be sure and align the screw holes where it will be easy to locate after the membrane covers up the bulkhead. here i drew a line at a 90 degree angle from the sides, all i have to do is set a framing square or any true square guide so that I have a perfect alignment with the bulkhead screw receiver holes.
left over EDPM membrane from a previous project happens to be 20' long just enough to handle the length of the two 2'x8' grow boxes. remember when purchasing the membrane to allow just a little more than the length or width plus the sides. a 2x8x1 requires a minimum membrane of 4'x10', that does not include any surplus for the wrap over the top of the side edges.
once it is lightly tacked in place by the top pour just enough water into the grow bed or tank for the weight of the water to push the membrane into the corners and allow the corners to be folded and the wrinkles to be straightened. if you overfill the GB you will not be able to move the membrane.
the top ring is screwed through the liner into the bulkhead fitting prior to having the center removed. this really makes it easy to place the ring. on a regular bulkhead, even those as i originally showed there is always a chance the membrane will move as the holding nut is tightened. i have installed a number of this type however and it is certainly doable. two other negatives is one, cutting a perfect hole in the membrane, the membrane is not that easy to cut, and then if the membrane is just a little off of alignment with the bulkhead fitting it can cause a problem trying to relocate the membrane for the hole to allign with the bulkhead fitting.
the membranes are in and the bulkheads have had the center holes cut out. the next step that i will do is to add 2x stiffeners on the long sides (8') at the top of the grow beds then i am going to attach steel cross braces to preven the GB from bowing. (I could probably get away without doing this since they are constructed out of 1-1/8" plywood subfloor material which can span 4' each way as a subfloor material.) after the stiffiners and trim are on and painted i will trim back any excess membrane.
1.run electrical with GFI's (the extension cord is plugged into a GFI receptical). if your area does not have a GFI recepticle get an extensin cord that has an intregal GFI, don't be a penny wise and a dollar foolish, life is too precious, not just yours, but your family, your fish and someone visiting. DON'T EVEN PLUG INTO A STANDARD OUTLET TEMPORARILY!!
Looks awesome! I can’t wait to see it flowin.
Is that asparagus???.
Unless someone like you cares a whole awful lot, nothing is going to get better. It's not.-- Dr. Seuss, The Lorax
Simplicity of character is the natural result of profound thought~fortune cookie