LEE BOW EFFECT

Big fleet racer then.

Somebody must have covered it all, start lines, gate starts, tidal timing, tidal bends v wind bends, obviously lee bow has been heavily debunked wrongly imv but debunked just the same, which suggests no-one has done the definitive article.

I'm wondering if this has got to do with Sydney Harbour syndrome, like a lot of recent dinghy accepted theory according to the Lord Bethwaite, complete tosh and our incredibly rich heritage from past names (where most of my knowledge initially came from) has been lost in a mire of skiff-spin. (Fast planing hulls pay a lot less heed to tide than slow displacement craft, it has a much lessor effect, it has an effect but I imagine is a lot more difficult to spot and or take advantage of. A planing hull will see a body of water as exactly that, it doesn't make that much difference wether the body of water is moving toward or away.

Now I bet foilers however have to take a bit more note, not that I've ever sailed one, but foils are in the body of water rather than skipping over it.. Formula windsurfing Sailors never really have to consider tide anything like longboard displacement riders.

It's a fascinating study.

The rules of thumb are straightforward. As always, the devil is in the details....

1) If the tide is with the wind - e.g, a northerly wind and a tide setting south, then you want to be in the weakest tide when beating, and the strongest tide when running. The tide is effectively decreasing the true wind (relative to ground wind. )

2) If the tide and wind are at 180 degrees - e.g. a northerly wind and a tide setting north, then it's the strongest tide when beating, and the weakest tide when running. The tide is increasing true wind relative to ground wind. 

3) If the tide is at 90 degrees to the wind, then the true wind will be shifted relative to the ground wind. E.g. a northerly wind, and a tide setting west gives a left shift to the true wind. So you're lifted on port, and knocked on starboard (relative to ground wind). If the tide is even across the course, then what you "gain" on the lift you "lose" on the header, so it all evens out. If, however, the tide isn't even across the course, then you may be able to sail on one tack with a greater tidal lift, and not get knocked so much on the other tack by sailing in less tide. You've gained on the swings, but aren't losing on the roundabouts. 

4) If the tide is at some other angle to the wind, then there will be a combination of the above factors - a wind shift, and a strengthening or weakening relative to ground wind. As to whether it's worth sailing in stronger tide - where the true wind is more shifted relative to ground wind, or weaker tide, well, it all depends on the boat & the relative velocities of wind and tide. 

5) Sailing with the tide on the lee side is sailing on the lifted tack (upwind). Downwind, sailing with the tide on the windward side is sailing on the knocked gybe. As has been said, if the tide is even across the course, then (in tidal terms) it makes no odds. However, if the tide isn't even across the course (or the leg is long enough such that tide will turn - the classic example is crossing the channel, where you start with the tide on the lee side (the lifted tack), then tack when the tide turns and lifts the other tack), then you can look for the opportunities to maximise the tidal lifts and minimise the tidal headers. 

6) There's a fair degree of misunderstanding about start lines - lots of talk about starting at the uptide end. If the start line is so long such that the ends are outside the layline(s) (not forgetting that tide shifts the laylines relative to the ground wind) for the first mark, then obviously you want to start at the end that lets you lay the mark. If, however, it's a true beat - and the RC have placed the windward mark downtide, then it's back to starting at the windward end (ceteris paribus). 

The second is the angle of apparent wind is slightly different, due to the component parts when the wind is up - think about it. Fast planers sail shallow angles, don't really present a true 'lee bow' in fact most have no bow at all in the water..

Foils? I know nothing but would love someone to explain, they're travelling fast but not planing, then thinking about it dinghies don't really plane in the same way boards plane, since for the most part the faster boats still run with a fixed daggerboard, so I guess not so much different from a foiler, i wonder if anyone has ever run the numbers..

Interesting shift in position presuming ED all very well repeating all that, it's what everybody knows, the trick is also to spot the anomalies, a magic carpet that's running faster in the middle of say a beat at Whitby where the channel is deeper, how do you know this when you turned up and it was dark and the locals are not going to tell you..

The answer is the wave shape, and how to look for it.

 Then wave speed(s), are they fast waves or slow waves, is the tide slowing the wave, what is the wave length in relation to your waterline length, what does it mean and why..

Then there are Eddys, caused by breakwaters or sandbars, inshore that at first glance might be favourable but can sometimes screw up those who would creep up the coast and other times when they don't.

It's almost an entire book, certainly more than a chapter.

And you know what I'm wondering, after posting what is it now nearly 8 years on this and other yottie forums, how come it hasn't really even been discussed other than to bullsh*t the lee bow theory by muppetry?