The wings are the next item to be completed. The first thing to do is expose the servo cut-out by cutting the covering. One of the pictures below shows the film already cut at 45° to each corner. The other wing hadn't had this done. The cutting wasn't very neat as you can see but once trimmed and ironed down it looks ok.
You want to allow approximately 2-3mm of overhang on the film so it can be ironed down the edge of the Servo cutout. My iron temperature was set to 100°C for this film.
BJ Craft doesn’t fit the aileron servo tray but one is supplied in the light ply panel. In some respects this is a good thing. It allows you to use a mini servo and make a new servo plate to suit. The supplied plates suit a standard 20mm servo. For this build Futaba BLS171SV servos will be employed on the Ailerons. Cut the two aileron servo plate from the ply panel. You may need to adjust the slot length to allow your servo to fit through the Servo plate. The BLS171’s required a very small adjustment to the length of the opening. Once your servo is in, use some cardboard either side of the Servo to centralise it prior to marking the screw holes. The screw holes were marked with a sharp pencil poked through the eyelet. Another advantage of the Servo trays not being mounted is you can easily adjust the cutout and also drill the Servo holes on a drill press. A 1mm drill bit was used to make the holes. Then screw the Servo in to make the threads. Remove the screws and servos and hit each screw hole with some thin CA to harden up the threads. Dry fit the Servo trays to each wing panel and adjust the width or length as required. The trays only go in one way with the angled end butted up against the main spar. You may need to remove some adhesive from where the tray mounts to get things in the right position. I set the tray 5mm down from the wing surface. Next the tray will be glued into position. You could use medium CA here or do as I did and use epoxy with some glass rovings. The best way to do it with epoxy is to push the Servo tray to the bottom of the Servo cutout. Then apply your epoxy to the cutout walls where the tray will be glued. You can then pull the Servo tray up into position and wipe of the excess epoxy with cotton buds. The tray should be a neat fit so it will hold its position just fine until the epoxy cures.
Once all cured, the Servo can be fitted along with a temporary extension. Set the Servo at neutral using the Jeti box and the fit the Servo arm. For this build 1” Futaba Aluminium arms will be used. This will allow enough throw for snaps. Before fitting them to the servos, I thread the pickup point holes with an M2 tap. Then fit the arm to the Servo and neutralise the Servo with your Jeti Box or similar. At this point the aileron hinges were dry fitted and the control horn hard point located. The hard point can be found by gently squeezing the aileron around the area where the hard point should be. The hard point should be on the outboard side of the Servo position.
Now we'll look at the control horns. Interestingly, the aileron control horns have a 5-6mm hole in them for glue keying. The process of marking out the control horn position is similar to the stabs only that you don’t need to cut a clearance hole for the linkage and servo arm. Again, masking tape is used to mark things out. Put a strip of tape from the Servo arm pickup point (outermost) down over the aileron hard point following the linkage path. Measure the distance from the side of the Servo to the middle of the outermost Servo arm hole. In this case it was 15.5mm. At the front and back of the Servo measure out 15.5mm from the Servo side and make a mark with a fine point sharpie or equivalent. Using a steel rule, join the dots and mark a line down the tape and onto the aileron tape. This is the centre path of the linkage at neutral. The pictures below will illustrate this better than I can explain in words. :-) We are using the same 2.5mm Dual Axis Ball Ends as used on the elevators. They have a 4mm wide ball so make another line 2mm inboard of the linkage centre line. This is the edge of the control horn slot. I noted some variation in the thickness of the control horns so check yours before marking out the other side of the slot. The extent of the control horn slot can then be defined. The front of the control horn should be right on the bevel edge as can be seen in the pictures. This puts the pickup point right over the hingeline. This is easy to mark out by simply laying the horn on its side on the aileron with the glue tab going over the slot side marks. The control horn slot is now defined. Carefully cut the slot out with a sharp scalpel to the required depth. Take care to keep the slot at 90° to the aileron surface. If all worked out correctly it should look like the picture below.
