slow leaning curve in sail design

[lunatic]

These are observations of repeated sailings in various conditions, occassionally matched against a Zuma ( approx same SA, OAL, weight ) of experimental rig on Sunfish hull, see drawing. Surprising what holds up in makeshift prototype. I abandoned labor intensive seam ripper and sewing machine for knife and Barge cement, a commercial shoe repair glue, solvent based contact cement will do, to reshape the sail, often still rigged up to quickly see effect. Looks like hell but even on dirty, salty sail fabric never lost a seam, yet can still be pulled apart for reconfiguration. Rig's stress was enough to bend 2" sch 40 al pipe of lower mast extension at gooseneck and deck. Sprit's 1" light tubing finally broke on last sail of season. Righting waterfilled partial double skin sail in high winds standing on dagger board was quite the stress test for all involved.
After much added luff round and broad seaming aft single skin panel I had a battenless sail capable of going from full bag to flat board with high purchase downhaul, vang and tensioned leech cable. Had little use for bag, dead down wind added stretched frontal area proved best, same even on beam reach, perhaps due more to twist control. Easily out sailed Zuma except upwind. Flattening aft section of battenless sail required high vang and downhaul force resulting in too little draught. This made the rig, unstable enough tolu capsize at rest, a good high wind sailer but demonstrated the need for battens. Glued strips of vinyl house siding around luff onto tapered wood stiffners directly glued to sail fabric. Unfortunately vinyl has little memory and kinked in luff area but sailing showed potential of batten trim by tension.
Sail draught dependent on luff round, broad seaming and mast bend diminishes toward head and tack as seen in photo, losing driving force especially at tack where there is little heeling penalty. I rigged a top edge tapered batten with a fixed tension line from sprit tip to mast head for some camber at top of battenless sail. Capsizing in wind gusts shows need for quick and/or self trim control. If the flat top is supported by battens compression highly loaded fabric in tension increases camber and heel or it must twist off losing drive, in light to moderate air sail will be too flat. Support by sprit allows relaxed fabric for full camber along entire luff length. Tensioned concave leech cable and outward extension of downward swinging spars flattens fabric and battens for less camber, heel and controlling twist to maintain drive in high winds. Whatever gain might be lost in weight, windage and complication aloft ; looking for good arguements sgainst this design before third prototype and warmer weather.
With heavily telltaled sail at considerable heel,leeward and trailing edge telltales stream aft, in field windward ones stream up spanwise except those 6" aft of leading edge which curl up, forwadd and around mast to lee side; increased upwash here? Might account for some of the windward performance even during excessive heel.
All this may not lead to a practical rig but it has been fun and instructive sailing.