Ah nowt as riddled as the tide, no mistress as fickle as the wind!
I have been lucky I feel to sail with three types of boats - winners, losers and those prepared to learn enough to become winners.
Dog boats have their day usually due to huge shifts in weather or carnage in the fleet, but by in large they talk a lot about 'lady luck' not being on their side that day. That really just throws away any notion of actually learning from your mistakes or listening as to why some boats put themselves in a favourable position when it comes most significantly to tide and wind across the race course or at decisive points in a passage (longer distance) race.
Winning boats are very clear about wind and tide. Tide is not just something you see in the middle of a race and ponder about while scratching your head, it is something you need to plan for in advance in coastal waters. Weather is something which is usually pretty well predicted too, but more in terms of the sequence and general type of weather you will get. Often that sequence can run through faster or slower, and in temperate areas of the world such as the UK and US northern seabord, the sun can modify a slight gradient breeze to produce more or less wind than forecast. Wind blowing over several days from the SW in the English Channel for example, will also affect tidal characteristics, enhancing a flood tides approach in speed and timing. In Oslo fjord with its' deep water the same effect with a southerly can completely negate the weaker sides of the tide because this 'top drift' effect is powerful enough to force the ebbing tide under it into deeper water.
So we know roughly what the wind is going to do, and pretty exactly what the tide will be doing from our forecast and almanac. We then check this locally and look for any local variation in tide, and time from the nearest datum point . By checking I mean we go down to the harbour wall and look at what is happening, like our old boy scout days looking at wet sea weed on the beech line and flotsam going in or out on the tide. We can also look on the water for wind against tide, likely to affect a beat of course, and once out we start to look at bouys and stationary objects in the channels or sounds which give away the direction and stregnth of the tide.
A lot of mid to back fleet boats do not set any price on finding out about the tide, seeing it as a minor disruption that all will have to put up with, and possibly following folk on close tacking up the shore once they do notice it being the only concession, in a kind of sheep like way. But remember a 2 knot tide is very significant. To compare to a car journey, it is like a car on a wide country road meeting a cross or head wind of force five relative to their 60mph progress! Even a 1 knt tide with or against you then is significant, especially in one design and even more so in light airs when it can constitute 50% of boat speed at times! An average cruiser racer beating at 6.5 knts had better pay good attention to the tide.
In a team of experienced acers, one man, and not the helm, should be allocated tidal strategy for the day. They should know exactly the local high water times for the day, not just the alamac as an index to somewhere nearby. With the Isle of Wight for example, the Inner solent experiences a 'double high water' effect as the tide rushes first up the west then round and from the eastern approach. The text book tide rises and falls with a velocity profile, or relative speed over time like this 123321, thus building to a max time of flood or ebb and then tailing off until high or low water is reached. However some places are more affected by funnelling effects so ask locals or folk who have done well at these venues or coastal passage races. As mentioned a steady top-drift direction driven by the wind for many days can alter the pattern, negating it completely even. In combination with low pressure this can lead to a far higher high tide at an earlier time than predicted. High pressure established for a long time suppresses flood tide and can render moderate springs to look more like neap tides, or delay high water time during that period. A higher tide level means more volume of water in roughly the same time, or shorter when blown in too, so it can mean that a sailing mid channel is a real big amount of pain only to be taken when you most have to. The guy having coffee at the commodores table with an almanac may well not have seen that this is going to happen early and be a tougher tide to stem than you on the course!
Tidal vectors are then really worth making for the presumed windward marks or windward headlands of the day. Rodney Pattison gives some good introductions to these in his books, and there are more discussions on these in day skipper and yacht master material so I wont go into redrawing diagrams to avoid copyright, you can google 'sailing tidal-vectors- and look them up on youtube. As a rule of thumb when you really have to take the pain of stemming the tide at its worst, ie fastest point, then you want to do that on a tack which is bow right into the tide if is is running generally against you. Lee bowing with tide lifting your bow towards the weather mark on a beat or towards a mark you are reaching or running towards is often seen as a lovely situation. However when on a beat the effect is messing up your wind vector a bit and in those fickle wind conditions it can be better in fact sailing on the other tack with the tide more on your sterrn or quarter. This is because the tide is pushing you into a header, so when you get a 'knock' from a relative wind stop up, it is experienced as far more catastrophic with the sails collapsing and making you feel that the wind has changed radically in direction instead of only having died for a few seconds. A tide on the stern will lift you 'geographically' as in being in a big bucket of water walked by a giant, just as much and will also increase the apparent wind which will help fill your sails during lulls in the day.
It can be very hard to work out the direction of the tide when you are helming or sitting on the rail, it is far better to look at the charts and take bearings mid channel, parallel to the shore as an indication to tidal direction on flood and ebb. When plumbed into your wind direction results from your practice beat to the weathermark (oh yes you will be doing this if you want to improve dear reader!!) you then have a pencilled set of tidal vectors to give the best of the worst so to speak, take the least pain the in the best way, and then capitalise most when going with the tide. At the simplest level this means just staying out of the channel and near the shore when the tide is against you, and the opposite when it is with you, but on a beat or reach a pencilled tidal vector on the chart or race instructions will help you get that extra little polished performance, most notably on the last tack to the weather mark or a reach to a headland.
