As many on the list are aware, we who have turbo rotary housings (without an
attached turbocharger) have created a noise monster with our 13Bs.  Tracy
has a reactive muffler produced by Spin Tech which appears to have provided
a better a match to the noise challenge than any other muffler tried thus
far.

I have been trying to see if I could get two pipes to quieten the exhaust
note, but not as successfully.  One of the main problems is that he shock
wave and heat quickly destroys any muffler packing material I have tried.
The traditional fiberglass simple transforms into dust in short order.

Well, today I received a sample of a new material.  It is a silica product
also, but rated at 2000F and apparently has more substantial structural
integrity than traditional fiberglass.   Its trade name is SilcoSoft and is
produced by BGF Industries.  This sample is in form of a 3/4" thick blanket
about 36" wide and they shipped me several feet of it.

I thought to  get it installed in my two exhaust pipes in time for the
trip to Sun & Fun and that should give it a fair inital try out.


Well, after wraping the stuff around a stainless steel mesh rolled into a
3/4" dia tube then placing aluminum screen on the outside (next to the walls
of the two exhaust tubes I use as mufflers) I proceed to stuff approx 36" of
the Silcosoft materail into the exhaust tubes. The tubes have approx 260 1/8
dia holes drilled up and down their length (on the side away from the
fuselage).   I fired up the engine and could tell of no perfromance loss.
Let it run at WOT for a minute and it did deaden the sound quite a bit.
Small bits of tuff were sticking out the holes drilled in the exhaust tubes,
but the material did not char or melt, Soooo, decided to go flying with it.

Flew for two hours and landed, hurried to the hangar and hopped down to see
what the material looked like.  It was GONE!.  While it apparently could
withstand the heat of the exhaust, the pressure pulse appeared pulverized
it. I guess its not surprising as the exhaust pulse had completely
disintegrated some mild steel inserts after a month or so.  So another idea
down the drain.  So, I'll arrive at Sun & Fun with the Master Noise Monster.

It is looking like the reactive type muffler such as TRacy is flying with
may be the only feasible answer for the turbo blocks (without turbocharger).
Guess, I'll just have to stick on a turboharger - just for noise abatement
of course (:>).


Ed Anderson
Matthews, NC
RV-6A N494BW
eanderson@carolina.rr.com