{Stus-List} keel reduction

Colin Beckmann alchemist1 at rogers.com
Wed Feb 6 12:29:23 EST 2008


Allen,

As you mention it I do recall that I know someone with a Beneteau 
35S5 that has a wing and it is actually quite fast.  I will take a 
look at it and see how it differs from mine.   I bet it not nearly so 
thick and wide.

Cheers
Colin


At 11:27 AM 2/5/2008, you wrote:
>I don't completely agree that winged keels are slower in all 
>instances.  On Septima, a 1990 Ball designed 30-2, my winglets are 
>really streamlined bulbs mounted 8 inches above the keel bottom.  I 
>have noticed in some venues that my PHRF is less than standard 5'11" 
>draft 30-2s.  We were very successful racing against "faster: larger 
>boats in NJ and informally in LI Sound.
>
>Further,  I raced on 1988 built sister ship that had been draft 
>reduced and supplied with the bulb addition you describe.  This was 
>a necessity in the shallow waters of Albemarle Sound where we sailed 
>at the time. We could not point nearly as well as Septima could and 
>had to really overstand to make a mark.  When both boats were on the 
>blocks side-by-side I struggled to see the difference which caused 
>the other boat's degraded performance.  Perhaps my streamlined 
>winglets, small as they were, provided an end plate effect.  This 
>former Aeronautical Engineer couldn't spot any other difference
>
>Allen Miles
>S/V Septima
>Portsmouth, VA
>
>
>----- Original Message -----
>From: <mailto:alchemist1 at rogers.com>Colin Beckmann
>To: <mailto:cnc-list at cnc-list.com>cnc-list at cnc-list.com
>Sent: 2/3/2008 6:03:20 PM
>Subject: Re: {Stus-List} keel reduction
>
>The only problem with wing keels of the design we see on our C&C's 
>and like boats is that they are slow.  My C&C 38-3 came with a 
>wing.  I did not know it at the time I bought it because it was not 
>a local boat, but it was regularly finishing right beside C&C 34's 
>that were on the same start line.   I brought it to Lake Ontario and 
>it was sometimes being passed up wind by C&C 33-2, C&C 33-1 & 
>C&C34's.   I reduced the wings from a 4' span to a 3' span, and it 
>did marinally better, but it could not come anywhere close to 
>keeping up with a sister ship with the full depth fin.
>
>Last summer I was racing against well sailed C&C 34's  on long 
>distance races.  They consistantly finished right there with me some 
>times ahead of me, even though I often owed them 35 minutes.   These 
>are boats I raced against when I had my 34 and I had no trouble 
>keeping up with them.  My C&C 38 has all new sails, the best 
>equipment, decent crew and yet still could not really pass a C&C 
>34.   This fall I reduced the wings to a 26" span and the boat seems 
>to have become quite a bit faster.  We are way tender and we will 
>have to  reballast almost all of the removed lead into the (deep) 
>sump to try and retrieve the stability, but in my mind, lead wings 
>on a  boat to reduce draft are the wrong way to go, and I would 
>never buy another one.  I think the form just has too much drag from 
>too much wetted surface and too much leading edge.  I would 
>definitely consider a bulb, either a torpedo or the new triangular 
>style that we see on the modern C&C's.
>
>I did see some nice wings on a new modern 8 meter in the Toronto 
>area.  These are long thin bronze, approx 4 ft long each. Pointed 
>down at a 25 to 30 degree angle, flat on top, curved on the bottom 
>like an upside down airplane wing.  When the boat is heeled, they 
>provide pressure on the leeward sided to push the boat to 
>weather.  These wings work...
>
>Colin
>
>At 12:21 PM 2/3/2008, you wrote:
>>I have seen this done at Bayfield Marine Services.  They take a chainsaw
>>and cut-off the keel at the desired depth and then bolt on two half
>>bulbs and fair and paint and you would think that it was designed that way.
>>
>>Basically keel depth gives you upwind performance.  If you look at the
>>Cruising Club of America (CCA) boats designed in the '60's they all had
>>shallow draft in relationship to length or a keel/centreboard
>>configuration.  The C&C designed Corvette31, keel/centreboard, or the
>>C&C Redwing 30 with a draft of 4' 6".  I think C&C may have looked at
>>the Hinckley Bermuda 40 to see what was current in sailboat design at
>>the time.  My opinion anyway.
>>http://www.yachtworld.com/core/listing/boatFullDetails.jsp;jsessionid=agSv0fmmhXQh?boat_id=1567116&ybw=&units=Feet&currency=USD&access=Public&listing_id=38184&url 
>>=
>>
>>In the '70's the draft increased.  The  C&C 35 MK I has a draft of 5'
>>3", my C&C 35 MK II draws 5' 6".  The Viking 33/34 draws 5' 6" and 6'
>>respectively and the C&C 35 MK III has a draft of 6' 6", I think.
>>
>>The winged keel reduces draft and is supposed to make up for loss of
>>upwind performance because of lack of keel depth.
>>
>>A long time ago I read that a boat needs to be able to claw of a lee
>>shore under sail alone.
>>
>>Peter
>>S/V Tangerine
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