By Brian Austin

Having assembled and flown an Alexi XXL E last year (see review on this web for more details), I was rather keen to try out the Electric version of the Xperience Pro. The bigger size would I felt produce a better thermal glider than one that had started life as a slope soarer. Having said that, the Alex XXL did perform well in the 200Watt competitions that I flew it in last year.

The two designs share a common type of fuselage, all be it the Xpro is larger being some 3.3 metre span as to 2.6 metre’s for the Alex.  What appealed to me on both these designs was the thought that had gone into the siting of the Rx & servo’s in the fuselage. These components are housed in compartments behind the wing, so leaving the front of the fuselage clear to fit the motor, ESC & battery for the motor. I have personally never liked the sheath type of nose on electric models as it makes checking power settings & access to the battery more time consuming than need be.
Both designs could in my view be made a bit lighter in their construction, particularly in the wings, as they do not need to be stressed for winch launching. ( one benefit is with the purchase of a glider fuselage you also have a top contest F3J model aswell!) The weight of the Xpro ready to fly is given as 2.5 kilo’s, about .5 of a kilo greater than the Alex. As I wanted a model to fly when the wind speed increased for electric competitions, the weight is no bad thing.

 

Fuselage
I used a Schultz 835W receiver & 2 Futaba3103’s in the fuselage, for the elevator & rudder controls. There are not a lot of Rx’s that will fit in the limited area that is available, so check for fit before buying. The arms on the servo’s need to be bent down slightly to conform to the fuselage section, so as the clevis will clear the sides when operating. This can be done with a heat gun; do not play direct onto the servo, it is best to remove the arms when doing this to be on the safe side.
The connection to the rudder has been described in the review for the Alex XXL, so it can be repeated for the Xpro.
However on the Xpro the wire driving the rudder from the servo, which is pre-installed, is of a tubular section rather than piano wire and would appear to be stainless steel or similar material that does not solder. See the Xpro Build Forum on the Flyquiet site for a complete account of ways around this. I did however slide a piece of piano wire inside the tube, so it did not weaken it, where it was bent at right angles to pass through the rudder horn.
Next is to make up a 4-servo lead wiring harness, to run from the 9 pin female socket that is recessed into the fuselage, this connects the Flap & Aileron servo’s in the wing, to the Rx. (Always use the female in the fuselage, so as there is no chance of shorting out if the battery is left connected without the wing on)

The motor mount needs to be drilled to suit the motor of your choice & then epoxied into fuselage. I used a Kontronik Fun 500-27 with a 5.2: 1 gearbox, as I like these motors for various reasons.
An Aeronaut 45mm dia Precision Spinner Assembly plus 47mm Folding Prop Adaptor, driving a 16X10 Aeronaut Propeller, completes fixed set up.
An Electronic Speed Controller of minimum 60 amp capacity will also be needed, as will a battery of choice, I used a 2100 3 Cell LiPo.

Tail plane
Not much to do on this item, but my one required a bit of careful adjustment to get it fitting properly. This was in regard to the fit of the actuating wire. It was very tight and well nigh impossible to assemble, as received. So I made up what is known in the trade as a Whistle Drill, with which I reamed out the bell crank 2mm hole to allow the wire to pass through easily. This was repeated in one half of the tail plane, leaving one half tight so as the pin does not fall out during storage. The centre pivot pin did not need any work on it at all.
The front of the tail planes, where they are moulded to fit around the fin, will need to be sanded at an angle to allow full up elevator to be reached. The two halves should be taped when set up for flying as a safety precaution. As a guide, the trailing edge of the tail plane should measure 69.5mm from the top of the fuselage rudder fairing, or bottom of rudder, this is an approximate guide for setting the neutral position of the tail plane.

 

Wings
These follow the time honoured practice that we have seen for some time now,  requiring 4 servos for full control( I opted for Futaba 3150 digital servos in the wing) The servos are glued into position when you are sure of their correct operation in regard to centring & direction of travel. A wiring loom needs to be made to connect the 9 pin plug D plug that is fitted to the moulded aperture in the centre panel of the wing. Be aware there is not a lot of room between the pins that the wires are soldered to and the upper skin of the wing. A bit of fiddling is required and some patience to get it right. The brass horns supplied for the ailerons and flaps are 3mm threaded and screw directly into the pre installed nuts moulded into the wing. The length of the brass horns do require shortening so that they do not screw through the bottom surfaces of the ailerons and flaps. They have been cunningly arranged so that the clevises do not need to be ground away as they do on some models of this type.
I then bend the pushrods at right angles so they pass through the outside of the output arm on the servo’s and put an M2 thread on the small length that is on the servo body side. An M2 nut is then screwed on retain them. (See pics) This allows the rod to travel fully without fowling the collar on the arm.
The CG should be at set at about 101-103mm from the Leading Edge of the wing, measure from  the mid point where it sits on the fuselage.
Mine balanced out with the battery placed right up against the motor.

Flying
After the terrible spate of weather of late, (Jan2008) a lovely day chanced upon us to try the Xpro out. I was using a BEC on the speed controller to save a bit of weight and there seems to be a move back to these rather than the Opto ones now.
The Xpro was launched away for about a 15 second motor run, in a Speed setting on the Flaps & Ailerons. This setting is what I normally use, to keep the model in a steady climb without going too vertical. I was only using about 200 Watts at this time but she climbed away well up to about 350 ft. The elevator felt like it had too much movement so rates were put in which seemed a lot better. Also down trim was applied to the elevator, this cured a slight nose up tendency and gave a nice sit in the air with a good glide angle. Coming in to land, the crow braking seemed a bit fierce with the big flaps, and more down elevator compensation was needed.
On landing, adjustments were made to cure the above problems and a new battery giving just on 400 Watts when checked, was installed.
This time the climb was very good and I settled in to enjoying myself with the model. I cut the motor after 20 seconds run time and a fellow flyer with me reckoned that the height was approx 500+ ft, this gave a flight time of about 5 minutes. Not bad, as by this time 2.30- 3.00 pm, there was not a lot of lift around.

Brian Austin.