Yacht mary

Leeboards

mounted port & starboard, these allow the ship to sail straight when the wind direction is from the beam.   The board to the lee side (ie downwind) is lowered to provide sideways drag.   They function similarly to a deep keel or centerboard/daggerboard

Thanks I thought they were for some kind of stableazation alway wondered

no image.

Pretty typical back when on things like sailing barges which operate in shallow water and need a big open hold.

I want to reemmber the term-of-art is "bilge board."

As noted succintly above, they serve the same purpose as a dagger board or centerboard, to increase latteral resistance when sailing upwind.

Hanging the board off the wale means not having to cut into the keel structure for a box or slot for the board, which also leaves the hold clear.

They fell out of favor from several issues.  Like being larger than a center or dagger board of effective size, the complications of the pivot joint, and needing two of the things.  

Being on the lee rail, they could be complicated to work, as well.  Made of wood, they needed two tackles per each, a downhaul as well as an uphhaul.

Eventually, people realised you only needed to trunk a centerboard to just above the water line, and it only needed one tackle when made of metal, or metal clad wood.

Thanks everyone for all the help, very interesting 

With all of the canal commerce, the design was popular with the Dutch. Mary in her turn was patterned on a Dutch design that the English King admired.

Bill

Sailing in canals boggles my sailing mind a bit.

keeping off the bank edges against a contrary wind, just rubs wrong somehow.

Which may well explain the goofy and strange sailing rigs seen on canal boats.

Although favored by the Dutch in past years and no longer in common use, the leeboard has not entirely disappeared. The German owned two masted schoomner, JOHANNA, approaching Hamburg, Germany, still retains a relic of the past with her leeboard.

Photo submitted to Shipspotting.com by Eckhard Dhrbrock.

Happy modeling  Crackers

I also recall a sailing dinghy or two with leeboards like the Sabot.