Originally Posted by C249
If we're talking speculation (and it seems we are) then we have to accoount for the fact that
the longboard has a much faster speed in displacement mode. That allows it to go faster in light winds, and planing lift increases by the square of the speed so low-end speed is important.
And the weight of the sailor AND GEAR (not just board weight) is vital, and the extra 8kg or so of a longboard is less important when viewed against the 90kg or so of the slalom board + sailor unit.
So since the longboard is faster in displacement mode, the lift increased by the square, and the width and weight are only slightly greater, that may well be more important than weight and width. Personally, I feel a longboard planes a lot earlier (and this seems to be confirmed every time I sail one against slalom boards in marginal conditions) but since there's not a dramatic difference between fast displacement, semi planing and planing, it may not look dramatic from the outside.
This isn't attacking slalom boards, which are great to sail.
I agree that a longboard has huge advantage of a much greater non-planing speed, and smoother transition to a full plane. I think this is often overlooked when discussing early planing.
However, I don't agree that board weight alone is "less important" when total weight is taken into consideration. I'm pretty sure 8kg or so is vital even if the whole "package" is 100kg.
My experience is this: marginal, flukey on/off wind - a longboard wins every time.
Marginal, but STEADY - say 10-12 knots - wide slalom wins except on extreme upwind course.(please note, when I say "win" I refer to early planing/speed).
Still, no hard data here, and for some sailors displacement speed and comfort will get them going earlier/easier, while for others a different technique and shortboard feel will play an important part.