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Originally Posted by ghrocketman
Rudder-control-only even on the simplest of models just plain sucks even if only for trim the elevator gives.
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No they don't--it's a matter of setting them up properly. The single-channel, rudder-only power models (such as "Dick's Dream," a popular old high-wing, Cessna/Piper Cub-type model) and rudder-only R/C sailplanes (often purpose-designed for radio control, although larger F/F [Free-Flight], often scale or scale-like gliders are commonly fitted with R/C rudder control) were/are equipped with two aerodynamic features that make rudder-only control quite versatile:
The rudder's hinge line is angled so that actuating the rudder (or , depending on the specific model's design, *not* actuating the rudder--that is, leaving it in the "centered," neutral-yaw position, with the rudder moving rapidly to and fro between the two electromagnets) produces a pitching moment as well as a yawing moment. (With today's digital-proportional R/C systems, the rudder doesn't move unless the transmitter's rudder control stick is moved, of course.) Also:
The model airplane or sailplane has wings that have centerline dihedral ("Dick's Dream" has such wings), tip dihedral, or polydihedral. This works in concert with the rudder control inputs to produce banking turns instead of "draggy," altitude-shedding sideways-skidding turns. I have a West Wings Free-Flight Slingsby Swallow semi-scale sailplane model (see:
http://www.samsmodels.com/slingsby-swallow [here are a few videos and links:
http://www.google.com/search?ei=Nu8...HXPhCWIQ4dUDCAo ]), which is designed to be easily convertible to R/C if desired; its wings have centerline dihedral, and:
While it *can* be fitted with two-channel, rudder/elevator control using micro-R/C gear, it's not uncommonly flown as a rudder-only model for weight/performance/internal space reasons (at least one of the above-linked videos shows one flying with rudder-only control). It's agile enough in rudder-only mode to slope soar--and even do aerobatics--along a sea wall in a breeze, as a British modeler reported (it's online somewhere--I read his report a few years ago); he and a friend used the sea wall location to race their two rudder-only-control Swallow models. Plus:
In flying a properly set-up rudder-only model (especially a glider), the rudder actually combines yaw with pitch (and altitude change, via banking). While most to the movement--and the most quickly-activated movement--is left or right yaw, one also gets a slower pitch down (a downward left or right bank, depending on which way the rudder is moved). In the old days, when pulse-proportional, rudder-only control was ^all^ there was (unless one used "cascading" escapements for elevator or ailerons that were "tripped" by rudder movements, but these had to be used in precise sequences--only a few experts did that), people were nevertheless able to fly all normal maneuvers, and even aerobatic ones, by keeping in mind the combinations of movements that single-channel, rudder-only control make possible. In addition:
Using such rudder-only control, either pulse-proportional or digital proportional, would enable small, low-cost, and simple R/C boost-glider and rocket glider kits to be produced. A pulse-proportional system could probably even be fitted to such small B/Gs as the Estes Falcon, Tercel, and Sky Dart, and the now-Semroc-made Hawk and Swift. The constant to-and-fro movement of the rudder would not cause any hinge longevity problem if living hinge material (polypropylene is a common one, see:
http://www.google.com/search?ei=Yvk...7.U 5jy2fL2fM8 ) was used, and the permanent magnet (the new alloy and ceramic magnets are very powerful) and electromagnets could be very tiny and lightweight, yet have ample control authority.