Originally Posted by phollings
What's the difference between a centerboard
and lifting keel
We are actually a lifting keel
- but can be also classed as a centreboard.
A real centerboard
is a keel that is in a trunk that slids vertically up and down. A lifting keel like ours has a pivot pin in the front of the keel and it lowers on that pivot. There are other variations of this basic theme as well.
The advantage of a lifting keel over centerboard is that substantial weight can be put into a lifting keel so that when down it can lower your center of gravity even further.
Two exceptionally important considerations in a boat of anytype with a "variable keel" are
1. There is no silver bullet in a monohull
that will get you the shallow draft
of a Cat without sacraficing blue water
suitability. The boat will still have draft
- ours for example still pulls 1.4 meters all keels up. This draft
combined with an enormous amount of encapsualted lead in the bilge
keel (the keel that is part of the hull
not the lifting keel) give us exceptional righting moment and a stability angle of vastly greater than the 140degree minimum to prevent us from ever being locked upside down should we have a serious knockdown
2. If you have a lifting keel you must make sure that it is designed so that should you "go beyond 90" the keel will not slam back up into the trunk and potentially cause serious damage and or hole the boat. Many lifting keels are via a strap or wire and are held by gravity. Unless they have a cable that also holds them down or are hydaulically held into place they are not offshore
hope that helps