Jazz Xtreme Review

By ROB JOHNSTON 

Hi, I’m Rob Johnston, a flyer of both full size, in the shape of Boeing 767s for Air New Zealand, and a model flyer from the age of around 8 or 9 with a break of about 13 years with family and full size flying financial commitments. My full size flying career started with part time charter flights and then instructing and running a flying school before joining Air New Zealand at the beginning of 1988. I presently live at Waiheke Island, out in the Hauraki Gulf, off Auckland in the North Island of New Zealand. I mainly fly model gliders off the abundant slopes here, and some flat land thermal soaring. I have some electric powered aircraft as well.  

 So a flying wing to review!!!, and the new Jazz Xtreme as well.  Should be interesting-especially as I’ve not had a ‘wing before.   It set me to thinking about flying wings in general.   They have to have an aerofoil with reflex at the trailing edge to give them a stable pitching moment.   This gives them a lower lift coefficient (C/L) from the wing but not having a fuselage or tail and hence not much drag makes the overall lift to drag ratio perfectly acceptable for gliders.  The low drag means good high-speed prospects for the likes of dynamic soaring.   There’ve been several flying wing style full-size gliders that performed well for their time, but they aren’t the favored layout at present.   The Jazz wing is also swept back and this should make the stall less pronounced (the L/D curve is flatter at its peak with a swept wing) meaning it can operate well at the very low speed end of the range also.  Deltas usually have the biggest speed range of any platform aircraft; other things being equal.  Sweepback gives stability by virtue of the big difference in effective wing chord when the wing sideslips due to unintentional upset.  This increases the camber on the down going wing, therefore producing more lift, resulting in roll to restore the aircraft back towards its original attitude.  Therefore you don’t need much, if any, dihedral for stability.   One long look at the Jazz and sure enough it seems to match with the theory.

So, I’ve got a day and a half to kill in Hong Kong on a layover; should be plenty of time to go from boxed up to ready to fly.  Got the instructions out on the bus ride from the airport to the hotel and had a good read.  If you’ve made a foam model before it will seem very familiar and follows the usual Canterbury Sailplanes spar method of fiberglass rod spars joined together in the middle with an aluminum (alloy) joiner that is pre-bent to shape for the sweepback on the wings.   Shaped balsa trailing edge stock is used for the elevons on this model unlike the polystyrene foam of the rest of the range that they produce.

Now get out all the bits and have a look.  Very neat cutting of the EPP foam cores with no sanding needed to remove ridges or fibers that are clinging on.  (The speed of the cutting must be spot on and CNC accuracy).  The spar slots are nicely cut too;I just slightly bend the core leading edge down away from the spar slot to open it wider and the spars snuggle neatly into place.  The two wing roots seem to be identical in size and shape as well so should give the same incidence to both panels.   Elevons are of good grade balsa that seems stiff and yet not too heavy and ready to use apart from one could do with a sand to remove the saw marks if you are really particular.   (I didn’t bother and you can hardly see it on the finished article) Tape and glue and usual bag of horns and pushrods all there so I’m all ready to go.  Push aside the hotel literature and the fax to give me some table space and we’re off.  I built exactly according to the instructions for the evaluation and found them plenty comprehensive enough so I’ll just make comment on a few points I found along the way or things I thought of that might improve things a little.  If this is your first foamie; but you’ve built other models; you’ll have no trouble following along; some of the techniques will be a bit different to usual that’s all.

When I was gluing in the spars I only put glue inside the spar slots, which glues them in fine but leaves a small indentation to the aerofoil shape, which wasn’t very obvious to me until I covered the model. I suggest after you’ve inserted the spars; with the aforementioned slight bending of the core to spread the slot to easily insert the spar; run a bead of glue along the top of the spar, and smooth it out with a piece of plastic or scraper so it will flatten out as it dries and fill the gap nicely.

The Elevons for my model were exactly the right length for the job, just requiring the ends cutting to the necessary angle.  Don’t measure in from the centerline and cut off the 15mm or it will be too short.   But you look at things like that first before you cut it anyway don’t you?

