Adjustable Outhaul On Mainsail
Posted: January 27th, 2016, 4:02 pm
Why do SC and ARC products not have an adjustable mainsail ourhaul?
Years ago, back in the 70s and early 80s I experimented with adjustable outhauls on the foot of mainsails.
I tried many different rigs. One was a simple adjustable manual rig, lever on the boom actuated system. After several hundred tests sailing against standard boats, no outhaul adjustment, no benefit was found.
Another system was an outhaul system that varied the outhaul position, clew corner, with mainsheet tension. At max or much mainsheet load, the outhaul was in the full outward position. As mainsheet tension was eased for off wind sailing, this eased the outhaul pulling force was overcome by a strong shockcord that pulled the clew corner of the mainsail forward. Again no boatspeed benefit sailing against a standard SC20.
Why these results? Some other brands of beach cat came from the factory with adjustable outhauls.
Well, here we go: As the outhaul on a mainsail is eased, the sail becomes fuller, more camber. This can, according to Aero 101 text book, lead to a higher cift coefficient for the airfoil. Sail thrust is a function of lift coefficient X sail area X wind speed**2. So what's wrong. Well first of all as you ease the outhaul and the leech moves toward the mast, the projected sail are goes down, becomes a smaller number. With no change in boat speed at test, it means the lift coefficient went up about the same percentage as the sail area went down. So it is just an even trade off.
Another possibility is that the sail camber for sailing to windward was also the optimum sail camber for reaching. (I'm talking prespinnaker days.) because at test the boat with the more cambered mainsail went slightly slower that the standard, non adjustable outhaul, boat.
I even went further than this. I made a set of soft fiberglass battens, easily bent. Then I rigged a wire leech line, 1/32" flex cable, that went out and around the end of each batten which extended out beyond the leech of the mainsail at each pocket a couple of inches. I sewed a fishing rod eyelets to the exit of each batten pocket at the top and bottom of each pocket. The wire ran up the leech through the eyelets and out and around the end of each batten. The wire terminated at the head of the sail and on to a little 6 to 1 Holt Allen winch fastened to the boom. By tightening the wire the sail battens were put in more compression against the mast and they bent, bowed, more. This was another way of controlling sail camber with a much greater sail camber variation range. Guess what??? The boat with this fancy sail camber control system at test went slower than the standard non adjustable mainsail boat.
At this point I decided adjustable outhauls on mainsails was not a benefit. Today with spinnakers which keep the mainsail sailing to windward when the boat is sailing off the wind or even downwind, the nonadjustable mainsail outhaul conclusion is even more substantiated.
Years ago, back in the 70s and early 80s I experimented with adjustable outhauls on the foot of mainsails.
I tried many different rigs. One was a simple adjustable manual rig, lever on the boom actuated system. After several hundred tests sailing against standard boats, no outhaul adjustment, no benefit was found.
Another system was an outhaul system that varied the outhaul position, clew corner, with mainsheet tension. At max or much mainsheet load, the outhaul was in the full outward position. As mainsheet tension was eased for off wind sailing, this eased the outhaul pulling force was overcome by a strong shockcord that pulled the clew corner of the mainsail forward. Again no boatspeed benefit sailing against a standard SC20.
Why these results? Some other brands of beach cat came from the factory with adjustable outhauls.
Well, here we go: As the outhaul on a mainsail is eased, the sail becomes fuller, more camber. This can, according to Aero 101 text book, lead to a higher cift coefficient for the airfoil. Sail thrust is a function of lift coefficient X sail area X wind speed**2. So what's wrong. Well first of all as you ease the outhaul and the leech moves toward the mast, the projected sail are goes down, becomes a smaller number. With no change in boat speed at test, it means the lift coefficient went up about the same percentage as the sail area went down. So it is just an even trade off.
Another possibility is that the sail camber for sailing to windward was also the optimum sail camber for reaching. (I'm talking prespinnaker days.) because at test the boat with the more cambered mainsail went slightly slower that the standard, non adjustable outhaul, boat.
I even went further than this. I made a set of soft fiberglass battens, easily bent. Then I rigged a wire leech line, 1/32" flex cable, that went out and around the end of each batten which extended out beyond the leech of the mainsail at each pocket a couple of inches. I sewed a fishing rod eyelets to the exit of each batten pocket at the top and bottom of each pocket. The wire ran up the leech through the eyelets and out and around the end of each batten. The wire terminated at the head of the sail and on to a little 6 to 1 Holt Allen winch fastened to the boom. By tightening the wire the sail battens were put in more compression against the mast and they bent, bowed, more. This was another way of controlling sail camber with a much greater sail camber variation range. Guess what??? The boat with this fancy sail camber control system at test went slower than the standard non adjustable mainsail boat.
At this point I decided adjustable outhauls on mainsails was not a benefit. Today with spinnakers which keep the mainsail sailing to windward when the boat is sailing off the wind or even downwind, the nonadjustable mainsail outhaul conclusion is even more substantiated.