[chriss]

Decided to make a weir comb, but can't decide on the 'spacing'. Slots are 3mm wide. In the pic below the ones at the top are 7mm between slots, the ones at the bottom are 13mm between slots.

Total length of comb will be 52cm, so that works out at either 52 slots (156mm/6 inches) or 32(96mm/3.5inches) slots. The length of each slot is 25mm, water can rise right to the top if required.



So, top or bottom??

Chris

[SLAPPY]

I would personally make the slots wider thean 3mm, I would increase them to 5mm to allow more water to get through.

There was a thread on Ultimate Reef about this a few weeks ago.

[ben]

id have the top one, its surprising how much water they will let through

[bobba fett]

How about the top ne and take every other tooth out?

My weir if topped with eggcrate, just enough to stop fish going through

[djjd]

if it was me i'd go with the top comb as it is allowing more surface area of water through it and also you would be breaking the surface tension more which i would suppose aid further in the oxygenation of the water .

[chriss]

Thanks guys. I went with the top one, but the cutting wasn't as neat as I'd hoped so just lopped the teeth off and gone with a straight edged top.

Chris

[SLAPPY]

What did you cut it with?

[chriss]

I found the calculator on RC for weir sizes, and it reckons I need to be aiming for something like 9 inches of linear flow to get me around 500 gph, not that I expect to get that but it was something to aim for. With the 'top version', I had about 6 inches. I would need to make more/wider slots which kind of defeats the point of having a comb in the first place, hence I might as well just use a straight edge and put some egg crate on the inside.

Then again, 5mm slots with a 5mm spacing gives me 25cm, thats about 9 inches. See how I get on this weekend.

Cutting it? Uh, for the slots I used my chop saw , obviously very carefully, and it wasn't too bad really, it was easy and accurate, but obviously not the right blade. If I'm going to do it again, since the slots will be wider than the blade, I've got a better saw that won't be a problem. I did try my router witha single flute cutter but it was going to be a pita to align accurately each time.


Chris.

[SLAPPY]

chriss, on Apr 18 2009, 07:19 AM, said:

I found the calculator on RC for weir sizes, and it reckons I need to be aiming for something like 9 inches of linear flow to get me around 500 gph, not that I expect to get that but it was something to aim for. With the 'top version', I had about 6 inches. I would need to make more/wider slots which kind of defeats the point of having a comb in the first place, hence I might as well just use a straight edge and put some egg crate on the inside.

Then again, 5mm slots with a 5mm spacing gives me 25cm, thats about 9 inches. See how I get on this weekend.

Cutting it? Uh, for the slots I used my chop saw , obviously very carefully, and it wasn't too bad really, it was easy and accurate, but obviously not the right blade. If I'm going to do it again, since the slots will be wider than the blade, I've got a better saw that won't be a problem. I did try my router witha single flute cutter but it was going to be a pita to align accurately each time.


Chris.

Yeah, the router a PITA to use on small sheets of acrylic.

I use a tile table saw to cut all my acrylic.

[Dave.I]

Yeh i was going to say the same thing Tony.

Dave