By Nick Kidd.

Having taken the plunge in purchasing the Xplorer, I thought I would share some build techniques that work for me. There may be a few different ways of solving certain problems and adapting solutions to suit your own radio gear and/or tools. Many of the following details I have employed on the Xpro and Shadow and should be useful for building those models.

Antenna

I find it a good idea to sort this out first and before the rudder linkage is installed. I like to run the antenna inside some tubing. I split several drinking straws at one end and cyano them together to form a long tube. Carefully pull the rudder to one side and  drill a drinking straw size hole in the bottom of the balsa stern post. Feed the tube up into the fuselage to one side of the servo tray and glue the back end of the straw into the stern post. You will then be able to feed the antenna down the straws and out through the rudder post.



Rudder

The linkage installation on the X tail is always difficult but it is possible to get decent throws with a little care. First, take a clevis and place in a vice. Then grind away upper and lower clevis blades on the outer edge as shown in the picture. Pay attention to keeping the line flat at the threaded end and bevel the edges, it is the clevis that will bind on the fuselage fairing so trim it fairly aggressively. You can remove a lot of material without any fear of compromising its strength. Next, carefully file out the wall of the fairing at the rear as much as possible. You can trim the fairing back a little if you need to, but you should be able to get it to fit.



Next, cut the thread on the brass rudder horn shorter, so that it does not push through the skin on the other side of the rudder. CAREFULLY drill the centre of the rudder horn fixing area. If you use the right size drill, you can thread the horn straight into the glass (and epoxy it later). Now dremel out a small section of rudder immediately in front of the horn, including the gap seal because if the rudder is hard right, the clevis will foul at this point.



Assemble the clevis onto the horn, screw the horn into the rudder and have a test run. See if you can get the correct amount of movement, it will be left rudder that is the challenge. It may foul a little but not enough to cause problems. When you are happy, roughen the underside of the horn and the rudder horn boss and epoxy it in place. Finally, pull about a foot of the snake inner out. Clean up the end with abrasive paper. I use a gas miniature blowtorch type of soldering iron and it is the only way to do this part. Hold the clevis in some pliers or small vice. Heat the clevis thread, apply some good flux and fill it with solder. Then flux the end of the metal snake, apply some heat and place the clevis onto the end of the metal snake inner, making sure it is level and straight. Hold it for a while until the solder hardens. Reheat and adjust if not straight. Once soldered properly, it will not come adrift. Double check throws and for any excessive binding.

Fuselage Servo Installation

Futaba S3150 servos will drop into the servo apertures. Make sure, however, you push the servo at the front fully over to the left before drilling the mounting screw holes. This will allow you to place the clevis on the servo arm one hole further out and give you more elevator travel.

Set the rudder straight. Assemble a clevis mid way onto a threaded rod end. Measure the end point of the inner (twice!) and cut it to length. Carefully cut the outer back with a knife. You can solder a standard threaded end onto the rod, but the best method is to use the brass ends available direct from Acemodel. These are precisely engineered with a 2mm lock thread drilled. I put some cyano or epoxy on the rod, and then push the brass rod end fully on, tighten the 2mm screw into the locking hole. Snip off the lock screw and cyano. Quick, easy and secure.



Tailplane

Fit the tail plane and set the neutral position with the servo crank in the central position before cutting the snake to length as described above. WARNING!! The pushrod linkage on this model operates in the reverse direction to the Shadow and Xpro. If you forget to change model memory program when flying this one, you will almost certainly fire it deep into our beloved mother earth after it leaves you hand. Xplorer will become Xcavator. Or maybe ExXplorer, you have been warned!

Canopy

Trickier than it would seem! Use carbon rod or piano wire. Roughen the inside of the canopy and secure the rod into place with epoxy and micro balloons. I place a scrap of fibreglass sheet on the top (or similar) just to hold the epoxy onto the rod. If you find the rod is not holding the canopy on tight enough, add a couple of extra blobs of epoxy further out.

Switchgear

I make up a DPDT switch as per the photo for each model. It takes a bit of effort but is 100% reliable (using both sets of contacts), can handle the current without problems and has a lead for easy charging. I do not bother mounting the switch, it lies on top of the receiver.



