle)	Vugel going "easy now"	Winch from rear right	Winch from above, showing parachute
Winch from front, showing parachute	Pulling the cable out	Pulling the cable out (with ZIG)

Super Wench Factsheet

Name	Team Grecet "Super Wench 91SE Pro" Winch
Powerplant	1x Suffolk Punch single cyl. 75cc engine
Chassis	Box-section steel, welded
Drive	Centrifugal clutch, belt drive, 2:1 reduction
Drum	Plywood, steel, aluminium core
Line	Braided nylon kite line
Brake	Band type brake, applied to clutch
Parachute	Ripstop nylon
Exhaust	Stack-pipe, steel, with flap cover
Wheels	2x, shopping trolley
Bodywork	Steel sheet
Colour	Chassis; red, bodywork: yellow, engine: grey
Total Cost	£50 or so