Anytime you use a fog machine and couple it to hose, pipe, or any other ducting material you must include space between the body of the fog machine and and the ductwork. Rosco manufactures a device expressly for this purpose. It allows the hot fog to combine with cooler air which causes a better encapsulation of liquid particles in the air. It also creates what is known as the "venturi effect" in which the fog rushing in pulls an equal volume of air into the pipe. This increases the the over all fog effect and leads to much happiness.Also - If you are using a fog machine, you will want to not put the fog machine right up against the PVC pipe. If you back it off about 2 - 3 inches - the fog will still go in the pipe, and you will get a much better volume of fog. I don't know the physics behind this exactly, but when you allow the fog to interact with the cooler air, it just works better.
@Mike A few thoughts for you worth every penny you've paid. (Thus they may not be worth much.)I built a 3 1/2' wide ufo. I want to place a fog machine inside and vent it to three or four ports (space ship exhaust) venting it from the bottom of the ship. It will have 3 legs and be about 5' up in the air. I have a light mounted underneath so it will also give the light a tighter "beaming" effect (I hope). Just not sure how to make the fog go around the tubing and make the 90 out the bottom. Help
...then trickle out as a slippery-wet discharge.
I think I ended up in the wrong forum again....sucking rather than blowing, you merely need to flop it over to suit your needs. (A lot of things in life are like that but more than enough said.)