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Fluid Dynamics
During the 2005 pre-season haul out and upgrades I
decided to reprofile the trailing edge of the keel to
eliminate the singing problem at speed. This
video shows
what happens when a blunt object moves through a fluid
and sets up a resonance.The solution is to change the
profile from a square cut-off to some other profile that
sets up the singing resonance at a higher speed, one
that the boat is unlikely to reach. It turns out that
overkill on this is not a good idea because the trailing
edge profile is important to drag and this is, after
all, a race boat. We do not want to induce drag just to
get rid of a little noise.
I found this on a research website. It shows the
relative amount of noise emitted by various profiles.
Svendsens did the work and were
instructed to profile the keel to the 45 degree rounded
profile except that the chamfer should not go all the
way though the edge, but should leave about 1/8" of
flat. This helps to maintain strength in the edge and
hopefully reduces the affects of drag on the keel that a
full chamfer would cause. The same was done to the
rudder on the other side.
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