Ah the fuselage assembly... This is where most of the work is to be done.
I find the best task to tackle first is the undercarriage. This then allows the model to be easily positioned on the work bench.
The Alchemy main undercarriage Legs are of a new design. The mounting tongue is actually flat with the only bend in the leg at the wheel pant mounting point.
The tongue of the leg is tapered and is pushed into a matching carbon module/socket in the fuse. An M3 screw near the point of the tongue retains the leg in the fuse. To spread the load better, I fit a cone washer to this screw. To tighten this screw you’ll need to use an ordinary Allen key due to access constraints. A small drop of Locktite 243 on the screw is a good idea too. The legs themselves look quite thin particularly where the wheel pant mounts. Have no fear though as they have proven to be quite strong.
To improve strength in the undercarriage area, I strongly suggest adding some carbon cloth around the undercarriage module. See the pictures above. I used some 2.9 oz carbon cloth for this task but you could also use 6 oz as it might be more readily available. It adds very little weight but adds plenty of strength to this often abused part of the model.
Main wheels are not supplied in the kit. This allows the builder to choose any wheel they want. In this case, I chose to use Ralph Schweizer’s 57mm Ultra light wheels. You could also use the 62mm variant but any bigger than that will cause issues fitting into the wheel pants. The factory provides some long screws for the main wheels. These should be consigned to the round filing cabinet under your bench. In other words, the garbage... Fotunately, there are some good options on the market. You could go with Aluminium Axles for weight savings or stainless steel for durability. I chose to use Ralph Schweizer’s 4mm Titanium Axles for the best of both worlds i.e. light and durable. Everyone has their own favourite method of attaching the wheel pants and Axles. My preferred method is to place a 4-40 or 3mm screw about 10mm above the axle centre along with a small ply plate and blind nut glued inside the pant.
The photos below are of my last Allure but the process employed is exactly the same. I make up a couple of Ply plates on the CNC router to support a blind nut and also the outside end of the axle. This makes for a very robust pant assembly.
The first thing I do is mark out the location of the axle and the retention screw on the UC legs. This is simply done on masking tape with permanent marker. I normally allow 10mm between centres. Centre pop the marked hole positions to stop the drill bit drifting & then drill the axle and pant retention screw holes. A drill press is best used for this. Now we want to mark the "axle hole" only onto the wheel pant. Use the trusty masking tape again to do this. Measure the length of the wheel opening in the pant and mark the centre onto the tape. Then with the wheel to be used on the side of the pant, mark the position of the axle hole. This dimension will differ depending on the wheel diameter used. in my case, the hole centre was approximately 10mm up from the bottom of the pant. Again centre pop the marked hole centre and drill with a 4mm bit. I place a piece of 12mm ply inside the pant to prevent crushing the glass whilst drilling. A drill press and vice is best for this. Now fit one of the thin Titanium nuts to an axle and push into the 4mm hole just drilled in the pant. Then trace around the nut with a permanent marker. I then use a Dremel and needle file to cut the pant to suit the nut. The picture above probably tells one thousand words...
Now fit the Axles to the undercarriage legs and fit each undercarriage leg to the fuse. We need to fit the tail wheel assembly before continuing with the wheel pants.
Tail Wheel - The kit does come with a tail wheel assembly but no tailwheel. I replaced some of the parts to improve the tail wheel. See pictures below.
The factory supplied coil spring is replaced with straight piano wire. A new Aluminium bracket was made to lock the piano wire and tail wheel spring in place with grub screws. The steering piano wire passes through a delrin pin which is screwed into the bottom of the rudder. A delrin Bush was made to seat the tail wheel assembly in the rudder post and allow it to rotate. The factory Aluminium retention bracket is reused to hold the assembly in the fuse.
The next thing is to fit your tail wheel. There are a few options here. I chose to use what I sell, the Precision Aero Products tail wheel. These are made from delrin and have an O-ring on it as the tyre. The tail wheel is held on with a spring clip washer (supplied). These washers simply push on. Use a spin tight or socket so you don’t impale your finger on the wire...