Wing Servo Installation

Not the easiest part of the build with many pitfalls to make so concentrate! By this stage, I will have extended the cables to the two tip servos. You can use extensions BUT make sure that they cannot come unplugged when disassembling the model. I always use servo frames. There are other solutions but they are so well made and comparatively cheap, allowing you to easily remove and refit servos if you need to. Mark each servo with its location so you don’t mix them up later.

Support the wing panel(s) carefully and deflect the flap/ailerons down to near 90 degrees. VERY CAREFULLY drill/ream out holes in the balsa rear spar to allow access for the control surface push rods. Remove wood right up to the top and bottom wing skins to avoid the clevises fouling, try not to pierce the wing skin! (As I once did). There is very little room to do this job, especially on the Xplorer and it is easy to damage things unless you keep the Dremel very steady!

Next, run a pushrod through and mark where it sits across the servo bay so you can bond the servos in the correct position.

Get a grinding wheel in the Dremel and roughen up the floor of the servo bays, making sure you use a damp cloth to remove all the dust. Get a scalpel and score a cross hatch pattern into the underside of each servo tray. Now wrap your servo in some cling film and assemble each one into its tray with the screws. Mix up some epoxy and micro balloons and bond each servo in the correct position in each servo well. Check and double check they are in the correct position. It is important (particularly on the Shadow/Xpro) that the servo is as close to the spar as you can with the servo output shaft also nearest the spar. This will allow the crank to have full movement and the servo bay covers will fit if you are using slightly thicker servos such as the DS362/368.

Do not clamp the servos into the wing (see below) whilst the epoxy is hardening but make sure they do not move – you will have a bit of a job trying to get one out and re epoxy!

Do not be tempted to just epoxy the servo trays in without pre-fitting the servos. The result if you do is the wing skin stresses and distorts when you screw the servo tightly into position, leaving a visible bumpy bit on the upper surface of your wing. I know. I have done it. When the epoxy is dry, unscrew the servos and remove the cling film will allow them to just pop out.

Draw a centreline in pencil on the upper surface of the wing from the centre of each recessed control surface horn fixing nut. Then you can mark the slots that need to be cut to allow the clevis to articulate. These should be 5mm wide and 15mm long for the tips. In the case of the inner panels, I also cut the slot to 15mm. You may well be able to use 10mm or less here, depending on how far in the flap control horns are screwed. The way the Xplorer horn fixing points are arranged, you have a choice. My own preference is to have the horns fairly well out so that I have the maximum amount of throw available. This also means you can attach the clevises easily but the downside is that you need the longer slots to allow the clevis to clear the upper skin when the flaps move upward. You can grind away the edges of the clevis to help here (as with the rudder clevis) but DON’T BEND THE PUSH RODS to fit!! The horns and clevises do stick up a little (as on all models of this type) but there is a negligible drag penalty for cutting the slots slightly longer. Experiment, you can always elongate the slots. Check your measurements and carefully dremel out the slots, finishing with a file and rounding the slot ends. While you are at it, dremel out a little material immediately in front of the horn fixing nuts on the ailerons to avoid the clevis binding when the aileron is deflected downward.

Try threading the control surface horns into the control surfaces, do this a few times. The threads are quite tight and you should avoid any possibility of crossing the threads. I find it easier to wind them in with a clevis attached. Cut the brass control horns to length. Screw on a nut before you cut. Hacksaw them to dimension and finish with a file, then you can use the nut to make sure the ends of the threads are good.

For the ailerons, I cut the brass horns to 16.5mm total length. Screw them in and test with a clevis and dummy pushrod. Cut the flap horns to approx 19mm. Use a vernier / calliper to measure an equal distance to the aileron/flap trailing edge so that each horn is screwed in equally. Differences will show up by giving you differing throws later on, particularly in the case of the flaps and it can be difficult to iron this out satisfactorily with transmitter programming.

