brian eiland: Aftmast Ketch Overlay of Fractional Rig Sloop

There is another big plus for a ketch rig on a multihull. The overall center of effort, CE, is lowered by a considerable amount compared to the sloop rig, and particularly the fractional sloop rig. Have a look at the illustrations below, and the illustration I will be providing for a big tri project I was consulting on. The rig heights can be a good 25% lower, and the overturning moments considerably reduced. The overall sail area could even be increased on this lower aspect ratio rig. Besides, too much emphasis has been placed on hi-aspect ratio sailplans that are really only good for windward work. Marchaj, et al, have shown the virtues of low-aspect ratio sails for off-wind sailing.often two times more efficient!! Lets design cruising rigs for cruising sailors ......that rarely want to go out bashing to windward For a moment look at the profile drawing of my rig and picture it as though the mast was standing straight up vertically with its masthead in the same location as mine now is. Contrary to some statements, my forestays are really no longer than a conventional sloop rig, in fact they are likely shorter. And certainly my CE, and thus overturning moment, is lower for an almost identical overall sail area Aft-mast Origination and Justification http://boatdesign.net/forums/showpost.php?p=198605&postcount=98 ******************************** In big gusty conditions going upwind and reaching both the racer and the cruiser can play the steering-up/falling-off routine to limit heel. And they both can play the mainsheet so as to spill wind from the top portion of the mainsail. However in those same conditions I don't believe you will find the pleasure sailor, nor the cruising sailor playing that in and out of the mainsail. Rather I think you would find that sailor reefing down that tall sail so as to not get overpowered by the conditions. But wait a minute, isn't my rig already 'reefed down'?? My mast aft rig on the 65 foot cat is approx 15 feet shorter than the comparible fractional sloop rig of the same sail area on this other 65' foot cat. And the rig on that 65' trimaran is approx 15 feet shorter as well...same sail areas. I would call this quite a reef. Too often in the past the cruising sailor has been asked to bow before this altar of 'hi-aspect-ration-is-the-best' theme that permeates the racing crowds concerned with upwind performance...as though this is some sort of ultimate configuration. I think the cruising sailor will be much happier with the lower aspect ratios that Marchaji found VERY effective for all other points of sailing. My rig seeks to use those lower aspect ratios. http://www.boatdesign.net/forums/sailboats/aftmast-rigs-623-25.html

Posted by: brian eiland - website: http://www.RunningTideYachts.com