The cowling of an experimental aircraft has two primary jobs. Fair the engine into the fuselage and provide a cooling opening that cools the engine. In the case of the carbon fiber cowling I built for my formula racer Wasabi for the 2009 air races I hoped to make the cowling better at both of these jobs.
Fair the engine into the fuselage. fundamentally the cowling takes the conical shape of the spinner and continues it around the engine and back to the shape of the fuselage at the firewall. The cowling that I had run in 2008 was all aluminum and was therefore pretty boxy. By using composites I planned to be able to incorporate more curvy shapes that would result in less drag.
Provide cooling air to the engine. The aluminum cowling that I ran in 2008 provided too much cooling air, over cooling my cylinders to the low 200sF. By closing the inlets on this new cowling I hoped to limit the cooling air and by doing so reduce the overall drag of the installation.
I am going to mostly focus on the handforming of shapes for making composite parts rather than the technical aspects of particular design choices (it is for racing afterall). The act of handforming composite plugs is quickly becoming old world as a sanding block is replaced with a CNC mill. In the case of this particular project in order to CAD model the cowl I would have neeed a model of the engine which I don't have. So I took advantage of the opportunity as a chance to learn a bit more of the art of hand forming.
Attached below is an air to air picture of the original cowling that we were hoping to improve upon.
Step 1: Protect the engine
Step 2: Get Messy
Step 3: Moving to the hard stuff
Step 4: Inlets
Step 5: Final contouring
Step 6: Parting Planes
Step 7: Layup tools
Step 8: Check on your engine!
Step 9: PARTS!
Step 10: Taping and everything else
Step 11: Primer
Step 12: Flight test
Flight test of big changes to an airplane is serious business. In the case of this particular flight test the card was pretty simple. After breaking ground i would go to climb speed until I reached a safe bailout altitude. At safe altitude I open the speed envelope using stick raps to check for flutter in 5 knot increments out to a speed 10% over any speed I will see in a race.
Step 14: More Flight Test
Step 15: Racing
I would like to thank the Sharps and team Nemesis, Ralph Wise, Curt Carter, Andy Chiavetta, Robby Grove, Roger Hayes and last but certainly not least my Crew Chief, Composite Fabricator and Backup/Chase Pilot Jennifer Whaley. Experimental aircraft are more accessible than you think. Check out your local EAA chapter to get involved. If you are an active homebuilder but want more consider Mojave; the Mecca for homebilding we have everything from ultralights to spaceships. If you are interested in Air Racing come out to Reno this September and see it first hand. The Formula class is a great place to start if you are looking to get involved in air racing. Wasabi Air Racing is always looking for help, be it hardware, cash, labor or all of the above, please feel free to contact us.