Flutter-By (oz16892)

About this Plan

Flutter-By. Rubber powered ornithopter model. Wingspan 11-1/4 in.

Quote: "THE HEART of this model is the crank and connecting rod system. The crank has been designed so that the lower wings are 90° out of phase with the upper wings. This means that when one set of wings is in its stationary position - ie highest or lowest point - the other pair of wings is still moving. Also, as the attachments of the corods with the wings are some distance apart, each pair of wings 'rocks' laterally. These two effects together produce a system in which only one wing stops at a time, or in other words, at least three wings are giving power at any instant.

The fuselage is a single flat framework 1/8 thick, built straight over the plan using -1/8 square hard balsa, with a small piece of 1/8 sheet at the tail end. Care must be taken to ensure that all the joints are well glued - PVA being the best glue for this job - as the whole framework is subjected to considerable forces when the wings are flapping. When the fuselage has been removed from the plan a hole is drilled through the front piece to take the brass bush for the crank. The nose is then strengthened by gluing the small 1/32 balsa doublers to each side.

The rear motor hook is bent from 20 SWG piano wire, pushed through the rear fuselage and the end turned over as shown in the plan. A coating of glue should be put on this 'tail-piece' to prevent it from cracking.

Finally, the pylon is covered on both sides with lightweight tissue, and can be doped, although this is not necessary.

The tailplane and fin are cut from 1/32 balsa. DO NOT DOPE and use the lightest grade of sheet. The fin is glued directly on to the top of the tail-plane, and the tailplane is glued directly on to the -1/8 square mount provided at the back of the fuselage.

The large negative angle of incidence is essential to keep the model pointing upwards, therefore pulling itself into the air. (As the wings are always moving, the model cannot stall.)

Four identical wings are made. The leading edge of each wing being made first. This LE is built up from three laminations of 1/32 x 3/32 balsa.

Fix pins into the modelling board along the line of the inside (rear) side of the L.E., and carefully bend the first strip round these pins, pinning it in place as you go, and using these to pin the two strips together. DO NOT PIN THROUGH THE WOOD!

The third strip is added to the front of the first two in a similar manner. PVA is again the best glue to use. When the glue has completely dried, cut the ends of the LE to size and add the 3/32 square balsa wing root, and a generous 3/32 balsa gusset. The joint between the LE and wing root has to be strong and rigid, so do not make the gusset too small, and glue it in well..."

Direct submission to Outerzone.

Quote: "Flutter-By is an ornithopter designed by A.J.Brown and published in the August 1969 issue of Aero Modeller. Wingspan 11 1/4in. Thank you for your dedicated work.
PB_guy"

Supplementary file notes

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