With the slot cut and horn sitting nicely, remove the masking tape from the wing and aileron. Prepare the control horn by roughing up the area to be glued with sand paper. The control horn was glued in with 30 minute epoxy with some glass rovings mixed in for extra strength and body. Ensure the slot is filled with epoxy and the also keying hole in the control horn tab. Any excess glue will be squeezed out when the horn is pushed in. Wipe up the excess with cotton buds soaked in methylated spirits. Set aside and allow to cure.
The linkages are done the same as the stabs. Using Masking tape, tape the aileron to the main wing to hold a neutral position. The dual axis ball ends are fitted to the Servo arm and control horn with M2 x 8mm screws and M2 locknuts. Attach the Servo arm to the Servo in a position that will make the angle between Servo horn screw, dual axis ball end screw and linkage 90º. Again, I find using the end of a steel ruler helps setting this. I should mention the Servo should be at neutral 1.5ms. I use a Jeti BOX for this. Once you have the Servo arm in the right position, you should then be able to measure the required length of linkage. I measure the distance between the plastic threaded sections of the ball ends and then add the depth of the holes in the ball ends. In this case the depth is 8mm so 16mm get added. So this meant a total length of 95mm with each end having 10mm of 2.5mm thread. To thread each end of the link I use a HSS M2.5 Button die. Titanium is not the easiest material to work. I use a Dremel cutting wheel to cut the links to length and thread each end in a lathe on the slowest setting. You’ll also need a good thread cutting compound too.
With the linkage threaded on both ends we can now test fit it. On one end I place an M2.5 nut which acts as a locking nut. This completes the linkage.
Aileron Hinging - The same Dubro pin type hinges as used on the elevators will also be employed on the Ailerons. Just like on the stabs, a small relief on the hinge slots needs to be cut for the hinge knuckles. Note, if using the kit supplied CA hinges there is no need for cutting this relief.
As with the stabs, a little bit of Vaseline is applied to each hinge knuckle to prevent the glue locking the hinge up. I’m not sure if this is 100% necessary but I’m not willing to take the risk... The Pacer Hinge Glue takes the Standard ZAP nozzles which makes it easy to squeeze the glue into each slot. I start with the wing doing all the hinges and the apply glue to the aileron slots. The glue sets pretty fast so don’t waste time. Then carefully fit the aileron. Any excess glue can be wiped off with a wet rag or wet paper towel. I used masking tape (as pictured) to hold things in position whilst the hinge glue cured. The hinge glue is supposed to be touch dry in 30 minutes but I prefer to leave it overnight. If all went well you should have a nice free moving Aileron (once the tape is removed) ;-). The Servo linkage can now be reconnected to the Servo and control horn.
The Contra Drive Element will feature MKS servos. The below gallery shows the MKS HV747’s being installed.
It’s fortunate the ply servo trays are NOT pre-installed by the factory. Reason being, the MKS HV747 to be used in this model are smaller than a standard 20mm servo. That said, new Servo trays to suit this Servo were designed and manufactured. Each tray was set 5mm below the wing skin surface. A small depth gauge was used to get this right. Epoxy was used to glue the trays in.
Anti-rotation pins - Are made from 8mm carbon tube. In your kit you’ll find two 30mm lengths which are used on the front of the wing and a longer length which I should used on the rear. My preference is to make two extra 30mm long pins from the longer length of tube. I’ll detail the adjusters used in the fuselage blog.
Each carbon pin needs to be glued into the wing root rib. It’s important that each pin is glued at 90° to the root rib. This will make it easier to fit and remove the wings. A small jig was turned on the lathe to assist gluing each pin. See the picture below.
The last thing to be fitted to the wings is the retention screw blind nuts. You may need to run an M4 tap through the blind nuts to clean up the threads. The blind nuts are pressed into ~20mm diameter 3mm light ply discs. A vice was used to press the blind nuts into the discs. Some zap is applied to glue the blind nut as well. This assembly is then glued to the inside of the root rib. I used epoxy for this task and an M4 screw was used to hold things in place.