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Date: Thu, 09 Jun 2005 19:19:46 -0600
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
From: Bill Dube <bdube@al.noaa.gov>
Subject: RX-8 Six port manifold
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I've been thinking about how to make a manifold for my six-port. Tell me 
what you think of this.

         I plan to chop off the stock manifold a bit past the injectors and 
just before the secondary valves. (I may reconsider and cut just after the 
secondary valves.)  I plan to fly-cut that area flat and make some sort of 
flange. Perhaps I'll weld on an aluminum flange.

         I'll carefully measure out the position of the openings in the 
truncated flange and then CAD up a manifold that will emulate the stock 
manifold in the "full-power" configuration, but I will make it hug the top 
of the engine. I plan to just CAD up the inside surface of the manifold. 
Next, I'll define a "web" surface that joins all the tubes at their 
midpoint. I'll then CNC machine two blocks of foam, one for the bottom and 
then one for the top. (Split at the web.)

         I'll coat the resultant foam plugs with epoxy fiberglass or 
whatever to make a smooth, hard surface.  Next, spray on mold release and 
lay up some carbon fiber (perhaps with Kevlar) on these plugs. Once I 
manage to separate the parts from the plugs, I should be able to epoxy the 
two webs together, trim it up, and have a complete manifold.

         Alternatively, I could lay up the carbon fiber / Kevlar directly 
on the foam, then carve and dissolve the foam away, but I'm not sure if the 
surface finish would be acceptable.

         If it works well, I can CNC a more durable mold (like aluminum) 
and then make duplicates.

         Bill Dube'