RACING SAILS
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KEVLAR / MYLAR FILM BASED SAILS
Durable mainsails for offshore use are best built from taffeta backed kevlar, this also applies to 36 feet upwards heavy genoas, the fronts of these sails can be transparent film on film fabric if required for lightness and ease of handling. It is possible to build an exceptionally light kevlar/carbon sail, but it will have a limited wind range and short life with poor durability, if however the fabric weights are increased by about 10-15 % a considerable life increase can be expected.
mainsails ,a maximum of 2
rows of reef are fitted so the sails load path panel construction is not
compromised by local reefing strains, panel joins near reefs are reinforced for
durability ,because laminate sails hold designed shape in strong winds reef
depths are increased and each reef will cope with a higher wind speed than a
dacron sail.
sail design for laminate sails
taking into consideration the yacht type, displacement, stability and rig height etc a maximum anticipated fabric load is calculated for the leach above the clew and the head, these are the highest loaded areas of the sail. it is vital that the fabric in use does not stretch beyond 1% (the elastic limit of the mylar film) ,so a fabric is chosen that will contain the sail loadings within this limit ,plus a safety margin , the triradial panel layout allows a lighter fabric for the lower loaded front of the sail ,often 3 different types of fabric are used in all. the panel layout is computer generated to align each panel to the local load path out of the corners and up the sail.
because of the low stretch of the laminates ,it is critical to get mast bend and rig characteristics correct so the sail sets to its designed shape ,factors such as leach roach are largely constrained by backstay/mast crane position and the IRC rating rule girths.
modern laminates particularly kevlar are manfactured with a preload on the fibres as they are glued to the films, this means sails from these fabrics can be built right up to or over maximum size knowing with use the sail will not stretch and may even shrink.
a laminate sails reliability is dependent on the reinforcement detailing around batten pockets and reefs etc as well as the right choice of fabric.
RACING SPINNAKERS
Basic racing inventory starts with 0.75oz all purpose, this sail does what it says on the bag , triradial cut with large corner patches which extends the wind range , with larger yachts a heavier narrow headed and flat cut reaching spinnaker is also required.....
This brings us to the 1.50z heavy air sail either full size (fractional rig) or 85-90% masthead rig, this can be asymmetric if this suites the yacht, those with longer spinnaker poles and fractional rig benefit most.
sports boats with bowsprits often improve running speeds with a more symmetric sail with a longer leach but more care is required when reach to reach gybing ,
modern spinnakers require a more forward sheeting block position to give best speed when reaching often a tweaker or floating block does this job , otherwise a block position level with the aft face of the cabin works as a guide (15% forward of stern)
A 0.5oz runner for light/medium airs is also a good addition ,with modern sail construction techniques these can be used running in quite strong winds and are very fast .
with a new range of portable roller furling systems for easy sail handling , code 0 size (half way between genoa and reaching spinnaker area) sails are more popular ,the roller gear has a high strength rope luff that transmits the furling torque up the sail. the code 0 has a necessary straight luff to match the high luff tension required for the roller to operate, (this can impose high compression loads on the mast ).the sail when not in use can be easily stuffed in a sail bag with roller attached.
spinnakers can be supplied with turtles or valise type bags as required,
BLADE
JIBS/ROLLER
BATTENS
The trend towards short overlap or blade size genoas for both racing and cruising has meant a compromise roller furling genoa being used for IRC racing as the only genoa, when roller battens (TM) are fitted a straight open leach can be expected so the performance is near that of the race only non furling sail.
PRESERVING AND EXTENDING THE LIFE OF MYLAR SAILS
With modern high strength fabrics it is usually the sail handling, tacking and abuse from the mast and rigging that deteriorates the sail. So don't : pull a folded sail in deck bag around cockpit or hatch edges. Store sail flat on the cockpit floor so everybody tramples on it.
do not leave sails for extended periods soaking wet especially with rain water as this encourages mildew which breaks down the glue joining the laminates together.
do not Leave runners and checkstay wires unprotected in contact with sail fabric. Leave spreader ends unprotected.
Once a sail fabric has been sharply folded, the sail will always tend to hinge about that point, this repeated flexing delaminates the mylar, this area should be overtaped to stop the hinging.
