Onto the fuselage assembly now to bring it all together. To kickstart, we’ll get into the undercarriage assembly first.
The undercarriage on the Allure Bipe is the same as that used on the Alchemy / Alchemy Pro. Although I’m trying to save as much weight as possible with this build, some extra reinforcement around the main gear module is worth a little extra weight. The carbon undercarriage module itself is quite strong but it’s fixed to the fuse with epoxy and microballoons. Not exactly the strongest of fixing methods in this location in my opinion. That said, anywhere I see the white of microballoons I cover it with a strip of 120 g/m plain weave carbon cloth. The area around the undercarriage module is roughed up with 120 grit paper first. Then carbon cloth is cut into strips about 30mm wide and lengths as required to go right around the module.
Each undercarriage leg is held in place by a single M3 cap head screw. I replaced the factory supplied steel screw and washers with M3 x 16mm Titanium screws and aluminium cone washers. Each undercarriage leg should be a very neat fit into the socket as both the leg and socket are tapered.
The factory does provide aluminium axles for the main gear (but no wheels). I’ve used these wheels in the past and you can expect to get about 200 flights out of them upon which they will either be worn out or fail. I elected to replace them with Ralph Schweizer’s 4mm Titanium Axles. They’re not cheap but will last longer than the model. The factory doesn’t supply main wheels in the kit. This gives you some freedom to choose your favourite wheels. Ralph Schweizer’s 57mm Ultra Light wheels were used on the Allure Bipe. They are very light and feature quite a dense foam which helps keep the pants from being damaged due to flex.
You don’t have to do this but I key the thin titanium nut provided in Ralph’s axle kit into the side of the wheel pant. I do this by firstly making a 5mm hole in the side of the pant and then inserting the axle with thin nut fitted and mark out around the outside of the nut with a pen. Then take to the pant with a needle file. Further up the pant I fit a small ply plate with a blind nut so an M3 retention screw can be used to hold the pant on and prevent it from rotating. I used to support the outside of the pant with the end of the axle in a ply plate. I’ve deliberately not done that with this build.
The factory does provide a tailwheel assembly minus the wheel. The spring/axle was used along with some upgrade parts. One of our tailwheels was also used.
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 new Delrin Bush was made to seat the tail wheel assembly in the rudder post and allow it to rotate smoothly without slop or binding. 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. A 2mm flat washer was soldered onto the axle for the wheel to run against. 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... Once these clips are on they won’t come off easily.
To save weight the Adverrun Single Drive was chosen as the power plant. This actual drive is a prototype and as it turns out some issues were encountered during the maiden. More on that later. Anyway, the weight of this drive system is a meagre 501 grams. For comparisons sake, a Plettenberg Advance 30-10 weighs in at 570 grams.
The nose has a fibreglass nose ring glued in place. This was not used in this instance. Prior to fitting a firewall, some light weight carbon cloth was laminated onto the nose area to provide extra strength.
A plywood firewall was made from some 4mm AC ply. It took a couple of goes to get the final shape just right. The firewall is somewhat odd in shape at the top as can be seen in the pictures. Because this drive has a longer main shaft the firewall is further aft than what a production Single Drive would be. Reliefs in the firewall were also made for the chin cowl blind nuts and screws. As this is not a contra build, the drive system could be aligned to the nose ring thrust settings of the designer. A nose ring template was made from 3mm MDF which included the Adverrun mounting hole centres. The outside diameter of the template is 86mm. Four standoffs were screwed to the template. The length of the standoffs determines the spinner gap. The nose ring template is levelled to the fuse and taped into position on the nose. The firewall is then trimmed to fit the fuse and line up with the four standoffs. Once all trimmed, the firewall is held in place with screws into the standoffs. It was then glued in with 30 minute epoxy and glass powder. The motor is not needed with this method which is an advantage. Once cured, carbon tow was run around the outside diameter of the firewall front and rear to create a string fillet.
The rear support featured two (2) Ralph Schweizer 10 x 10mm Rubber Isolators along withM4 Aluminium Nyloc Nuts. To connect the rear of the drive to the fuse sides, carbon side parts were used. The ends of the carbon parts are sanded to match the fuse sides and then glued in place with epoxy and glass powder. Some serious alterations were made to the rear support of the drive after maiden. More on that later.
Next cab off the rank is the rudder. As per the Allure and Alchemy, the rudder comes pre-hinged to the fuse. The hinge is actually moulded in. If the rudder hinge seems a Little stiff just warm it up with a hot air gun or hair drier on low heat. Cable exits are not cut in the fuse. The builder needs to do this.
If you were making a GP Allure Bipe Bryan recommends locating the rudder servo down the back of the fuse under the stabs. Then directly drive the rudder with a linkage and ball ends. This is for more favourable CG reasons. EP is a different story as you will want your weight further towards the nose. With this build utilising the light Adverrun Single, a pull-pull rudder was the best choice.
The rudder servo Tray is provided in the kit. It’s made from laser cut light ply. I tart up this ply tray with some light weight carbon cloth. Not only does it add that bling factor, it also stiffens the tray a little. A ply doubler is added to the underside of the rudder tray around the Servo cutout. I decided to use an MKS HV747 Servo for the rudder which is smaller (and lighter 38 grams) than the 20mm Servo cutout in the tray. The HV747 has just under 12kg of torque at 6V so it's perfect for the rudder. A new ply doubler was designed and CNC cut to suit the smaller footprint of the 747 and was then glued to the rudder tray. As with my other CK Aero builds, the rudder tray was further stiffened with the addition of some 1/4 x 1/4” contest balsa to the underside of the rudder tray. One thing that is pleasantly better on this model is access to the rudder servo once the tray is installed. The tray was located so the rear edge was in line with the top wing screw tabs and approximately 50mm down from the wing saddle. The fuse was levelled laterally and wing set to 0°prior to gluing the rudder tray in with epoxy. A small line level was used to get the tray level in all directions.
