How to get a sharp edge on channels?

[stoneburner]

For my Coanda Channel, a hard edge (90 degree walls) is critical for proper hydrodynamics, especially related turbulence affecting the boundary layer. As a shaper referred to it during a discussion we had, the hard 90 degree at the edge of the cliff — where my channel wall meets the bottom surface of the SB.

I developed this technique for hand lamming my channel (I used epoxy for this one). Since I have been using XLPE and CNC for prototyping my current BB/Paipo projects, I haven’t used it (No glassing required). However, I am one prototype away from using it now. (BTW I built my own channel shaping tool using large dimension square dowel with sandpaper on one side).
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Stoneburner's assist build 48 1/2" body board

My glassing skills with epoxy are mediocre.  The biggest challenge for me on this channel was a clean glass job on the channel’s 90 degree edges and inner bottom angles.  I figured Charlie could do it without problems. While Charlie was working on this build, I was trying to come up with a good way to hand laminate the channel.  The standard recommendation from several members has been to use spray adhesive to tack the dry cloth to the channel walls.  The biggest drawback to that method is find…