RV-12iS heater muff -- making one larger?

[CTCole]

After chasing down air leaks, I'm still hoping I can make the -12 suitable for winter flying (I'm in Duluth), perhaps with heated seats or a longer heat muff surrounding the muffler: the stock muff is only 4" long. That brings up some questions about how the stock muff is made:
1) What is the function of the FF-00090A Heat Muff Inner Wrap? This band of 0.0179" 304 stainless steel surrounds the central portion of the muffler. Is it there to prevent exhaust leakage into the muff, in case a hole develops in the muffler wall? Is it insulating the aluminum Heat Muff Outer FF-00090H so it doesn't over-heat?
2) Where are the seams in the muffler? I can't remember from when I was building a couple years ago.
3) What is the function of the two circumferential beads, ca. 1/8" high, that the heat muff fits between?
And if anyone else has already solved this problem, I'd love to hear your approach.

 

[rockyfatcat]

Contact custom welding products LLC [email protected]

They can make anything you like. Customizable heat muffs.
Exhaust pipe diameter/heater length/opening orientation.

 

[rcarsey]

I messaged support a couple weeks ago to inquire about the possibility of having some of the new 2026 RV12iS features available "for this winter" - ie. better sealing. They said they're busy getting the RV-15 out the door. Tough it out for one more winter?

 

[subpar_bucker]

Whenever this topic comes up, Scott usually points out that besides sealing the cockpit you need to make sure you are turning at least 5000 rpm in flight to produce significant heat. IIRC heat production drops off significantly below 5000 rpm. I usually cruise around 4.4 gallons/hour which keeps me around 5300 rpm. I get toasty warm air from the heater while cruising (things cool off quickly when landing

I also have the optional oil cooler cover installed and usually have a strip or two of duct sealer tape on the water cooler to block it off partially.

 

[CTCole]

All good advice-- "necessary, but not sufficient" as they say. I'm imagining a longer muff, but without the inner (stainless) liner on the muffler. But before eliminating it, I'd like to know what its function is...?? And yes, this may be a project for a warmer season, maybe along with heated seats.