Ok, with the tail wheel assembly now mounted on the fuse, we can get back to finishing the wheel pants. Take your chosen main wheels and temporarily fit them to the Axles along with the wheel pants. Then place the fuse upright on a flat table or bench. If you look at the wheel pant pictures above you’ll see a picture where I’ve placed a couple of pieces of 12mm Ply under the back of the wheel pant. This should keep each pant positioned correctly. Then take the same drill bit that was used to drill the pant retention screw hole in the UC leg and push into each hole and rotate clockwise by hand. This should make a mark on the masking tape still on the pant. You did leave the tape on there didn’t you? :-) If not, just put another piece of tape on the pant. Remove the pants and wheels and then centre pop the marked position. The hole in the pant can then be drilled on the drill press using the same drill bit. If you look at the wheel pant pictures you’ll see some Ply parts that I cut on the CNC. The thinner 3mm one has an M3 or 4-40 blind nut pressed into it. This plate gets epoxied to the inside of the pant. The other ply part secures the end of the axle. The Ralph Schweizer Titanium Axles are adjustable so you shouldn’t need to trim the axle length. Next take the fuse and turn it upside down so you can work on the pants and see what you’re doing. A cradle is good for this or you can rest the fuse on a toolbox with the canopy off. As you can see in the pictures above, I used a toolbox with some old folded sheets padding. Don’t use your wife’s good sheets as you’ll get shot! :-) Dry fit the pants along with the ply parts. You may need to shape the outer axle support to match the wheel pant contour. Dremel party time with a sanding drum... Once happy with the dry fit, the ply parts can then be glued in. Rough up the inside of the pant with sandpaper, clean with methylated spirits or IPA and then epoxy the ply parts in. I use 30 minute epoxy and small clamps along with the retention screw to hold things in place for curing. Once cured, you can then reassemble with the main wheels. The beauty of the Ralph Schweizer Titanium axles is their adjustablity. You can even pre-load the wheels to tighten them up.
Rudder Tray - Time for some bling! The kit comes with a rudder tray laser cut from some 3mm light ply. Whilst you could use it as is, I prefer to stiffen this area up a bit. First step is to add some carbon cloth to one side of the rudder tray. I used a couple of pieces of waxed Perspex for this. The cloth used was 2.9oz but you could just as easy use 6oz if that’s more available in your area. A small foam roller is great for dispensing the laminating resin for this job. The resin used was Epiglass HT9000 series with standard hardener. A coat of resin is rolled onto the waxed Perspex and the the carbon cloth is layed over the resin. The cloth can the be wetted out with resin using the roller again. Once the carbon is fully wetted out with resin, place the light ply rudder tray onto the carbon. Next place the second piece of Perspex on top and then weigh down with some bricks or weights. You could also vacuum bag things. After 24 hours curing, remove the weights and pry the carbon off the bottom Perspex. If you waxed things well it should come off real easy. You can then trim the excess and cut out the holes. You now have a blinged rudder tray! Well, almost... The factory used to supply a light ply doubler for around the Servo cut out. That’s no longer the case. I think it’s a good idea to have some extra meat in this area particularly with servo screws being screwed into this area. So, I made up a doubler and CA’ed it to the rudder tray. To stiffen the rudder tray further, I add some 1/4” x 1/4” balsa to the underside of the tray as shown in the pictures. Now is a good time to mark out your servo screw holes and drill them on a drill press. The Servo I used was an MKS HV1220.
Location, location, location... The rudder tray was located directly under the rear edge of the canopy opening. See photos. You could mount the rudder servo further forward if wanted but that option may require a wider plate to be made. You’ll find the rudder tray width will set the location within the fuse. The balsa added to the tray on the sides can be sanded at an angle to better match the fuse sides and give more surface area to the glue joint. You’ll find the tray will sit ~1” below the canopy rail. I find it best to laterally level the fuse with a small string line level. This same level can then be used on the rudder tray to get it level. You can then make some marks on the fuse sides indicating the tray position. The rudder tray was then removed and then glued in place with 30 minute epoxy.
