Building a tail boom support and tail clamp for the ECO
The clamp
Let's suppose the tube is 4mm thick. Take a piece of balsa the same thickness as the tube and cut out three squares each 5 by 5cm. Glue these pieces on top of each other, making sure you rotate the middle piece 90 degrees so that you get a piece of balsa plywood of 5 by 5cm. Try to bend it, you'll be amazed on how strong this is. Draw a horizontal and a vertical line halfway so you find the center of the piece. Take out your compass or a piece of tail boom (from a previous crash) and draw a circle of 18mm diameter in the middle. Draw some extra lines 13mm and 17mm each side of the center line that runs parallel to the nerves of the top layer. Cut the excess of the pieces by cutting along the lines 17mm from the center. Turn the piece by 90 degrees and cut 2mm outward of the circle. Cut two pieces of 1mm plywood the size of the top of the clamp pieces. If you use 4mm tubes you will need two pieces of 12mm by 34mm. Glue them on top and on the bottom where the tailfin and the balls links will be. Start up your drill press using a drill the same diameter as your tube (4mm in my example). Position your piece with the plywood pieces at the top and bottom. Drill through the plywood and the middle layer exactly at the position of the extra lines (13mm from center). Use your scroll saw to cut the piece in two in a right angle to the holes you just drilled. Now it is very easy to cut out the two half circles. If the circle is a little rough use a piece of tail boom, wrap it in some thin sandpaper and sand it smooth. Don't take off too much. Glue the brass or plastic tubes in the pieces. Decide what piece is going to be the bottom part and make sure you leave 1mm sticking out at the side of the plywood. If you don't do this, the ball links will be too close to the plywood. Fit the pieces and sand them so that you have a gap between them. If you don't have a gap, you won't be able to tighten them sufficiently. Cut two 2mm threaded rods to length (approx. 35 mm). Glue or solder a nut at one end thus creating a pretty long screw. Drill the horizontal fin at the appropriate places and put everything together according to the pictures. Use a black felt pen to paint them.
You can download a PDF docment with a drawing of the tailfin here. Just print it with scaling or resizing OFF |
The supports
Take two pieces of 5mm carbon tube, each 39cm long. Use a 3mm drill to ream out the last 10mm of each end. Glue threaded push rod end pieces into these holes. Make sure they don't go deeper than 10mm. Put plastic ball links on each end. |
Mounting the supports
Drill a 2mm hole through the after landing gear at about 10mm out of the frame. Put a ball from a ball link through a 20mm M2 screw and stick it through the hole. Fasten it using a nut. Click one end of the supports on the balls on the landing gear and the other end on the balls on the clamp. Don't forget to use threadlock on every screw! |
The first thing you need to do is measure the outer diameter of the brass or plastic tubes you want to use. A piece of snake tube from the tail servo lead is perfect.
