Tools

I am dividing this list of tools into two categories. One is a list of necessary tools, the other a list of the tools that will get this project, and any subsequent project involving the gluing, bending, and in general manufacturing of acrylic items completed with the least amount of work.

This is the list of critical tools needed:
  • Hacksaw and coping saw
  • Drill bits and hole saw
  • Drill motor
  • Heat Gun, Acrylic bending tape, or (not the best choice) a propane torch
  • Disposable acrylic scoring tool (available at Home Depot and most hardware stores)
  • Sandpaper
  • Various flatfiles
  • A couple of good, strong straight edges and clamps
  • A non-permanent marker
This is the list of tools that will make your life a lot easier:
  • All of the above tools, and in addition
  • Table Router
  • 3/8 inch straight cut Router Bit with a ball bearing (for cutting the edging)
  • Drillpress
  • Table Saw and an acrylic blade (with at least 80 straight, not angled, teeth and preferably carbide)
  • Sanding blocks and preferably sanding cylinders for the drill press

If you do not have a router try to find somebody that does. Doing these types of projects without a router is very time consuming. I am not sure what the cost is, but most plastic places will do the routing for you.

Materials

The following list of materials will do this project and you will have enough glue to do do quite a few other projects so make sure if you are doing more projects from this same site that you factor in the amount of materials left from this project that can be used in others.

List of materials for an 8" wide Weir with a 1" bulkhead capable of 600-700GPH water movement:
  • 1 - 24" x 28" x 1/8" GE Acrylite Plastic Sheet (available at most Home Depots}
  • 1 tube of Weldon #16 clear, thickened, acrylic solvent cement (this is easier to use when the pieces are not cut exactly to dimension but less visually pleasing). If you can cut the plastic, or have it cut, to exact tolerances use Weldon #4. It is a lot less messy and definitely more pleasing to the eye.
  • 1 - 1" bulkhead or larger if you need more water flow. I would not suggest going over 700GPH unless you make the weir wider than 8" and use a larger bulkhead, or make two of them.
  • 1 - 1" piece of 3/16" hard air tubing (use a piece from an old undergravel filter or get some from your LFS)
The acrylite will need to be cut accordingly:
  • 26.5" x 8" will be the main body of the weir
  • 11.5" x 8" will be the "siphon containment" piece
  • 2 pieces - 8" x 9" that will be the side panels
  • 1 piece - 2" x 8" piece for a baffle in the rear section
  • Several pieces approxiamately .75" x 1.25" that will be laminated (for strength) to allow for a tube to be placed in a hole in the upper most part of the siphon containment section to allow for the removal of air bubbles, and for restarting the siphon when shutting down the return pump or in a power outage situation

Preparing the Materials for Assembly

The cuts are easily accomplished by scoring the plastic with the blade, and then breaking the pieces off along a straight edge. I used my "Workmate" workbench for all of the scoring and cutting, but any work bench will do. Score the plastic 4-5 times until the score is about half way through the thickness of the plastic for the best break. I would suggest practicing bending the plastic with some of the lefover pieces before attempting the actual bends for the weir.

Looking at the diagram, you will see that the main body of the weir needs to be bent in 6 places. Measure and mark all of the bends from one end of the 26.5" x 8" piece to the other with a marker. Unfortunately, the protective coating will need to be removed to accomplish this as it will burn. The first bend should be the 1" section in the middle of the main body piece as it will be nearly impossible to bend later.

Lay the plastic on the workbench (you can protect the surface of the bench with sheet metal or wood, but what's a workbench for anyway!!) with the edge to be bent along the edge of the table surface. Clamp a suitably thick piece of wood (1" in this case, it depends on the thickness of the wall of your aquarium) along the line for the 1 Inch bend so that the sheet sticks out revealing the second line of the 1 inch bend.

Using the heat gun on full power (some work gloves are definitely in order as these babies get HOT!!!) move the hot air along the bend you want to make but do not allow the gun to remain in one spot too long or you will get bubbles. Fairly soon the sheet will get limber and start to bend from its own weight. Bend the sheet up over the block of wood until it is 90 degrees from the remainder of the sheet, you might want to press the plastic against the wood block to get a nice crisp bend. Still moving the gun start on the second part of the bend and when limber go ahead and bend the sheet over the top of the wood block. The plastic will stay limber for a few minutes so that you can make adjustments and make sure the bends are 90 degrees. This is the trickiest bend and can also be accomplished one bend at a time if you prefer.

You will find that the rest of the bends go along fairly easily....TAKE YOUR TIME!!!! Also remember that if you do not like it you can get another sheet of plastic fairly cheaply. Once you have done one you will find that it is easy to bend this material and you will be overwhelmed with project ideas for what you can do with this new found skill....STAY FOCUSED YOU ARE BUILDING A WEIR!!.

When you are finished you should have one piece with six bends, one piece with two bends, two side pieces with no bends, one piece for the baffle, and several small pieces, plus whatever you did not use.



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