Power Pod for my 3-Meter Bird of Time Sailplane

I was gonna copy Travis on the details of the engine pod I made for my 3 Meter Bird of Time Sailplane, but decided to just post it here in case someone else could also make use of it. So far, I've used it equipped with Medallion and Olympic .15's (which pull it to altitude with authority, even when packing cameras), and my trio of Cox RR-1's.

Enlarging the drawing to get the tips of the base 5 1/2 inches apart will get you the size I use on the Big B.O.T.



The skins are 1/16th ply, as are the base plates, and have been plenty strong for their purpose.

The core is 1/2" balsa (a great opportunity to use up stray chunks of balsa that are bouncing around in the bottom of your scrap box). You can use odd-shaped pieces arranged to fit closely together and epoxied to the left skin. Let them extend beyond the ply side and, then trim them back when it's all glued together. The top engine bearer contours to the shape of the top of the pylon.



I moved the pylon back to provide elbow room for all the cameras I'd intended the B.O.T. to carry. It could be redesigned and moved forward, but I often fly it with the cameras replaced by ballast, and have had extended thermaling flights right at the limits of my eyesight. I don't know the angle of the engine verses the wing, but just employed TLAR (That Looks About Right) principles which have mostly served me well over the decades. Besides, I believe that is why God created elevator trim !

The rear of the pylon is secured by the stock wing bolts that come with the kit. The base is cut out to accept the ply plate on the top of the trailing edge, with another piece of ply capping it.



The front is secured by internally epoxying a dowel to the side of the wing's center ribs, with a hole large enough for a wood screw long enough to pass through and catch the pylon base (probably be a good idea to imbed a receiving dowel here, but I haven't done it yet). It's capped on the bottom with a piece of ply, and uses a slightly bent fender washer to match the wing's dihedral. (make sure that this will all fit inside the B.O.T.'s narrow fuse opening.)





Of course, the whole thing can be "prettied up" with some paint and streamlining instead of troweling on epoxy and hanging the tank out in the breeze with rubber bands, but I like seeing the wood, and getting at the tank and other stuff with ease.