Hot Pants (oz15030)

About this Plan

Hot Pants. Radio control sport pattern model. Wingspan 60-7/8 in.

Quote: "Realistic RC pattern design has large shapely fuselage, all-flying stab, built-in ailerons, retracts and all-balsa construction. Hot Pants, by Gerald Nelson.

The total design concept of the Hot Pants includes two major considerations: performance and realism. Almost all of today's successful competition stunt models are designed entirely for all-out competition with no thought given to realism. Sure, many ships have a canopy placed somewhere, maybe even a pilot and instrument panel. However, if a full-size aircraft were to be built with the same proportions as these models, we would normally expect to find a 100-ft span acrobatic aircraft. Today's full-size acrobatic aircraft are, of course, much smaller.

Taking a 25-ft span of a full-size aircraft, typical of current full-scale acrobatic aircraft, and scaling it down to a 5-ft span, we would come up with a fuselage shape and cockpit size as presented here with the Hot Pants design. The additional width and height cause such minor extra drag that it becomes negligible. The by-product of the wider fuselage is that of Dutch roll elimination, the so-called Kwik-Fli wiggle. An obvious advantage of the larger fuselage is easy placement of the RC equipment - the four-abreast servo placement is quite functional.

Perhaps the most interesting design feature of this model is the flying stabilizer or stabilator. The entire horizontal stabilizer moves as one unit. The major reason for choosing this system of pitch control is that there is less aerodynamic drag. Deflecting the entire surface produces much less drag than the conventional deflected elevator/stabilizer combin-ation. This type of stabilizer also produces a very positive control feel about the pitch axis at all airspeeds, so necessary for today's competition flying.

A practical advantage is the ease of transporting the aircraft, since both stabilizer sections are easily removable. Yet another plus is one which I have not fully explored: because the stabilizer sections are removable, it would be simple to fabricate different types of stabilizers to test for the optimum design. Perhaps the unit should be smaller, thicker, highly tapered, semisymmetrical, and so on. As there would be no other variable other than the stabilizer, one could easily evaluate the test results.

There is no reason to be concerned over the servo power required to move the full pivoting stabilizer. As only a small amount of throw is required, an excellent mechanical advantage is obtained. The mechanics of the system shown are quite simple. During tests, more than twice the amount of elevator travel was tried; the pitch control was of course very sensitive. This did provide proof of servo power required. Ample power was available to drive the stabilizer. Reducing the travel to half the amount (now normal travel) increased the mechanical advantage of the system by a factor of two. In other words, we have more than twice the power needed to drive the stabilizer.

Perhaps another unusual design feature is the use of the regular type of ailerons. Certainly full-span ailerons would be quite satisfactory with this design, but the regular ailerons do offer some outstanding features: they have a more positive feel, especially with 1972 Kraft servos and their improved resolution; one is easily able to check the neutral setting of the ailerons prior to flight; and they look like ailerons should (certainly a minor design point, but a valid one if realism is to be considered).

Construction: The construction of Hot Pants is straightforward. Start with the wing first, as the fuselage cannot be finished unless the wing is completed.

The wing can be built on two 3/16 dia steel wire rods. The rod locations are shown on the ribs. The two rods are supported at each end by metal or wood brackets firmly attached to a rigid surface - a workbench top, for example. A precision level is used (placing it across the rods at each end, observing the reading) to line up the rods. By shimming one of the brackets before firmly securing it to the rigid surface, the need for an accurate building board is eliminated. The wing sheeting used on the original model was 3/32 thick (1/16 thick balsa can also be used).

Assuming the wire rod jig system is employed, proceed with the wing as follows: Glue plywood landing gear doublers to ribs 4 and 5. Locate the retractable landing gear unit mounting bearers before attaching to rib. Drawing shows proper location for Rom-Air landing gear system. Place ribs in approximate position on rods and mark rib locations on spars. Glue top and bottom spruce spars in place, as well as the two-in wide trailing edge sheeting on bottom of rib. Glue leading edge in place and four- or six-in wide trailing edge sheeting on top of ribs. (Note that the entire wing will eventually be sheeted, so keep the trailing edge joint straight by placing two pieces of 1/4 sq on each side of the trailing edge, clamping them in place with clothespins.)

Shape upper leading edge flush with rib contour. Glue four-in wide leading edge sheeting with rear edge of sheeting over the center of the main spar. (Leaving a portion of the spar exposed allows for easier attachment of the remaining sheeting.) Glue the remainder of the sheeting in place..."

Direct submission to Outerzone.

Supplementary file notes

Article, incomplete - missing p25.

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