Rudder Pull-Pull System - Ah, the job that everyone loves to hate... I read horror stories (ok, maybe exaggerating a tad there) of stickers being placed over incorrectly cut slots to disguise the screw up. Well, fear not, it’s really not that hard to get it right. Using the old rule of measure twice and cut once will see you right.
Ok, we need to define a few points of reference on the fuse.The rudder tray is already mounted in the fuse so we can determine the location of the cable at the servo end. I placed some strips of masking tape on the fuse sides around the rudder tray area. What we want to do is transfer the rudder tray top surface to the tape on both sides. A strong light behind the fuse side is an easy way to transfer this line.
At this point you want to cut out the included Carbon Rudder Servo horn and fit this to your servo output wheel. The arm has been designed for Futaba 21mm round wheels. These come standard with pretty much all Futaba Servos. Remove the moulded numbers on the wheels with a sharp scalpel. This gives the carbon arm a flat surface to pull up against. As with the aileron servo arms, the rudder servo arm is attached with M2 x 8mm Titanium Screws and M2 Aluminium Nyloc Nuts. Ok, you need to make a decision at this point. What ball joints will you be using on your pull-pull system. I used Dubro 4-40 at the Servo end and 2-56 at the rudder end. We need to work out where the cable centre line will be at the Servo end first.
1. With the rudder arm fitted to the Servo and mounted in the rudder tray, measure the distance from the bottom of the arm to the rudder tray.
2. Your ball end probably has a brass ball in it. Next we want to measure the distance across the holes in this ball.
Ok, now the calculations... Firstly take the second measurement and divide it by two. Then subtract this figure from measurement one. The result is the centre line of the cable at the Servo end. Transfer this measurement to the masking tape on the fuse sides.
Are you still with me? ;-)
So we have one end of the system worked out. Now to the other end. The next step is to work out where the rudder hard points are. There are a couple of ways to do this. Depending on the paint colour in that area, a strong light behind the rudder might show up the hard point. If that fails, you can gently squeeze the rudder to find the hard point. With both methods, you want to have some masking tape on the rudder right at the bevel. This way you can mark the hard point position. Do this for both sides of the rudder. With the top and bottom extremities of the hard point defined on the masking tape, measure the distance between the two marks and halve it. Transfer this measurement to the tape. This will be the centre line of the rudder cable. This dimension needs to be transferred to the other side of the rudder. Measure from the top of the rudder down to your mark for the cable centre line. Transfer this dimension to the other side of the rudder and make a mark on the tape. All going well, this mark should be halfway between the hard point extremity marks.
Ok, get out that roll of masking tape again. We want to run two strips of tape about 30cm long on each side of the fin. The tape should follow the cable centre line approximately. Now it's just a matter of joining the dots! I find the best way is to lay a soft sheet or towel on the bench to protect the finish. Then run a 1m steel rule along the fuse side. Mark a line on the 30cm tape. The cable exit centre line is now defined!
This is a long winded process... On we go!
Alright, next we will define the rudder horn positions. Cut the two carbon rudder horns from the panel and clean up the machining tabs. You'll also want to rough up the section to be glued with sand paper too. I used Dubro 2-56 ball links at the rudder end. Measure the distance across the holes in the brass ball. Halve this dimension and transfer it to the tape on the rudder by measuring down from the cable centre line. Draw a line parallel to the cable centre line. This is the top of the horn slot. The horns are 1.5mm thick so draw another line 1.5mm lower. This is the bottom of the horn slot. Almost there... The rudder horns have small lips that limit how far the horn is inserted into the surface. The front edge of this lip should be mounted right on the rudder bevel. The width of the lip is 2mm so measure back 2mm from the bevel and make a mark. This is the front of the slot. The mounting tab of the horn is 12.5mm wide so measure another 12.5mm back from your 2mm mark. The horn slot should now be marked out.
