For my RV peeps: DIY generator exhaust stack, or "Syn-Turi"

Generator exhaust rises, right? Taking all that nasty CO with it so you're not spewing it straight out into your neighbor's seating area?

Which is why I understand a lot of crowded infield-type RV camping venues require a generator exhaust stack now. Camping World has one, the Gen-Turi, for something like $130, but here's a DIY version I ran across in an RV forum that you can build for about $55 in about two hours.

This is the one I built. I may paint it if I can find a paint that'll stick to galvanized metal (which I understand is a water-based latex spray-on that Krylon makes; I just haven't been able to find it at my local hardware stores.)

Overview:



(Gotta clean those damn stickers off.)

At the generator exhaust pipe:



The "manifold":

 

Support:

 


It's a pretty cool concept: the little...what, manifold?...uses the Venturi effect to draw cool air up the stack along with the hot exhaust, which is what keeps the pipe from getting too hot to touch (and helps muffle the sound of the generator.) The gap in the manifold is where the cool air gets drawn in. The length of the gap should be the same as the inside diameter of your stack pipe; here 3".

Parts list (from bottom to top)

-Two EMT bolt-on EMT connectors. These need to be the diameter of your generator exhaust pipe. Mine are 1 1/4".
-Two thumb screws to fit the threads in the generator-side EMT connection. Mine are 1/4 X 20 X 1/2" and 1/4 X 20 X 1". The height differential is nice because that way the wings don't get in each other's way when you're tightening them down.
-A 1 1/4" EMT elbow
-A 3" to 3" PVC coupling
-Aluminum bar - I bought a 3' shot of 1/8" X 3/4"
-Pop rivets and a gun - I bought a box of 3/16" medium-grip
-A couple of those push-down lock-on suction cup-mounted hooks (available in, I think, the home organization section of Lowe's)
-Bungees or whatever - in this case those twist-lock things that are essentially giant rubberized plastic bag ties. 
-The appropriate number of 3' shots of Selkirk 3" flue pipe...two in my case, because I'm only trying to to raise the exhaust a little under ten feet.
-A 3' adjustable Selkirk elbow

The build:

Everything just snaps together or screws on except for the manifold, which isn't particularly tricky to construct, but can get a little tedious. To make this thing you essentially:

1) File off the lip of the EMT coupling in three places. Picture the screws on the side of the coupling being at 12:00, so you want to file off the lip at 2:00, 6:00, and 10:00, so they're equally-spaced. When you see the coupling itself at the hardware store, you'll instantly understand what I mean.
2) Make three equal-length aluminum bars (for a 3" gap, these should be roughly 8 1/2"-ish). Use a pipe clamp to clamp them to the EMT coupling and then drill through the bars and the coupling at the same time for the pop-rivets.
3) Rivet everything together. Refer to the picture above.
4) Now bend the bars outward in roughly the same spot all the way around (helps to have a bench vise), and secure them to the PVC coupling with another pipe clamp (a 4 1/8" - 5" range one works well for a 3" PVC coupling).
5) Drill and rivet as before. You can see from the manifold picture above that I've left the pipe clamp on for mechanical support. Note that you don't want to drill the upper half of the coupling for rivets (as I discovered) because the rivets will interfere with the insertion of the flue pipe later on.
6) Screw this assembly to the EMT elbow using the screws on the EMT coupling.
7) Voila. Affix the EMT elbow to your exhaust pipe using the second EMT coupling. This is where the thumb screws really come in handy, as you can see in the picture. Makes it very quick to put on and take off.
8) The flue pipe snaps together and sets right down into the PVC coupling very nicely. (The pipes also snap APART easily, which is key for storage.)
9) Arrange your suction cup / bungee support to take some of the weight off your generator exhaust pipe (although this contraption isn't very heavy at all.) I put a pipe clamp around the Selkirk about halfway up one of the shots of pipe just to give the bungee something to lift up on.
10) You *may* want to put some sort of spacer -- a short section of PVC, maybe -- between the Selkirk pipe and the sidewall of your RV, just to keep the pipe from swaying too much. I'll probably make one of these. Just be sure to pad it where it contacts the sidewall of your RV so you're not scratching up your rig. If I build one I'll post a follow-up photo.

Anyway, I just tested mine for 1/2 hour. The generator stayed cool, the Selkirk pipe, which is double-walled, never got more than warm to the touch, and when I climbed up onto the roof of my rig and put my hand over the elbow, I could feel the warm exhaust rushing out.

To test how well it's working, start your generator and then tear off a little square of paper and place it on your fingertip and hold it up to the gap. The air rushing into the gap should vacuum the paper off your fingertip and shoot it out the top of the pipe.

That's it...