Flummox
Two days and a bit of 3mm Depron®is all that is needed for this fun freeflight sport model!
By Pat Tritle PHOTOGRAPHY: PAT TRITLE I
t all started on a rain-soaked morning. I looked outside and could see that there would be no typical Saturday morning “boat pond” this day, so I headed back to the shop and there, leaning against the wall, was a sheet of 3mm Depron® foam that some- how looked like it needed to be turned into an airplane. Couldn’t go out anyway, so I figured this might be the perfect time to see just what that foam sheet might end up looking like with the right treatment. The next stop was the “drawing board” where the goal was to work up a simple, quick building, full fuselage model that would fly within the confines of our local soc- cer field—and do it all in one rainy weekend. In that realm, it had to be freeflight, and though it was going to be a very basic and rudimentary design, it had to at least have
pleasing lines. The model needed to be small enough to fly in the chosen venue, yet large enough that it would be easy to trim for rea- sonably long flights. What came of all this, was the Flummox.
The fuselage is a basic box; certainly no high levels of class there, so the wings and tail were done up in an elliptical form to draw the eye away from the lack of shape elsewhere. The wing platform is reminis- cent of the old Comet Sparky, and the tail section was done basically to complement the wing. The airfoil is nothing more than the curvature held in place with a single root rib that doubles as the attach point on the fuselage. Then with a simple balsa nose block and a 7-inch Peck plastic prop in hand it appeared that this whole scheme might just work.
AT A GLANCE Type:
Construction:
Wing span: Wing area: Length: Weight:
Wing loading: Prop:
Power: Day 1
All of the foam parts were hand cut from 3mm Depron® using a straightedge and an X-Acto knife. The curves were cut freehand.
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After the model was drawn up, the parts templates were printed on standard copy pa- per. The model spans 193⁄4 inches so the wings fit on a single sheet. The fuselage is 161⁄2 inches long, so the sides and bottom were printed on two sheets and match lined to make the full size templates. The parts were hand cut from 3mm Depron sheet us- ing straight edges and a standard X-Acto knife. The curved lines were done freehand. Once all the parts were cut out, assembly began with the fuselage. Now, being as my experience with Depron is extremely limit- ed, I wasn’t exactly sure what glue might work best without excessive drying times or damage to the foam, yet still get good adhe- sion. I know foam safe CA won’t eat the foam, but the adhesive qualities aren’t the best. Gorilla Glue works great but is excru- ciatingly slow drying, so what I ended up us- ing was Crystal Clear Flexible Foam-Cure glue from Bob Smith Industries
www.bsi-
inc.com. Drying time is around 30 minutes, and it’s tacky enough to hold things in place while it dries.
Construction began with the fuselage. DECEMBER 2013
F/F sport
3mm Depron® foam, balsa and ply
19.75 inches 46.8 sq. in. 16.5 inches
(less rubber) 17.1 grams 0.37 g/sq. in.
single 20-inch loop of 3
7-inch Peck Polymer’s ⁄16
Tan Rubber; 750–800 turns
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