Double check your measurements and markings and then using a sharp scalpel, cut out the rudder horn slot. Remove the masking tape from the rudder ONLY. Next take each horn and rough up the tab to be glued into the rudder. Some 220 grit sand paper does the trick here. This just gives the epoxy more bite on the rudder 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 into the rudder 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 horns into the rudder and wipe off the excess epoxy that squeezes out. Cotton buds with methylated spirits works a treat for cleaning up with epoxy. Then tape the horns into position to hold them flat against the surface and at the right angle.
Now we have just one more critical measurement to do... The cable exit position! To mark this position I use some cotton thread tied to the rudder horns and the rudder servo arm. Basically simulating the path of the cable. See picture below. The length of the cotton needs to be adjusted to get the arm in position above the Servo. The cotton threads, like the cables are crossed. This places the exit further aft in the fuse. The path of the cotton will be above the turtle deck. This is probably a two person job but is possible by yourself particularly if you use both hands and both feet.. Just kidding! With the cotton thread simulating the cable above the turtle deck and either side of the fin, it should be very obvious where the exits need to go. Make a mark on the horizontal line previously marked for the cable. Then with the ruler, make two more marks 1/2” either side of this mark. This will be the length of the slot. To cut the slots, I use a Dremel with a cut-off wheel. This makes a thin slot and does a clean job of the task. If you’ve done things right, the slot should sit above the stab adjuster pin. That’s the hard stuff done!
The cable supplied in the kit is fine to use. I replace the connectors with Sullivan eye bolts. 4-40 at the Servo end and 2-56 at the rudder end. Dubro 4-40 ball ends at the Servo and 2-56 at the rudder. It just so happens that for this build I had run out of Sullivan 2-56 eye bolts. Why not make some? Well I did as you can see in the pictures. I had some 2-56 Rod and a 2-56 die. Then it was just a matter of bending to shape. Some nails in a piece of ply held in the vice did a great job of this. Just like a bought one! Well, almost...
The cables can now be run. I start at the Servo end and then terminate at the rudder. Remember to loop the cable through the ferrule twice. I also hit them with a drop of thin zap and cover with a small piece of heat shrink. Once both sides are terminated you can then adjust the tension by screwing the eye bolts further into the ball ends. They don’t need to be as tight as a guitar, just tight enough so they’re not loose.
Motor Mounting - If using a conventional drive like a Plettenberg Advance or the like, the nose ring of the model can be used to align the thrust. Consider using some 4mm Aircraft grade ply for your firewall. Ply has better sound dampening properties than carbon.
For this build I’ll be using the Ralph Schweizer CRS (Contra Rotating System). This drive utilises a Hacker C54 inrunner Motor and a planetary gearbox. Setting up the thrustline for a contra drive is not quite as easy as just using the nose ring as your reference. With a contra you want 0° right thrust and -0.5° downthrust. You may wish to play with the downthrust later but start with -0.5°. The downthrust is referenced to the canopy opening base as are all other measurements (wings and stabs).
Below are a sequence of pictures showing how I aligned and mounted the CRS.
Mounting the CRS is not an overly difficult task if you use the drilling gauge along with a straight piece of 8mm threaded rod. The 8mm steel threaded rod can be bought from most hardware stores. You’ll also need a couple of M8 nuts as well. The CRS come supplied with an integrated soft mount which consists of three rubber isolators at the front and a POM Rear Support which has a large O-ring. The rear support O-ring is lightly greased to allow the whole CRS to move a little.
