Brian Camet wrote:For just playing around you don't need to be to worried about small imperfections.
That may be true, Brian, providing your foil do not cut water surface. Else, you will experience ventilation, the annoyance of which depends mostly from geometry (dings are as important as a type of profile and its thickness), from water surface tension in relation to foil surface (oils on surface) and water vorticity ( white caps are the worst for me), water saturation with air (white water rich in small air bubbles promote ventilation and cavitatio) and, last but not least, speed. More speed, more ventilation usually, but not always. The air cavity may be stable, difficult to get rid of = explosion, or, on thinner, more " intelligent" foils "deattach" quickly=chance for survive.
Air cavity may attach to your mast passing white cup, or to your foil that cuts water surface on a tight wave turn.
Mast surface perfection is a must for me on thicker masts, like old 80 cm Ketos.
Foil surface perfection is not so critical for me when my max speed is below 30 knots.
After several hundreds of hours your muscles will recognize the risks.