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Old 23-03-2006, 09:35   #1
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Centerboard Performance

I have read the past discussions on different types of keels, but I would like to hear input on the performance of keel/CB boats such as the Pearson 36 compared to their deep keel versions. I am aware of the maintenance issues, but unsure of the performance tradeoffs. I expect that there would be some performance improvements when motoring or when sailing downwind with the CB up. Would pointing angles be much different? Would the boat be more tender, even though extra ballast is usually present on the CB versions. Any input would be appreciated.
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Old 23-03-2006, 18:22   #2
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Pearson 36-2 has a PHRF of 132. The 36-2 CB has a PHRF of 141.
The Bristol 35.5 w/ fin keel has a PHRF of 150 and our CB model has a PHRF of 156.
The CB version is a little tender, but the boat is easily driven, so we have a 120 jib. Don't need anything bigger.
Sounds like Pearson added more weight. You can figure that out on YachtWorld.
We specifically wanted a 3'9" board up draft for obvious reasons. If you are not going where the water is skinny, keel would be better for a number of reasons. I'll take the 3'9" and reef as needed.

Larry
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Old 23-03-2006, 21:04   #3
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As Lar's suggests, the impact varies a lot, depending on the boat.

Some centerboard boats have nominal differences -- others more significant.

The Pearson "off" the wind probably wouldn't perform much differently. On the wind, you'd notice a great difference --not only because of the keel -- but also because of the relative large foretriangle which is consistent with the design approach for that era boat.

Where you pan on sailing the Pearson?
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Old 24-03-2006, 06:18   #4
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I have a Wauquiez Hood 38 which is a Ted Hood keel/CB design. The boat sails great without using the CB on all points of sail. I find that off the wind and downwind, we have an advantage over some other boats due to less resistance and wetted surface below the waterline. On the wind, the performance is also terrific and we rarely crank the CB down. I find that when I want more windward performance, I can get it with the CB. In that case, the extra drive is worth the greater resistance.

To me, the CB excels in reducing leeward slippage at SLOW speeds (3 knots or less). That is where I tend to use it.

I am not familiar with other K/CB boats and thus cannot comment on how the Pearson would do. I do feel that ...for me...the more shoal draft I get with this K/CB is a big positive with no negatives of the design. The Hood 38's have a 4.5 ft draft....very nice for the ches, down the ICW, all of FL and the islands. SO many more places I can anchor, so many shoaling spots on the ICW I can ignore.

Hope this helps.

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Old 24-03-2006, 21:05   #5
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There are Center board boats and then there are center board designed boats.

Bristol for one, built identical hulls as full keel and centerboard designs. For the C/B boats, they just cut a foot or more off the keel and added a centerboard. Other boats were also designed and built this way like the Tartan 41 and sounds like the Pearson 36. From what I've heard, these hermaphrodite boats tend to be a bit tender in the C/B versions. In the case of the B40, have heard of owners adding up to a 1,000#s of additional lead in the bilge to stiffen the boat. At least one boat, the Tartan 37, was designed as a C/B boat a few were built with deep keels

Since the ballast in a C/B boat is not carried as deeply as in a deep keel boat, they need to be designed differently for optimum performance. A C/B hull should have greater form stability, for instance, to make up for the effect of the higher ballast. That would translate into flatter sections instead of the classic wine glass underwater shape. Or should I say the difference between a red wine and white wine glass.

If I was looking for a centerboarder, think I'd look more seriously at boats like the P35, Hood/Empacher designed Bristols that were strictly C/B boats, Hoods own C/B boats, The Tartan 34 and 37, Allied Seabreeze 35 and XL 42 to name a few. They were designed to be center boarders from the ground up.

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Old 25-03-2006, 06:57   #6
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Good point about which boats were designed from the beginning to be K/CB boats. They should, as a general rule, have greater stability and better performance, than boats that are hybrid designs.

The Bristol 35.5 and 38.8, both Ted Hood designs are examples that I am aware of. The Wauquiez Hood 38 and Bristol 38.8 are sisterships (with the exception of different rudders).

True K/CB boats, designed to be suitable for offshore work tend to have higher ballast to displacement ratio's in order to gain there greater ultimate stability (or higher AVS). The ultimate stability or AVS of the Hood designs are impressive....the price you pay is that the 22,000 lbs displ Hood 38 has 11,000lbs of lead ballast (quite adequately placed as low as possible in the keel). This results in the need for more sail area.

I personally....and can only speak for myself and my own experience...don't mind. I don't find the amount of canvas on the boat daughting in any respect and as noted above, was seeking a boat with more shoal draft. In my own experience, the draft has been a great asset whereas the greater amount of canvas has been no detriment.

And actually [apologies for such advertising] I have found that the boat is very stable and has an incredibly comfortable motion in a seaway.

[again ...apologies for being so long winded...I guess you can tell I just like my boat ]

My best to all

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Old 25-03-2006, 08:16   #7
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The other consideration is that there are also lifting keel designs which are different again. Centerboards are typically not ballast that moves down. They tend to be fairly light and are designed to just add lateral resistance in layman's terms. Other boats the 'lifting keel' itself has significant righting moment.

