I reckon the wings is where I spent the most time on this build. Locating the control horn hard points and strut fit were the main issues. This model is a pre-production release so small issues like this were to be expected.
The servos used in the wings were MKS HV69’s as per the elevators. Again to save weight. New Servo trays were drawn up and CNC cut from 2mm light ply. Before gluing these Servo trays in, the factory cut Servo holes were checked for alignment and adjusted as necessary. Masking tape was used to get the tray alignment set and then 30 minute epoxy was used to fix the trays in place. Servo screws and scrap balsa worked well to hold things in place whilst the epoxy cured.
No servo extension holes were cut in the wings. This leaves an opportunity to screw up if you’re not careful by cutting holes on the wrong side of the wings. On the bottom wing the exit holes should be on the top surface and with the top wing it needs to be on the bottom surface. That said, one needs to take care!
The internal structure of the wings is made up of ribs. These ribs do have holes in them to allow for the extensions. On the top wing masking tape was run between the two Servo holes. The actual extension exit centreline is approximately 10mm behind the aft edge of the Servo cutout. It was then just a matter of working out the wing centre and the position of each exit hole from this point. Two 10mm holes were cut with a Dremel tool and suitable stone. Now the fun begins... Because the wings on a Bipe are so thin, it can be a challenge to one’s dexterity (and patience) to run extensions. At this stage I didn’t know what the final length of the extensions would be. The plan is to usePowerBox One 4 Two extensions which feature Muiltiplex connectors to make assembly at the field super simple. So, in the interim pull through strings will be used to make fitting the final extensions later much easier. Normally I’d use an old nyrod to run extensions but in this case it wasn’t going to work. What did work was some 1.6mm solder. The solder is able to be formed to a shape which makes it easier to get through the middle of each rib. I started at the Servo end and could easily see the solder when it got to the hole at the root. Then it was a matter of hooking it out with tweezers and then tying the string to the solder and pulling it back through the wing. Both ends of each string line was taped to the wing to prevent movement out of place. After doing this four times you’ll be an expert. :-)
Mounting the control horns is the next fun task. This is another job that is possible to screw up and as it happens I did just that... Locating the hard points in control surfaces can be difficult at the best of times. Normally you can feel them by gently squeezing the skin or using a strong light against the surface. Neither of these methods located the hard points with this model. I had come to the conclusion that the factory had possibly forgotten to put them in. Time to contact the designer Bryan Hebert... Bryan advised that hard points should be on the inboard side of each Aileron servo. Well, this is where he wanted them to be. Occasionally what Bryan wants and what gets delivered differs. Anyway, I carefully measured out where the Aileron control horns were to be placed for all four ailerons. Then a sharp scalpel was used to cut out the first slot. Oh no! Air hard points! Upon further inspection I found that hard points were on the outboard side of the servos. Bryan advise that on production wings the hard points will be inboard. Anyway, how did I move forward from here? Easy, I made my own hard points with 6.5mm balsa. The balsa was stripped to about 20mm width. The control horns will be mounted in the same position as the slot already cut but the slot needs to be opened out to the size of the balsa. This is marked out on the tape first and then cut with the scalpel. The 6.5mm balsa plug should be a neat fit. The end of the balsa needs to sit flat on the top skin too. This will require a small angle being sanded on the end. The balsa plug can then be glued into place with epoxy and glass powder. When the epoxy is cured the balsa plug was sanded flush with the skin. An area approximately 25 x 25mm around the plug was sanded to take the gloss off the surface. A 25 x 25mm carbon cloth patch was then glued onto the skin with laminating epoxy. The end result is quite a strong and neat fix. The control horn slot is then marked out again and then cut out to fit the horn. The horn was roughed up with 120 grit paper and then glued in place with 30 minute epoxy and glass powder. Like with the elevator horns, the horn is set at 90 degrees to the surface. I should mention that the same dual axis ball ends were used on the Aileron linkages and also theMKS 6mm Hubs along with 2.5mm titanium rod for each linkage. The only difference being thecarbon servo arm at 20mm long.
As this Allure Bipe was pre-production, there were bound to be some issues. Firstly we had the Aileron hard points as noted above and the next issue was with the wing strut fitment. The struts have since been redesigned so this should no longer be an issue with production Bipes. If you look at the photos below you can see that the alignment was quite poor. One side (left) was only slightly out of alignment but the right hand side was over 1/8” out. A lot of measuring was done on the model and corrections made to improve alignment of the struts.
Here are some pictures of the new struts to be supplied with production Allure Bipes.
I started on the bottom wing and worked my way up. The first thing checked was twist in the wing surfaces as this will impact strut alignment. This was done with a Robart incidence bar with a DXL360 fitted. The reference was set at the root and then the wing was checked at mid span and then the tip. Any error was carefully corrected by warming the wing surface top and bottom with a hot air gun and twisting in the opposite direction. It takes time but removing small twists will pay dividends during the trimming process.
The lower wing slots into the fuse so there is absolutely no scope for adjustment. However, the top wing sits on a saddle and there is the possibility to adjust things by relocating the rear blind nuts. After careful measurement I determined that the top wing could be adjusted a little to improve alignment to the fuse and alignment of the struts. The factory fitted M3 blind nuts were pushed out and the holes filled with epoxy and glass powder. The top wing was then realigned and new screw holes marked out and drilled to suit the blind nuts. I used M3 x 20mm CSK head titanium screws. The screws are not included in the kit. The blind nuts were refitted and then hit with thin CA. Then some epoxy and glass powder over them locked them into position. They’re not moving again anytime soon.
Screwed into the top surface of the bottom wing are the strut bases. Just two wood screws secure the base to the wing. I found that some excess paint and resin was causing the strut basses to not sit properly in their recesses. This was carefully removed. Bryan advised that he actually glues these bases to the wings. This was done after I was happy with the overall strut alignment.
The factory provides some 3D printed pins to secure the strut to the lower bases. At the other end a piano wire pin is used. I chose not to use these but if they were used a body clip as used in RC cars would be fitted to retain the pins. I decided to make a new pin and socket arrangement out of delrin. The sockets are left in the struts and they in turn mate with the bases. A neat friction fit pin then holds it all together. The bottom of each strut was filled with epoxy and glass powder. The pin holes in the top of each strut was drilled out to 1/8” to allow for some adjustment. Wooden pegs protrude from the top wing to interface with the struts. These pegs mate with slots in the top of each strut. With the pin holes opened up in the struts and some adjustment to the slots I now had struts that fitted. Well, roughly fitted. With the struts now in position, the lower holes could be drilled to suit the new sockets. The new holes were drilled using the base holes as a template. They were drilled undersized and then opened out with a round file to get a nice fit.
At the top, some suitable carbon tube was used to create a neat socket for the piano wire pin in the struts. With everything now fitting nicely, the struts were filled and cleaned up where necessary ready for repainting.
The wings were now done with exception to the Servo extensions. This was deliberately left out until the receiver location was defined.