PlaneKrazee

My Feedback: (14)

What is the recommended clearance between a canister or tuned pipe and tunnel for proper cooling? 1/16", 1/8", 3/16"? I plan on making the tunnel out of manila folder stock and glueing balsa longerons inside (in a rifling pattern) as spacers. I would like the air flowing thru the tunnel to do the most work minimizing inlet and outlet area. I think setting up a spiral airflow should give a good scrubbing of parasitic boundry layer flow.

At this time I have a rectangular hole in the firewall with 1/32" balsa making a box around the can and removed the covering over lightening holes under the stab for exhaust air. I glued the aft end of a couple Kaos canopies over the holes as air extractors. They work very well to keep the fuse cool and are unnoticeable. The engine is fully baffled, air must pass thru the fins into the cowl and again down the back of the cylinders before exiting out the bottom of the cowl. The cowl has a lithoplate airdam added to create low pressure in the cowl bottom and the scale carb intake has a clear plastic sliding door to seal it off after the manual choke is opened. This entire setup seems to work well but if I can improve it all the better.

The plane is a AW 50cc Extra 300 with a MT70s, y header, KS 86s can, Mejzlik 22X8. Very quiet and 7400 rpm today.

PlaneKrazee

My Feedback: (14)

Photos.

When the plane is on the ground or in the air the air extractors can't be seen. I need to paint the deflector white. Could have made it from clear also.

I'll be adding smoke and didn't want any slime entering the fuse thru cooling holes in the bottom.

pe reivers

Clearance should be enough to allow heat expansion of the muffler system, and prevent heat transfer to the fuselage parts.
in most cases, 6mm ( 1/4" ) will do.

TheRickster

My Feedback: (12)

I rolled mine out of 1/64th ply and put some collers on it to keep it round..

pe reivers

Looks good.
you can use silicone fuel tubing pieces, lengthwise tied to the canister, as spaceholders.

PlaneKrazee

My Feedback: (14)

Very good Rickster. I was going to use 1/64 ply but figured the manila stock was good enough.

Pe, The lengthwise fuel tubing is a good idea.

PlaneKrazee

My Feedback: (14)

Rickster,

You might want to remove the brazing flux from the tubing. It can cause stress cracks in the stainless over time.

Kimhoff

My Feedback: (22)

Rickster,

What did you use to cut the nice looking holes in the cover over your canister?

TheRickster

My Feedback: (12)

I made the covers out of 1/64th ply.. I coated them with CA to stiffen them and then drew out the pattern of the "gills".. I drilled the holes at each end of the slot with a 3/8ths drill bit then just connected the holes using a dremel and cut off wheel..

Rick