During my early years sailing on an old gravel pit, I learned the importance of tacking efficiently. Perhaps it was the 12 tacks to the first mark, using every shift and avoiding the islands that rammed it home. Later when team racing for Aston University's BUSAwinning team, that it became clear that if you could tack well, you were a tactical genius! I think I have probably taught more crews to tack, than I can remember. Team Racing in the Royal Navy with a regular crew meant finding a keen youngster and teaching him/her how to tack, to find that they were back at sea by the time the team work was perfected. To help me and theshell-shocked crew through the difficult settling in period, I found that going back to first principles was the best place to start.
The philosophy of tacking which we would commonly go over would put the basics into perspective. What's amazing is that it works for single handed, double handed and big boats. Watch out, talking to yourself in a single-hander might look a littlestrange!.
Tacking Philosophy: 1st Principle: That the speed of the craft prior to the tack should be converted into distance to windward. Commonly I see people trying to get their boat to the other tack as quickly as possible with no consideration for cheating the wind. 2nd principle: The rudder should follow the turn set up by the weight distribution and movement and the sail trim, rather than induce it. Less rudder action means less speed reduction 3rd Principle: That any acceleration induced by the final pull up should be at the optimum rate to give maximum speed.
These principles are perhaps obvious, but with a little more investigation and application of some basic scientific principles, we can develop the reasons behind why some can tack more efficiently with what seems less effort. I will be breaking down the tack itself into easily determinable key stages: 578 KB
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· The Luff to Head To Wind · The Pump to Windward · The Sail Trim · The Pull Up
At each stage I will be considering angular momentum, apparent wind, the rudder and sail trim. However, I have not limited the discussion to any craft in any breeze condition.Lets take the first part of the tack for example: Since we are not allowed to come out of the tack faster than we go in, there must be a way of gaining a little for our effort somewhere. Commonly we are tacking because of a shift that allows us to sail closer to the ideal direction to the next mark. However, if the tack is notefficient then often we find that it might be as well to carry on to the layline for the mark.The key to the efficiency of the tack is in the first stage.
The luff to head to wind. This part of the tack should not be a push with the rudder. In fact it could be said that the rudder plays no part in the tack at all, but it is probably used to control the rate of turn rather than induce the turn. It can probably be gained the most in this part of the tack. If the boat is at maximum speed prior to the tack, the feel on the rudder should be neutral.
Now to begin our tack, we must not repeat not push the rudder!!!!! So how do we get the boat to begin the tack? Simply over trim the main sheet slightly, under sheet the jib slightly, and if needed, a tiny, repeat tiny bit of leeward heel. The center of effort ofthe sails has moved back behind the hulls pivot point and the boat now will naturally wants to begin to luff to windward. As the boat progressively sails closer and closer to the wind, there are more things to consider: If the helm and crew are not conscious of the balance of the boat, it will begin to heel to windward very soon, which if not corrected, will be trying to send the boat back away from the wind. This would induce the use of more rudder to keep the turn going, due to the naturalshape of the boat trying to turn the boat away from the wind.
Assuming the boat is steady turning to windward, then the boat will experience a continual lift due to the new apparent wind on the bow of the boat, which is the turning wind, see diagram one) This turning lift is often overlooked and is a real helping hand insailing to head to wind.
When finally you get to head to wind, the jib or luff will back.Phase 2 then starts.
If you followed phase 1 correctly, then the boat will still be almost upright, and the crews weight will be further in the boat than the norm for the conditions, and the main should be still in tight
A quick technical thingy we will consider in this phase of the tack is angular momentum. Without going into the physics of it, just think about how an ice dancer speeds up a turn on the spot by pulling his/her arms into her body (or the center of the point of theturn).
The center of this point in a boat when tacking is over your shoulder. If the crew move to the center of the turning point, then the speed of the turn will speed up. However, if the crew move to the centre of the turning point before the boat has began to turn, thennothing happens. This is why we should wait for the boat to start its turning to head to wind before we make our move to the centre of the circle. Thankfully if we have carried out stage 1 of this tack correctly, then the angular momentum part of stage 2 will work even better.Remember the sailors have moved their weight into the boat as the boat headed up. This has actually increased angular momentum, and has stored up loads of the stuff ready for the reduction in stage 2.
