Wiki Sail by GRF

Priceless

Originally posted by Medway Maniac Ah, so you agree with us now.  I sense shifting goalposts again.

Originally posted by fab100 Originally posted by Medway Maniac If the true wind was really square to the current, then the apparent wind would have been more forward on one tack than the other, meaning the sail force vector would have been more sideways and the resulting thrust less. Beat me to it, but, yup, apparent wind effect of tide

This...

No way either of you can deny you wrote this.

Which is total and absolute let me spell it out for your next book B O L L O X

and to think folk pay to read your crap...

Oh look a useful and handy guide to the variable nature of apparent wind.

So, now lets say we're at anchor with 4 knots of true wind from the north.

In a channel with 4 knots of tide heading North...

You are about to head West. How much true wind is there from the moment you raise anchor?

Originally posted by 2547 I'm not sure if anything can be said to address the complete b o l l o c k s above, but I will play along a bit.  If you are in the middle of the Atlantic your only reference is the water, how do you tell the difference between the two scenarios?

Things mariners have been doing down the ages, sun, time of day, stars, moon, it is always important to be able to reference the ground over which you are travelling, but as I said back there to make your argument for you, if you were teleported into that spot instantly in time, with no previous course reference or sense of direction onto a body of water, it would be difficult at first to tell wether the airflow was wind or current driven , but that never happens and it wouldn't take too long to work out even with just a watch.
Sailors develop a sense for tidal ebb and flow and use it to advantage, if you sailed in a tidal environment all your life it would become second nature, in the same way inland guys develop a second nature for gusts and shifts, tidal sailors get it for water, if there is any airflow you can read where the tide is strongest or weakest just by the look of the surface water, just as river sailors know where there are reverse eddys, reef surf and windsurfers read rip tides and back eddies to help them up wnd for their next wave ride.

Folk have been known to drift out on a sailboard using the rip, in no wind, then pumping onto a wave and ripping along it just using the tide generated airflow.

Don't fall into the trap of believing those two hacks, they're wrong on this one.

Edited by iGRF - 30 Mar 13 at 5:14pm