A great deal of mythology is built around the riddled tide and especially on just how it is riddled up. This is all in fact a matter for science, or at least local knowledge. Usually it relates to the above phenomena with weather of the week to do, and weird stuff like the solent double high water, however the mythology most revered is that of the back eddy! The many possibilities of a fastnet race against a flood tide to landsend and beyond, the passage to Tobermory with the bays and lochs toying with the tide and the infamous Lindesfarne cliff flyer back eddy whcih will put you a day ahead of other sailors me hearties a-harr! It is very true to say that some back eddies are very predictable and occur for the large part of the first half of a flood tide. They are mostly predictable in form from sea charts, being created by deep bays, islands and you may not know, invisible shallow banks and channels which we otherwise pay little attention to, bar a little oh, it's only 5m deep here way out from the coast! Some are very much bigger and this makes them more powerful because of the correolis effect from the earth's rotation. The best know of these is the Gulf Stream which is a constant revolution of sea water in one direction which spews out warm water round the tip of Florida and this then is so powerful that it reaches Scotland and Norway. Another in Norway and Denmark is the anti clockwise tide of the Skagerrakk - the true tide only ever flows in along the Danish coast and out along the south Norwegain coast, at a peak in neaps of about 2.5knts.
Chasing back eddies is not just a matter of getting a few hundred meters of glorious advantage, that may be very short lived. If the end of the eddy places you in more tide or at a very poor tidal wind vector compared to the fleet then the gain may soon be destroyed. In a series of bays though with a tide against you, it pays then to go into the shallow and then come out at the next head land where the eddy will start rather than try and stem the tide on a shorter course out in the channel, sailing clear of the headlands. Vector diagrams will help you decide this. To you make a chord across the bay and have better wind speed and apparent wind driving the sails than deeper in the bay to get to the next back eddy? Or do you go right in and then shoot out on the headland to get the eddy? Often you can persist in shallow water as near as you dare on a headland, on the Tobermory route in the sound of Mull there are several channels between rocks and shelves if you dare, which means you short cut the navigation of the headland and get lifted by the wheel of an ebb tide working in the next bay. On a beat with a tide against you it is very clear at headlands where the back eddy is in effect because there will be suddenly tide against wind, or even the odd standing wave - this is the good place to be! Now when beating you want to make the most progress to windward on the tack which positions the boat best to both use the eddy, and come out of it and scoot into the shallows again. Sometimes you may even end up maxing out your use of an eddy, falling off that ferris wheel, and scuttling on a reach over to shallow water as fast as you can!
A word of caution on the wonder of eddys- some eddy's only 'work' during a certain phase of the tide, most of the 123 first half, then being replaced by a general flood or ebb, while others are more preturbed by weather conditions such as a lot of top drift destroying their effect for yachts, or that they only work during spring tides or only during neap tides. Also the ideal point to exit them is either with their estimated circular / arch centre point abeam, or when if you have been able to tack with the very tip of the tongue. After this you may not just face tide ag'in you but also strange circular tides whcih in light winds on a thin chord keel racing boat, make a mockery of your best intentions to sail towards the beach!
Tidal vectors are useful in decision making on the run as well because you may expect to be making good speed out in the true wind, and with only 1.5knts of tide against you, is VMG not going to be better direct to mark? When planing in a Melges we rarely take any notice of the 2-3 knots tide against us here when we are planing under kite. We pay some attention when beating though. The tide-wind vector diagram will also show you pretty clearly just how bad a spinnaker header you are going to get when the tide is with you, and that in turn reduces the efficiency of the kite running DDW on what looks like a shortest course to the leeward mark. Conversley a tide against you on the nose will fill your spinnaker more and give you a better speed through water (boat speed) which may feel all hunky dory, but boats which have reached off into shallow water or a nice back eddy sail further over the ground but come out far ahead.
Acetates (transparent sheets you can write on with a marker pen) are a really good means of plotting tide over the day for a given race course, or along a given route. Also they are useful to have for tidal wind vector diagrams if you have a proctractor on board or available. Using acetates means you can simply overlay them on the chart you have used as a template for them on certain refernce marks. If races are postponed, or slower than anticiapted, you can then update the next race with a later acetate showing the tidal flow by direction and stregnth. You don't have the luxury of that in dinghy racing really, but you can have some chinagraph notes onto laminates with you. Dinghies have the advantage of being able to sail in the shallowest of waters and often with other fleets around to show them where it is best ot eventually take that inevitable pain to get to the mark with the tide against you.
Allocate a crew to the job, sit with them the night before and discuss the tide for the day ahead in light of the wind forecast. The day on the water is then from the dock onwards a case of comparing reality to predicted and being confident in what is coming next, and where will be best to place your boat to avoid tide against and use tide with you, where you will want to take the necessary pain on which tack, and if there is a better pay off from more wind rather than more/or less tide respectively especially on a run.
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