Hi Normster

Valid question,,

The cut outs helps on the early planing on bigger boards and also foil boards.

The board feel more 'free on the water' with the cut outs. The smaller the boards the less you need them.

Also with the cut outs you have better ability to 'pump the board up with your movements' , as with the less surface / cutouts (but still having the width), you can slightly change the 'trim angle' when you pump / accelerate more efficient and you don't have the whole surface (slightly draggy) to deal with

Hope my plain explanation make sense

Cheers
Jesper

The cut outs are ate trade off from maximum width for leverage against a higher drag from total width vs narrower tail when with less drag to get on the foil

As said...
Formula width tails need cutouts, unless you weigh more than 120 kgs.
60 cm boards with 38 cm tails do not need cutouts.

I thought the cutouts were to reduce wetted area at high speed, if anything they increase drag at low speeds. For a foil board which is only in the water at low speeds, I really don't see why they bother.

LeeD said..
Smaller foils need more speed to lift.
Not everyone is using huge foils.

I am

I don't like cutouts. They hurt early planing in my opinion.

I did some googling into tail cutouts and found one top race board with vent tubes drilled from the cutout inside corner to the deck. They were venting the suction/drag cutouts create when trying to plane.