In our particular region, the Santa Cruz mountains above Palo Alto, we can find flying sites with fantastic lift as Pacific winds blow over the San Francisco peninsula mountains on their way inland. We found that the basic 2-meter balsa airplanes were not sufficiently tough to survive the repeated rough landings typical of these rugged flying sites.

I then met a flier who had a "Geek", an innovative slope soarer made by Steve Hinderks' Birdworks in Oregon and now, unfortunately, no longer in production. This had to be the answer! I bought a kit, then built and flew it. The use of plastic composites and durable foam in the Geek was well before its time. This was our first experience with an "indestructible" airplane. The could survive the most violent crashes due to its construction.

We had lots of fun flying in driving rain, darting about with our Geeks, loving every minute of it. We even had some "combat" collisions, and enjoyed the excitement of watching our Geeks tumble out of the sky. But there was a problem. While the Geek was superb in very high winds, it just didn't fly very well in lighter lift. With its small wing span it had a fairly heavy wing loading, and needed lots of lift to fly. We found it flew best in near storm conditions.

We then discovered Dave's Aircraft Works foamie fighters. Dave Sanders is the respected leader in PSS slope gliders, and we built and flew kits of his P-51 Mustang. The foamie fighters are a great series, and they fly well. We learned how to line-up an attack, and how to fly out of a collision (the two basic combat skills), and had tons of fun.

During this time, I had the good fortune to pick up a used SR-7, a great design made by Bob Martin. It has a duralene fuselage and a 1/64" ply-skinned white foam wing. The SR-7 is a screamer on the slopes! With this airplane I was able to do more consecutive rolls and to achieve higher speeds than I had ever before in my life. The SR-7 was a great design, but unfortunately it was heavy and did not survive rough landings or crashes very well.

So you can guess the next step. Why not learn from the advances made in the SR-7, and make them available for the sport flyer in EPP? What we liked about the SR-7 was its highly tapered wing planform, a design that allows the airplane to generate fast roll rates. We knew that the SR-7 was fast, highly maneuverable, but it was heavy and therefore needed strong winds to keep it aloft. Besides, despite the duralene fuselage, it still suffered damage during rough landings or crashes.

We went to the drawing board, and using some of the basic parameters of the SR-7 adapted a somewhat similar planform to an EPP design. One of the technical challenges was how to cut EPP foam with a high degree of taper. If one looks closely at the currently available EPP designs, one will notice that most of the wing planforms are made with minimal taper. This is due to the fact that it is difficult to cut a wing core from EPP with significant taper, more difficult than from blue or white foam. What generally happens is that the cutting wire is too cold at the root and too hot at the tip of the wing core.

We have found a proprietary method for making a highly tapered cut with EPP wing cores. It involves fine tuning the cutting wire in terms of diameter, current, temperature, and cutting speed so that we obtain a good cut all along the wing. This takes a considerable amount of skill, much more so than for the average mildly tapered wing. Our wing cutting expert has mastered this, and is turning out excellent quality wings with a high degree of taper. Measured without the ailerons, our cores have a 12" root chord and 3" tip chord, for a taper ratio of 0.25. Full span ailerons (2" chord) are used, and they give our EPP design its tremendous roll rate (note that the ailerons area full 40% of chord at the tip!) The large (% of chord) ailerons coupled with the highly tapered wind results in high rotational forces (from the ailerons) and a low damping in roll (due to the distribution of the wing area). For a wing spar we have chosen wound-glass-fiber/black epoxy tubes, which are light and strong. This spar combined with EPP cores make for a wing that is quite nearly indestructible. I have yet to see one fail!

We also spoke to our EPP manufacturer, and were able to obtain a higher density EPP for the fuselage of our new design. Most EPP is 1.3 lb/ft3 density, and but decided to use 1.9 lb/ft3 EPP for our fuselage (the wing uses 1.3 lb/ft3 density EPP). This gives us a fuselage that is quite nearly indestructible. It efficiently and safely houses the radio gear. Tail surfaces are coroplast. We chose the RG-15 airfoil for its proven performance (good lift with good speed penetration). This airplane is able to achieve greater top speeds because of its special low-drag fuselage coupled with the modestly cambered airfoil. There is a significant reduction in drag with a highly tapered wing. When pulling Gs (i.e., at high lift coefficients) the induced drag of an untapered wing results in a significant increase in total drag. The differences in actual flight are noticeable and are truly amazing!

Put it all together and you have one great looking airplane that has outstanding flight performance. It will soar well in light air; it will do high rate axial rolls; it will fly inverted with ease, and will do inside and outside loops. It will thrill both the pilot as well as onlookers. In a combat zone, it can hover above the pack, then quickly dive and swoop on an opponent. This airplane can score kills like no other. And all this while looking great!