Right on both counts.
I originally build a table with a downdraft under the machine - no good.
Printable View
I use the dust collection from fwharris too, and recommend it highly.
http://www.ringneckblues.com
Once you have a good "Vacuum Head", I feel you no longer need the downdraft.
As you know, when you have wide boards there is little or no way for external air to enter the cutting area. This is due to the rollers, and sandpaper belts being compressed against the board and restricting possible air-flow.
I took this theory and reversed my thinking on the old downdraft system and reasoned (and tested) sending the air that was vented via the muffler into the old DD piping. This gives me a good source of extra air into the cutting area as long as the cut motor is active. Thus, even on the widest board I'm blowing dry air into the cutting area without having to rig another air supply. The point is to keep as much air-flow as possible to keep the unit clear of dust & chips. You notice a great difference with the cleanliness of the unit, and very little clean-up time.
AskBud
Here are some plans for a system you can make yourself:
http://forum.carvewright.com/showthr...ht=Frederick_P
FW,
What I have found, is that my Exhaust Reversal helps on cut-outs by venting the cut dust upward and the Vacuum Head(s) draws it off the project.
Further, by not attempting a Downdraft, at the same time I use the vacuum, I maintain maximum draw (vacuum) with the vacuum head.
I know, if I had a much stronger Dust Collector (600 CFM or better), I could do your "dual" method, but I only have a small DC.
AskBud
I built a down draft box out of 2X6's and a 3/4" plywood base. I attached the CW on to the top of this. I used a 4" line to the side of the base. I also added a second 2" line to the exhaust port of the motor and tied this into my dust collection system as well. this stops all that really fine dust escaping though the cloth bag originally provided. I get very little dust escaping and most everything remains clean while the system is running. I get some sawdust collecting on the shelf below the clear lexan cover but beyond this all is well. I use a Powermatic PM1300 as my collector.
Good Luck
Thomas