QBIT
Method of gluing carbon strips to fuselage longerons. Pin 1⁄8 × 1⁄4-inch longerons (above left) against a straight edge and clear backing of Ultracote covering and apply CA. Carbon fiber is being attached to two longerons in this
right if enough is added to keep the right wing up.
Every successful pylon model has washin on the right wing panel. The true flight path of a pylon model is right hand climb with a small amount of left roll to keep the right wing from dipping. A strip of 1⁄2-inch trailing edge stock may be added to the underside at the dihedral break in lieu of the washin, added in 1-inch increments so as not to over- do it.
Too much washin or trailing edge stock will cause excessive left roll, a catastrophic power pattern for a pylon model. You want just enough left roll to keep the right wing up preventing the plane from rolling right and crashing under power.
Glide testing
The wing should be positioned so the plane’s c.g. is at 75–78% back from the lead- ing edge. This is a good starting point for the glide tests. Test glide on a calm day over a
view. The side facing viewer is already attached. Right center of main wing panel. Note optional 3 mm × 0.5 mm carbon strip (above right) on top of main spar.
grassy surface if possible. If the plane ex- hibits a stall, move the wing back on the wing platform until the stall is gone. If the plane dives, slide the wing forward until it’s gliding properly. I usually make the wing platforms slightly longer to accommodate this. Once determined, the extra length is trimmed off. If the wing movement is insuf- ficient, some trim weight will have to be added.
Glide direction is achieved by tilting the stab or shimming the wing accordingly, the plane gliding to the high side when viewed from the rear. QBIT climbs right and glides left. Many fliers prefer a right climb and right glide as they feel the model transitions better from power pattern to glide pattern. Your choice.
Power flight testing
A timer with a quick DT is the most im- portant factor in trimming as this will re- lease the stab in time to prevent a power
crash. (Texas Timer Max III A is used, and has announced a new lighter weight fuel cut-off/DT timer called Micro Max www.
Texastimers.com). The desired power pat- tern is a climbing slow right turn simultane- ous with a slow left roll, which will be con- trolled by stab incidence, washin on right wing and rudder tab.
For the first flight set the engine run timer for three seconds and the DT for five seconds. With the engine running slightly rich of peak rpm, launch at a 70-degree an- gle and 30 degrees to the right of the wind, with about a 10-degree right bank. (Never launch straight into or to the left of the on- coming wind).
The model should climb at a steep angle to the right with no tendency to dip the right wing. If it dips too much add some left roll by increasing the washin on the right wing or adding trailing edge stock to the underside of the right wing main panel. If the model experiences a tight sideways loop, decrease
The stabilizer is built directly on the building board. It is important to use the lightest wood possible. Note (above left) that the main spar tapers. The fuselage front end (above right) showing the firewall, radial mount, Cox TD
44
.051, Texas Timer III, a fuel cutoff/DT and the plywood mount for the timer. Carbon fiber strip located on the lower portion of the fuselage longerons can be seen.
MARCH 2014
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