Kestrel (oz16059)

About this Plan

Kestrel. Radio control indoor aerobatic model, for electric power. Wingspan 32 in. Uses foam construction.

Quote: "Kestrel, by Jeremy Chinn.

During the winter of 2005, several members of my flying club and I began to do some indoor flying to escape the harsh weather. At the same time, I started working on a 3D-capable foamie-type airplane that would be suitable for flying in the smaller indoor flying sites we were using. I wanted the design to have a very light wing loading for slow flying speeds, and good stiffness to allow for more precise flight than the other indoor models I had flown. The Kestrel is the result of my efforts.

The Kestrel is easy to build and fun to fly. It uses some commonly used building techniques and a few that are not the norm. The Kestrel excels at 3D flight, and its size makes it perfect for flying in one-court basketball gymnasiums or outside on calm evenings.

Specifics: Much of the success of the design relies on keeping the wing loading low. For best performance, you should work toward a ready-to-fly weight of 5 3/4 to 7 oz. I would add that you should not be tempted to put a higher power motor on the airplane, or beef up certain areas such as the wing by doubling the thickness of the materials. Doing so will result in a heavy airframe that will perform poorly at best.

This means that equipment choice is extremely important. In an effort to find a suitable low-hassle and lightweight motor for my Kestrel, I contacted Jim T. Graham (a.k.a. Billy Hell) of Hobby Lobby International. He and his co-worker, Jason Cole, recommended the AXi 2204-54 to power the Kestrel. The little AXi is a jewel of a motor with excellent power and efficiency. When used with the Jeti Advance 04 Plus electronic speed controller (ESC) and an APC 8x3.8-in. Slow Flyer propeller, it is a perfect match for this airplane's airframe.

Construction: The other important factor in building a lightweight Kestrel is getting the correct building materials. The list includes enough material to build one Kestrel, but I normally buy enough materials to build several at once to save on shipping costs. Construction is relatively simple, but following the assembly instructions will make it go much faster.

Start by cutting all of the Depron and plywood pieces per the plans. An easy way to cut these pieces is to have a full-size copy of the plans made at a copy shop. Then, cut the patterns from the paper with a 1/4- to 1/2-in border around them. Rub a removable 3M Gluestick on the pattern. Place the pattern on the material to be cut, and cut through the paper and the material. Use a new #11 X-Acto blade to make the Use a fresh X-acto blade to cut out the Depron and plywood pieces to shape. cuts, and a steel straight edge Note that the lines are from the plan, which is attached to the foam. to keep them straight where appropriate.

When you have your Depron and plywood pieces cut, pull out some of the flat carbon fiber from your parts stack, as well as the wing and elevator. Cut a piece of flat carbon fiber just long enough to fit in the indicated locations in the wing and on the elevator. There is one piece of carbon fiber on the wing leading edge that goes from one curve to the other curve at the wingtip, another piece approximately 1 in from the trailing edge of the wing, and a similar piece in the elevator.

Cover your workbench with waxed paper. Place the elevator on the waxed paper and test-fit the carbon in the slot. When you are satisfied with the fit, remove the carbon and run a bead of thick foam-safe cyanoacrylate (CA) glue down the groove. Push the carbon fiber into the slot carefully and then let the glue cure. Make sure the carbon fiber is flush with the surface of the foam. Put a drop of CA on each end of the carbon fiber. This will strengthen the joint and ensure that nothing catches on the sharp ends of the carbon.

Install the rear carbon fiber reinforcement in the wing just like you did the carbon fiber in the elevator. For the wing leading edge reinforcement, place the wing on your waxed paper and cut four 4- by 2-in. pieces of 3M packing tape. Place half of the packing tape on the leading edge of the wing and press it firmly in place..."

Kestrel from Quiet Flight, June 2005.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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