PVC Dust collection ducting problem


I am building my ductwork out of 6" PVC drain pipe. The only problem I have had is in the locations that I have used flex lines to complete a drop. How have others joined the flex line to the PVC? It fits inside of a PVC fitting, but will not go on the outside of a pipe so that it can be clamped. My best solution so far (that I am not thrilled with), has been to buy 6" metal duct fittings (maybe called starters or stubs IIRC). The ones I used come flat and you snap the ends together into a round fitting. I have inserted the finger side into my PVC pipe and run a few screws through some of the fingers. The flex line fits the other side well enough with a band clamp. My biggest complaint is the deformity and possible potential for turbulence where the fingers enter the pipe, as well as the fact that the flange that divides the finger side from the solid side is slotted and allows leakage. I suppose the leakage can be alleviated with duct tape, but I was wondering what others had done.
SteveP.
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This is what I did - seems to work well.
I have a run along the wall w/ blast gates that drop down. After the blast gate I have a about a 12" peice of PVC. I made a few cuts in the end that will connect to the flex about 4-5" long (I did 8 of them, did it on the band saw - push into the blade - rotate - push into the blade rotate..etc..) enough to compress it a bit to get the flex to fit over it - secure w/ a band clamp and it works great.
Its a PITA and you will have to wrestle w/ it a bit to get it on.
A few others I had some "inside" couplers from my old system that worked ok as well.

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The cuts make sense. What are inside couplers?
SteveP.

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Can't you reduce to 4" for the flex duct. I don't think the losses can be worse than any other method used to attach the flex duct. IIRC, my flex duct fit right over the 4" PVC. In fact, I would assume that a plumbing supplier could get a reducing wye that goes from a main 6" trunk line to a 4" drop. One is listed on this site http://www.pep-plastic.com/manufacturers/plastinetics/d-wyes.htm , so I know one should be available.
Preston

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Be carefull:
http://groups.google.com/group/rec.woodworking/browse_thread/thread/19e02e0029451948/bbed79e10b5927bd?lnk=st&q=duct+%22david+merrill%22+group%3Arec.woodworking&rnum=3&hl=en#bbed79e10b5927bd
David Merrill

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