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post #2 of Old 01-30-2012
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That rig really does not make a lot of sense for a boat like the Mac 26s. When you look at how that rig works, you would want to engineer the boat for that rig from scratch rather than add it after the fact, since, the tripod puts a lot of compression at the rail and stem, which normally only deal with tension, and a huge amount of tension, somewhere forward of the normal mast step, where the boat normally deals with compression.

While there are some theoretical advantages to Lateen sails for reaching, as you might do on the Nile, and the Lateen was one of the first western rigs which could go to windward, they offer few, if any real advantages over your existing rig.

There is a lot of weight and windage to combination of the tripod and with yard (the traditional name for what the call a luff spar) raised. This woud limit your ability to go to windward and would mean more heeling. That kind of windage forward means that the boat would be more likely to kite around on the anchor, heel at the dock and generally behave badly with the sails down. You might be able to lower the yard, but raising and lowering the yard in a breeze would be trickly as you would have this uncontrolled spar whipping back and forth.

Another issue that is true of most lateen rigs is that they do not go to weather well unless you can control the leech of the sail. (more below) In this case, trying to control leech tension would place a huge bending load on the boom, but at least in the prototype the boom does not appear to be shaped for that kind of bending loads. Running and jibing you would have to be careful not to damage the yard and boom on the tripod.

On a lateen rig, in heavy air the leech needs to be controlled in order to go to windward or reduce heeling. In small boats, the sheet creates the necessary tension when beating by working against the halyard. But in smaller boats, since there is no way to control twist when close or beam reaching all you can do is end up hiking hard. That is not a great strategy for a small cruising boat. But with the absense of a vang, it is not clear how you would control the leech. If the deck swivel is adjustible (like a vang) and the boom were stiff enough, it might be possible to play the deck swivel tension and control leech tension. But as mentioned above, looking at the photo's, the boom does not appear to stout enough to act in that manner. The long yard would also make luff tension difficult to maintain as flexure would ease the halyard. A loose luff would allow the camber to move aft in the sail.

I understand that the flying lateen is intended to have in-spar furling, but looking at the rig proportions, it does not appear that it could be reefed in a manner which would result in a good heavy air sail shape and allow proper balance. In conventional sloop rig, you start by reefing the mainsail which helps control weather helm, but at some point you need to also reduce the jib size which keeps the boat balanced. With the rig, as you reef the center of effort is moving forward with no way to keep in in balance. Without being able to move the center of effort aft, the boat is highly likely to develop a lee-helm, which is very dangerous in gusty conditions.


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