Keeping it more fun
What device takes a board upwind ??? The Fin is responsible for perhaps 90% (more ?) of the drive upwind?(rail helps aswell?) Without the fin the board would simply never go upwind.
First indication I get that I`m approaching overpowered (irrespectivce of rig) is boards desire to head upwind and both mine and boards reluctance to bear away. Solution? Change to smaller fin. Result ? I can bear away easier and boards looses desire to head upwind ... Yes I know all theory about CoE and CoR but results speak for themselves..One of symptoms of too large a fin is
a) Difficulty bearing away
b) Board heading into wind (without sailor input)
c) board wanting to rail (ie flip)
Changing to a smaller fin can alleviate sall above.
Having said that I would /could use a 42cm fin in a 67cm wide board with down to perhaps a 6.5. Especially if I weanted to stay upwind well and wasnt too bothered about Vmax. But I weigh 105 kg.
As for sailor steering upwind ??? Best progress upwind is made angling windward rail up slightly.Driving off fin and leeward rail; in "theory" board should steer down wind ! But it doesnt; it flies upwind if you get it rightr and balanced. (Railing)
Board luffs up when overpowered for 2 reasons.
a) Sail CoE moves rearwards. (can be offset by moving lines back)
b) Fin produces more lift than required.