Cliffmaster (oz1032)

About this Plan

Cliffmaster. Radio control glider by Ken Willard. From RCM 1969.

Quote: "A top slope machne, with unique profile fuselage, the quick-building Cliffmaster is adaptable to thermal soaring.

The Cliffmaster is not so much a design as it is a design concept. The reason I say that is because, since the original prototype was built, there have been four variations constructed. And all four of the designs have at one time or another won an event in which they were entered.

The idea behind the Cliffmaster evolved from a desire to have a small, but fast, entrant in RCM's annual slope soaring pylon races at Sunset Beach. And, at the time the idea hit, there were only a few days before the races, so the construction had to be simple and fast. And it is.

The best thing about the design is its adaptability to various wings. In fact, I had planned to include the drawings for a thermal wing along with the racing wing, but time didn't permit. However, for those of you who want to experiment, you can draw up your own version. I would suggest a wing with 74" span, root chord 7", just like the racing wing, and taper to a 4" chord at the tip, with the leading edge to be kept straight and the trailing edge tapering forward. As for the section, a 9% thickness, with maximum camber at the 40% point, and a flat bottom, should do a reasonable job. That's what I plan to try, anyway. Keep it light, too.

But back to the racing version. The wing is ultra simple to build, although I did complicate it slightly for you by tapering the spar thickness from 3/8" at the root to 1/4" at the tip. The original wing did not have this taper, and thus the thickness ratio, which is ten percent at the root, increased to about 15% at the tip - and this slowed the model down.

There are better wing sections than the one l used - but I doubt if there are any that are faster to build. The bottom and top sheeting is 3/32" sheet, and when you pin the bottom sheet to a flat surface, add the trailing edge stock to the leading and trailing edge positions as shown, glue the spar in place, and then bend the top sheeting over the spar; the top sheeting takes a natural curve from leading edge to trailing edge and only needs a couple of aligning ribs between the root and the tip. The 1/8" x 3/32" strip just ahead of the trailing edge stock at the rear of the wing gives you a good gluing surface.

Admittedly, it's rather unusual to use trailing edge stock at the leading edge of a wing..."

Supplementary file notes

Article pages, text and pics, thanks to DougS. Quote: - "Another RCG request. The original article had several paragraphs put in the wrong locations. Ken Willard mentions the mess up in the Feb 1970 column 'Sunday Flier'. I took the liberty to correct the mistakes and my compilation is laid out correctly."

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