Finished the heat muff, The rotax 912is engine uses a muffler that is biger in dia than the standard muffler. I used end rings from Skytec, they provide parts for Zenith Rotax 912is engine installations. I used .016 6061-T6 Al sheet, and the Rans inlet and outlet stubs. Riviteted together with solid 3/32 dia rivets. I have heard reports that the bent-up sheetmetal heater muff provided in the Rans kit is leaky and dosn't work very well, so I wanted to eleminate any leaks.
First made a cardboard mock-up, then the real thing.