Constructing the weir

 

  1. Cut plywood to more than fit a cross section of the channel.

 

  1. These instructions are for a 90 degree v-notch three feet from the right side of a 2’x8’ plywood weir. Cut a 90 degree v-notch. Mark on one edge (the top) at 1’ 8” and 4’4” from the right side. Mark the other (bottom) edge at 3’ from the right edge. Find a perpendicular from the 3’ mark, and mark a new spot 8” from the (bottom) edge. Draw lines from this new point to the points on the top edge (the 1’8” and 4’4” points). Cut along those lines.

 

  1. Cut the aluminum. Mark a line 3” from the edge of the square along one side, and mark a line 3” from the edge of the square on an ADJACENT side. Cut into the aluminum along the lines, STOPPING WHERE THE TWO LINES INTERSECT. When you are done, you should have a Thin (3” wide) 90 degree V. A Skil-saw with a metal cutting blade seems to work ok.

 

  1. Draw a line on the aluminum V that is 1.25 inches from the outside edge. Starting from the intersection of the two lines, mark dots every 4” going out the lines.

 

  1. Brace the aluminum V on the wood so that it will make the edge of the weir. It should be about ½ “ above the wood. It will not make it to the top of the plywood, it will be a few inches short.

 

  1. Drill holes to fit the bolts through the aluminum and the plywood.

 

  1. Now remove the aluminum, and brace the lath onto the plywood. The lath will form a strip that will put pressure on the aluminum evenly. Drill holes through the lath using the plywood as a template (or use the aluminum as a template, if that is easier).

 

  1. Place the weather strip over the holes in the plywood. This will be on the DOWNSTREAM side. Use a screwdriver or a narrow file or something to poke holes through the weather strip.

 

  1. Feed bolts through washers, and work them through the weather strip. If possible, place a small bead of caulk around the shank of each bolt near the head as it goes into the plywood.

 

  1. Fit the aluminum sheet over the weather strip, followed by the lath strip, followed by another washer

 

  1. Put on the nuts. This will be a huge pain in the neck, because the bolts are not quite long enough to get through all the layers. However, the weather strip compresses, so with two hands to squeeze all the layers and two hands to do the nuts and bolts, it should work. When it is tight, the weather strip will be all but invisible.

 

  1. When everything is tight, caulk the joint between the plywood and the aluminum.