Righto, first thing to do is mark out the position of the three mounting screws on the nose ring. This is where the drilling gauge comes into action. I normally place two screws on the bottom and one on top. This allows for easy thrust changes latter if needed. Make sure the fuse is laterally level in the cradle and secure. A string line spirit level is great for this. The nose ring on the Alchemy is approximately 86mm diameter. This suits the 85mm spinner set for the CRS. Out comes the masking tape on the nose ring. You don’t need to mask up the hole nose ring, just where the holes are going to be. The CRS drilling gauge is almost the same diameter as the nose ring. That said, you can roughly align the gauge to the nose ring by eye. I then push a couple of M4 screws into the bottom two holes and use the string line level across the screws to get the holes level. Holding things in position, carefully remove the level and screws. Then with a 4mm drill bit, mark each hole rotating the bit with your fingers. This marks the masking tape with a small divot. That’s your hole centre. You can mark each divot with pen to make them stand out more if you wish. Centre pop each hole centre to stop the drill bit wandering and then drill the three holes with a 4mm bit. With the holes drilled, you can temporarily fit the firewall to the nose ring with M4 screws. If things were done right it should be nicely centred.
The CRS uses Aircraft grade ply spacer rings to adjust the offset or spinner clearance. The less spacers the better. The CRS also has an Aircraft grade ply firewall. This ply is superior in strength and noise absorption as compared to carbon fibre. The firewall used is 85mm in diameter. To reduce the spacers required on the CRS, I removed the factory installed fibreglass nose ring with a Dremel. It’s held in with epoxy and microballons so removal is not too difficult. You’ll see in the pictures above the glass nose ring in position and then with it removed. The ply CRS firewall is then able to be glued as far forward was possible. The circumference of the ply firewall may need to be beveled to allow a nice fit. The bottom of the drilling gauge will certainly need to be flattened off on the bottom to fit in the required position.
Now the fun part (in a sarcastic sense), alignment of the firewall. This task sets the alignment for the whole CRS assembly. Take your time here. You’ll need to cut the threaded rod to a length of about 60cm. Long enough so some hangs out the front and the rest goes past the wing tube socket. Then attach the CRS firewall and drilling jig to the nose of the model with three M4 screws and nuts. Screw one of the M8 nuts and a flat washer onto the threaded rod about 10cm from one end. Insert this end into the drilling jig and put another washer and nut on. From here you should be able to see the small amount of right thrust built into the nose ring. Stick some masking tape on the top of the wing tube socket. Then measure the middle between the two fuse sides. I used a piece of scrap balsa to help with this. Mark the centre on the tape. This is where you need to adjust the threaded rod back to. Now it’s just a matter of inserting shim washers between the firewall and nose ring to get the rod centred (0º right thrust) and -0.5º down thrust. The down thrust can be measured with your angle meter that has been referenced to the base of the canopy opening. Speaking of angle meters, previously the Wixey was the unit of choice. We’ve now moved on to another device called the DXL360 which is available off eBay. It’s more expensive than the Wixey but the DXL360 resolution and accuracy is superior. We’re now working to 100th of a degree vs tenths with the Wixey.
Ok, it will take a bit of mucking around with shim washers to get the thrust right but once right, mix up some 30 minute epoxy with fibreglass rovings added. Remove the firewall, drilling guide and threaded rod noting the positions of all the shims. Add the epoxy to the nosering and firewall and then reassemble everything including the shim washers. I leave the shims in place and use old M4 screws as they’ll get epoxy on the threads. As the screws are tightened any excess epoxy will squeeze out. Wipe the excess resin off and recheck your thrust again. If all is good, go make yourself a coffee and then watch the glue dry. Riveting! ;-)
After half an hour the epoxy should be cured enough to enable removal of the M4 screws, threaded rod and drilling gauge. The epoxy should reach full cure after about 24 hours. After this period I sanded the nose area with a Dremel sanding drum to match the CRS firewall. This allows the CRS to be removed from the front of the model. To allow the CRS to rotate for removal, some of the fuse floor needs to be removed between the two blind nuts. I’ve not actually done this on my Alchemy yet as this build was completed in record time (for me) prior to the 2018 Australian Masters and World Cup event. My CRS is now due for its first service so that may be an opportune time to do this modification to the nose.
