heres a picture of it, as viewed from above.
the orange thing is a 15mm copper pipe, the dark brown is aluminium, the black is bolts.
it will be about 40cm high and ill try keep each fin at a maximum length of 5cm.
(the fins will all be about 40cmx5cm)
(ive done a test before, clamping an aluminium plate to a copper pipe and the aluminium felt as hot as the copper pipe for about 5-10cm. that was 1.6mm alum)
there will be a whole lot of these stacked next to each other. then mounted to the side of my pc. (at least 4)
note, i will tighten the bolts quite a bit to squash the pipe a bit and give some good contact area.
assuming each pipe has 10 fins around it with 4cm on each fin exposed, 40cm high, thats 3200 square CMs.
per pipe.