Reason I point this out is my Moody is more like the latter. The 'board' which is hydraulically controlled weighs roughly 1000 lbs. When I drop in going up wind I can really tell the difference. It makes a bigger difference as the wind increases as the foil really starts to work. We can improve pointing and reduce leeway significantly. OTHO off the wind or motoring when I raise it -- +1/2 knot or more.

FWIW
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Old 25-03-2006, 12:20   #8
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Could you various “movable foil” owners comment on the “rattling” issue on your particular boats?
Thanks,
Gord
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Old 25-03-2006, 13:05   #9
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Gord - non yet for me
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Old 30-03-2006, 18:31   #10
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Not a hermaphrodite. Both would be male with one being retractable. There were 183 35.5's built and the CB version was specifically what they wanted to achieve in addition to the traditional keel option. These were not full keel boats that someone later decided to convert. They did simply cut off the bottom 18" but they were designed, with some compromise, to work well in both configurations. Bristols CBs are known to be initially tender. In small words, this means you can put the rail down. With my 31.1 full keel, we never managed to put the rail under. Very stiff boat. Building one hull was a realistic production decision and a challenging design criteria. You can always call Dieter Empacher in Marblehead at 781-631-5705 and discuss design specifications. Clearly they came up with a design that sails well in both configurations.
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Old 31-03-2006, 08:52   #11
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Gord - no rattling here either.

I have not sailed aboard the Bristol 35.5 but have heard it is a wonderful boat. It is a very similar hull form to the B 38.8 and my Wauquiez Hood 38. Certainly would be an interesting conversation to have with Dieter (even better if in person in Marblehead) but in my experience the notion of "being initially tender" is a highly variable one: different from boat to boat and means different things to different people.

Certainly the Hood/Empacher hull design has a slightly more narrow beam (11'9" vs 12' for many 80's era 38's) to improve speed (to counter the greater displ). The boat should and does have a tendancy to heel more than beamier boats. At about 15* (for the 38) these boats lock in and find their point of stability and they do this rather quickly and very well. After that, it takes a tremendous amount of effort to get to the point of the rail being near the water. I have in fact tried ....purposefully so...to buring the rail. No possible way on my boat. And to be sure, if you are getting to that point...you should have reefed a long time ago.

If you read Olin Stephens chapter in Adlard Coles "Heavy Weather Sailing" (chap 3, I think), you will understand just why these boats have a much greater ultimate stability than many others. The slightly narrow beam plays a role in this. I will not attempt to explain it, since I am no expert, but urge you to read this volume, as well as David Gerr's "The Nature of Boats".

Again, I can only speak for the 38 ft Hood designed K/CB. Other Bristol's and Pearson's that were designed as modified full or fin keelers and then re-modified to accomodate a CB....are a different story.

If you are looking for a K/CB in the 36ft range...my understanding is that there are few if any boats finer than the Bristol 35.5 and I would strongly consider doing whatever it took (financially) to get into that boat. I think it well worth it.

Hope this helps

John
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Old 04-03-2012, 15:26   #12
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Re: centerboard performance

Dear Capt:
I just read your entry on c/b vs keel Bristol 35.5. I might be jumping on such one - the C/B version. I am coming from a Carter 33 that had a deep fin keel and could sail close to the wind from the Race to New York city often in one line, during... calm July !
Would I feel a big difference if I go with the C/B from Bristol vs the keeler? Is it really more tender?
Thank you so very much!
- robert coles -
www.belwoony.com/swan ( the former mistress ... )
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Old 04-03-2012, 16:18   #13
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Re: centerboard performance

So, I'll chime in here.

We've owned our Bristol 35.5 CB for 20 years and had her in calm to post-hurricane weather (45 knots and 10-12 foot seas) and just love her. When puttering round the bay we never put the board down. Off on a cruise and tacking to windward, we will, although it often depends on our timeline.

I would say that it is a more tender boat than a deep keel- putting a reef in can help, but we have enjoyed the ability to sneek into shallow areas where others fear to tread.

While she is not quite as fast as many of the newer boats, my wife and I think she is prettier, and her speed has never embarrassed us.

Like everything else, it is always a trade-off.
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Old 06-03-2012, 04:56   #14
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Re: Centerboard Performance

We have a Tartan 37 tall rig with a center board. I am amazed at the difference it makes beating to weather with the board down. Definitely helps stop leeway slippage through the water.
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Old 06-03-2012, 05:15   #15
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Re: Centerboard Performance

Guess I'll throw in my experience with Tortuga's Lie, a 1977 C/B Tartan 37.
I've had her since 1995 and have sailed her hard through all sorts of snot. She has a ballast/disp. ratio of 48% which makes her stiff to the wind but she can dip a rail if over canvased. She likes to settle in at around 20 degrees of heel and the smile on my face tells it all. With the board down, I can tack through about 85 degrees, with it up, it's more like 95. I really like the keel arrangement on the T-37 with a long fin and a false-skeg that protects the rudder and improves directional stability. The board is of a simple design and easy to repair and you can actually change the pennant while in the water.
Like John Drake above, I find that I don't use the board much at all unless I want to gain as much pointing as possible, but for stability reasons, she sails just fine without. The deep keel version of the T-37 is supposed to be a faster upwind performer, but in the Chesapeake, I'll take the shallow draft any day.
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