I used two standard servos (Futaba 3001’s) and a 600 mah nicad flat 4 cell battery pack and a mini Futaba 7 channel receiver which all fitted fine and left me only needing minimal nose weight to balance.  The Futaba 8UAPS took care of all the mixing etc so I didn’t use an electronic mixer on board.  With the sweepback all the radio gear is in front of the C of G so no advantage in using mini gear I didn’t think.  

A tip for pushing the radio gear wires into the cuts you’ve made for them.  A flat file handle is ideal as it is blunt and has a reasonable area to push with so as not to stress the wires.

The comment in the instructions about there being only just enough strapping tape is right; don’t use very much overlap around the leading and trailing edges or you won’t have any left to hold the tips on with.

After the layer of the strapping tape it’s a good idea to mist spray again; as the previous spray has probably dried off by now; to ensure good adhesion to the foam of the first layer of the clear tape.

If you are going to use your model mainly for combat there are a couple of good hints I’ve seen elsewhere.  First cover the area of the servo control horn with the bowl part of a plastic disposable spoon, with the gap where the handle was to the rear for the pushrod to exit.   (Or there are purpose designed parts available apparently)

The second is to use flexible pushrods; both inner and outer; so that if you are hit on the pushrod it won’t permanently bend and affect the neutral setting but simply spring back afterwards.   I’m hoping to use the speed range of the wing to good effect with some dynamic soaring so I used the wire pushrods.

I used coloured tape to apply different patterns to the top and bottom as you can see from the photos and this has proven to work well when it’s flying.  All up to this point including putting in a little weight in one wing tip and a little in the nose and then calibrating the control surfaces the total time was about 6 and a half hours.  Right it’s ready to fly- just got to get it home to New Zealand because I’ve run out of time in Hong Kong.

Completed Jazz with Hong Kongs Causeway back in the background

I’ve now had three decent sessions with the Jazz; the first in quite light winds, the second in 25 to 35 knots ( 45 to 65 kmph ) and the third in between the other two ; so have been able to explore the flight envelope a fair bit.

I usually set up a new model with the recommended control surface throws as full rates and have about 60 to 70 % set up on low rates in case I find things a bit too powerful or twitchy. Most of the time I’ve spent flying the Jazz I’ve found the low rate setting to be adequate especially at the higher speeds in the stronger wind, but if you are using it for combat you’ll want the full throw settings to give you the whole range of possible maneuvers.

 Full elevator control (up or down) quickly brings the Jazz to a full stall from which recovery is near to instantaneous; good for surprising the competition. Full aileron on its own gives a quick rotating spiral dive, and combined with elevator gives a spin; after a bit of a hesitation following the initial flick roll; from which recovery is usually less than half a turn by simply releasing the controls back to neutral. If its not properly unstalled after a spin (by pulling out too soon) then a falling leaf type maneuver results. Some of the range of maneuvers that you can come up with are not possible with a conventional platform aircraft and I haven’t explored the range completely yet. It’s possible to hold the Jazz in deep stalls and it will flutter about or plunge downwards in attitudes I haven’t seen before; a feature of flying wings I guess. More gradual application of the controls give all the range of normal aerobatic maneuvers possible with two axis controls; your skill is the only limit it seems. 

The differential settings seem to be about right to me because some yaw in the correct direction is induced by the ailerons giving a reasonably balanced turn even without rudder. This suits what I’m doing with the Jazz, but if you like more axial rolls then you may like to reduce the differential a bit ( i.e. have virtually the same up as down ).

The stability is reasonably neutral in roll, or in other words the Jazz goes basically where you point it; pretty much what you’d expect from this type of model. It does have good damping in turbulence though so I found I quickly had a lot of confidence to fly close in to the terrain even in the stronger wind conditions. The pitch stability is close to neutral; when trimmed for slower speed in level flight it will just start to pull out of a steep dive on its own. It needs only a small bit of down elevator to fly inverted.

