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General control line discussion => Open Forum => Topic started by: Roger_Pion on March 14, 2009, 08:15:31 AM
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This has been bugging me for a while. It seems to me that where control lines are concerned, a big source of drag would be the wing ends where the lines are clipped to the leadouts. Neither the clips nor the wrapped ends can be made very aerodynamic and they're being dragged through the air at speed. So I'm wondering ...
Why have I never seen an airplane which has either the lead-out-to-line connections buried in the wingtip or wing, or even the lines connected directly to the bellcrank?
If the plane is built from the start with this in mind, accessability to the connections should be no problem. In fact if the lines are connected directly to the bellcrank one would not even need to worry about fouling clips or such. They do not have to detach; one could simply wind up one's lines on the reel and lay them on or under the plane's wing when not in use.
If the lines get damaged it wouldn't be that much harder to replace them than usual. One would simply make the handle ends as usual, tape the unprepared wing ends of the new lines to the old lines and pull the new lines to the bellcrank while removing the old, and attach the new lines.
I must be missing something because I never see this. What is it that I'm missing, guys?
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If you limit your perspective only to stunt models and flying, you will miss a great deal. >:D
Most Racing, Speed and Combat models attach their lines just as you suggested: either inside the wing with some sort of connector and short leadouts, or directly to the bellcrank. The MAJOR difference is that lines are changed and old ones discarded much more frequently than a typical stunt model.
The primary down-side to internally connected lines is that the abuse that is imparted at the wingtip is much more easily handled by a leadout of substantial diameter than a flying line.
Regards,
Bill Lee
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Roger,
As Bill points out, in events where speed really matters, these things are important.
However in Stunt, where the wing leading edge sometimes has the radius of a slow pitch softball ~>, the drag due to 2-3 inches of leadout wire and clips just isn't a big deal
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Roger,
As Bill points out, in events where speed really matters, these things are important.
However in Stunt, where the wing leading edge sometimes has the radius of a slow pitch softball ~>, the drag due to 2-3 inches of leadout wire and clips just isn't a big deal
I don't know about that. I would estimate that, in level flight, the drag of the clips is probably on the same order of magnitude as the wing. The drag of a nice NACA0018 isn't very high and bluff bodies are pretty terrible. I did figure out once that a bare landing gear wire was more than the wing, by a good margin.
The real answer is that parasitic drag is not that bad of a problem, in fact, the trick at the end of the 4-2 break era (and continued even into the current 1st-generation of tuned pipe airplanes like the Trivial Pursuit and Infinity) was to make the airplanes relatively small but with absurdly thick wings to get a larger ratio of parasitic to induced drag for better speed stability. The total drag doesn't matter much since you can use as big an engine as you want, or, alternately, make the airplane smaller enough to ensure you have enough ponies to overcome it.
Brett