What are the advantages of sheeting the jib inboard or outboard of its normal position? Upwind /downwind? The reason I ask is I’m planning a self tacking track, no boom, and I could extend it past the present position outboard or could add controls to the car to move it inboard. Seems it might have possibilities, but is it worth it?
jib sheet in/outboard advantage
- Thread starter Quoddy
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There's a lot involved for this answer but I'll take a swing:
Sheet inboard for better pointing but your driving groove will be narrow and you not have power for waves when sheeted in all the way.
Sheet outboard for better power but you will not be able to drive upwind as well. There will be better sail shape for close reaching.
Now the buts: Your sail should be cut for the sheeting angle - more flat for the narrow angle. If your boat isn't a good upwind boat sheeting the jib closer will not make it one.
The best solution is to be able to move the clew forward and back and in and out.
Others?
Sheet inboard for better pointing but your driving groove will be narrow and you not have power for waves when sheeted in all the way.
Sheet outboard for better power but you will not be able to drive upwind as well. There will be better sail shape for close reaching.
Now the buts: Your sail should be cut for the sheeting angle - more flat for the narrow angle. If your boat isn't a good upwind boat sheeting the jib closer will not make it one.
The best solution is to be able to move the clew forward and back and in and out.
Others?
A lot will depend on the current 'shape' of your mainsail. 'Cruising cut' sails usually have a forgiving 'rounded' luff-entry shape, racing cut sails will have a flattish cut luff-entry shape requiring precise helmsmanship. The relative flat or rounded shape will determine how close the jibs leech can be operating to the 'point of maximum draft' in the mainsail - for 'sail interaction'. Bringing the jib leech closer to the main will also require that your mainsail's outhaul be strained somewhat tighter to lessen the amount of draft.
Before you go to all the trouble and expense of permanently setting up such an 'inboard' jib sheeting arrangement, I would suggest you do some trials with a 'barber hauler' system - an independent auxiliary jib lead system that can 'pull in' the jib clew along the horizontal plane. Experimenting with different barber hauler positions will establish the best attack angle (the angle between the jib's tack and clew line from the boats center line, AND the 'slot open' distance); but, this is all dependent on how fast the wind is blowing - the slot opens with 'more' wind velocity and closes with 'less' wind velocity -- and 'it will be different every day'.
Such a set-up and to arrive at full optimum (for varying wind/wave conditions), starts with a comprehensive and exhaustive 'program' of data collection (of settings) while using a FULL set of tell tales to arrive at the 'best' slot open distance, including incremental sail 'shaping' exercises. To do this, Id recommend starting with www.arvelgentry.com ---> magazine articles ---> (in sequence) Checking Trim on the Wind, Achieving Proper Balance, Sailing to Windward, Are You at Optimum Trim? .... the 'mechanics' of using a barber hauler and the expected reaction of barber-hauling on the tell tales is found in the "optimum trim" article. The Arvel Gentry articles deal with 'trim' and little to do with sail 'shaping' (it assumes you already know how to 'shape' sails).
The data set that you accumulate (slot distance vs.: wind speed, boat speed, heel angle, VMG, amount of draft, position of Max. draft, etc.) will determine 'how much' the clew can come "IN" and with what 'angle of attack' for the jib. Plus, you really have to start with a perfectly 'raised' mainsail, as described in: http://forums.sbo.sailboatowners.com/showthread.php?t=120970 ; plus, near perfect rig tension to match 'each' days sailing conditions: http://www.ftp.tognews.com/GoogleFiles/Matching Luff Hollow.pdf
The 'con' of all this is if you dont already have a suit of well cut 'racing' sails with relatively 'flat' luff-entry shape, those angles that you set for the hardware will be quite different when you do use 'racing cut' sails.
The second 'con' of all this is holding the jib leech in proper close position to the main will require immense concentration and precise steering by the helmsman ... and your boat will no longer be 'forgiving' and you will have to be constantly 'on' the helm. This is why for 'cruising boats' with plain vanilla sails, the tack-clew/fairlead angle of the jib is always set between 10-12° offset from the boat's centerline.
