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Old 11-14-2012, 11:27 PM   #4
Bill G
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Yep this one's unusual. I thought I had an unmodeled subject, until I came across the Nijhuis build after deciding to build the model. There's a lot of options on this one, as far as locating the gear is concerned. With the tail heavy tendency, gear will be located forward. The simplest method for tail control would be to mount the servos at the base of the boom, but in the interest of forward weight, I now have a tail assembly with long pushrods hanging out of it. The servos will probably mount in front of the wing, and slightly below. Since the tri-rudder and split elevators are a bit unusual, I figured on starting with the stab fabrication. I now have a stab frame with a "Y" pushrod configuration for the elevator halves, and a bellcrank setup for the rudders. The pushrods travel about 5/16" before binding, which provides ample elevator and rudder throws with proper control horn linkage geometry.

The rudder setup is similar to what I used on the Dornier Gs build, although this plane has a center rudder adding to the complexity, which will be driven from a bellcrank mounted pin that inserts into the rudder bottom. The bellcrank center aligns with the rudder hingeline. The outer rudders are driven by a pushrod mounted inside the stab, which exits the stab bottom at the hingeline, roughly 2 inches from the rudders. The distance from the pushrod exit point to the rudder horns is necessary to provide ample distance from the exit point to the rudder horns, allowing for some lateral movement when in motion to prevent binding. A slight downward pushrod angle from the exit points to the rudder horns will prevent interference with the elevator when moving downward. The stab will be sheeted with 1/32" balsa.

As Barry said before, one advantage of twins is that the needed motor power and size is reduced. Looking at the nacelles, some cheat will be needed to house outrunners, slightly lowering the props from scale location. It shouldn't be much however, as 200 class outrunners should power the plane, with reasonable weight. I have small Axon outrunners that are barely 200 class size flying a 19oz Guillows DC3, probably with less than ideally efficient props.


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