Sixty (oz7007)

About this Plan

The Sixty. HL glider.

Quote: "Unusual HL Glider design for the usually windy flying conditions. Short nose moment and vortex wing tips add to performance. The Sixty, by Howard G Evanson.

The Sixty was designed with an eye to flying conditions in Minnesota. Weather is windy and it is important to have a very stable airplane. The Sixty is stable, very strong, and it is a real altitude grabber. The higher a glider starts its glide the better its chances are of catching that elusive ther-mal. Sixty goes up with ease and it is easy to adjust.

It represents a successful attempt to get out of the rut. I've found that the more conventional a glider, the more successful it is, The great HL glider designers of today (Lee Hines, Larry Conover, and Stewart Savage, etc) have settled on the conventional layout for a good reason -t's best! I tried tandem wings, flying wings, canards, even biwings, and have always found the conventional force layout superior. This is quite maddening, but it is one of the things we glider men have to put up with. The 'Sixty' is still enough in the rut to be a good consistent contest bird capable of 60 seconds.

My flying partner, Bill Grimes and I tried to figure out just what we wanted in a glider - and how important the various 'essentials' are to the successful HL glider. We fly three to four times weekly, and have been doing this for over a year now; we've butchered enough balsa (and sod) to draw some conclusions. The most important thing is adjustment—to get the most out of a design. The second most important re-quirement is the flyer's ability to throw, in both control and in speed of launch. Least important is the design and the workman-ship, although these have a definite hearing on performance. The contest is won on the flying field, not on the drawing board.

The two things which set this glider off from most others are the short nose (ala A/2 tow-line glider) and the vortex wing tips. The short nose concentrates the weight close to the wing and, in effect, is a stabilizing factor. The vortex tips are definitely worth the extra work. The tip design is by Don Monson of Minneapolis and is most effective. Bill proved just how efficient these tips are. He had a bird which would either stall or spin in. Bill added vortex tips and presto! Not only did this bird exhibit a fine glide after the new tips were added but, he lost it OOS the same evening!

Construction tips: As this is a high-perform-ance airplane, it entails more time to build than an ordinary chuck-glider. To give any design a reasonable chance you must build more than one at a time. I always build two at the same time and some flyers will build at least six! I recommend tracing templates from the plans and making your own patterns out of cardboard. This way you'll save a lot of building time per glider.

The wing halves are cut from very light balsa (SIG balsa 4-6 lb stock.) You should be able to get two complete wings out of one sheet (36 x 4 x 1/4) of wood. The airfoil is a consistent one. Because the wing outline is straight line there is no difficulty in shaping it accurately. The high point of the airfoil is at 30% of chord. Notice that, from the high point to the trailing edge, it is flat. The wing thickness is tapered from 1/4 in to a little under 3/16 at the tips - giving a consistent airfoil from root to tip. Both wing roots should be beveled at an angle until the wing halves meet exactly...."

Howard G. Evanson's The Sixty from American Modeler magazine issue 08-67.

Direct submission to Outerzone.

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