Building Without Plans
The fuse is typical slab-sided construction for the most part (above left). The rounded top was made by rolling a sheet of ¹⁄₃₂-inch balsa curved over the
terpolated. The fine fit would be handled by a sanding bar—these drawings only had to be “close enough.”
As long as I was working on making extra parts, I quickly traced the fins onto a sheet of paper, and then added root and tip ribs for the wings. Why only root and tip? Because that’s all that’s needed, a sanding bar will provide the others. Aside from the nacelles, that’s all the plans needed to start construc- tion. If you’ll forgive me, at this point I need to assume you’re somewhat of a builder, so I’ll only touch on some shortcuts I have al- luded to earlier. I spent another two hours the same evening making these pseudo- plans, and still made it to bed on time.
On to construction
For the wings, I made a stack of 1⁄32-inch balsa blanks, bolted together, and sanded them. This provided the ribs for the constant chord center section as well as the root rib for the tapered outer section. I then built the center section. For the outer panels, I made the tip rib, then pinned down the LE, TE, and
formers and gluing in place. Glue the sheeting dry (above right) so there is no sag between the formers. The forward top will be a hollowed light balsa block.
spar. The other ribs were fashioned from 1⁄32- inch rectangles that were first cut to length, then notched for the lower spar, and glued in place. After this glue dried, the rectangles were roughly trimmed to an airfoil, then sanded with a bar to match the shape needed for the root and tip. Finally, the top spar notch was marked with a straight edge and cut with a sharp new blade, then the spar was glued in. On most of the ultra micros I would add a 1⁄16 × 1⁄8-inch spar between the main spar and the LE just to help the cover- ing maintain shape. I skipped that this time. The fuselage was built using the same concept. The formers were all installed, the tail pulled in, and the top curve was sanded to match the curve of all the ribs and onto the top of the side pieces. Next, a sheet of soft 1⁄32-inch was wetted and bent over the formers and held in place with rubber bands until dry. (Note: Only put rubber bands right on the formers, otherwise you will get a 3-D bowed curve that looks awful). The ex- cess wood was removed from the sides, then the formed top was glued in place.
The fuselage was trimmed flush with the last former, the bottom was added, and then a tail cone block was built of several sheets of soft balsa, laminated together. The idea was to make it the exhaust for the cooling air while providing a convenient place to locate a hidden elevator control horn. The hatch and nose are compound curves, so these were built up of several laminations of soft balsa that were tack-glued to the fuselage. After sanding to shape, the nose block and hatch were removed and hollowed to reduce weight. My favorite hollowing tool is a sec- tion of 1⁄2-inch diameter brass tube with one end sharpened using a #11 blade on the in- side edge. My second favorite is a Dremel sanding drum. The nose block was reat- tached and then sanded again to fit the fuse sides perfectly.
A canopy was formed by sanding a block of hard balsa to the appropriate shape. Since this would be too heavy on a long nose, I used the block as a mold. The actual trans- parent canopy was made from clear battery heat shrink around the balsa mold, with
The wing center section is light and of simple construction. The small sheet with hole (above left) will allow servo leads to exit easily. A single nylon 4–40 bolt threaded into the fuselage at the TE is sufficient for a small model like this.
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Blocks (above right) have been added for the nose, tail, and wingtips. Light- weight balsa along with a motor tool with a sanding drum will keep weight to a minimum.
JANUARY 2013
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