Keel Types
Posted: Fri Jun 17, 2005 11:54 am
Hi Al
By 'wing' , I assume you actually mean 'twin' - often wrongly called 'bilge'
I would expect a 'wing' keel to be a modern developement - a fin with a horizontal wing on the bottom. This adds mass at the lowest, most effective position to improve righting moment in the same way as a bulb. The wing also makes the water flow across the keel more efficient by preventing spill around the bottom. An efficient keel reduces leeway.
'Twin' keeels are primarily used to allow the boat to take the ground without any complicated devices to stop it falling over. By splitting the weight into two keels, they can be made shallower. 'Twin' keels are considered less efficient than fin, but that is only because they are usually shallower. A twin keel of the same draught a fin could actually be more efficient.
Twin keels which are bolted on, as opposed to moulded into the hull, can be splayed outwards, can be toeded in, and can be asymetrical. Splayed keels mean that when the boat is heeled, the leeward keel is vertical, increasing and maximising the draught. Toed in keels reduce leeway. Asymetrical keels give more lift to reduce leeway.
Twin keels will initially be more tender as the weight of the two keels balance each other out, until the boat heels so that the leeward keel is vertical.
As with other things in life, its 'horses for courses' - it all depends on where you intend to sail - whether the boat is small enough to trail - whether you intend keeping her on the hard at home during the winter, etc.
Despite what I've said above, unless other considerations took a higher precedence, from a sailing point of view I would pick a fin.
Regards
Ash
PS I started sailing on a 17' twin keeled Leisure 17, and now sail a 27' long keeled Vega.
By 'wing' , I assume you actually mean 'twin' - often wrongly called 'bilge'
I would expect a 'wing' keel to be a modern developement - a fin with a horizontal wing on the bottom. This adds mass at the lowest, most effective position to improve righting moment in the same way as a bulb. The wing also makes the water flow across the keel more efficient by preventing spill around the bottom. An efficient keel reduces leeway.
'Twin' keeels are primarily used to allow the boat to take the ground without any complicated devices to stop it falling over. By splitting the weight into two keels, they can be made shallower. 'Twin' keels are considered less efficient than fin, but that is only because they are usually shallower. A twin keel of the same draught a fin could actually be more efficient.
Twin keels which are bolted on, as opposed to moulded into the hull, can be splayed outwards, can be toeded in, and can be asymetrical. Splayed keels mean that when the boat is heeled, the leeward keel is vertical, increasing and maximising the draught. Toed in keels reduce leeway. Asymetrical keels give more lift to reduce leeway.
Twin keels will initially be more tender as the weight of the two keels balance each other out, until the boat heels so that the leeward keel is vertical.
As with other things in life, its 'horses for courses' - it all depends on where you intend to sail - whether the boat is small enough to trail - whether you intend keeping her on the hard at home during the winter, etc.
Despite what I've said above, unless other considerations took a higher precedence, from a sailing point of view I would pick a fin.
Regards
Ash
PS I started sailing on a 17' twin keeled Leisure 17, and now sail a 27' long keeled Vega.