These make the most sense for our application.

http://www.coastfab.com/mufflers.html

One can inspect the guts of the  muffler from time to time to
make sure it is not plugging up. Can be over hauled if necessary.
A perforated Inconel tube could be added internally to handle our
1700 F.

They are also the lowest drag configuration.

They could be as much as four feet long without adding
much to the drag if you have an airport noise problem.

Finally a viable rotary muffler solution.

These people have a great printed catalog for our purposes.
Much better than the web site.

Tons of useful bits and pieces.

Paul Lamar



Paul-- these guys at Coast Fabrication are an excellent supplier.  Provide
all kinds of top class stuff.   The welds on their mufflers are a sight to
behold.

Of the available packing for their mufflers, the stainless mesh they offer
is the most durable, followed by the less durable stainless "scrubble"
following that.  Their design is very similar to the straight-through
muffler we built for testing prototype rotary engines back in the
day--turned the ends from billet and outside tube screwed to those, with
removable stainless packing.  But it  would never last long. There was never
much to remove.  Sometimes nothing.  We never could source Inconel shavings
for the packing.  But they did work, even with 304 scrubble packing if the
guts were replenished regularly.  So the Coast Fab muffler may be a workable
short time piece on which to build. But folks need to start with inspection
on an hourly basis and build any time increments from there to be safe.

The CoastFab guys serve up the admonition that even on recip engines, the
guts of these need to be inspected and replaced  regularly.

A friend of mine is the  top pro race car builder in this area and has his
large shop compound about a mile fom Van's Aircraft and has used these
CoatFab mufflers since they were available.  He uses them almost extensively
on just about every imaginable race car built or serviced by his
shop....including two Roush-built "funny car" road race Mustangs, couple of
Corvettes, Nascar, open-wheel sprint cars, and full tilt V-8 off-road race
trucks.  He also fabricates rotary mufflers for national SCCA GT cars to
customer spec.  But it is generally recognized that any muffler and/or
component for the rotary is basically a sacrificial piece and degrades much,
much faster even when built with top of the line materials.

My understanding is that all the top three-rotor guys in the Rolex GT
classes  rent Francescos Ianetti's highly proprietary NRD/muffler.  He works
with them in testing.

But the exhaust system is quite a challenge for us and bottom line we are
still on our own in terms of developing an effective, low-backpressure
muffler that sounds good. I've been working on a compact design of a muffler
for a couple of years for the RV-3.  It's ready for dyno tests.  But man, it
is always a crap shoot.  It looks trick, but based on past experience, it
could very well be a total pig.  Just never know until we get the numbers
and accumulate the hours.

Steve Beckham

Paul,
Our mufflers are used on Mazda rotary race cars.  We are continuing to
do development work with a Mazda team running endurance races such as
the 24 hours of Daytona.
Generally the thickness of the muffler body is .030".
We have packing that can stand up to 1700 F.
No problem in making mufflers 24 inches long or longer.
Certainly making mufflers live for long periods at 1700 F is a
challenge.  Please call me to discuss.
Regards,
Gary Donahoe
Coast Fabrication

Rob please pass this on to Gary. I don't have an email address for him.

We find 321 better than 304 and the thicker you make it the longer
it last. I know it adds weight but up front, near the honest parts go with
.064" thick 321 and then work down from that as it cools off. Some guys bucks
up will pay for Inconel.

Not that I recommend it but I know of one rotary flying for over
ten years with .090 304 hand rail down pipes. Could be 3/16 :)
They are so strong they could be used for motor mounts :)

Paul Lamar