Melges 24 gybes are typically the "oversheet, big-ease" approach to gybing. That is to say when through DDW and coming onto the new course, the sheet is strangled in on the New side with the foot of the sail almost stretched flat and the clew way back in the boat, This is also the standard for most J109s/105s last I sailed or saw them. But is the "over sheet, big ease" the best Method in a really fast boat like the M24?
This over-sheeting during the gybe does two jobs:
Firstly something everyone knows, is that this technique drags most of the sail round the forestay. Job 1.
Assys when flat have a lot of dead sail area suddenly to deal with when they are collapsing near the forestay or still flying all be it very squared off. The sail area which was nicely curved out on the last 'reach' is now a hindrance to getting the boat through the gybe. It is in the wrong Place, and risks wrapping round the forestay, going in the water and so on as it collects itself over the bow.
This is in stark contrast to a traditional spinnaker, which needs to be sqaured off DDW, yet is still functioning in any weight of breeze and ready for the New gybe angle.
For the assymetric this techniques is a big drag over the forestay to get all that mid-girth round, until the foot of the sail is brought taught and in effect very over-sheeted at first on the new course angle to the wind after the gybe.
The second, less well known job the over-sheet technique does, or rather antagonising power it negates, is that it breaks the old flow on the assy' by dragging the sail flat and destroying the aerofoil shape on the old gybe in the whole sail, especially the mid to top luff area.
Upwash- Why Gybing an Assy Sucks!
Attached flow is much more prominent on assy spinnakers when manoevring than for upwind foresails. Assy' spinnakers fly longer basically, to a wider range of wind angles.
All types of aerofoil sail configurations generate significant "upwash" areas which train the air infront of the sail as far ahead of the luff as a fifth of the chord length. They are an invisible bubble, and actually an extension of the whole sail-aerofoil system if you like. When sailing upwind, it is quick to change off the old upwash and establish a new one as you follow the wind's direction- you pass head to wind and the wind blows off the old upwash and collapses the aerofoil shape. So taken simply the upwash and aerofoil on a "white sail" is destroyed with ease (by default - head-to-wind does the job each time) and then become re-established as the helmsman reacts on the new upwind course.
Upwind, you can see a kind of index visually for the invisible upwash on boats which do not have a very taught forestay, where the jib luff bows, lifts and bounces in and out from the centre line as the upwash wains and gains with the wind strength and the height the helmsman steers to. It is called 'upwash' because the low pressure bubble extends downwards towards the bow for a foresail, but in fact forewash would be just as good a name. Vertical elements in flow vectors over sails is a little beyond me, but you may like to read up on for example upwash or square top mainsails if you are in winter anorak mode.
On assy's the apparent wind strength and angle is sufficiently different from upwind sailing. The sail can hold its attached flow as the sail is sheeted out, with the upwash training the air in front of it over the sail. In other words the sail is making its own relative wind angle by drawing air in over itself and maintaining its aerofoil shape and power on a proxy of the old course.
Gybing then, sucks! The sail is still flying like a wing moving into still air when you actually want it to just be collapsed.
In order to gybe and invert the sail to its mirror image aerofoil on the other side of the boat after the gybe, this "remnant" flow has to be detached.
The over-sheet achieves this, but at a cost:
There are drawbacks to the over-sheeting technique, which is admittedly good at getting the sail killed and all over on the new side.
On the new course post gybe, the helm often does not know how high to luff and if there can be a poor cooperation with the trimmer. Then this becomes very often, a little vicious circle as steering and sheeting fight one another to get the sail stable and the course right.
A very over-sheeted sail will of course fly on a very high course, so an over enthusiastic helmsman can be seen steering the boat far too high in order to fill the sail. This being of course too high for a good VMG down to the lee mark just because he is trying to fill the sail asap. The helm also risks broaching the boat. Ideally the helm must watch that the clew is eased and forward before easing up on the Wind, and looking at the luff to see if the sail is flying.
Also (I speculate here a little) the oversheeted sail will perhaps start to create it's own premature upwash corresponding the very flat aerofoil shape and begin to fly a little, but become unstable and difficult to judge during the sheet-ou harden up correct-sheeting.
The big ease of a tight assy sail means the sail sometimes loads up suddenly, like a whip cracking! There is a lap-of-the gods second or two as you come out from the gybe then. This often follows with the right stuff for a big old broach, a slow moving boat and a big overload on the assy. The technique only gives a false sense of security as we have found out on the M24.
It has to be said that all this over-sheeting takes time. In a melges 24 especially when sailing in decent waves, every fraction of a second counts when gybing, the faster in, through and out the better.
The clew on an M24 wants to fly naturally a little forward of the mast, so it is dragged back about two meters further than it needs to be in my opinion in the over-sheet method. Also the top third of the sail is dragged through hard against the forestay, which takes a lot of pulling and places considerable stress and abrasion on the sail.
Alternative Gybe Techniques to Over-Sheet -;Big Ease
There are other ways of skinning a cat luckily. I take here the three I at least know, one of which is not very applicable on the m24: All three use the wind in your favour instead of the rather over zealous and literally drawn out affaire of dragging the clew most of the way back to the block on the new side.