;-)
Before you go to all the trouble and expense of permanently setting up such an 'inboard' jib sheeting arrangement, I would suggest you do some trials with a 'barber hauler' system - an independent auxiliary jib lead system that can 'pull in' the jib clew along the horizontal plane. Experimenting with different barber hauler positions will establish the best attack angle (the angle between the jib's tack and clew line from the boats center line, AND the 'slot open' distance); but, this is all dependent on how fast the wind is blowing - the slot opens with 'more' wind velocity and closes with 'less' wind velocity -- and 'it will be different every day'.
Such a set-up and to arrive at full optimum (for varying wind/wave conditions), starts with a comprehensive and exhaustive 'program' of data collection (of settings) while using a FULL set of tell tales to arrive at the 'best' slot open distance, including incremental sail 'shaping' exercises. To do this, Id recommend starting with www.arvelgentry.com ---> magazine articles ---> (in sequence) Checking Trim on the Wind, Achieving Proper Balance, Sailing to Windward, Are You at Optimum Trim? .... the 'mechanics' of using a barber hauler and the expected reaction of barber-hauling on the tell tales is found in the "optimum trim" article. The Arvel Gentry articles deal with 'trim' and little to do with sail 'shaping' (it assumes you already know how to 'shape' sails).
The data set that you accumulate (slot distance vs.: wind speed, boat speed, heel angle, VMG, amount of draft, position of Max. draft, etc.) will determine 'how much' the clew can come "IN" and with what 'angle of attack' for the jib. Plus, you really have to start with a perfectly 'raised' mainsail, as described in: http://forums.sbo.sailboatowners.com/showthread.php?t=120970 ; plus, near perfect rig tension to match 'each' days sailing conditions: http://www.ftp.tognews.com/GoogleFiles/Matching Luff Hollow.pdf
The 'con' of all this is if you dont already have a suit of well cut 'racing' sails with relatively 'flat' luff-entry shape, those angles that you set for the hardware will be quite different when you do use 'racing cut' sails.
The second 'con' of all this is holding the jib leech in proper close position to the main will require immense concentration and precise steering by the helmsman ... and your boat will no longer be 'forgiving' and you will have to be constantly 'on' the helm. This is why for 'cruising boats' with plain vanilla sails, the tack-clew/fairlead angle of the jib is always set between 10-12° offset from the boat's centerline.
;-)
downwind outboard
Thanks for the ideas. Our boat has been characterized as not particularly close winded, 50-60 degrees, so in hauling probably isn’t going to happen. The jib will be 100% so it will self tack. What about moving out past that 10-12 degrees downwind? Any advantage?
Thanks for the ideas. Our boat has been characterized as not particularly close winded, 50-60 degrees, so in hauling probably isn’t going to happen. The jib will be 100% so it will self tack. What about moving out past that 10-12 degrees downwind? Any advantage?
For downwind, resetting the fairlead cars 'forward' is your probable best bet to control the so-called 'twist' of the jib.
For such a boat (and if that jib clew can actually pass in front of the mast when tacking), you might want to consider the addition of a 'hoyt boom' on that jib - self tacking, easy to 'sheet inside', keeps the jib flat and untwisted when going downwind (no need to move the fairlead cars 'forward') ... and best of all: single-line-control. Depending on your current jib dimensions, the hoyt boom may require some sail modifications.
http://www.forespar.com/products/sail-hoyt-jib-boom-system.shtml
For such a boat (and if that jib clew can actually pass in front of the mast when tacking), you might want to consider the addition of a 'hoyt boom' on that jib - self tacking, easy to 'sheet inside', keeps the jib flat and untwisted when going downwind (no need to move the fairlead cars 'forward') ... and best of all: single-line-control. Depending on your current jib dimensions, the hoyt boom may require some sail modifications.
http://www.forespar.com/products/sail-hoyt-jib-boom-system.shtml
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