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Review of the Zagi Flying Wing

ADVANCED ARTICLE

SLOPES - AND THE PLANES THAT FLY THEM

The Perfect Slope; What plane for the Beginner; Polyhedral Floaters; Flying Wings; Colour Schemes; Radio Requirements for Flying Wings; Cost of flying Wings & gear; Other EPP slopies; Learning to fly; Weather Protection

Slope soaring is the flying of unpowered radio controlled planes from a hill or cliff, using the updraft of the wind coming up the slope to provide lift.

The great thing about slope soaring is one can stay up as long as there is lift and as long as the batteries in your transmitter and receiver have power. This could be a long time! For the beginner, this means PLENTY of time to get used to the sticks and the control of the plane. It is invigorating, close to nature and a lot of fun.

It is very important that you start with a plane that is within your capacity before venturing into those which are as yet beyond your skills and that you receive training from a competent flier. Joining a club will give you access to a wealth of experience regarding flying, local sites and also the all important insurance cover. To find out about clubs in your area, ask at your local hobby shops.  

THE PERFECT SLOPE

The perfect slope will have: the land owner's permission for you to fly there; a good amount of height; no other hills or obstructions to interrupt the wind from the plain or water up your slope; a large grassy area at the top on which to land; the slope itself being grassy, safe to climb on and forgiving for planes that don't make it back to the top; a lack of powerlines, roads, barbed wire fences and bulls; good access and, most importantly, the right amount of wind in the right direction on the day that you wish to fly. To make the most of the slope's lift and learn its hazards, local knowledge is invaluable.

WHAT PLANE FOR THE BEGINNER?

The first thing the beginner needs to do is to learn how to fly.

POLYHEDRAL FLOATERS

The easiest plane to learn to fly is the polyhedral floater, that is, the sort of plane described in the Unpowered Gliding From The Field article.

A 6 foot / 2 metre polyhedral glider (ie, with wings bent about half way out and also sometimes in the middle) controlled by a 2 channel radio with rudder and elevator controls is very forgiving for the newcomer and flies well in calm conditions. Most experienced pilots keep one of these in their hanger as some light days they are the only thing that will stay up.

Sometimes coming down is the biggest challenge of all(!) so having spoilers to slow you down and/or reduce the lift is an advantage.

FLYING WINGS

A relative newcomer to the range of popular planes is the flying wing. These are becoming recognised as an appropriate next step after the floater for the beginner, but some beginners prefer them as a trainer.

Although they are less forgiving in the stall and they do not have the "look" of a real plane, they can be flown gently or quite adventurously.

Being extremely damage resistant, newer pilots can gain skills very quickly as a result of them being able to be put back into the air immediately after an unfortunate (crash) landing. Reducing the fear increases the fun and the ability to learn.

They are also easily transportable, don't require assembly at the site and don't suffer much from hanger rash (i.e. damage in transit or storage).

Flying wings are even sometimes used for "combat" where the aim is to cause a midair touch and send the other plane to the ground.

 

Construction

They are usually made of polystyrene foam, EPP foam (which is heavier but more resilient) or a combination of the two, with the leading 40 or so millimetres being of EPP.

The servos, receiver and batteries are simply pushed into cutouts in the foam wing, towards the front to keep the centre of gravity forward.

The wings are usually swept back and vertical fins, (often made of thin Corflute or Correx, the plastic "cardboard" that real-estate signs are printed on) are mounted on the wingtips.

The control surfaces consist of full length ailerons across the full length of each wing. These are called elevons as they are a mixture of ailerons and elevators. Both up gives nose up, both down gives down. One up and one down banks the wing on its side for a turn then a little up elevator will be required to bring the plane around.

Size

The Zagi SI which I fly has a wing span of 1200mm (47 inches) which allows it to do rolls particularly well. Wings much larger than this tend to wallow around the sky unless they are heavily loaded and are flown in a decent wind at high speed.

Weight

A light flying wing (around 450 grams) will fly in light conditions, but may give disappointing aerobic performance because of its lack of both penetration and momentum. They tend to stall when looping or if they are inadvertently given a little too much up elevator and they don't have the penetration to allow the high speed required for quick rolls.

A 1200mm flying wing that is around 650 to 700 grams will fly faster and will retain its momentum to proceed through manoeuvres without stopping.

Thus, your options are to:

  • Build light (say 500 grams) but have provision for adding additional ballast if the wind is stronger.
  • Build heavy because you would not bother flying a light flying wing anyway.
  • Own two flying wings!

Colour Schemes

Make sure the bottom to be a different colour from the top as it is very easy to become disorientated with a flying wing, confusing top with bottom. A different colour again on the leading edge could also assist.

Hints

Most of the hints and building tips for flying wing are contained in the Review of the Zagi Flying Wing article on this site. Also see HINTS.

I am quite happy to recommend the Zagi range of flying wings.

