I am building a model from a very old set of plans. The engine called out is difficult to find, and so am planning on installing a common K&B .40 glow engine.

Now, the plans are not that good, but it called out for the nose cone to be carved from a solid chunk of balsa, and gave the diameter for air cooling around the cylinder. It was about 1/4" but have spots of 1/8" clearance and some larger.

The question is just how much should I hog out for air cooling the cylinder and crankcase? Instead of using one big block of wood, am doing this with laminated 1/4" balsa now. Would an overall clearance of 1/4" be acceptable to pass and circulate air? Thing is if I get too much clearance, the shell gets too thin, and then subject to damage.



Wm.