Hi Jaro,
I would say planing with an active pumping technique on the Blast, should be able to go in about 12-15knots, maybe lower if you are a better sailor/light on your feet. Should plane thru 10 knot holes easily. But remember this board is just 66cm wide, so if you are looking to sail more often in 10-15kph, then you may need something bigger. What sail size did you use/previous or other boards/your sailing level/fresh water or salt water etc?