Initial Servo Set up

Set up a brand new blank model program on your transmitter. Connect up the battery and receiver and all four servos into the correct channels as previously marked. Make sure each servo is marked with its function and is thus operating on the correct channel. Centre all the trims and centre points and set up your flap/brake mix. Then alter both flap servo centre points way off to the appropriate ends. Cut the horns and fit to the servos in the appropriate place on the splines. The important thing here is that each pair of servos must have the horn fitted in the same corresponding position on the splines. With the surface horns and the servo horns in the same position, you should have exactly equal throws whatever the pushrod length. This method applies to JR/Graupner R/C and may differ with other equipment.

Working one panel at a time, push the servo into its mount. Cut the pushrod to an approximate length taking care that the surface is centred. Solder a clevis onto the servo end of the rod with a mini blowtorch or soldering iron. Do this with the pushrod away from the model to avoid any problems with heat. Link up your battery and receiver to each servo and test each surface for travel and any binding. When you’re happy, screw the servo horns onto the servo and fix the servos into their mounts.

Install the wing wiring loom. I make life a lot easier for myself by buying the excellent pre-made wiring harnesses from Acemodel, but if you make your own ensure you take the wires off of the D plug at a sharp angle or you will end up not being able to fit it into the wing aperture or ending up with an unsightly bump in the centre of the wing upper surface. Use small screws to fix the D plug to the wing, mark the holes, pull the harness out slightly and drill two small holes in the skin, Replace the D plug and fix it in place with screws that are short enough to miss any wires beneath. A good tip when trying to thread the sockets through the holes in the ends of the inner panel is use a long length of piano wire, push it through the open end until it appears at the servo well and then use a small piece of tape to fix the end of the lead and connector so that you can pull it through.



Setup

Assemble the model and setup all the throws carefully. Get as much rudder movement as you can, as much down stab as you can and pay particular attention to amount and equality of flap movement. Try to make initial adjustments by physically altering the linkages first, rather than having servo centre points all over the place. Aim for a setup with central servo points and equal travels if possible. Only when I’m completely happy with the linkages do I cyano the horns into the control surfaces and the clevises onto the rods to get rid of the slop in the threads. Once set up, there should be no reason to have to move them.
 

Initial setup of the elevator

From the very trailing edge of the stab, measure down the rudder hinge line to the bottom of the FUSELAGE (not the rudder - its a couple of mm higher) should be 95mm. Similarly upward to the highest part of the rudder hinge line should be 245mm. This is neutral for about 110mm CG.

Up is 115mm and down is 77mm ..... but that's way more than you'd even need.

Check the model for lateral balance and epoxy an appropriate bit of lead into the appropriate servo well if necessary.

Fit the radio gear and route the antenna. I extend my antenna so that approx 30cm dangles out of the back of the fuselage. Contrary to popular thinking, this is perfectly OK to do and I have never had any range issues at all however much carbon in the model construction. Personally, I would not run the antenna to the tip of the fin for several reasons but mostly because when at altitude, the antenna is shielded from below by the carbon fuselage underneath it. There are other more elegant solutions if you want to experiment but ALWAYS do thorough range checks. Rig the CG. Your local gunsmith can supply a container of lead shot. I put this into two mini freezer bags folded to the appropriate shape and taped. In this way you can get very precise and easy CG adjustment. Finally set the hook position.

Finishing

Cut the servo well covers to shape and tape into position, making sure the servo horns do not foul too much. (On the shadow and Xpro, you can carefully grind down the rear post of the servo tray and chamfer the bottom edge of the servo if the cover will not sit down properly)

Fit clear tape to the wing inner panel/tip joints on the wing skins. This will prevent any paint from being pulled off by frequent taping of the gaps.



ALWAYS go some place with a lot of room and do a THOROUGH range check. I look for 100m or more with the transmitter aerial down / rear aspect. In other words the model is on the ground nose away - with the antenna pointing straight towards me. If you can, check at different aspects but this should be the worst aspect for reception. Take binoculars if you need to!

Test fly, making sure you read the earlier warning about the stab pushrod sense. i.e. make sure up is up and down is, err down. Crashing the model on its test flight earns you 1000 points and a league badge!

That is it. Feel free to email me on xplorer@kynetyx.com if you have any queries about this build or contact Austin at Acemodel.co.uk to order one!

Additional information and pictures will be added to this review over the coming weeks. So come back and check regularly.

Nick kidd.