By Tom Houle
Build one for sport freeflight and another for micro R/C. Either way this little plane performs!
PHOTOGRAPHY: TOM HOULE T 48
he inspiration for my Retro Sport design began with a Model Air- plane News article dating back to the 1970s. The original model was
named The Zip and had a 14-inch wingspan. It was a simple design, all 1⁄32-inch and 1⁄16- inch balsa sheet. Back then, my boss and I built two Zips. They climbed like rockets and flew like stink. I went back to this de- sign when I recently decided to design and build something that flew as well The Zip but was larger in size. This time it would have built-up stick and
tissue wings and stab. I wanted the new de- sign to be lightweight and suitable for both rubber freeflight and R/C electric. If I do say so, I think I have succeeded. Retro Sport is super fun to fly and very stable in the freeflight mode. The only problem is if you opt for the rubber freeflight option, you’ll need a big flying field. This puppy will easi- ly stray from a Little League sized ball field.
The original Zip and my Retro Sport both feature lifting stabs with a flat-bottom air- foil cross-section. I’m not smart enough aerodynamically to say much about this lay- out except to say I know a lot of the old gas and rubber powered freeflights had lifting stabs, which I think moved the c.g. back. In any case, my model balances on the rear wing spar at 60% of the chord. Yup. I said 60%. Yet, it climbs nicely and has a flat glide. When it’s 200 feet up in the glide pat- tern and slowly circling to the right, it re- minds me of a hawk. If you build the R/C electric version, I sug-
gest making the wing removable and re- taining it with dowel pegs and a couple of rubber bands. The c.g. is so far back, the mi- cro servos, receiver, battery, and speed con- trol will easily fit into the spacious cabin. I didn’t need to add any nose weight to my rubber-powered model. Without rubber, bal- ancing the R/C version should be even more
AT A GLANCE Type:
Construction:
Wing span: Wing area: Length: Weight:
Wing loading: Motor:
F/F rubber sport balsa sheet
stick & tissue 28 inches 132 sq. in. 24 inches 23 grams
10-strands 3
.77 gm./
sq.in. ⁄16
-inch TAN SuperSport rubber, 23 inches long
forgiving. Construction is simple, just a mat- ter of cutting out some balsa components and bending wire for the landing gear legs. I built my Retro Sport the old-fashioned way. I used a flat section of ½ inch thick ceil- ing tile. Let’s get started. Maybe you’ll be the first kid on your block to fly a Retro Sport!
OCTOBER 2012
RETRO
SPORT
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