Ballasted Centerboard?

Discussion in 'Sailboats' started by mcm, Jan 26, 2008.

  1. mcm
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    mcm Senior Member

    I'd like shoal-draft, drawing less than 3', yet in a seaworthy blue-water cruiser.
    Is a ballasted centerboard my best option, and can it be simple and practical on a small 8500lbs.disp., 28' sloop?
    Can a centerboard carry, lift and lower 1600lbs. of ballast?
     
  2. PAR
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    PAR Yacht Designer/Builder

    I'm currently designing a 26' 7" open water sloop for a client with a shoal requirement. Draft is 32", board up, ballast is 2,400 pounds with a 900 pound centerboard. The remaining 1,500 pounds of ballast are in a stub keel, which houses the majority of the board, so much so that it doesn't intrude into the cabin sole, like most board boats. This does increase the minimum draft, which could have been 20", but the interior options, because the case doesn't divide the cabin in two, is such an attractive argument, that the extra draft isn't as much of a bother to the client.

    So yes, you can have a ballasted centerboard, but you'll have design limitations, with the volume the board can comfortably contain and still providing a reasonable foil section. Most find it necessary to divide the ballast into fixed and board mounted. My solution uses 37% of the total ballast in the board, which isn't unusual.

    Ballasted boards do expose some interesting design and engineering issues, but not insurmountable.

    The design I'm working on is a "in the spirit of" Friendship Sloop, with faithfully reproduced above LWL works, but divided appendages below for some performance gains.
     
  3. mcm
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    mcm Senior Member

    Thanks PAR,

    Where can i find scantlings and construction details for such a ballasted centerboard if the stub-keel, centerboard and case are welded steel plate?

    I'm looking for off-the-shelf, stock-plans for a blue-water, off-shore, yet shoal-draft, centerboard cruiser modified for 3mm[1/8"] steel plate construction, yet still displacing less than 9,000lbs.

    So far all I've come across is the 'Benford 30' in its centerboard configuration.

    Do you have any other suggestions.
     
  4. Pericles
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    Pericles Senior Member

  5. SeaSpark
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    SeaSpark -

    Van de Stadt Vita

    http://www.stadtdesign.com/products/vds409.htm

    Their multi chine steel quick assembly method was developed with the amateur boatbuilder in mind. Plans are not the cheapest but very good for the price and they have a good reputation for after sales assistance in the build.

    http://www.stadtdesign.com/English/history11.htm

    [​IMG]

    Holland has a reputation in steel boat construction as we cut most of the trees in our country (and the surrounding ones) for building wooden boats a long time ago.

    Also contact http://www.dickkoopmans.nl/uk/index.htm he may have something for you.
     
  6. SeaSpark
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    SeaSpark -

    As mentioned in this thread http://www.boatdesign.net/forums/showthread.php?t=20590 28 feet is on the small side for a steel sailboat. Performance will suffer greatly as it is very hard to build steel boat at this size with a low enough displacement compared to its waterline length.

    Can you explain why it is impossible to scale up to 30 or maybe 32ft? It would really make a difference in how your boat will behave.
     
  7. Pericles
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    Pericles Senior Member

    SeaSpark,

    Those were my thoughts as well. Putting it simply, spread the weight of steel steel out to enclose a larger volume and a more successful boat will be the result. Steel construction is best reserved from 50 feet upwards, where its weight is less of a liability.

    http://boatdesign.net/forums/showth...=3&highlight=best size for steel construction

    That said, the Stadt Design yacht you posted looks quite useful. Tack and weld rather than stitch and glue:D :D

    Pericles
     
  8. PAR
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    PAR Yacht Designer/Builder

    MCM, your requirements seem specific enough to merit a custom or at least a semi custom design. The design I mentioned above has a steel internal element to the keel and the case. Picture an "I" beam inside a wooden sandwich and a plate steel case attached to the top in the center of the boat. The board also has an armature of steel (as does the rudder) with lead in plate form attached, skinned in fabric.

    Scantlings and construction details will likely have to be purchased. Study plans will provide you a hint of scantlings and no construction details other then general method employed.

    Jay Benford may have other designs that are suitable for your needs as will several others. If you'd like to contact me by email (click on my name) then we could discuss some options.
     
  9. mcm
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    mcm Senior Member

    I'm beginning to think your right, because, even though i have no problem finding great steel designs for small cruisers, only the Benford 30 is shoal-draft with centerboard.

    Benford, however, likes beamy and heavy boats.

    Brent Swain proves that steel doesn't have to be heavy.

    Brent Swain's 26' twin-keel cruiser uses 3mm[1/8"] steel plate and displaces only 6700lbs.

    Maybe i shouldn't worry so much about getting twin-keels stuck in the mud, because, if i remember, Brent's twin-keeler only draws 3'.

    Also, i want a real shallow cockpit, ala' Larry and Lyn Pardee, but instead of their bath-tub/work-table under the cockpit, i would prefer a large sea-bunk under the cockpit.

    And, like the Pardees, no inboard engine; i'll mount an outboard.

    One picture is worth a thousand words, but i lent my scanner out.

    So you're probable right about needing a custom design, but i can't beat Brent Swain's $200 price for his stock-design plans, plus he sells his origami construction book for $50.

    Still, when i get my scanner back, i'll send you my conceptual side-profile, end-view, and interior-layout, and maybe you could give an estimate for custom design plans.

    Ok, i was picturing a welded box-beam for a stub-keel with a plated slot for the centerboard case.

    Pericles, and Sea Spark,

    Thanks for your suggestions, but i've seen and rejected those designs because they are not shoal-draft centerboarders.
     
  10. SeaSpark
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    SeaSpark -

    Attached Files:

  11. SeaSpark
    Joined: Mar 2006
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    SeaSpark -

    I do like the origami method, Brent do you have a website apart of the Yahoo group? i can remember it from a couple of years back but can't find it anymore.

    If you want a true "blue water cruiser" and insist an having an outboard please put it in a well in front of the rudder and not on the transom or it will be worthless on a lee shore.

    Is there a reason you do not want to scale up to 30ft?
     
  12. SeaSpark
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    SeaSpark -

    The sailing characteristics of a steel twin-keeled 26ft boat, even if relatively light, will not be "seaworthy". Imagine outboard failure on a lee shore.

    Most Dutch designers have low draft options in their portfolio. Many of the waters here are shallow, hence the leeboards on classic boats.
     

    Attached Files:

  13. Milan
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    Milan Senior Member

    Do you know Gerd's Yago? http://www.yago-project.com/content/blogcategory/76/58/lang,en/ Why 9.000lbs limit?

    There is "Vita" version with a shallow keel (95 cm) and centerboard: http://www.stadtdesign.com/products/vds409.htm

    I would highly recommend Brent's Swain "origami" building method. Who ever follow this path, aside from plans and book, should buy Alex's DVD's as well. They are excellent, show whole hull, deck, cabin and keels building process in detail.
     
  14. mcm
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    mcm Senior Member

    SeaSpark, my mistake.

    I saw the fin keel on the Vita 30 and did not realize that there was also a centerboard version.

    I'm avoiding heavy displacement for the usual reasons: such as needing a smaller rig to push the boat through the water; easier to maneuver; cheaper to build and cheaper to maintain and operate.
     

  15. mighetto
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    mighetto New Member

    Are we destined to be ruled by a bunch of old white men who are programmed to defend? Lets get this topic into the 21st century. We need only look at Icon, to see that ballasted centerboards are seaworthy. Icon lost the Van Isle 360 only owing to a leg that was canceled.
     
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