Well, today I just bit the bullet and melted a hole in the upper side of the 7-gallon (very) heavy-duty poly cone, for the tangential high-velocity water injection tube. Since the whole point of the filter is non-turbulent circular perimeter flow, I wanted the 3/8" ID copper tubing to enter the cone at a very low angle to the perimeter of the cone, but I wasn't happy about cutting the kind of complex shape in the poly cone that would fit the tubing at that angle.
I think I may have avoided that complexity by first melting a 1/2" round hole in the plastic, and then warming the copper tube with an ancient but massive electric soldering iron while I moved the tube from the position of a radius of the cone to a position much closer to tangential. This way, the plastic distorted so that the flow should be almost tangential, but the hole in the cone is not too far from round. I think it's a success, but no water has flowed yet.
I'm testing adhesives/sealants so I can fasten to polyethylene, PVC, copper, and whatever the hell that black plastic cap is that tops the cone. Plain silicone sealer is a failure, but both Shoe Goo and Sugru show real promise, I'll know better day after tomorrow which works best. I'm pretty sure that Shoe Goo will adhere, but Sugru is billed as a very good adhesive that you work with by hand like putty, until it cures to a silicone rubber.
Here's an image of the flow in a cyclone filter, so you can get an idea of the principle: it may not be clear at first that after the high-RPM flow at the bottom of the cone, the (hopefully) clean water exits back up the center of the cone.
This is the actual cone that we're using, but with our own stand:
I didn't take photos today, and I won't see it tomorrow, but I'll get some photos. Whether I'm a genius or a dunce, we may not know for a while.
Oh, why are we doing this you may ask? The stillhouse is on the bank of a well-travelled boat channel into Cultus Bay, and there's too much visibility to have anyone see anything
flowing from us into the water.