Sheet the top of the fuselage (above left) from the windshield to the ply nose former with soft 1
⁄16
the stab from 3⁄32-inch hard balsa sheet. I built the stab right over the plans. The framing is 3⁄32-inch square topped with 1⁄16- inch square strips. I filled in the stab cen- ter section with 5⁄32-inch thick balsa sheet. I added small 3⁄32-inch balsa sheet triangu- lar gussets at the trailing edge of the cen- ter section. I block sanded the center sec- tion and the 1⁄16-inch square strips to achieve a curved airfoil section. The bottom of the stab is flat. Round off the leading edge and tip outlines and fair out the trail- ing edges. I made sure I had a clean 1⁄16-inch wide slot in the stab center section to accept the vertical fin. The stab is now ready for covering. The wings were next. I cut the ribs from
1⁄16-inch balsa sheet. The wing tip leading edges are cut from 3⁄16-inch balsa sheet. The trailing edges are cut from 1⁄8-inch sheet. The wing spars are 3⁄32 × 3⁄16-inch hard bal- sa. I began assembly with the two wing tips. I left the tip spars long and trimmed them to the correct angle and length when I as- sembled the tips to the center section. The wing center section is straightforward:
3⁄32 × 3⁄16-inch hard balsa spars, 3⁄16 × ¼-inch soft leading edge, and a 1⁄8 × 3⁄8-inch trailing edge. I shaped the leading edge after the cen- ter section came off the plan. I shaped and block sanded the trailing edge to conform to the ribs before I pinned it down to the wing plan.
Next, I blocked up the wing tips (tip dihedral is 23⁄8 inches at each tip), trimmed the tip spars to mate with the center section spars, and glued the tips to the center sec- tion. After the tips were joined to the center section, I added 3⁄32×½-inch balsa sheet tri- angular gussets to the dihedral joints. Final shaping and block sanding of the leading edges completed the wings. Ain’t they pret- ty? I’m loving those outlines…shades of the 1930s. I covered the stab and wing with the same
1953 vintage Japanese tissue. I used Office Depot purple glue stick to attach the tissue. I shrunk the tissue with rubbing alcohol. I pinned down the stab and wing to flat sur- faces while the tissue shrank. Later, I
FLYING MODELS
-inch sheet cut into tapered strips. Tom held the strips in place
with rubber bands while he attached them with gap-filling CyA glue. Sand the 1
⁄16-inch sheet nose wrap (above right) to a 1
sprayed the wing and stab with two coats of Krylon Matte. I checked the wing for warps (there were
none) then glued the finished wing to the fuselage, checking for squareness as I went. Next, I glued the lower vertical fin to the un- derside of the fuselage. It ensures correct longitudinal positioning of the stab. While waiting for the lower fin adhesive to cure, I glued the upper vertical fin to the stab. That done, I glued the upper fin and stab assem- bly to the fuselage. Make sure there is no stab tilt, which will induce unwanted turn- ing tendencies. Nose block and prop construction:
The nose block consists of five cross-grain laminations of 1⁄8-inch balsa sheet. The nose plug is four cross-grain laminations of 3⁄32- inch balsa sheet. I sized the 3⁄8-inch deep nose plug to match the square opening in F-1. I inserted the rough nose block into F-1
and then shaped and sanded the nose block to fair it into the front of the fuselage. I drilled a 1⁄16-inch hole through the nose block and inserted a length of 1⁄16-inch brass tub- ing. I left the tubing long to make sure there was no horizontal or vertical thrust offset. When I was satisfied, I glued the tubing into the nose block with CyA and trimmed the length of the tubing. I gave the nose block three brushed coats of Sig clear dope, sand- ing between coats to get a nice finish. The prop was the next item on the agen-
da. You could use a Peck Polymer 9-inch prop, though I have no idea how it might perform with this model. Personally, I lean to hand-carved props. They seem to break less and I think they are more efficient. I have included a series of photos for a slight- ly different prop I carved awhile back for a scale subject. While that prop layout isn’t exactly the same dimensionally as the one I carved for the Retro Sport, it does illustrate the steps to carve a prop. To read more about carving your own
prop, check out Don DeLoach’s “Prop Carv- ing” in the September 2008 issue of FMor Don Carkhuff’s “Prop Checks and Bal- ances” in the January 2010 issue. You can
⁄32 -inch thickness. Light and strong.
also find information on this subject on the Internet at
http://tinyurl.com/cztgyfm or
www.keveney.com/prop3.html. The prop block dimensions are: 1 × 11⁄2 ×
9 inches. If you don’t have 1-inch thick hard balsa on hand, you can laminate it, just be sure the grain is running the same way in all of the laminates. The prop block outlines are shown on the plans. After band sawing
the block to the outlines shown, I drilled a 1⁄16-inch diameter hole through the prop cen- ter and then CyA glued in a 1⁄16-inch O.D. brass tube to support the prop shaft. We’re ready to start carving. If you work slowly and follow the step- by-step photos, you should have no prob- lems. If you do, like maybe cutting too deep, hey, balsa’s cheap. Glue up another block and start over. Carving always starts on the back side of the prop blades. There is no undercamber. The back sides of the blades should be perfectly flat. Strive for a maximum blade airfoil thickness of 3⁄32 inch. I use a Stanley utility knife and X-Acto
knife with a #11 blade to carve my props. I always use fresh blades and strive for mini- mal cuts. When cutting with the grain, you may tend to cut too deep. You can prevent this by cutting from the other direction. Af- ter you’ve cut away the backs of the prop blades and tapered the back surfaces into the prop hub, block sand the rear blade faces smooth. I start with 80-grit and work my way up to 220-grit. Make sure both blades are perfectly flat before you begin carving the fronts of the blades. The blade fronts are carved into an airfoil section. Maximum blade thickness is 3⁄32 inch. The blade’s airfoil cross-section should peak about 35% aft of the blade’s leading edge. I radius my prop leading edges down to a 1⁄32-inch radius. I round off the blade tips using a circle template as a guide. When the prop is fully shaped and sanded,
form the prop shaft from .040-inch music wire. On this model, I chose not to use a free wheel- er. Let the prop shaft extend 6 inches beyond the nose plug to allow bending of the rubber hook. I use Jasco ball bearing thrust washers
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