Another way to collect water
is from your main sail if you're a sailing boat. It's a huge area and an amazing amount of water runs off it.
All you need to do is sew 2 flaps along the foot (one for each side - maybe 10cm wide each) which curl up, creating a gutter each side. Sew an end cap piece at each end - effectively creating an enclosed gutter. Put a takeoff pipe fitting at the fwd end of each gutter. The gutter sides can be held up by putting small through-eyes in the mainsail
every metre or so along it's length just higher than the gutter height, and tying the 2 edges of the gutter together with line. You could achieve the same thing with small loops sewn to each side of the sail if you don't want through-eyelets. It doesn't have to be perfect - just good enough to move most of the water to the take-off.
You'd be surprised how much water you can collect this way - much more than from the bimini.
We also collect from our soft bimini by having small stand-up cloth "gutters" on each side which direct the water to the aft corners.
Agree that you have to let it rain enough to wash the mainsail
and bimini before going into your tank.
I'd also suggest that you filter the water at the galley
sink if you're going to drink it - amazing how dirty rain water is these days.