Woodwind A2 (oz12650)

About this Plan

Woodwind A2. Competition towline glider model.

Quote: "A breakaway from the usual thin, undercambered, fragile, warp-loving Nordic wing is the main feature of this all-sheet design - built for normal rather than ideal weather conditions. Woodwind A2 by John Krouse.

DESIGN PHILOSOPHY Most Nordic A-2 enthusiasts 'get their kicks' by building high-performance 'still-air' gliders - they are aerodynamically challenging and aesthetically pleasing. Unfortunately, these fragile, sensitive craft seldom live up to their designer's optimistic expectations. Consequently, 'Woodwind' was conceived to cope with the actual weather conditions which usually exist at most FAI trials - namely, WIND!

The principal objectives were to develop a model having the following flight characteristics:

(1) good gliding efficiency.
(2) excellent stability (static/dynamic-longitudinal/lateral).
(3) ability to manipulate fairly tight turns for remaining in the core of small-diameter, low-altitude thermals; and also to keep the glider within reasonable retrieving distance (and timers' eyesight) for all those three-minute-plus flights.

In addition to these rather ambitious perfor-mance goals, durability and reliability were essential for FAI competition.

Aerodynamically, a close-coupled lay-out employing a relatively large horizon-tal/vertical tail and rudder were selected. Generous amounts of dihedral (both inboard and outboard) and tip washout were incorporated into the rectangular planform wing to avoid spiral dives while 'thermaling.' Structurally, sheet balsa covered wings were chosen to resist warps and flutter - two problems frequently encountered by Nordic flyers (usually with disastrous results). The spruce spars are absolutely necessary to prevent buckling!

It is the author's opinion (based on some early British wind tunnel data reproduced in the 1970 and 1971 National Free Flight Society Symposium Reports) that properly designed flat-bottom airfoils glide almost as well as similar undercambered sections, in addition to being less critical to trim for varying weather conditions. So far, 'Woodwind's' performance seems to support these claims.

CONSTRUCTION Fuselage: Start by building the vertical tail/rudder assembly from 1/32 -1/16 - 1/32 inch balsa ply (see plans for auto rudder details). Then proceed to the slab-sided fuselage, which was chosen for its simplicity and accuracy in aligning wing/stab/fin. After cutting a sheet of medium soft 1/8 x 3 x 36 inch balsa into 1-1/2 inch wide strips, glue the upper medium hard 3/16 x 3/8 inch longeron in place with a slow drying adhesive such as Titebond (used almost exclusively).

Make 'keel' from two 3/8 x 3/8 inch pieces of spruce, cement lower longeron in place (leave space for FAI Supply adjustable towhook), and allow to dry overnight..."

Direct submission to Outerzone.

Supplementary file notes

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