Underdog (oz16358)

About this Plan

Underdog. Simple chuck glider model. Wingspan 19 in.

Direct submission to Outerzone.

Update 28/10/2025: Added article, thanks to RFJ.

Quote: "With a promising new scooped-out airfoil and a drooping tail, this airborne pup will sniff out thermals and hound them for a ride. This particular Under Dog is a Handlaunch winner. By Larry Kruse.

When a Free-Flighter contemplates wings and things for any given period of time, he begins to recognize that the airfoil any design employs is of great significance. It not only controls the penetration of the power climb, but also contributes heavily to the attributes of transition and glide. If our modeler is perceptive, he also discovers certain similarities in airfoils - (a) they are necessary (b) there are lots of them (c) they are not all alike.

Keeping these last three items in mind (which should tell you something about my perceptivity and my mind), I determined that I would design something to offset the accusations of my flying buddies. I was tired of being hounded by friends who constantly growled about my doggy-looking planes. I was sick of being collared by wags with tales of their latest mongrelized ships. I was rabid in my desire to muzzle their complaints. I was ready to unleash - the Under Dog!

However, my wife threw me a Gaines-burger and a chew-biscuit and my fit of distemper gradually subsided to a snarl and a slight twitching of my tail. The 'Under Dog' airfoil was developed from a photo of the new McDonnell-Douglas high-lift, low-drag airfoil appearing in a recent issue of Flying magazine.

The full-scale version, designed to improve boundary-layer airflow, prompted me to speculate on what applicability this airfoil might have in Handlaunch glider design. The Under Dog foil is a variation of the McDonnell-Douglas, modified to conform to standard wood sizes typically available to the HLG enthusiast. (See Fig. 1)

Due to an unbelievable It's-not-nice-to-fool-Mother-Nature winter and spring in the midwest, the design has had little actual testing as of this writing, so I make no claims as to what a fantastic contest machine it has been or will be. The most accurate comment that can be made is that the Under Dog is an airfoil experiment in progress, showing some excellent glide potential and some problems in transition that can be corrected with proper adjustments.

Construction: The overall construction is typical of most Handlaunch designs. Only the airfoil itself merits special treatment. Begin shaping the airfoil by selecting a Sig 4 x1/4 in tapered sheet and marking the high point of the wing with a soft lead pencil in accord with the plan. Using a razor plane, taper the leading edge to a rough shape and sand it down to final size.

You will note that the rear portion of the airfoil, from the high point on back to the trailing edge is concave. The easiest way to shape it is to wrap a sheet of sandpaper around one end of a felt chalkboard eraser and apply fairly heavy pressure to the wing blank. The pressure will cause the outer felt strips of the eraser to splay out and allow the deepest sandpaper cut to occur in the centre of the sanding area..."

Supplementary file notes

Article.

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