Sailboat Keel design

Balance

A cylinder would offer good balance, but would have a few other disadvantages. This is why a scow is well balanced and long thin metre type boats. The trick is to be able to balance a conventional yacht with enough beam for stability and space for living.

I would like to know if there is anyone who really knows about design methods for obtaining a balanced hull.

I cannot find anything at all on Lystergrams. Would welcome any leads you can give.

Ian Ward

 

Balance

Steve,
I am aware that a reliable method has recently been developed for obtaining a balanced hull at all angles of heel and speeds!.

The end result is not only a well balanced hull, but it also has less heeled resistance and requires far less equipment to manage the boat, less power is required for the autopilot and of course it is a pleasure to sail.

As it turns out, the most difficult configurations to balance a very light, wedge shaped hulls with fin keel configuration. It therefore appears that the more conventional style moderate displacement hulls are best suited to producing a well balanced hull.

Unfortunately this style of boat and these properties do not seem to be qualities normally sought in a modern design.

Do you see any real opportunity by using such a design method and any market for balanced hulls?

 

Back to the Beneteau....

I have sailed on a smaller version of this boat that exhibited the same misbehaviour. Minor gusts would have the boat heel and instantly round up. A situation that the (first-time) owner could not cope with. It took a vigilant mainsheet hand to keep the boat on course. This boat was fitted with the optional deep keel.

The imbalance of the hull was a given, however the dramas were triggered by a factory supplied mainsail that was grossly too full at the head. Atrocious would be the only word for the entire package. The main need recutting and a full length top batten fitted.

A trip to the sailmaker seems a little cheaper as a first step than radical keel surgery.

Hans

 

If the boat is rounding up when hit by a gust, then she sounds too tender. That is why she loses speed so quickly when reefed.

The head of the sail, as the guest has said, may need to be flatter, with a little more twist. This way she can get power lower.

To give her a little more inertia to resist rounding up too quickly, put a bit more area into the rudder. Move a little more weight forward of amidships.

Hope this is food for thought. Cheers.

 

I'd endorse the idea that a large, well faired rudder and a new, relatively flat mainsail with the draft well forward would likely solve the problem. If the rudder is not deep and the stern is wide much of the rudder may be lifting out of the water. If making the rudder deeper is not an option try winglets or an endplate on the rudder. If you are willing to lose a little sail area you might try shortening the "E" measurement (the length of the sail along the boom). If the mast is raked aft, can it be repositioned to be more upright? Also consider moving weight aft in the boat. If you have any tanks in the stern try filling them. If you have a lot of chain in the forward chain locker try moving it to the lazzarette.

The discussion of hullform and balance is continued at http://boatdesign.net/forums/showthread.php?threadid=2517&perpage=15&pagenumber=1