Wednesday, November 5, 2014

Rotmilan Midi Assembly

Note: you can read the first part here: kit overview

The rotmilan doesn't reserve any real surpise during the assembly. There are however some particular points to to take care so I will develop. On the fuselage, the most delicate operation is the wire routing from the front of the fuselage to the green plug print location. Because of the bassat tube already in place, there is very little remaininf space on each side to route the 4 wires. They must be under the ballast tube, then go on the side to reach the wing plug hole. Here is the technic I used. I prepared the servo wires, around 45 cm long (the standard 30cm servo wires is too short). then using a thin piano wire (0.8mm) or a thin plastic sleeve, I passed it from the joiner location to the fron of the fuselage, then taped the wire extremity to it, and pull carefully until the wire exits. You need to do it 4 times (2 on each side), given that the second wire has even less space since the firt one is in place. Doing like this, it is not painful, but still requires some patience. The plug holes doesn't have recess to block the plug in place. I created it by gluing a 1mm plywood piece going from one plug print to the other, top and bottom. Once done, yuou can exit the wires, sloder them on the green plug, protect the soldering with hot gun glue and glue them in place with rapid epoxy.
On the rear side of the fuselage,

I used MPjet brass threaded coupler. There were with a 1.3mm, so I drilled to 1.5mm. The linkage provided has a layer of teflon that you need to remove first. The core of the linkage is fiberglass. I glued the coupler on it with some rapid epoxy, and crimped twice (at 90°) to secure it totally. To finish I glued the metal clevise on it to suppress any slop. The rear end of the linkage being done, I connect them to the tailplanes. I neede to sand the inner side of the fuselage to gain some space and allow the clevise to move freely. I also cut the recess that receive the end cap, and milled the end cap to allow the elevator horns to move. The result is very clean, simple and nice. No slope, free moving nice fit and junction of the parts together. This is obviously well designed and moulded.

Let's continue with the elevator servos. The tray is designed to receive 12mm servos like the MKS 6125e or equivalent. The hole is at the right size to not damage the wire when inserting the servos in its location. Here again, I used brass MPjet coupler after cutting the linkage at the right length. I then installed plastic MPjet (with metal axis) on them to have a tight mounting without any slop.

We can then start the wing servos installation. I used 2 MKS 6125 mini at the ailerons, and 2 MKS 6125 glider at the flap. As I said in the overview, the LDS is factory installed on the control surface, and is removable which is clearly a plus for any maintenance, or for the installation. for this a tool is provided. This is a long brass rod with a threated hole at one extremity. The LDS axis hae also a threated end. From the root of the wing, it is easy to screw the axis, then pull to extract it or push to install it. This is really well designed !

The linkages are epoxy board arms, the short ones being for the ailerons, and the long arms for the flaps.
On the servos side, after putting 2 extra layers of 93g/dm2 carbon fabric to avoid any deformation of the skin once the servo is installed, I sanded the surface, glued in place the wood servo frame. Make the operation carefully as the likage, LDS, servo head is mounted tighly and that any deviation will create friction or blocking point, so the servos will not work properly and the return to the neutral position won't be accurate. There are 2 servo head types: one with the hole at 5mm from the center which is for the ailerons, and one at 6mm which is for the flaps.

Once in place, I added a S-BEC in front of each servo as I use 2S LiIon battery, so high voltage. The wire extension done, I glue the green plug in the wing with the wing mounted and connected to the fuselage, and using some PVA release agent everywhere it is needed, in addition to some thin tape to protect the fuselage or the root of the wing. The flat servos covers are finally cut a the right dimension (there is a thin line to indicate where to cut) and taped in place.

Let's finish with the battery installation, and balance lead melting. As I said, the battery is a 2S LiIOn 18650 cell format, providing 2900 mAh. Once in place, the receiver takes place on top, with some plastic sleeve to guide the antennas. I needed 150g of lead to do the balance for a CoG at 106mm.

Finished component weight are the following:

  •     Left wing: 692gr
  •     Right Wing: 690gr
  •     Fuselage: 742gr
  •     Wing Joiner: 88g
  •     Left tail+ joiner: 40g
  •     Right tail + joiner: 42g

    Total 2294gr

No comments:

Post a Comment