| The 18m proa has evolved slightly. It started out with two under hull rudders that were 900 span and 450 chord. With those, the successive tracks for best VMG were about 110 degrees apart. If the hulls had any slimy fouling that would get out to 120 degrees.
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| When we were working out how best to sail it I would not bother trying to get any data unless I knew the hulls were clean; usually by spending about 80 minutes in the water with a scrubbing brush.

I searched the list for fouling and found how you have regularly pointed to the gentle fouling of a hull easily doubles the drag of a hull.
It seems defouling tech is, perhaps, more important than hull shape. Although hull shape won't be fixed by rubbing.

I did have another question regarding hull shape. Given the simple mold of the HP has 90° sides, how much does that cost a long slender hull vs 23° sides, in your estimate?

Given your experience actually building boats, would you consider adding a 23° side, or stick with the simple sides? I would guess adding the angle would basically double the complexity of the mold.

Finally, does the radius of the corners matter? I am looking at building molds now, and was curious about your thoughts.

If you have already answered these, feel free to suggest what I might search for.

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