Cutters are VERY different
Sailmakers serve primarily sloop racing as their primary customers Riggers primarily serve sloop racing as their primary customers Cutters simply aren't raced and probably thats the reason for the lack of expertise. VERY little has been written (as least written that makes 'sense') on the sail interaction of 'cutters'. definitions for this discussion: Headstay ... stay that the jib/genoa is attached Forestay .... stay that the staysail (forestaysail) is attached. With respect to cutters, probably the prime item of 'difficulty' which adds to much of the confusion is the headstay/forestay combination and only one backstay. This 'interplay' of forestay/headstay tensions will drive you absolutely nuts especially when flying any headsail larger than a yankee and the resultant genoa SHAPE anomalies that WILL occur. The shape of a headsail (any boat) is dependent on the tension of the foil/stay its attached to. On cutters and because of the TWO headstays, unless the genoa is especially cut at the luff to match the headstay sag you will/may as youve found wind up with some severe shape issues. As stated, unless the sailmaker is VERY familiar with cutters and this critical interplay of tensions with 'double headstays' you can easily get into shaping problems. If you are flying both genoa and staysail it will be impossible to ascertain if the rig tension is incorrect or the cut of the new sail is incorrect. Reduce the rig back to a 'sloop' and do your assay from there..... 1. Totally slack or remove the forestay/staysail and go totally slack or unload on the intermediate stays if you have them. 2. set the rig up like you were sailing a sloop (slack forestay and slack intermediates).... 12-15% headstay, shroud tension, then 20-25%+ backstay tension. (mast prebend, etc. if you know how). With the forestay (forestaysail) totally relaxed, Staysail NOT flying/removed, see if this doesnt RADICALLY change the shape of the genoa, radically improve performance, etc. Here's where Im going with this: That genoa was probably cut by a sailmaker who only (rightly perhaps) knows sloops and doesnt know that on cutters, the headstay 'unloads' when the staysail tensions the forestay OR that if flown without a staysail but with the forestay still loaded the headstay will have only 50% of normal tension in it ........ and the headstay will DRASTICALLY fall off to leeward, have a GREAT curve at the luff, the leech of the GENOA will tighten, the foot will tighten, the midcord of the saill will be EXCEPTIONALLY FULL (cant touch the spreader but the sail is 'fully powered up') ..... draft will go aft in the sail, the boat will heel over, the boat wont point worth a damn and will be a slow pig .... plus you may feel a lot of helm pressure as the boat skids off to leeward, thinking that you have 'weather-helm' but really dont. Then for correction of the 'weather-helm' you might even rake the mast farther aft (a bad thing to do) and that will mmake the effect even worse, etc. When the extreme headstay sag develops, the tigher you grind the genoa winch the WORSE the genoa shape becomes. Off the shelf sails for sloops are normally designed to be applied to (assumed) rigging tension at ~15% of ultimate breaking strength tension .... on a cutter with two 'headstays' and the backstay running at 15% each headstay will only be a 7.5% tension !!! ..... and that 7.5% tension is going to cause severe luff sag in a headsail and will result in some 'gawd-awful' sail shape. The genoa shape and set REALLY depends on rig tension. The genoa performance depends on how well you set/shape the staysail flying underneath the genoa, especially on a beat. How I set up my cutter ... to avoid adverse headstay slack/sag when flying large genoas 1. All stays ..... side, lower shrouds including forestay/backstay set at 12-15%, mast prebend set at 3/4" forward bow for single spreader mast. Then go sail the boat as a sloop and make sure that what you tensioned is keeping the rig in column, etc. 2. Rig the forestay with soft ONLY tension (~5%) .... when sailing with a staysail I want most of the tension to be born by the LUFF (boltrope) of the staysl (if the staysail is on a furler ... youll jam the furler with such high halyard tensions) , I want the staysail halyard to be bar tight so as to produce a very rounded shape to the luff entry of the staysail .... improves upwind performance of both the mainsail (staysail shape reduces mast turbulence, etc.) and aerodynamically 'bootstraps' the genoa. THEN either adjust the intermediate shrouds to be equal in tension to balance the resultant load of forestay AND staysail luff as caused by the luff tension i n the staysail .... or apply tension from the running backstays to support the tension in the forestay/staysail-luff. If you see additional 'curve' develop on the luff of the ***genoa at this time*** meaning that the staysail tension is UNLOADING the headstay tension .... 1. reduce winch tension in the genoa and increase genoa halyard tension ... AND then use a BARBER HAULER and bring the clew in closer to the boat's centerline .... just barberhaul while watching the speedo, haul in until the speed (VMG actually, to be more precise) drops then open an inch or two. This kind of discussion is quite hard to do as there are many thing going on simultaneously ....; the summary is: a staysail will unload the tension in an adjacent headstay and that will cause excessive luff sag in the headsail (jib or genoa). Excess luff sag will cause extreme draft, draft aft, will falsely make the helm feel like it has weather-helm. The 'easy solution' is to sail with your normal headstay/forestay/backstay tensions ... measure the ACTUAL headstay sag as found when sailing in ~15kts .... and get the sailmaker recut the genoa properly to this leading edge shape .... and NOT the typical shape as if the boat was just a sloop !!!!!!! .... or correct the tensions (if you can live with such HIGH backstay tensions) as described above to MATCH the shape of the luff/leading edge of the sail that sailmaker cut .... ask your sailmaker how much "luff hollow" he/she cut into the sail .... then simply MATCH the actual sag with what 'he/she' cut. If your sailmaker did not go out sailing with you in ~15kts and observed the ACTUAL headstay sag.... your new genoa was probably cut for a sloop!!!!! Since cutters dont race and 95% of sailmakers expertise is in sloops ... this is a very innocent and usual outcome when cutting a large genoa for a cutter. On a hard beat and when flying a staysail under a genoa ... set HARD staysl halyard tension to make the staysail luff become 'rounded', max draft position will be well forward and with a FLAT leech/exit shape, ******dont expect the staysail to be 'drawing'********* .... but expect the boats speed to INCREASE and the boat be able to point MUCH higher. Its all aerodynamics and the human eyeball simply cant see 'aerodynamics' and the human brain cannot intuitively 'figure out' whats going on with aerodynamics!!!!!!! (Especiallly since most USA highschool science classes, 'vogue' sailing books, have been offering WRONG info on how sails work since the time of the Wright Brothers .... even the Wright Brothers knew different than the bad info being offered in highschool 'science' classes and sailing books.)
