Good question. It's hard to tell because everyone says it's "cross-off" as soon as it gets a few degrees offshore (i.e. close to cross-shore), but it should mean 45 degrees offshore. I don't have an exact figure for how much is too offshore, but I reckon once it gets to 45 degrees offshore you have trouble finishing your top turn and getting down the wave. Bear in mind that it's the angle of the wind to the wave rather than to the shore that matters, and when the wind is offshore there's a better chance that the swell direction will be opposing the wind direction because the swell isn't generated by the wind, thus making it more "offshore."

sandy point yesterday sunday 10/10/010 was off shore

That's crazy offshore - where's that?

I've thought about this more and reckon 45 degrees is about the magic number; but there are too many factors to make a hard and fast rule of thumb....




In lighter winds anyway (I think) it is all about generating enough speed to match wave speed (20 m/s for a 13 s period wave, 26 m/s for a 17 s). Surfers do this by paddling - the smaller the board the closer the peak you need to be (angle theta needs to be greater to get that sliding happening). For really high period waves (e.g., Jaws) you can't generate that much paddle power - hence the tow-ins and sail boards. For us wave sailers we can pick up a wave before it breaks, if there's some wind blowing, dogg along on it until it starts to jack up and we can gain enough velocity to ride it. The wind has got to be coming from the right direction - sideshore is best (but the waves often crumble), 45 degrees is great - still have 7/10ths of our speed in the direction of the wave and nice clean waves, offshore - have speed but in wrong direction (especially in non-planing conditions). I read somewhere we can achieve up to 0.9x wind speed. If you're planing in 20 knots (10 m/s) I guess you'd be doing up to 9 m/s which from experience makes it easy to pick up a 13 s period wave doing 20 m/s. That's enough science for now - there's still plenty of magic in this.

How to optimise the light wind wave sailing experience?
I guess (don't have one myself) multifin boards help you head up wind more and put your speed in the direction of the wave.
Bigger sails? - though I'm not really comfortable out in waves with more than 5.2- too much foot for the wave to catch onto going out - one of the videos has the Pros saying they use up to wave 5.8's and 6.0s.

I think it all depend of the spot you are sailing. If the wave break nicely on an offshore break with no shorebreak...or no wind in the inside, a lot of current, closeout..no channel.....

Slim Jim said...

Been sailing these fluky NE'lies which should be a good wind direction for the S facing beaches near Adelaide, but NE'ly forecast usually means N or NNE at best and it is super hard to snag a wave - have to be close to the peak, get a gust (not too strong else get blown off the back, but strong enough to match wave speed, etc). Anyone got a wind - wave angle rule of thumb to decide whether to sail or surf?