Utility Special (oz1819)
About this Plan
Utility Special. Free flight rubber model. From Popular Science, May 1937.
Quote: "This new flying model won't crack up. Utility Special, by Frank Zaic.
SPEEDY and extraordinarily stable, this new streamline model air-plane, known as the 'Utility Special', is a fine design to open the season's flying. On normal power it will average flights from half a minute upward, and by the addition of a few extra strands of rubber it can be made to buck stiff winds or fly at racing speed. The materials cost about 50 or 60 cents.
Fuselage: Laminate 1/64-in balsa sheets for the entire set of bulkheads. When the cement has set, tack each bulkhead to a drawing board and mark the outline, longeron slots. and stringer marks. Trim and cut the slots with a razor.
Select four matched longerons. Mark the bulkhead spacings while all are held together. Cement longerons to bulkheads 4 and 5. Let the cement set well. Then cement the rest of the bulkheads, work-ing from center towards ends. Keep the fuselage lined up. The 1 , 16-in. square stringers arc next cemented so that they are superimposed above the marked points on the bulkheads. Trim longerons flush with front bulkhead, and cement an extra sheet without slots in front of them. In rear, trim longerons and stringer to a point. cement them together, and cut on slightly to accommodate trailing edge of stabilizer. The 1/64-in sheet covering is applied after stabilizer and front plug made.
Landing Gear: Make the laminated platform and cement to bulkheads and stringers. Cut and bend the wire struts. Cement them to the platform and reenforce with wire staples. After the cement has set, the lower wire extremities are bound to-gether very tightly with rubber bands. The streamline 'pants' are made by cutting the sides and center to shape and cementing them together. Standard hard-wood wheels are used. Set the pants parallel to the fuselage and fasten them to the wire with a generous amount of cement. To line up landing gear, cement a long strip of balsa on top of the center longerons just in front of the bulkhead and measure up from table to each end. Keep the strip in place to check the wing and stabilizer during the later assembly.
Wing: This is built in one piece, but the center or flat portion is made rather loosely as it has to be taken apart and reassembled on the fuselage. Draw a full-size plan. Cut all ribs to same size, and shape the leading and trailing edges. Now superimpose the spars over the full-size drawing and hold them with pins while the ribs are tapered and cemented. Note that the spars are cut in three sections. Use cement generously while placing ribs. Be sure to shape tips well to reduce drag.
The dihedral angle is made by raising the wing tips 2-1/8 in and beveling the center and the outer-panel spars at their junction to the correct angle for a butt joint.
Separate center section of wing from the assembly and let one rib hold the spars to correct spacing. Pass the spars through the fuselage stringers and cement the front spar to bulkhead 4. Make certain the spars are parallel to the line-up strip. Replace the rib, and also cement the ribs which nestle against the fuselage. The outer two panels are joined to the center section. Check the dihedral by noting the distance from tips to table; also correct any difference in incidence. If you are doubtful of the cement, strengthen the joint with a bamboo sliver..."
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User commentsHere's a few pictures of the 'Utility Special' I recently built from plan oz1819 [main pic, 005-009]. Build was straightforward, finish is all tissue and was inspired by the TWA Constellations flown in the 1950s. Models weighs ~34g without rubber, and flew well in its first outing on 2x18" loops of 1/8" rubber (~6g motor weight).
Flight video at: https://www.youtube.com/watch?v=C4lvZmXgbho, build thread on RCGroups at: https://www.rcgroups.com/forums/showthread....
Thanks for all you folks do to keep these plans available!
Mike Kelly - 06/10/2020
pit - 06/10/2020
Roberto Grassi - 06/10/2020
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