1) The Clew Grab Gybe or maybe "Californian Gybe"
" Clew Grab Gybe" For want of a better term, maybe the "Californian gybe" could be coined for this, due to the Melges 32 practicing this, with their massive kite area which would shame many a forty footer racer of yore.
Here the clew of the kite is gybed round the forestay rapidly ( after the fall off and the clew reaches forestay level at DDW point) and the bow man then takes the clew as it reaches the bow again, and "snags" it down. The bowman continues tightening and gathering first the leech as it passes round the headstay assisted by this grab, and then he gathers the foot through, round the forestay.
Here then the collapse of the aerofoil shape is forced from the bottom upwards, and the sail is made into roughly a cylinder over the foredeck and round the forestay, with in the upper third or more as still on the old side as the boat heads up to the new course. A large proportion of the sail though is collapsed and round the forestay before the harden up on the new course.
The boat rounds through the gybe, and the bow man releases the clew when about three-quarters of the luff is round the forestay. The boat is rounding slowly up onto the new course and the kite then blows through at the top and starts to fill. The clew is then trimmed to about average flying position "indexing" it for the right there-abouts when the whole sail fills and flies. They may want to mark the sheets for this "index".
Infact you have probably done a similar gybe already many times, by necessity in very light winds when the kite collapses and needs to be gathered and hauled round in order to prevent fishing net behaviour under the bow.
In an M24 it means the helm has to be careful. There is not going to be any standing on the foredeck, so the bowman is going to be down in the danger zone for a smack from the boom or kicker.
I recommend then that this is a sub planing gybe ie up to12 knts true, and probably from the cockpit in more than 4 knts true. On the big sister, the Melges 32 and boats which are sensible for bow work then it needs to be done on the bow to make it effective, otherwise in effect you are half way between the two techniques above.
2) The Skiff Gybe- Blowin' Through
This is a well known gybe amongst better M24 fleets and operates in higher wind speeds , when you by necessity for this gybe, are flying three sails down wind.
Here there is no real pretentioning of the new sheet, it is simply taken in until it is a little taught as you go into the gybe. The boat is gybed with only a small ease forward on the old angle, and then brought right through the wind rapidly, and hardened up a little.
The kite, as in a mexican drop, collapses onto the jib and then the wind blows it round the forestay and you sheet on as this happens. The jib loads up a little to keep the boat balanced before the kite fills AND of course the jib prevents the kite from wrapping round the forestay as a prerequisite for this gybe.
A very slick gybe , but it needs a clean forestay , ie no piston hanks, open pop fasteners or damage on the tuffluff.
In effect in our M24, we have only used this accidentally-on-purpose so far. This is when we are coming into the leeward mark expecting to be on the last gybe angle in, job is thus hoisted, and we are set up for a take down to leeward upon and after rounding. If we need to gybe tactically or due to the wind, then we let it blow through, and most likely twice as we reposition for the mark. On a bigger boat you could hedge your bets on a mexican "soak and drop" take down, or a new gybe angle given fickle conditions or a crowded mark area.
Useful from 12 knts true, to max wind conditions in the Melges and probably in bigger boats if they remember to hoist a jib. It may be worth hoisting the jib on a J109 just for the gybes!
3) The Outside Tripped Gybe into the last Lee Rounding
Since a melges has a single sheet with a Y splice, then this is not relevant, but for any boat with snap shackles or carabiners on each sheet for the assy' this is a runner.
This gybe is one of those odd in the repertoire which is to be used at the two extremes of sailing with an assy' : just enough to fill and blowing-old-boots.
The kite is rigged for outside gybes. Look this up for your own type of boat. It is best set up though with barber haulers (policemen, in-haulers) so that the clew can be brought inboard, within reach of the bowman. You can use the new side sheet to draw in the clew to the foredeck though.
It is a fast gybe that makes the wind do a lot of the work, and has only a slight modification for light airs vs heavy.
The boat is borne off near DDW, the bowman grabs the clew or uses the new, currently slack sheet to get it Down to them. They then trip the old sheet out of the clew as the boat is still bearing away. The clew whips forward long infront of the forestay with the wind blowing it, then the helm goes through the gybe and the main is brought over. As this happens the trimmer is on the new side and hauls in the sheet.
The benefit here is that the kite keeps drawing and is uninhindered by the old sheet, which adds weight, friction and occaisionally sticks on the worlds best jam cleats, trimmers feet. It is also one less issue for going under the pole and worse, under the bow.
Flow is dettached as the spinnaker becomes first a flat shape then a ragging flag as it passes DDW, the wind doing the work of the "oversheet technique" in getting the sail around the forestay and detaching the old flow over it.
In light airs the main can be force gybed a little earlier to get the kite flowing forward of the forestay out of its' shadow, or the main is held in the middle of the boat through the whole gybe procedure after the boat is first borne off.
This is ideally to be used as the last gybe on the course with a leeward drop necessitated, but with a barber hauler you can reattach the old sheet once it is run round the forestay, however it is likely that the next gybe becoming an inside gybe depending on how it would need to be rigged. On a short A frame boat it should be easy enough to lead the tripped sheet round the luff of the kite and reattach it, and in so doing maintain outside gybes.
Outside gybing is a little un-trendy on boats with bowsprits, but most A frame boats need to do it due to the small gap twixt sail and forestay. Several successful j109s have used it often, suggesting it is fast for a displacement boat at least.
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