Windows in the keel

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I have a boat with a hole in the keel _ a large hole _ put there by the manufacturer who is no longer with us. I remember from my dim and distant past that around the early 1970 s these substantial holes had a reason... can anyone jog my memory? Excusz the typing please _ its a French keyboard.
Many thankz

Brian

Brian
 

burgundyben

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Laser 28

In the late 80's the Laser 28 had a 'tandem winged keel', as you describe, had a big hole in the middle plus wings.

Not really shore of the purpose, or if it worked that well, remember seeing one such keel in Port Hamble which had been removed, so maybe not a great success although Laser 28s still a couple racing in Solent and quite competitive.

Also trendy to have 2 rudders about that time, can broach a Spring 25 and get both out of the water, only did it once mind!



burgundyben, coolest of men, by all I'm called, cool burgundyben.
 

Trevor_swfyc

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Sorry to hear the manufacturers is no longer with us, hope he didn't fall down one of his large holes.
Not sure what the large window in your keel is for but its nice to see so many are looking into it!
Maybe when ashore you pass a chain through it to secure your bicycle or even your ladder for getting aboard.
Maybe it was just an attempt to reduce the keel weight (boats displacement) without undue effect on the righting moment of the keel.
On reflection who knows.
Trevor
 

NickHarley

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Was common on Windsurfers

Was a period when it was trendy to put holes/slots in Windsurfing Skegs.
Supposed to change water turbulance pattern & improve 'grip' on the water, preventing something called 'spin out' - suddenly loosing all sideways resistance & crabbing sideways.
May be something along the same lines, although think it only made a difference when planning at high speeds!
 

castaway

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I SEE THAT THE GENERAL CONSENSUS IS THAT YOU HAVE GOT A TANDEM KEEL BUT WHEN I FIRST READ YOUR POST I WONDERED IF YOU WERE REFERING TO A BALLAST TRIMING HOLE? TYPICALLY THESE WERE LARGISH HOLES CAST INTO THE BALLAST KEEL AND FILLED WITH A LIGHT FILLER. IF YOU FOUND THAT YR BOAT WAS UP/DOWN BY THE BOWS/STERN YOU COUNLD FILL THESE WITH LEAD.

NICK
 
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Hmmm. I'm not sure exactly what you mean by a window in the keel. If you mean a window through the hull, perhaps this was a genuine, Bill Gates style market fix to force you to buy a needless high power pump as a very expensive "optional extra". I suspect, however, that you mean a hole in the keel mid chord when you look at it from on the beam. This was a cunning plan (still in use occasionally), that can work in certain circumstances, to improve keel flow. It's (as some people have previously pointed out), called a tandem keel. The idea is, without boring you to death with physics, formulae etc etc, that two smaller foils are more efficient in terms of how they create drag that one large foil (think of a biplane!). It's all to do with lift and drag loading per unit area, and how that is influenced by shape etc. to produce vortices and flow circulation (as I said, all rather boring). It does work for certain circumstances, but I think it was a bit of a "go faster" style fad for a while for some hull designs. Hope this helps!
 
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