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Old 11-15-2012
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Re: Thoughts on jib sheeting inside the shrouds

Sheeting inside the shrouds 'may' be a good idea for better upwind performance.

Certainly the problem of hanging over the rail and adjusting fairlead cars is easily and economically solved by changing to something like the Garhauer EZ glide adjustable (from the cockpit) genoa car system - Garhauer Marine Hardware -5217233

However bear in mind that several things may adversely occur at the same time when sheeting in overly close:
1. reduction in aerodynamics due to the jib leech operating at 'too close' to the point of maximum draft in the main - and the 'bootstrapping' which enhances both jib AND mainsail aero-performance rapidly falls off.
1a. possibly needing a new / flatter mainsail as in 1 above (so-called backwinding) Typically to bring the jib clew within the 10° tack angle you need 'racing cut' sails - Not a forgiving 'rounded luff' cruising cut sail for the unprecise helmsman; rather, a 'flattish' shape at the luff sections instead of 'rounded' and a 'precise' helmsman.
2. Jib LP interfering with the spreaders, as Faster already stated.

Normally on most boats the jib clew position for 'best upwind' angle of attack will best optimize at a line at 10° offset eminating from the tack of the jib ... running back and across the 'rail' at that offset angle; 12° on boat with 'cruising cut' sails. Any (attack) angle much less than 10° on non-high-end designed boat is usually 'pointless'. Cruising boats usually best optimize between 10-12° jib attack angle, the 12° line favored to compensate for the use of 'forgiving to the helmsman' / unprecise sails.

Before you fully commit to an inner rail, Id recommend that you 'experiment' by using a 'barber hauler' - a line that is lead perpendicularly along the horizon from near amidships to the jib clew and simply 'tied' additionally to the clew ring.
Then do some data collection of various attack angles vs. boat speed with varying 'in' settings on the barber hauler .. or better yet, watch your VMG to a very far waypoint. The boat's VMG will optimize at the 'best' attack angle and important 'slot open distance' for the exact wind and wave conditions at the time.

You will probably have to slightly loosen the main halyard to flatten the 'luff entry' shape a wee bit ... but that creates a more draft aft mainsail shape, so dont 'overdo'. If your mainsail is cut for 'cruising' - a 'rounded' rather than flat luff entry shape you will most probably experience a LOT of so-called backwinding when you do barber haul .... just ignore the backwind, especially if the VMG numbers are getting 'better' as you pull in.

How to barber haul: Set up the boat with the FULL set of tell tales (including steering tales)... once the sail shape is correct and the tales are flying perfect, ignore them except the row of 'steering tales' or 'gentry tufts' about 'head high' and emanating from the jib luff back for a few feet. Begin to pull in the barber hauler while recording and noting VMG (this takes a while and doesnt happen instantly as it takes time for the aerodynamic flow to 'settle in and adjust itself' to changing sail interaction of 'the slot'. The optimum barber haul 'in' setting for the days wind and wave conditions will where the boat 'maximizes' its VMG. You will need to do a lot of data recording, etc. to make this 'work'.
Then once youve determined the best barber haul 'in' setting vs. various wind and wave conditions, then simply install the inside track based on these optimum recorded data numbers.


When questioning so-called backwinding, especially in lighter wind condition when the vectorial sum of the attached flow of airstreams on the windward side of the sail is actually and visibly seen in the tell tales as 'going forward' ... you have to make the 'guess' if what youre seeing is 'actual' aerodynamic flow .... or that youve simply 'closed the slot' to where the 'aerodynamics' are simply decreasing. The way around all this when barber hauling is forget the tell tales (but not the 'steering tell tales) and simply look at the speedo or the VMG and no matter what you 'think' is happening as 'backwinding'.

To help understand what is going on ... the aerodynamic flow CIRCULATES mathematically 'around' a sail/sails (most 'sailing books are simply 'wrong'). The best explanation for the non-technical person in: The Origins of Lift .... and shoots to hell the erroneous concept of 'backwinding', etc. but yet what looks like backwinding will develop when the jib gets too close to the mainsail when barber hauling, etc. Use your speedo or VMG when barber hauling or using an 'inside track' and simply 'ignore' any minor 'backwinding'.

Hope this helps.

Last edited by RichH; 11-15-2012 at 01:42 AM.
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