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post #17 of Old 10-20-2012
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Re: Fin vs bulb vs wing keels

Now comes the interesting possibilities of a wing keel.

One aspect I find intriguing is the possibility that a wing keel is capable of increasing its leway resistance as the boat heels because its effective vertical surface area increases as it heels (as long as the wing is large enough). Neither the bulb nor the fin keel provide this benefit. Rather both the fin and bulb keels reduce their vertical surface as the boat heels. This increase in leway resistance can be quite dramatic for a wing keel designed to optimize this effect. The wing must be a resonable size. Also, as stated, the dynamic effects of water at the root of the keel.

The next aspect I find intriguing is that the wing keel is the only keel of the three that actually creates damping in the vertical direction. Furthermore, it can damp in the rising motion of the boat! This damping could be advantageous in reducing the dynamic motions of sailboats. Obviously, the hull creates damping as the hull falls, but the wing (unlike the hull) additionally provides damping as the hull rises.

The third aspect of the keels is damping to rolling. The wing keel also provides damping benefit to rolling due to its overall surface area and flow resistance at the root. The bulb keel provides no damping benefit from the bulb design, only due to the vertical area. The fin keel provides more damping benefit to rolling than the wing keel only if it is deeper.

I have a wing keel as I want shallow water capability. In the numerous times I have grounded, I have not ever needed to be pulled off, nor have I required a kedge. One interesting advantage, is that my wing keel increases draft as the boat heels (to a point). The result is that I suspect I am less likely to sail onto a shallow without my keel hitting. And when it hits, the large frontal area does not allow the wing to travel much into the shallow. These two effects, I suspect may make it less likely to get heavily grounded.

However, I appeciate the viewpoint of the wing acting as a disadvantage on a heavy grounding.

Last edited by BryceGTX; 10-20-2012 at 07:57 PM.
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