Sadly, most used sails are for sale for good reason .... someone replaced it with new because the performance or shape of the old sail is BAD.
First thing when evaluating a used mainsail is the overall condition: Stitching integrity, amount of UV 'burn', integrity of the slugs attachment, .... and more importantly:
A. what are the precise dimensions of the luff & leach (to the nearest 1/8") and how do they stack up to the sail's OEM dimensions --- is the sail stretched out of shape or 'shrunken' out of shape?
Go to a sailmaker's dimension datasource, such as Sailrite Sailplan Database
, and look up the sail's as designed dimensions, then compare with the used sail ACTUAL measured dimensions.
• For a (dacron) boltroped sail (which needs to be 'stretched out' by halyard &/or outhaul to arrive at its 'designed
' shape), add 1" to these MEASURED dimensions for every 10-11ft. of luff or foot length .... this is not checking for 'fit' but to see if the sail is distorted in its shape. measured dimension + (1" for every 11 ft. of luff length) = 'as designed' luff length !!!!!!!!!
• Then carefully look at the condition of the leech, especially between the battens to see if the leech hasnt been stretched out of shape by too aggressive mainsheet tension.
Push each 2 battens apart, then look to see if the area ALONG the leech between the two is relatively 'taught', not 'floppy'.
B. If the boltroped luff (and foot) dimension are LESS than databook (including that 1" for each 10-11 feet of luff/foot length, then the boltrope has probably shrunken with age, and either needs adjustment or replacement. Shrunken boltropes are THE cause of 'baggy' / draft-aft, poorly performing, poor shape mainsails
C. For sails that are NOT boltroped but are TAPE luff, etc., once the sail has 'stretched' much beyond its OEM design length = put in trash container; .... 'boltroped' sails can be 'adjusted' back into shape.
Rx: Before you go to all the trouble of a new/used sail, I suggest you fully evaluate your 'old' mainsail. Most times with woven dacron 'boltroped' sail mal-shape is due to a 'shrunken' boltrope - which causes: FULL draft, draft aft, hooked up leech ... slow boat, boat that heels aggressively, lots of 'weather helm', cranky boat. Go to:How to properly RAISE a woven dacron mainsail - SailboatOwners.com
and follow the directions there for evaluating YOUR current mainsail, HOW TO PROPERLY RAISE (stretchout) a boltroped DACRON sail .... and what to do about it if its radically changed luff, etc. dimensions simply because the boltrope has shrunken and needs to be 'adjusted' or replaced.
cruisers and beginning sailors simply do not know how to raise a boltroped dacron sail .... you have to 'stretch it out' along the luff (and foot if its also 'boltroped') AFTER you raise it.
Boltroped luffs are the most common preferred configuration on dacron mainsails ... and the boltropes SHRINK over time and usually need to be 'adjusted' or 'eased'. A boltrope adjustment by a sailmaker (or DIY) can 'usually' restore the proper shape in an old 'baggy' boltroped dacron mainsail.
hope this helps. ;-)