Hummer (oz10235)

About this Plan

RCM Hummer. Radio control sport model. Forward swept wing canard, for electric power.

Quote: "Hummer. Sport Canard For Geared Speed 600 Electric Motor. Design by Bill Winter with John Hunton. Photography By Bernie Stuecker and Tom Schmitt (Construction Photos By Authors)

The Hummer is an idealized, contemporary design for optimum enjoyment of wide-open spaces and infinite skies. It is not a wee-hours doodle. Let's cut to the chase.

To the designer of both wet and dry models, the former has one correct engine, tank, and prop, and that's that. Electric has a multiple split personality in that there can be many correct motors, combinations of batteries, and a wide variety of correct props, both tiny and huge. All are justified by various combinations of drives with gear ratios, volts, amperes, watts, smoke, and mirrors!

Nikola Tesla (alternating current mastermind) demonstrated an R/C model submarine in Grand Central Palace (NY) at the turn of the century; he'd love this wild stuff!

The facts: Speed 600 motor, seven 1400 mAh cells, 2:1 gearing (ours is a Hobby Lobby 1.8 Titanium bolt-on gearbox), Graupner 11 x 7-1/2 folder, an Airtronics MA-6 controller (BEC type), and the current draw is 10-12 amps. Airframe: 62 in span, 558 sq in wing area, 138 sq in canard area, total lifting area is 696 sq in, gross weight is 53 ounces, wing loading 13.677 oz per sq ft, total lift area loading 10.97 oz psf.

Since the motor run is 7 min at 12 amps, 8 cells would boost power without a short-run penalty. 800 mAh cells at 12 amp yield 4 min, 1700 mAh cells 8.5 min. Ratios of 2-1/2:1 and 3:1 on eight sub-C's will go well.

The Hummer's configuration combines features of previously published 'X' ships, notably the QED canard (March 1996 ModelAviation), Javelin delta-canard (oz6067), and Goblin (July 1997 Model Aviation) with its forward sweep and V-tail. Hummer is a forward-swept, short-coupled canard. Forward sweep, in this configuration, requires wingtip wash-in, not the familiar wash-out.

If you must know more, a detailed explanation of canard layouts appealed on page 11 in the March 1996 Model Aviation. That reference shows how to find the MAC (mean aerodynamic center) of the whole airplane, not just the wing, a calculation necessary for any model with a lifting tail wherein both surfaces lift and share the weight load. On the Hummer, we found that locating the CG on the MAC resulted in an 'iffy' rearmost CG location. The final CG location is 1/2 in forward of the MAC to provide an adequate margin of stability with the amount of lift generated by the large canard which is set at a necessarily high angle of incidence.

A few cautions are warranted for this advanced design. While the model is exceptionally simple to build and fly, you should be aware of the following differences: The Hummer has a high lift to drag (L/D) ratio with a very shallow glide angle. You will usually have to 'fly' the model onto the ground to land it, not just let it float across the field, for it will not stall. Also, with the super-stall stable characteristics inherent in the canard, it is easily possible, on the other hand, to get 'behind the curve' in landing and not have enough velocity to flare. So, when landing, keep your speed up and fly the Hummer onto the ground.

In the air, the Hummer presents a completely different aspect, being a 'tail first' model. Just keep it high and close-in until you get accustomed to its visual feedback. It has a very low frontal area and it is easy to lose sight of it during a high climb-out; you just see the 'razors edge.' Keep your colors bright and always climb into the wind so it will tend to drift toward you if you lose it momentarily.

The Hummer is a very stable soaring platform and frequently reaches the clouds. Often, you can set up neutral trim (by adjusting one or two clicks of trim at a time) and it will turn by itselfeither way into lift. After you have climbed to a comfortable altitude and have powered down, establish a neutral trim and the model will start turning on its own; don't over-react and change anything, it is trying to tell you something. Just let it be and it will climb if there is lift.

Construction. Keep your wood light. This model is not designed for aerobatics (although it will loop nicely) or to be subject to high stresses. When buying wood, get plenty so you will have a stock to make specific selections from. Use medium/light wood (but not mushy) throughout except for the wing spars and any other areas called out on the plan. Use film covering because it has a good strength-to-weight ratio..."

Supplementary file notes

Article, thanks to hlsat, JHatton.

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