RADIO REQUIREMENTS FOR FLYING WINGS

The control surfaces are simply the two elevons at the back of the wing. ELEVONs are a mixture of ELEVator and ailerON. Both up gives up, both down gives down. To turn, one goes up and one goes down. To do this, mechanical or electronic mixing is required. Mechanical mixing can be achieved by having the "left/right" servo (which is attached to the elevons) being slid along rails or rocked or pivoted by a fixed "up/down" servo. The problem with this is that it requires a number of linkages (thus giving more room for slop in the controls) and the servos to be behind each other in the centre of the craft - weakening it structurally and requiring the second servo to be placed further back, and in consequence extra ballast is required in the nose. The better arrangement (and this is a requirement of the Zagi SI kit, since the servos are in a fixed position) is the use of electronic mixing, either by an electronic mixer placed between the receiver and servos, or, if you have it, the use of the electronic mixing function in your computer radio.

Electronic mixers come in two types - those with the ability to adjust the amount of up/down compared to left/right, and the cheaper ones that don't. You are likely to be disappointed if you go for the non-adjustable model as flying wings require a considerable amount of left/right but not too much up/down.

Computer radios with an inbuilt mixing facility usually also have the ability to adjust the travel/sensitivity of the respective functions, allowing both good up/down stability but plenty of left/right manoeuvrability. If you also put in some exponential into the left/right function, you can reduce some of the sensitivity of your turning in the middle ranges of the stick whilst still having the craft being able to roll real fast with full stick movement.

Sumarising; your basic 2 channel or multi channel radio is fine provided a quality electronic mixed is included, or if you have computer mixing on your transmitter then a separate on board electronic mixer is not required.

Cost of Flying Wings - From around A$400 including radio; plus club fees

A Zagi Flying Wing

Top and bottom are different colours.

My Spitfire

Item

Approx Cost A$

Your cost $

Radio - 2 channel OR

120

 

Radio - Multi Channel

300-800

 

Dry Cell batteries - 12 (for most 2 channel sets)

12

 

Flying Wing Kit

100-150

 

Covering Tape per roll (2 colours - one may be included in the kit)

5

 

Glue - 5 Minute Epoxy

10

 

*Knife

5

 

3M77 - now sold as 3M-Multi-Purpose spray in the GREEN can

18

 

Electronic Mixer (if you don't have mixing in your transmitter)

33-70

 

Battery Tester

45

 

Certification of radio

25

 

Frequency key

3

 

Club Fees, including Insurance

75-200

 

Total

$

 

OTHER EPP FOAM SLOPIES

Unlike flying wings, these look and fly like normal planes.

They are also a little less twitchy and are a little easier to orientate, but not quite as damage resistant as a flying wing.

Span will generally be from 1200 to 1500mm.

Examples of these can be found at: www.davesaircraftworks.com and other places. (If you know of these - please email me.)

D.A.W. Schweizer 1-26 Foamie

Span: 59", Length: 34", Area: 422 Sq.In., Flying Weight: 16 to 20 ounces, Airfoil: SD7037
Price: US$59.95 + S/H

ALTERNATIVES FOR THE BEGINNER: As stated in the Intro article, other models can be used but none are recommended. The models described fit the requirements of the beginner particularly well.

(Plenty of beginners have started on other planes on the slope - but on average they also spent more time repairing them than the above would require - hence my recommendation. Feel free to start with something else if you dare, or don't mind rebuilding - then give me feedback.)

TEACH YOURSELF TO FLY?

For those who try to teach themselves, the average first flight would be less than 4 seconds before the plane is crashed and badly damaged or destroyed. So seek training and save yourself a lot of time in the workshop.

Your trainer will also be able to tell you the best places to fly in what conditions, where the lift is on the slope, where to land, what to avoid, and frequency control, and be ready to take over the transmitter quickly if required and will land your craft for you. See Learning to Fly.

WEATHER PROTECTION

Slope soaring can be cold and you must not underrate the wind chill factor. Estimate the clothing that you will need then double it. You can always leave it in the car - or lend it so some other poor soul who is freezing!

A warm hat and scarf or balaclava, fingerless or thin leather gloves, a jumper or two and a windproof jacket and a pair of waterproof overpants will not look out of place. I popped into the Salvos and picked up a pair of bib and brace ski overalls and a ski jacket. I also sometimes fly with full length overalls.

Don't forget the sunscreen to protect you from both sunburn and windburn.

Moving on to other planes: (Having different models for different conditions is an advantage.)

- Aileron models

- Higher performance fibreglass models

- Large or small scale gliders

- Large or small Power Slope Soarers (PSS - they look like powered models but are actually unpowered).

- Just about anything that looks or flies like a plane or bird.

Above - a range of slope soarers at Camperdown, Victoria. We fly off the rims of extinct volcanos, so are able to fly no matter which way the wind is blowing.

Above and below - Max McCullough's Foam Airbus

Below - one of David Down's foam creations.

 

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Review of the Zagi Flying Wing