Exhaust re-route

[DanB]

While in the process of making my bird less draggy using farings, etc..., I got to looking at that exhaust stinger sticking straight out the bottom of the lower cowling. My thought is to re-build the exhaust to stay inside the cowling and shoot back to the side of the radiator. Was curious if anyone has tried this? My concerns go to more noise in the cockpit? fumes in the cockpit, etc...

[Esser]

Hey Dan,

Pick up a copy of the book Speed with Economy. It talks about doing this very thing to increase engine cooling too.

It's an ebook. I think you can get it for $20

[DesertFox4]

Dan, I think you would incure all those problems plus too much heat under cowl.

[jrevens]

It's a different situation with a fabric covered airplane than with a metal bird like the Mustang II that Kent Paser built. I built the exhaust system on my Thorp so that the tailpipes are close to the belly & point almost straight back. Even with the aluminum skin, I use thin stainless steel plates to help keep the exhaust from damaging the belly where it impinges on it. Those hot gases really spread out after they leave the tailpipe. I've often thought however that the Kitfox tailpipe could at least have a little angle or curve back instead of pointing straight down.

[DanB]

Thank you all for the reply, The heat buildup inside the cowl as well as too much heat on the fabric might just kill the idea. John's comment on perhaps angling the stinger to the back a little more instead of straight down might be a good compromise.

[DanB]

Esser, thanks for the lead on the E-book. I will take a look.

[Esser]

Even if the ideas aren't practical to our application, it still is an interesting read.

What about an aerodynamic shroud to go over the pipe.

[colospace]

From Kitplanes magazine a couple of years ago:
Barnaby Wainfan said "Fairing a cylinder into an airfoil shape can reduce its drag by up to 90%. For fixed components— struts, wires and landing gear legs—we can get this 90% drag reduction by adding simple airfoil-shaped fairings. Even a straightsided wedge fairing mounted on the back of the cylinder can decrease its drag by 60%."
So maybe a tapered fairing aft of the pipe would do enough for you.

[DanB]

Esser & Gary, I'm in the process of faring lift and jury struts and was toying with the idea of tig welding a trailing edge to the exhaust pipe. If I do I'll post a picture. Thanks for the ideas.
Dan

[DesertFox4]

Dan, I think you could shorten your down pipe a little as Papa mentioned some time back. Also the fairing sounds interesting.