Inverted performance is very close to upright; there is hardly any noticeable increase in sink rate and the elevator is equally effective for inside or outside loops so you can dive or climb to avoid that attacker when combating. 

In light winds the Jazz performed well with a reasonably low minimum sink rate so long as the speed was kept up. If you try and fly too slowly the drag starts to increase and the sink rate increases a lot. Fly it in the region of the envelope where there is good L/D and it’ll perform well. There wasn’t much increase in drag when turning gently either; so I could maintain height fairly easily in the turns. Throw in full control though and it’s a different story; you’ll need at least 10 knots (18 kph) on a decent slope to combat the Jazz I would guess, otherwise you’ll lose height too quickly with the maneuvering.

The strong wind day gave me a chance to really wring the Jazz out and it proved very able in the conditions. A few clicks of down trim was enough to increase the speed up to the prevailing wind and the total speed range available was quite a lot more than you usually get in a conventional platform aircraft without resorting to ballast. You’ll probably be familiar with the sight of an aircraft flying about 20 or 30 degrees nose down just to stay in one place when the wind gets up. Well, nothing like that required with the Jazz! Just ease the nose down a little and the increase in speed is quite dramatic; a function of the low overall drag that I talked about in the introductory theory bit. I managed to find a bit of dynamic lift by diving down behind the ridge line and some areas of bushes that were blocking the wind giving a calm region. The Jazz responded by increasing speed quite markedly so should work well if you’ve got somewhere to dynamic soar. 

The Jazz Xtreme at Redondo Beach, Los Angles June 2001.

I tried several different methods of launching the Jazz; fingers pointing rearwards on the top of the nose and launch with a backhand throw, index finger pointing forwards in the centre at the rear and launching with a push type throw, or a sort of discus launch holding the outer leading edge. My favoured method is the push type launch except in really gusty conditions when the backhand launch holding the nose gives better control.

I’ve flown the Jazz in a variety of different light and background contrast conditions and have found no problems with orientation due to the shape of, and contrasting coloured fins, and the completely different shaped colour schemes on the top and bottom surfaces. It looks really good swooping around, very jet fighter-ish. In fact you could probably put a semi- scale fuselage on and turn it into a tailless jet along the lines of a Mirage or similar.

Overall then I’m impressed. Good speed range and manoeuvrability make the Jazz Xtreme very versatile. Whether you’re using it for combat or dynamic soaring or as a different shaped general slope soarer I’m sure that you’ll find the Jazz able to the task. The kit is of top quality and contains everything you need to complete the model apart from coloured tape for decoration. You can build it in a night and a day and fly it the next. It’s tough and strong so should last well. Probably best for a second or third model than a first one for beginners; although if you cut the control throws down and have good help from someone experienced then you could probably manage it.

Its given me a lot of satisfaction so far, with plenty more to come. I’m sure it’ll give you just as much.

I’ve now flown a couple of other wings to make a comparison with the Jazz Extreme; the Zaggi 3C, and a custom made symmetrical section one by John Phan in Los Angeles; and find that it shapes up well. The Jazz and the Zaggi are about as maneuverable as each other in both pitch and roll axes while the Phan is a little more axial in roll but not quite as maneuverable in pitch as the Jazz. The Jazz definitely wins out in speed range over either of the others though, by virtue of the thinner wing section. I was able to go to Parker mountain the other day and try out that end of the spectrum with some dynamic soaring and the Jazz is AWESOME!!; limited only by the hill reaching out and grabbing it several times (or is there another cause? That’s what it looked like to me. ) Two or three circles in the 40 kph ( 25 mph ) wind had the Jazz really whistling along as fast as I’ve ever flown a glider I think. People there commented on how steady its flight path was compared to their wings (the damping I spoke of before) and how firm the skin felt and how stiff it was with the spars compared to what they were used to.

	Canterbury Sailplanes Jazz Xtreme features a new wing section designed by Joe Wurts specifically for EPP Flying Wings, and optimized for Slope Soaring Download CS Jazz Xtreme Manual Download CS Jazz Xtreme Plans