Model Airplane News

LET’S TALK GIANT SCALE ment bolt locations and install the engine using ¹⁄ 4-20 bolts, blind nuts, etc. Now attach the exhaust headers to the engine so you can work on the pipe tunnel.

glue the firewall in place. For additional support, I also glued spruce triangular stock behind the firewall. When it comes time to bolt the engine in place, remember, always measure twice and take your time!

This airplane has a two-piece engine cowl that’s split into an upper and lower half. The halves are joined together using 4-40 bolts, lite-ply blocks and 4-40 T-nuts, and the rear portion of the cowl has a ring that is factory-installed and drilled to bolt onto the fuselage. To properly install the engine, bolt the bottom half of the cowling in place and then use it as a reference. Then, when the engine is in the correct position (with the spinner back-plate on the engine shaft for guidance), secure it using wood screws. Once you’re satisfied everything is in proper alignment, mark the engine attach-

THE TUNNEL

While this may appear to be a rather tedious step, the hard work has been done for you as the main tunnel has already been installed. All you need to do is extend it, make an access hatch, make attachment points to secure the pipes and angle the rear portion of the tunnel so cooling air flow can exit smoothly out of the model.

Using caution, remove the angled back portion of the tunnel without damaging the tunnel sides. Measure the lengths of the tuned pipes and determine how long the tunnel extension needs to be. Use cardstock

paper and/or graph paper to make a template of the new tunnel sides. Now cut out the two tunnel sides from ¹⁄8-inch lite-ply and glue them to the existing tunnel with CA glue. Be sure to reinforce the joints with more lite-ply to add strength. For the Extra 260, I glued a piece of ¹⁄4-inch square spruce stock on the bottom of the model and made the pipe mount out of ¹⁄8-inch lite-ply with two half-moon cutouts to support the pipes. I then bolted large pieces of fuel tubing on the mount to isolate the tuned pipes from the supports. I attached plastic clevises on the ends of the half-moon cutouts so I could attach mounting springs to secure the tuned pipes in place. Only one support point is needed for each tuned pipe. This allows the tuned pipes some movement and also helped to relieve stress on the headers,

The pipe mount has been secured in place. Take notice of the shape. The half-moon shapes are so that each pipe can rest on the mount and be spaced from the mount using fuel tubing. Also, the top of the pipe will be secured in place using a heavy-duty spring.

A close-up of the pipe mount and specifically, the method I used to secure the fuel tubing in place. I simply drilled it out and secured it using 4-40 bolts, washers and lock-nuts.