The CRS can now be fitted to the model in preparation to doing the rear support. But first, we need to make sure the spacers on the CRS achieve the correct spinner to nose ring clearance. The clearance you want to achieve is 2-3mm. The spinner diameter of choice is 85mm. I found 4mm and 3mm Ply spacer rings together gave the right clearance. Remember to put some Locktite 243 on the six screws securing these ply spacers and the carbon mount plate. Don’t overtighten these screws either as the ply will compress and then distort the carbon plate.
There are a couple of options for rear supports on the CRS. The default is what Ralph calls a “POM” Rear Support. It basically made from delrin with an O-ring insert. The other option is a more conventional carbon rear support which has an O-ring integrated into it. For this build I chose to use the POM rear support. I made a 1.5mm carbon brace to mount the rear support. This was actually designed for my last EP nose Allure. This carbon brace is simply glued to the fuse sides and two screws along with nuts and washers secure the POM rear support to the carbon brace. The POM rear support allows for side thrust adjustment with elongated holes. To make up or down thrust adjustment shim washers would be required.
As the firewall was setup to have the correct thrust alignment, the CRS is simply refitted. Make sure the O-ring in the rear support is lubricated with some grease prior to installing the CRS. The Hacker grease used to service the CRS is perfect for this. Assemble the spinners and props to the CRS and check there is adequate clearance between the spinner and nose ring. You want between 2-3mm of clearance with a soft mounted system..
Wing and Stab Alignment - All measurements are referenced to the base of the canopy opening. You will need an accurate (and importantly repeatable) angle meter. I highly recommend the DXL360 device. You’ll also need a set of Robart bars (long and standard) with the brackets to attach to the flying surfaces.
The above gallery shows the DXL360 angle meter and the modifications I made to the Robart bars to mount the meter. The bracket is made from mild steel so the DXL360’s magnets stick to it. The bracket was actually cut from a piece of thin walled square section steel tube.
The above gallery is from my Allure build. Unfortunately, I didn’t get any pictures when aligning the Alchemy. The procedure and settings are the same none the less.
Set the angle meter to a zero reference first. This is done with the short bar and referenced to the canopy opening as pictured. Make sure you place the bottom of the plastic brackets on the edge of the fuse as this is the hardest spot. It’s important that you make your reference in the same manner each time and all measurements are made with the angle meter and brackets etc facing the same way. This ensures minimum error in measurements. Just as important is making sure the model is securely mounted or supported in a cradle. Tape it in place if necessary to prevent movement in the cradle. I now use a neat fitting cradle as opposed to being supported as in the pictures above. As you move to more accurate measuring tools the security of the model becomes more critical.
Ok, enough babbling onto the settings.... First thing is the wings. The wings should be factory set to +0.5°. Fit the longer bar and confirm this measurement. If you measure something significantly different recheck your reference and measure the wings again. If your wings are within 0.1° of +0.5°, then I would leave them as is. If they are out or each wing is different, consider adjusting the incidence by slightly elongating the anti-rotation pin holes and gluing on new ply doughnuts. Remember to apply Vaseline to the anti-rotation pins prior to gluing.
The stabs on the Alchemy feature independent adjustment. The adjusters have been placed closer to the root than on the Allure. This results in a much more robust and stable adjustment. Tape the elevator to the stab tip or use clamps to hold the elevator in neutral. Fit the short bar to the incidence meter and attach it to the stab root. Adjust the stab incidence by moving the top and bottom adjuster grub screws in or out as required. You want to start with +0.1° Incidence. Note, the grub screws don’t need to clamp down on the carbon adjuster pin with massive force. Take the time to make sure both stabs are adjusted the same and remember to have the angle meter and bars etc facing the same way for all measurements.
Battery Tray - A light ply battery tray is supplied in the kit along with a couple of Velcro straps. Whilst this tray is useable, I prefer to add some carbon bling. Below is a gallery showing the battery tray employed in my Alchemy. It’s adjustable, can use Velcro straps or the pictured clamp with foam rubber cushions. It also integrates a plate for ESC mounting at the front and it’s modular. The kit supplied carbon rods were used to hold the tray in place with six 100mm cable ties. Bigger square doughnuts were fitted to each carbon rod to better spread the load.