Foamie Bird of Time

I decided to build a scaled down Bird of Time RC glider out of FT foamboard. Even scaled down 61% she still has a wingspan of 72" (1.8 meters). This article covers the build and some test throws.

Here, the wing is made similar to the FT method, but a true airfoil shape is obtained by peeling the paper off the inside of the upper wing panel and curving it around the edge of a table. The wing has a C-shaped spar, and several foam ribs are glued throughout the wing. A very acute bevel cut is placed on the trailing inside edge and then the upper surface is glued down.  The over-hang is then sanded.

Outer panel with double bevel cut at leading edge.

Panel with spar and ribs glued in place

Bevel being cut along trailing edge.

Wing after bevel has been cut and sanded.

Wing after upper surface has been folded over.

Wing after the overhanging upper surface has been sanded.  Final cross-section.

The horizontal stabilizer is a true flying stab, controlled by a bell crank.  The bell crank was made from a servo horn but a small tube was glued inside to provide an accurate pivot point. Both the horizontal stabilizer and the vertical fin are made from a 1/8" thick sheet of balsa sandwiched between two sheets of foam.  This construction method has proven to be not very good as the stab was damaged in a relatively minor landing and the vertical fin required some fiberglass reinforcement. A strip of doubled over Monokote was used as the hinge material. 

Horizontal stabilizer. A 1/8" sheet of balsa goes in-between the foam pieces.

Vertical fin under construction. An aluminum tube is inserted at the pivot point.

Vertical fin complete.

The fuselage is straight forward.  As mentioned in the video, quite a bit of weight would have to have been added to front in order to establish the correct CG.  The plane's weight was 14 oz (396 gms). but would have required an additional 6 oz. (170 gms) of weight in the front to achieve the proper CG.  The nose was extended about 4 inches and then 3.2 oz (91 gms) in the form of 9 nickels were added. 

Fuselage side panel.

1/16 ply glued in for wing saddle.

cross-sections glued in place.

Front of fuselage. Battery pack is 3 AAs

Coffee stirrers were placed down each linkage and glued is key areas inside the fuselage.

Close up of Bell crank.

The baseball field was too crowded to attempt a true maiden flight, but several tosses reveal some issues with the plane.  I think she may still need some more weight in the front.  I also broke off one side of the horizontal stabilizer on a somewhat rough landing.  I will rebuild the horizontal stabilizer and may make it a bit larger as well.  By far, the wings are the best part of this build. Stay tuned for the second video where this bird will get a true maiden flight.

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