Here are the dimensions of the gates that I built.
7-3/4” x 7-3/4” x 1/2 Birch Ply
3/16 Hardboard cut to fit the opening.
7-3/4” x 1” x 1/4” Hard Board. The 1/4” HB that I have access to is the stuff that is smooth on one side and has a rough texture on the other. I used a hand plane to reduce the thickness a little on the “rough” side.
Cut to fit the diameter of the pipe that you’re using. I used a wing cutter on the drill press to cut the holes.
Pipe: (use what fits your system. This is what fit mine)
4” S&D Coupling cut in half (one half per gate.)
“Large” tin soup can. (Mine happened to be a can of fruit cocktail.)
3” DWV coupling. (This was a very tight fit with the hose. Hose had to be heated to install.)
4” Plastic Dust Collection Coupling
Poly Urethane Glue to glue the Pipe to the body. Spray a light mist of water on the body and put the glue on the pipe. PUG needs water to cure and the water acts a “kicker” to speed up the process a little.
Yellow Glue to glue the spaces to the bodies.
Generally these gates are larger than they need to be. I would think that you could narrow them up quite a bit if you need the extra room. They can be made smaller and still work just fine. I had to cut one gate down on the back side so that It would fit between the wall and the riser pipe. It still seals just fine.
Ok I’m done with blast gates, promise. lol
-- Chunk's Workshop pictures: http://spadfest.rcspads.com/thumbnails.php?album=135