The Alchemy wings are all new featuring a new thinner airfoil section and a reduced wing area over the Allure. The wing area is now 1000 sq” vs the Allures 1050 sq”.
Alchemy wings still feature the carbon anti-rotation pins and single retention bolt system as used on the Allure. The wing incidence is fixed but you could fit adjusters of some type or simply add Ply doughnuts to the fuse to make incidence adjustments. I’ve decided to leave the factory setup in place for the moment.
The wings come with the Servo hole already cut-out to suit a standard sized 40 x 20mm servo. For this build I’ll be using the MKS HV747 servos. These servos have a 35.5 x 15mm footprint so an Adaptor plate was needed.
The Servo Adaptor plate was drawn up in Fusion 360 and cut out of 3mm AC Ply on my CNC Router. This plate was glued under the factory fitted Ply plate. In the pictures above you’ll see that I made some notches in the factory servo plate to recess the MKS HV747 servos. The new Ply plate was then epoxied in under the factory plate.
Servo extensions are required for the aileron servos. I made my own from PowerBox premium wire and the matching male/female connectors. This wire is up to 30% lighter than normal extensions and doesn’t sacrifice the actual copper square mm. We carry PowerBox cable and connectors here. For the Alchemy, I found a length of 350mm was just the right size. I also use a sacrificial 100mm extension plugged into the receiver aileron servo channels. This prevents wear and tear on the receiver pin plating. When using extensions in the wings or on the elevators, I always tie the connectors together with HD cotton for security.
The factory has not fitted the extension paper tubes in the wings like on the Allure. This is not a bad thing in my opinion. The extension can easily be held in place with fibre reinforced tape. You only need a few 30mm lengths to tape the extension to the inside wing skin.
The MKS HV747 servos are fitted to the wings with the screws and rubber grommets supplied with the servos. No brass inserts are supplied so one needs to be careful not to overtighten the screws. TIP - an old nyrod with a small hook screwed into one end is a great help to pull Servo extensions through wings and fuselages.
The next step was to fit the (supplied) carbon aileron servo horns to small round servo wheels. If you have some Futaba 21mm Servo wheels then the horns are made specifically for them. I attached the Servo horn to the wheels with M2 x 8mm Titanium Screws and Aluminium M2 Nyloc Nuts. If you fit the screws from the bottom and put the Nuts on top you won’t have any fouling problems. The dimensions of these servo horns have been designed in conjunction with the supplied control horns to achieve the recommended surface throw (25 deg) for snaps. Now fit the Servo arm assembly to the Servo. We can now work out where to cut the control horn slot. TIP - I find it good practice to connect the Servo to a Servo tester and set the Servo at neutral (1.5ms), then ensure the pivot point is at 90 degrees to the Servo horn screw. If it’s not perfect, you can rotate the carbon arm on the wheel to find the optimum position. This will reduce subtrim later when we setup the models throws etc.
Time to breakout the masking tape again to mark out the linkage path and the location for the control horn. Firstly locate the aileron hardpoint. You should find it on the tip side of the Servo cut out. Then put some masking tape on the aileron and along the tip side of the Servo. Although it’s not pictured, we want to measure and mark the centre line of the linkage. This line should run parallel to the side of the Servo and should be the distance from the Servo side to the link pickup point on the arm out from the Servo. That’s a mouthful! Hope it makes sense... The line should be extended over the masking tape on the aileron. Now we need to measure our balls. Yes that’s right measure the diameter of the balls in your ball joints. I used the same dual axis ball ends that were used on the elevator linkages. The balls measure 4mm across the flats so halve that measurement (2mm) and you have one dimension for the control horn slot. Mark this line on the masking tape. Add 1.5mm to this line and the sides of the slot are now defined. The front edge of the control horn should be placed on the edge of the aileron bevel. See the pictures above. You should now be able to measure and mark out the front and back of the slot. TIP - Measure twice and cut once! Double check your measurements and markings and then using a sharp scalpel, cut out the control horn slot. Remove the masking tape from the Ailerons. Next take each horn and rough up the tab to be glued into the aileron. Some 220 grit sand paper does the trick here. This just gives the epoxy more bite on the control horn. I use 30 minute epoxy mixed with some glass fibre rovings for this job. You could just use epoxy but I like the extra body that the glass rovings give the epoxy. Push some epoxy into the slots cut in each aileron and also add some epoxy to the horn itself. Ensure the slots in each horn tab are filled with epoxy. This helps to anchor the horn into the control surface. Insert the horn into the aileron and wipe off the excess epoxy that squeezes out. Cotton buds with methylated spirits works a treat for cleaning up epoxy. Then tape the horns into position to hold them flat against the surface and at the right angle. See pictures above.
Linkages - I use lightweight 2.5mm titanium rod and dual axis ball ends on the elevators and Ailerons. This gives a light rigid and slop free connection between the Servo and control surface. With the servo and control horn in place, it’s easy to determine the length of titanium rod needed. Then it’s just a matter of putting a thread on each end. I used to run a die over the rod by hand but now do it in a lathe. The results are much better with the lathe. If you want linkages made just contact us with the dimensions. We also sell the dual axis ball ends here. The linkages are attached to the Servo horn and control horn with M2 x 8mm Titanium Screws and M2 Aluminium Nyloc Nuts.
The wings are now done.