Fixed bottom rotor

[Stechnoblade]

Hey guys,
I'm planning to build a motor stick with a fixed bottom rotor over winter break (Dec 22 - Jan 1 for me) and experiment around with it. My main concerns are
1. If I directly attach the bottom rotor to the motor stick, it won't be aligned with the top rotor since the top rotor isn't on the plane of the motor stick due to the front hook.
2. I don't have any extra balsa to use to extend the motor stick, so if I directly attach the bottom rotor to the motor stick, then the distance between to the two rotors would be decreased, possibly changing flight performance.
3. I would have to deal with the issue of having a lower hook because I obviously wouldn't have one if I attached the lower rotor to the motor stick, so I was thinking of bending a sewing pin and supporting it using balsa wood like last year's FFM plane.

Of course, all this hinges on my preconceived notion that the lower rotor would have to be attached directly to the motor stick. I think it could be possible to just superglue the bottom rotor hook attachment and all that, but I'd still have to make a new motor stick and lower rotor anyways. If any of the coaches could provide support, I'd greatly appreciate it!

[coachchuckaahs]

1. The slight offset of the rotors should not be a huge issue. If the axes are parallel. An angular offset would be a bigger issue. We put the middle of the rotor spars in the middle of the MS (deep grooves) and it flies great.
2. The change in length is probably not a big deal, but it would be better to extend the MS if possible. A greater separation seems to make a more stable heli. We used a solid MS cut from 3/16" sheet, about 3/8" tall, 6# wood, and used trusses. You can probably find some wood at Hobby Lobby, though it will be likely heavier. With heavier wood you might try 1/8" thick (1/8" sheet) and cut to about 3/16 or 1/4" tall to get the weight back down, and then truss it.
3. For the lower hook we bend one with some of the wire that was included in the kit. Music wire is better than a pin, as it is hardened. A pin may bend easily under motor load. Gluing a bearing up just to get a tail hook is wasteful, and heavy.

If you build an X-rotor (like FFM) but have a fixed rotor, the spars can go straight through the middle, eliminating the center gussets and yellow tubing. Then you can do one of two things. First approach is to mark the center of each spar with a white marker or whiteout, then slit the MS deeply and insert the spars into the slits. Adjust the spars until the rotor is perpendicular to the MS, and add a drop of thin CA to each joint. A second option would be to glue a small balsa stick (1/8" square for example, or even thinner if cut from scraps of FFM kit sheets) between the spars while in the fixture. Then this stick would be glued to the edge of the MS to install the rotor, ensuring good alignment.

Coach Chuck