While the paint on the fuselage has been drying...
... - very thoroughly, by the way - I started working on the dive brake linkages.
I think, I mentioned it earlier that I am not too fond of that often used idea of holding the doors closed with rubber bands or piano wire torsion springs as this requires the servos to work not only against the aerodynamic forces - what they are meant for - but also against the spring action, which applies additional load and battery consumption with humming servos.
In the case of this plane, the situation is aggravated by the fact that the lower door opens from the front side which in turn asks for additional spring force.
My aim was to find a way which allows positive control in any servo position at the lowest possible consumption and my first idea was to use the original wooden servo lever and to attach the brake doors to it with a sort of spring. A piece of 1/32" piano wire was held by a piece of tubing glued to the door and the free end of about 2" was routed through a hole in the lever arm. This worked basically o.k. but still the doors were either not kept shut positively or the servo started humming considerably. With the analogue servo in use, the current consumption was considered way too high!
I repeated the whole procedure with a "standard size" digital servos but the improvement was marginal - which led me directly back to the old method of using a direct "push rod" between servo arm and brake door which, at the end of the day, is always sensitive to travel adjustments in the TX. I decided that the improved accuracy of a digital servo and my devised building sequence should lead to sufficiently good results.
In view of the fact that the pivot points of the servo and the brake doors are far apart, I proceeded as follows:
* I marked the middle between the two points where the curved servo lever (part of the kit!) is touching the doors in the fully open and closed position.
* A piece of tubing was glued there on the LOWER door FIRST.
* With the servo in closed position, the length of the "Z"-shaped push rod was determined approximately and assembled to servo and door. Remark: The door pivot axis is a 1.2 mm piano wire in two pieces which slide into the hinges without further fixation. Thus the doors can be taken off at any time.
* Similarly, the length for the "upper" push rod was determined and now comes the point: With the lower door in fully closed position (and the servo groaning only slightly ;-) ), I closed the upper door against its stops and assembled push rod and tubing to the servo arm. With all this in place, I positioned the tubing on the upper door and applied the CA-glue through the servo mounting opening (which I had planned in the first place). With a slight bend in the rod, I am now able to do the fine tuning if necessary.
I admit that things look a bit complex and difficult to achieve but if you think of it a bit longer, it is definitely a simple and time- and cost effective solution.
(Upper door in the background)
The rest of the work on the 1-23 should now be a piece of cake: Covering wings and tail with Oracover and installing the rest of the gear...
... however, give me a bit of time because I have to throw in between a (very well made!) ARF-e-sailplane as a replacement for a recently crashed model - I wanted to control another fellow`s plane while mine went in in the meantime...
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