Whisper (oz14082)

About this Plan

Whisper. Radio control model thermal glider. Wingspan 60 in, wing area 400 sq in, for 2 channels.

Quote: "Whisper, by Randy Wrisley. Here is a floater of floaters that is just perfect for early morning thermal flying or any time the lift is weak and the wind is low. The Whisper will amaze you with its flat turns and its ability to climb out on the most insignificant thermal. You can build one in a matter of hours, so what are you waiting for?

This article details a different type of sailplane. Whisper looks like a European free flight glider, circa 1948. The very slim fuselage has only enough room for the Cannon Super-Mini or Super-Micro type radios. (Bantam Midget servos will fit.) Even so, the model spans 60 inches and has 400 square inches of wing area. The real difference between the Whisper and other gliders of this size is the ready to fly weight. This machine weighs eight, count 'em, eight ounces! Friends, that's a wing loading of 2.87 ounces per square foot. If you thought five ounces per square foot rode light air, just wait till your try three!

The model's light weight, combined with an undercambered airfoil, means this is a very slow flying glider. I also used a small vertical fin and sharply angled wing tips. These features add up to a very flat, almost bankless turn. All of the above contribute to Whisper's ability to stay up in lift so light the others can't even see it. The elevator is seldom used in flight, usually only to correct the pilot's mistakes.

Whisper also makes a great trainer. My wife soloed on ours, even making her own hi-start launch with only verbal assistance. By hi-start I mean 50 feet of 1/4-inch rubber and 200 feet of six-pound test fishing line. That's all it takes to haul an eight-ounce sailplane up.

About the only thing you wouldn't want to do is fly your Whisper when the wind blows more than 10 mph. Now, a word to you would-be hand launchers. Yes you can, but please put some 1/32 shear webs in the center first.

As for construction, it's very simple. Use all adhesives sparingly. Take some time to sand the model well before covering. Tissue would knock an ounce of dead weight off the total. I chose an iron-on film, however, because it's faster and doesn't warp the light structure. I also used an Ace 100 mah battery pack (Part No. 38K42F), combined with my Cannon Suber-Mini radio. Don't pull any components out of their cases, it isn't necessary.

At this point, you should be all fired up, so read on, and I'll tell you how to build one.

Fuselage: Cut two identical sides from medium-soft 1/16 balsa sheet. Cement the 3/32 x 3/32 hard balsa stiffeners in place top and bottom, then add the 1/32 ply doublers at the tail. Make the formers from hard 1/16 balsa. Lay one fuselage side down on a flat surface. Glue formers two through five in place using a triangle to align them perpendicularly.

The servo compartment floors are now installed. Check to be sure that your servos fit before you progress. When the glue dries, cement the two fuselage sides together. Taper the stiffeners down to nothing at the tail and cement the tail together..."

Direct submission to Outerzone.

Quote: "Steve, Mary, Find attached the plans and article for the Whisper glider by Randy Wrisley published in Model Builder on Aug 84. I found this in my stash of plans that I am trying to organize and thought you might like it for your site. I never built it but it would make a great schoolyard flyer with modern radios and would be under the 250 gram limit for registration. I have added some pages of templates for formers wing ribs etc that can be printed on 8 1/2 x 11 paper. Harry Kirkland"

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