RE: Gas engine cooling and test results
The ducting is glued with contact cement (AKA goop?) The cylinder jacket is tied with wire, and kept under tension using silicone tubing inserts between duct and fins.
So far, no RFI, but hard to tell for sure because I use 2.4GHz. which blankets a lot of RFI that is present.
It is however very easy to make the ducts of thin cardboard or mylar, or anything non-metal.