KAM AERO DESIGN RATIONALE
Some history about Cam McCausey & Kurt Koelling as told by Kurt –
Cam has built all of my competition IMAC and Freestyle airplanes for the past 12 years. Cam and I have had a great working relationship during this time and have both constantly been trying to tweak other manufacturer’s airplane designs to fly better and be more durable. After many years of working together, we decided to make our own kits the way we think they should be designed for optimal performance.
KAM Aero Design Rationale – In 2015 I started designing a new Extra 300 (Prototype #1) that could be flown more gracefully through slow rolls, would snap cleaner, show clearer stall break in spins, and fly at a more consistent pace than previous planes I have flown. We also wanted to design a plane that was durable and easy to maintain. All dimensions of this plane needed to meet scale aerobatic 10% design rules (following scale rules originally setup at the Tournament of Champions in Las Vegas). Below is a description of how we met these goals:
- The design incorporated a fuselage with significantly more side area than previous designs I had flown. This allows point rolls and slow rolls to be flown at a slower pace without using significant amounts of rudder. The rolls look clean and axial with less yaw through the roll. As the fuselage becomes larger, the drag also increases. This fuselage design is taller (creating more side area), but not significantly wider which keeps drag from becoming too significant (a problem with some of the airplanes with really large fuselages).
- To improve stall into autorotation for snaps and spins, a new wing was designed with a different airfoil type at the root and tip (including lower percentage airfoil at the tip) as well as sweep angle. This allows the tip to stall sooner. The result being cleaner breaks in snaps and more defined stall breaks in spins. This could not be accomplished easily (or at all) without the use of the 4-axis hotwire CNC machine. Many designs have identical airfoil type and percent chord at both the root and tip because it is easier to manufacture and does not require an expensive 4-axis hotwire CNC machine to perform.
- We wanted a plane that had minimal mixing in knife edge, rolling circles, uplines, downlines, etc. Unfortunately, this is rarely accomplished immediately with any new airplane design since there are a variety of different factors that can influence mixing. Thus, Prototype #1 was designed to allow for testing different design adjustments on a single platform. This included a wing that had four (4) different mounting locations through the fuselage (high/forward, high/rear, low/forward, low/rear), different angle of attack, thrust angle, CG, stab location, etc. Prototype #1 was tested during the 2016 season to determine optimum wing location, CG, wing incidence, thrust angle, cg, etc.
- After all of this testing phase was completed, I designed Prototype #2 (taking into account everything learned from Prototype #1). Prototype #2 has been flown throughout the 2017 season. I love flying Prototype #2 – it tracks beautifully, can be flown slowly and gracefully through rolls/point rolls, snaps cleanly, and presents well with a steady flying pace.
- We also wanted a plane that would be durable, easy to build, and easy to install components. The CNC router cut motor box is tab-lock plywood construction and builds straight and true. The pipe tunnel is large enough to incorporate any exhaust system size. The main fuselage has a removable ply top plate (8 machine screws hold it on) which allows components to be installed without worry of breaking any cross-braces. With the top plate removed it is possible to reach your arm and hand over 3 feet back under the turtle deck to mount extensions for rudder and elevator servos.
Overall this kit has been a very rewarding design/build process. We are now excited to offer this premium kit to the aerobatic world – Kurt Koelling