Leeboard size

O

Okeydokey

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I am looking to build two swinging leeboards to go on a 16ft rowing boat which is soon to enjoy a cat-ketch rig. Does anyone have a ratio to sail area or beam, LOA or similar ratio that could guide me as to their optimum size?

The boat will be sailing in the shoal waters in and around Poole bay, so wide is good, long not so good.

Many thanks
 
How long is a piece of string? The leeboard (ie keel) would be something like twice the area of the rudder. A deeper leeboard will be more efficient with higher aspect ratio. That means less end effect eddies so less drag more lift. However just like fixed keels on KBs a shallow draft long keel can work Ok albeit not good for racing against deep fin keels. Especially to windward. So your requirement for shallow draft may be the deciding factor. If you want really shallow draft why not something like bilge keels while if they are to swing up and back perhaps you can work with deeper lleboards. It is all a compromise. good luck olewill
 
I remember a long, long time ago sailing an ex parks department rowing boat (on a gravel pit) , complete with stern 'settee' seat and added lee boards. The main problem with it was trying to keep it as upright as possible because of the super low freeboard. Heel more than a few degrees and it would ship water and sink.
 
Thanks guys, I think I found what I was looking for. About 4% of sail area seems the common view. Won't be racing in this but will end up tight on the shoals (is the forecast). alahol2, that is about where the project is headed... ex-parks department rowing boat, but only for the fairest weather outings in the bay!
 
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