Sorry about that bit but here we are back thinking about stage 2 of the tack. Stage 2 begins when the jib backs, or for single-handed sailors, when the first third of the sail backs. I really do mean backs rather than lifts! Now a pump to windward does a numberof things: 1. The angular momentum is reduced and so the boat spins around the sailor. 2. The pump to windward at this stage means that only the main or back 2/3rds of the sail pulls in the pump to windward, which again turns the boat effectively. Note, the mainsail should be in tight at this stage to increase leach tension to help this effect. 3. As there is less sail filling in this part of the turn, the pump to windward is made easier, with less effort by the sailors.
All this adds up to little requirement for the use of the rudder to complete the turn, which is of course the one thing that if used would be a break, slowing the boat down.
Phase 3 is the Move across the boat to pull it back to flat giving it the required acceleration on the new tack.
Now for those of you who are feeling a little vulnerable thinking about the heel to windward and the problems of crossing the boat to get it flat before you fall in, read through this little parable. I heard it first told by Kathy Foster:
One no wind day, Kathy gave a class of youth sailors a little game. The task was to move underneath a table from one side to the other in the quickest time. The only rule was the tabletop had to remain above the legs. Remarkably it did not take the competitiveyoungsters to realise that if they turned the table onto 2 legs, then they could stand up to move under the table rather than craw across which had hurt their knees. Another was sharp enough to see the reason behind the exercise, which was to show them that a heeled boat makes iteasier to move under the boom quickly than a flat boat.
I was never sure if this parable is really true, but the concept is, if the boat is heeled then it saves sore knees and bent backs.
To add extra heel to the boat before the sailors move, the sails should be sheeted in. Commonly I used to say top the crew to sheet in the jib on the new tack before we both crossed the boat together. If the boat is pulled up before both sails are set, then allthat happens is the main is the only one pulling correctly as the jib is simply blown across the boat.
Sheeting in also helps the extra heel in light winds. I you don't sheet in at this stage the boat will naturally come upright too fast with little or no acceleration.
The movement from the leeward part of the boat to the new windward side, will also help the boat heel yet a little more, good old fashioned action and reaction for those of you who remember your physics lessons.
Now the Final Stage: The pulling up, acceleration bit.
Remember, we have the boat has been heeled by the combination of the first pump at the start of the tack, together with the sails trimmed in and the reaction of the crew moving. The rate of the turn of the boat will also be reduced by the crew moving back across the boat, (increasing angular momentum, or ice dancer moving her arms out). This should reduce the requirement for the rudder to stop the rate of turn.
Lets consider the new apparent wind on the sails in the pull up. As you can imagine, the new apparent wind will be a large lift on both sails. Commonly I try to ease the sails slightly to help the new apparent wind work effectively on the sails.
This pull up process has an optimum rate, too long and the boat slips sideways, too short and the boat does not have time to accelerate. The easing of the sails and the movement of the crew regulate the speed of the pull up.
The last and final stage of the tack is the sailing on the tack bit. As the speed reaches maximum, the sails are sheeted in hard to compensate for the increased and slightly headed breeze at the end of the tack. This is due to the velocity header, which isexperienced after the boat is upright.
The crew have often to move back into the boat to prevent it from coming over on top of them, which results in the rudder being used to keep the boat on course. The heavier the rig is, the more the crew have got to move back into the boat to counteract the weightof the rig continuing over to windward.
Take a look at this video clip 465KB
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For those of you who are keen to look - here are some other videos of Europes tacking - each time facing aft to keep the weight forward. The Europe has a long extension and little room to take it forwards without over tacking, and the back decks are so shallowthat if you tack forwards, then water comes in over the deck. Backward facing tacks are used by most of the top girls
Right mouse click to save to disk for playback at your leisure.271 KB
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