Identifying the rudder hard points was next. Usually this can be done by feel or using a very strong light. I make the extents of the hard points on both sides of the rudder and then locate the control horn in the middle. See pictures below. The picture also show how far I measured down from the top of the rudder (235mm). The control horn slot should be located right on the bevel of the rudder to get the pickup point as close to the hinge line as possible. The slots are then cut with a sharp scalpel. They can be quite tough to cut so take your time. You might find drilling some small pilot holes helps cut the slots. Both of the control horn tabs were roughed with 120 grit paper and then glued into the rudder with epoxy and glass powder as per the elevators and ailerons. They were also set at 90º to the rudder skin. The rudder end of the pull-pull system is now defined.
At the Servo end we need to define the location of the cable onto the fuse sides. I modified the rudder arm design to suit the MKS 6mm Hubs to get more adjustment options. But wait, there’s more! The ball links used were Dubro 2-56 at both ends along with the standoffs that come in the pack. The diameter across the ball end holes was measured, halved and then the stand-off thickness added. Mark this dimension up from the rudder control horns. This is the cable centreline. The same is done at the Servo end. I found using the rudder tray as a datum helpful. A strong light inside the fuse helps transfer the line of the rudder tray to the tape on the fuse sides. Both ends of the cable are now defined so now we just join the dots to project the cable paths. You can run a length of tape along each side of the fuse to mark out the path of the cable. Then just use a steel rule to join the dots. Really only the fin area needs to be marked. Next the cable exit point needs to be marked. I find the easies way to do this is with cotton tied to the rudder horns and rudder arm. The cotton lengths are crossed (as the cables would be) but above the turtle deck. Make sure the rudder arm is directly above the Servo. If necessary adjust the cotton length to achieve this. The cotton will intersect the cable path lines in the fin area. If all works out ok, this mark should be above the stab adjuster pin. I then measure 1/2” either side of this point. The slot length can be fine tuned later if required so don’t stress over the length too much. This will be the length of the slot. The slots are carefully cut with a Dremel cutoff wheel. It’s easier to do with the flexible drive cable on the Dremel as its smaller diameter allows you to get closer to the surface being cut. Inside the fin is a sub-rib which will probably need some trimming. A 3/4” length of dowel with sandpaper wrapped around it works well for sanding some clearance into the rib.
The rest of the pull-pull system is just a matter of running the real cables. Some things that I do specifically are:
- Use Sullivan 2-56 eyebolts at each end of the cable.
- Run a 20mm length of small heat shrink over the cable first.
- Loop the cable through the ferrule twice and crimp with a cable crimp tool.
- Hit the ferrule with thin CA.
- Cover the ferrule with the heat shrink tube and shrink.
- Do the Servo end first. This makes working on the system easier in my opinion.
- Don't forget to cross the cables.
This step is only applicable to the EP version of Allure Bipe. Ventilation at the front of the model is all done for you by the factory. There are vents in the cheeks of the fuse, gills on the sides near the wings and cutouts in the chin cowl. There are no exits cut in the bottom of the fuse. For EP applications this is important. For this build tear drop style exit vents were cut into the fuse bottom with a Dremel.
Exits for the elevator extensions need to be cut into the fuse sides. As can be seen in the pictures, the bottom of the stab tube and adjuster pin were used to mark out the extension exits. The slot is 6mm high by 20mm long and is located halfway between the stab tube and adjuster pin.
The fin former has allowance cut into it for a paper tube to house your extensions. There is nothing behind the rear wing for the paper tube so a 1mm ply support was designed and CNC cut. This support was then glued to the ply former behind the lower wing. The paper tube is made with drafting paper and a strip of double sided tape wrapped around a mandrel. These paper tubes can be a pain to make. Two sets of hands is a big help.
The tube was glued into the fuse with epoxy. The elevator extension holes cut in the last step ended up above the foam stiffener that runs the length of the turtle deck. The paper tube is in the bottom of the fuse. Small slots were cut in this foam stiffener adjacent to the extension exits for the actual extensions.
The receiver and receiver pack plate was Made from light ply laminated in carbon cloth. Slots and holes were milled into the plate to tie back the wiring and make the install tidier. The plate was mounted at the front of the lower wing to keep weight forward. With the receiver now mounted, the elevator servo extensions could now be run. PowerBox premium wire and connectors were used.
The flight battery and ESC tray is an evolution of the one used in the Alchemy. It’s made from 1.5mm carbon sheet and features a simplified And stiffer clamp system. Overall the tray is smaller too in order to minimise weight. The tray is attached to 6mm carbon tubes with small cable ties.
On the home stretch now.. Now to do some alignment checks and setup the radio.
Some of the alignment has already been completed whilst working on the wing struts. Some people set the fuse up in a jig to check alignment. My preference is to use a stable model stand that holds things firm. Foam rubber fuse stands don’t cut it here due to stability.
Some tools are required too:
- Robart or H9 incidence meter bars and brackets. Long bar not needed on the Bipe Wings.
- Digital angle meter - DXL360 or Wixey.
- Elevator Alignment Sticks.
- Laser Level (optional).
Items to check:
- Wing incidence. The designer has fixed this parameter.
- Wing alignment to fin. This was corrected on the top wing earlier.
- Stab incidence. This is independently adjustable. Make sure both stabs are the same incidence.
- Thrust. This was set to the nose ring initially. Trust the designer to begin with.
- Centre of gravity (CG).
With respect to throws and expo, the Alchemy settings is where I started.