A common misconception: the jib/genoa is 'the main driver' of a boat.
Without a well shaped and trimmed MAINSAIL the jib will not be operating in the 'proper upwash' of air that is being forced/stagnated 'forward' on the weather side of the mainsail and is being diverted all the way forward and then crosses the luff of the jib to the lee side .... the mainsail causes MORE wind to flow on the lee side of the jib!!!! So, if it is the combination of jib AND mainsail that does the work
efficiently, and the jib & mainsail are cut/shaped/ and 'timed' to good effect with respect to ONE ANOTHER, you can have the best jib in the world OR the best mainsail in the world and still the 'output' of the combination of the two can be quite 'dismal'.
If you're interested in PHRF racing, even beer can / PHRF racing, get thee to a loft that builds racing sails for the LOCAL fleets. Then tell the sailmaker what estimated percent of your estimated time on the water for both practicing to race and actually racing vs. 'just cruising' ---
where you will be racing; also, you MUST discuss your 'honest' helmsmanship ability. That loft will KNOW the typical wind strengths and sea states and will OPTIMIZE the shape of the sail; and also be able to dial-in your
helmsmanship ability into the design of the computer lofting program all based on the prevailing LOCAL conditions and your (honest) ability on the tiller/wheel. If you don't make this 'clear' to the sailmaker, all you're going to get is a plain vanilla, '
forgiving' (a 'well rounded luff entry shape for wide attack angle - for the typical 'inattentive' helmsman); but, a not very fast cruiser's (beginner's !!!) cut sail. Discuss in GREAT DETAIL the intended usage, your sailing venue,
including your 'aspirations' .... or suffer from owning a 'plain vanilla'.
Materials- If woven dacron and PHRF, then I'd recommend a high quality cloth such as 'high aspect ratio' Marblehead, Contender or Challenge - very stable, very long lasting, and can take a lot of abuse. For sail shape 'adjustability', choose a simple cross-cut; for a more 'firmer' shape with less 'adjustability' choose a radial or semi-radial panel shape.
Other -
1. for racing/cruising consider two full battens at the top and two LONG battens down toward the foot - easier to reef!!
2. for 'gonads to the wall' racing or long distance 'performance' cruising consider to have an
extra length of dacron luff bolt rope arranged and 'stored' (hand stitched) to the headboard so that when the bolt rope eventually shrinks (from hard usage of that mainsail) the loft can just 'clip' the bolt rope stitching at near the head and quickly, easily, and CHEAPLY restore the luff length back to the proper original design luff length. A few $$ once every year or two of hard usage; but only if the bolt rope is 'stored' and all ready to go. Don't do this and .... either LOTS of sail maintenance expense every two years or 'new' mainsail every two or three years of 'hard' sailing. If you do this, then its YOUR responsibility to keep a firm hard copy record of the OEM 'as built' luff length - ask for a copy of the computer design output with all the shape and length benchmarks and have the loft verify the as-built luff length. Sail lofts do not like to do this extra length bolt rope storage onto the headboard; INSIST this to be included in the quote ..... or buy another 'new' mainsail much sooner than later.
Really, if you're going to do Wednesday night beer can races on the Ches. ... usually in 'light' wind, NO-to-very small wave conditions- consider a FLAT/low draft shaped 'lighter weight' mainsail specifically for 0-10kts winds/waves .... then simply get the 'old' mainsail evaluated and 'corrected' (bolt rope length) and returned/rebuilt to 'decent' shape for 'cruiser stuff'. Use either of the two mains as the day's conditions warrant Here's how to evaluate the condition of your old mainsail (use 90° tack angle as your guide) and no matter if the sail was built with an old fashioned 'shortened' luff bolt rope or not:
How to properly RAISE a woven dacron mainsail | SailboatOwners.com Forums
Rx: Marblehead, Contender, Challenge for your woven dacron cloth.