1/ Make tuned piping out of Ceramic, for light weight and high temperature.

2/ Locate tuned exhaust pipes and muffler inside boom. Exhaust at tail. Have exhaust ceramic and exiting exhaust surrounding by flowing cool air.

 Consider making exhaust out of nextel.

 Consider making tailboom for exhaust out of nextel.

 See hand sketch on drg. page 0262.

 3M COMPANY

•Nextel Alumina-Boria-Silica:

•Cloth •Textiles

•Siconex - Silicon Carbide Impregnated Nextel.

Page on Nextel is in BUY/Composite folder.

If engines are timed to each other at 180 degrees, by cog belt and ratchet over-running clutch then can there be one tuned exhaust for both engines? This could be half-length because each engine will provide the "bounce" for the other. NO BECAUSE EXHAUST PORTS OF 2 ENGINES ARE IN DIFFERENT PLACES. COULD HAVE 1 MUFFLER?

If one tuned exhaust served both engines would the "bounce-back" and its back pressure cause (or be made to cause) the engine to come into synchronization?

Consider making the diffuser with a gradual curve, i.e. spin the shape into the stainless steel tube. A surface such as this has a double curvature and may have less ability to resonate and cause noise. Use a spline on points of abutting sections.

What about fluidic control on a single tuned exhaust for two cylinders?

Have the 2 cylinders located at opposite ends of one long tuned exhaust pipe.

The exhaust removal would exit from around the middle of this pipe.

Both cones will have to have the same taper.

It will make a difference in length if the cylinders fire together or at 180 degrees to each other.

The calculated and a rough string laid out around the F-33 full-size drawing are very close. This means that the RPM is around 6000 and or the duration is around 180 degrees.

 The taper of Hirth's diffuser and baffle is a lot less than the calculated ones. The parallel section of Hirth's pipe seams to be non-existent.

Hirth's shallower diffuser gives an extended wave duration, resulting in a broader powerband.

Hirth's shallower baffle gives a wider powerband.

Idea: - Since the engine will run a one speed only make a straight exhaust pipe; with a variable length device at the end which can be changed for current atmosphere (i.e. Temperature and anticipated flight altitude) before takeoff.

If tuned exhaust pipe is part of tail boom then there will be a need for flexibility (at high temperature) between exhaust pipe and engine.

If the exhaust is in the tail boom, since the tail boom is decreasing in diameter towards the rear the exhaust gasses are not expanding but having to speed up. If the boom, or at least the later portion of it. were to have small holes along its skin these holes would relieve the pressure and probably diffuse the sound into a continuous softer one.

A tuned exhaust will decrease the span of the 'green' RPM range.