Deltamite (oz15603)

About this Plan

Deltamite. Radio control sport modelo. Flying wing layout. Wingspan 41 in, for .10 engine.

Quote: "I have always been fascinated by delta wing and flying wing aircraft. I have also been a modeler for over 40 years and during that time, have casually noted any models of pure flying wing planform. They have been few and far between, and those few that have been published always have the engine hanging out in the breeze, thus spoiling the aesthetic qualities of a pure flying wing.

In 1993, I decided to design a model that would meet my requirements of a pure flying wing with a cowled engine. Since I like small models, I decided to base the design on my trusty OS .10 FSR. I used Chuck Cunningham's design parameters and the RCM Illustrated Plans Guide for a design that would have a similar planform, but came up empty. (I recently saw ads in RCM for this type model, but none were readily available when this design was hatched.)

The designs closest to my idea were those by Laddie Mikulasko and Bill Evans. Having exhausted my reference library. I decided to design the model scientifically. I got out a sheet of drafting paper, drew a fuselage centerline and firewall on it, set the engine on it, and drew the wing leading edge so that it would enclose the engine. The maximum sweep I could get was 25°.

My main concern was the wing airfoil and CG location. I had no idea what would work on a flying wing. Again, I relied on my vast grasp of aeronautical science and made the wing leading edge thick enough to enclose the engine and created the remainder nf the airfoil with my old reliable French curve.

Locating the CG was the next problem. I used Chuck Cunningham's method for locating the CG on a delta wing, which was the closest configuration for my flying wing that I could find. As it turned out, I either miscalculated the CG, or the delta wing configuration does not directly apply to a flying wing because my initial CG. was too far aft. I found this out on my first test flight. I confirmed that the structure was very robust.

After completing the model, I took the mandatory 'before' photos and departed for my pasture airfield. checked everything and launched it with much trepidation. To say it didn't fly off the drawing board is an understatement, It went straight up about 20 feet, did some indescribable maneuvers. and came straight down. I had no control_ Luckily, all it did was tear off a wingtip fin. I shakily gathered up the remains and took them to my workshop for repairs. After mental ly reconstructing the disaster, I concluded I had an aft CG problem. I moved the CG forward by scientific guestimation.

On the second flight I had positive elevator control but the model veered to the right on launch and I didn't have enough lateral control to completely level the wings. Another crash resulted and another fin torn off. My response to this latest tragedy was to enlarge the fin area by adding a third fin to the fuselage centerline.

I was euphoric on the third flight when it took off like a homesick eagle. However, on a low pass I noticed the model 'searching' around the vertical axis and made a mental note to add even more fin area. Then, when I retarded the throttle for landing, all hell broke loose when the nose pitched up. I added power and it flew well again, but every time I reduced power the nose would pitch up. To say I was confused is putting it mildly. While I was trying to get the thing on the ground in one piece, a tree solved the problem for me. More wingtip repairs, but this time I removed the tip fins and made one large fin on the centerline. To correct the pitch-up, I changed the engine thrust line from 0° to +3° (upthrust).

On the next flight, the model climbed gently in a straight line, but 1 was aghast when the model did not respond to control inputs. I had forgotten to turn on the receiver switch! I repaired the torn-out firewall and changed the large centerline (it looked like a shark) to two fins of equal area mounted midspan. It has flown well since these changes were made.

I am only relating these mishaps to assure those who are interested in building this airplane that it is well-tested and, if they encounter any trim problems, my experience may help solve them.

Before you select this model for your, next project, be advised you will need a small receiver and servos and an aileron/elevator mixer on your transmitter. It is also not a beginner's model to fly. It flies with straightforward characteristics, but will swap ends if overcontrolled. If you are hamfisted, you will have your hands full..."

Direct submission to Outerzone.

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