[Cob] Catching debris pre-gutter

[alex mackenzie]

Hi all
I was inquiring about corrugated drainage pipe as gutter a while back.
Wotked out great (thanks for your first hand insights Bernhard etc!).
Because I am using full pipe around a curved (oval) roof edge I have sliced
the pipe open with one long cut its entire length and it "grabs" on to the
roof quite nicely. I want to put something along that edge that runs the
rain into the gutter so as to catch debris before it gets into the pipe.
Having a closed pipe helps but it needs more help what with all the Douglas
Fir spitting needles down. Fine things, these needles!
So I know some people use scotchbrite pads as filters in their water
systems. Non woven, lets water pass but not bits and pieces. Same stuff as
the scrubby side of your scouring/dish sponge. They sell it 1" thick, 4"
wide in a roll 30 feet long. All great, except for the cost. Too
expensive.  I would need three rolls tallying up to over $500CN. Intended
for commercial sanding and polishing applications.
Any other ideas? Screen is not fine enough and too awkward to install on a
curve. Is there something akin to Scotchbrite but cheaper? Spongy/latticed
but non absorbent, lets water pass but not pine needles.
Cleaning this tube is not really an option except for water flushing it out
naturally.
Thanks!
Alex