Sm Tall alk W
ithout a doubt, the best part of modeling is the ability to try different things and experi- ment with new ideas. Having been involved in many different facets of modeling over the years, the best lessons have been learned from those off-the-wall ideas that were tried, “just to see what would happen”. In some cases things worked out great—like electric power when the masses said it would never work, or the 4- and 5-winged airplanes that defy all the laws of common sense in modeling. Other times, things didn’t work out quite so well, but those were safely tucked away in the “don’t even think about doing that again” column. But the good news is that something was learned from each and every one of those sometimes convoluted and usually crazy no- tions, and whether the results were positive or negative, it was never boring—sometimes frustrating, but never boring.
A new twist
So as long as we’re on the subject of cocka- mamie ideas, our good friend and local mod- eler, Mike Barker, decided that he needed a model that was controlled by wing warping. This is one thing I’ve never tried though have thought a lot about it over the years; so figuring on doing my part toward Mike’s success, I donated my old 1911 Eastbourne Monoplane prototype from the (now ancient) Hobby Lobby design to the cause. The thing about wing warping is that for the system to work, the wing has to be inher- ently weak, which is really not a good thing where strength is needed to take the typical flying loads that the airplane will ultimately be exposed to. So to design a wing to twist, it has to be weak in some areas, but strong in others.
The Eastbourne wing was built around two internal spars at the bottom of the air- foil, and as luck would have it, Air Span was used on the model, but was attached only to the rib bottoms since the airfoil was under- cambered. The wing was a certain amount of
PHOTO: MIKE BARKER
Mike Barker converted the original 3-channel Eastbourne Monoplane to wing warping using a servo arm actuated by a pull/pull system. An EZ-Connector and sewing needles provide a full range of adjustment to the system that provides more than adequate roll control.
stiff, and had the cover been attached to the rib tops probably would have been too stiff to work, but as it was turned out just fine. The answer to the span wise strength was of course, the external rigging; but where the trick comes in is placing the flying and landing wires such that they will add the necessary strength without hindering the warping process. The Eastbourne had four wires top and bottom, so figuring on simplic- ity, the wing was actually warped from the rear inner support wire outward in an at- tempt to keep the system as simple as possible.
To make it work, the rear outer cable was actuated from a single servo using a “T” horn on the bottom and connected with a rigid pull/pull drive system from the ser-
vo. The cables were connected to the horn using an EZ-Connector with sewing nee- dles on each side so that the system could be adjusted as necessary. Working to the best mechanical advantage, the actuator cables were located at the trailing edge near the tip of the wing. Then to transfer the motion to the other side, an idler cable was run through a fairlead on the king- post, so as the actuator cable pulls the trailing edge down, the idler cable pulls the opposite tip up, effectively actuating both sides at once.
One other factor in all this is that the taller the king post, the better the system will work. If the cables lay too flat against the wing, there will be too little twist to be effective. But as it turns out, Mike was able
by pat tritle You can reach Pat Tritle at 10313 Snowheights NE, Albuquerque, NM 87112 or via e-mail at
patscustommodels@aol.com
PHOTOS: MIKE BARKER
The original model Eastbourne was designed and built circa 1996 (above left) and laid dormant for many years until Mike decided he needed to try wing warp for lateral control. It is possible however that it’s Einstein’s flying skills that
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made it work. To make the wing warping system work, an idler cable (above right) runs from tip to tip through a fairlead attached to the kingpost. As the servo pulls the wing tip down, the opposite tip is pulled upward by the idler cable.
AUGUST 2013
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