40ft Daggerboard yacht?

Discussion in 'Boat Design' started by GBR4423, May 7, 2016.

  1. GBR4423
    Joined: May 2015
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    GBR4423 New Member

    Has anyone seen a light-ish displacement design around 40' long with a dagger board with a bulb.
    Twin skeg hung rudders.
    Would draw about 3mt with board down and 1.5m with it up.
    Can dry out on the bulb and rudder skegs?
     
  2. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Sounds a lot like a Pogo 40 but they use a swing keel not daggerboard


    Are you looking for suggestions or a specific boat?
     
  3. GBR4423
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    GBR4423 New Member

    The pogo gets close but as you say not designed to take the ground and would much prefer a dagger with a bulb.

    Its a boat I've been after for years,
    The three options are to find a boat that ticks the boxes,
    Modify a current boat that gets close,
    or build a new one.
     
  4. Stumble
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    Stumble Senior Member

    I am pretty sure the pogo is meant to rest on the keel when drying out but I would check with structures before doing it.
     
  5. Tanton
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    Tanton Senior Member

    A compromise.
    Daggerboard for beaching.
    Daggerboard + Bulb for Offshoring.
     

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  6. pogo
    Joined: Mar 2010
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    pogo ingenious dilletante

    I don't understand it.
    A daggerboard has no ballast (for RM) , it's simply a board that can be lifted.
    A " daggerboard " with ballast ( bulb) is a lifting keel.
    Both are for shallow waters , or drying out when lifted.
    Where is the "compromise" in the design above ?

    Either you go for a daggerbord/centerbooard with bilge ballast,
    or a liftkeel/ integral swing keel in a centerboard case.

    Actually one can also buy " in- betweens" or hybrids with heavy iron cast bottoms of about 80 percent of ballast and centerbooards with up to 20 percent ballast and down to zero ballastv
    See Southerlies Kelts and Dufours DI ( DI means Deriveur Integral --non - ballasted centerboards, ballast in bilge) and all those Ovnis.

    nearly all these boats have single rudders , centerboard rudders, protected by a skeg --shaft drive.

    There ain't no double rudders under those boats.
    Why ?
    when heeled , and the the centeboard/lifting kee iis up, the leeward rudder is the most vulnerable part, because it drafts more than the hull.
    here we go. most centerboarders and lifkeelers are designed for drying out only.
    alll those french stub-keelers with non-ballasted centeboards and double rudders are for drying out only. too oftenthose boats are titulated as " liftkeelers".

    a real liftkeeler (with or without bulb) , and a real swingkeeler has all the ballast in the fin . those boats either have long skeg protected centerboard-rudders ( fixed part and pivoting part) , or transom hung dagger rudders/pivoting rudders.

    there are only very few real liftkeelers and centerboarders with non -skegged double rudders.
    Again, non- skegged rudder are vulnerable. the whole hull design must be mube designed that those spade rudders ( of thos beamy ULDBs) never go deeper than the hull. Never !

    No one needs those boats.No one needs a a shallow draft, bullet proof Modern , beamy , fast, offshore capable ULDB.
    A i have written before, all those Pogos , Malangos, Djangos are for deep waters and occasionally drying out. always with bequilles ( these legs mounted on the rails - actually i don' remember the english word)

    In northern europe there are very few designers who have some of those " passepartouts in their portfolios.
    Those boats evolved from the dutch waddenzee , or german Watttenmeer.
    Dick Zaal is one of them.
    My favourite boat , a bullet prroof 40 footer of 7 tons with a draft of only 70 cm , is a rutenberg design.
    this boat is fast , can cope wind against current very good, she' s a performance cruiser for an owner who knows why.


    http://www.dickzaalyachtdesign.nl/yachts/moreinfo/?id=4659

    http://www.boat.com.pl/ruttenberg.htm


    A real bullet proof ( shallow draft , beamy, planable and sexy) ULDB ( say 40' and 4 to tons) with twin rudders is in my opinion impossible.
    Go for a compromise in weight., a fast one-off from a dutch or german designer for waddenzee/offshore boats.



    pogo




    P. S.
    Sorry for my bad english. It' s very late, ( two a clock in the morning , tide to catch gonna be tomorrow afternoon and im very thirsty. greetings from Spiekeroog, Wattenmeer , germany)
     
  7. GBR4423
    Joined: May 2015
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    GBR4423 New Member

    I like the daggerboard over the centerboard or swing for a number of reasons.

    On a 40' yacht, especially a wide one, the daggerboard case can reach from the bilge to the roof without causing too much inconvenience and would also serve to stiffen the hull deck and in turn the dagger case.

    A modern dagger design need not be wider than 700mm fore and aft, giving a case od size of something like 1m by .25m

    Given the rudders would preferably skeg hung and around 1.2m deep the keel buld would need to lift to a depth of around .5m below the hull.

    If internal headroom was 2m my guess is you could have a max draft of about 2.2mt

    Add a 1000kg lead bulb which would provide significant righting moment.
     
  8. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    There are a lot of unjustified assumptions here.

    no way a 40' biat is using just 1000kg of lead.

    Frankly I think you have combined some weird design elements into a boat that doesn't make a lot of sense. You need to start with a fresh sheet of paper and decide what you need, what you want, and let an experienced designer work around that.

    I can't even envision what a boat with these design elements would look like. A retracting keel with skeg rudders is just silly. Why bother retracting the keel if the rudders are fixed, you still can't access shallow water because of the rudders but now they are also exposed.

    You certainly couldn't dry out on a bank because with the keel retracted the rudders are going to push the bow into the mud, and have to handle serious non-compression loads. At most you would want to be able to retract the keel to the same depth as the rudder bottoms, but for that you don't need to go all the way to the cabin top, just a foot or so would do it. At which point, why bother with the complicated mechanism to lift a multi ton keel.

    Adding a keel bulb doesn't add much to this either. If the keel can only lift a few inches, why not just design the boat with a stock fin. It will be stronger, easier to attach, and won't cost much if at all in performance.




    I guess I just can't envision what you are really after, and you have combined design elements that just don't seem to mesh well together. If anything that are at opposite ends of the design spectrum.
     
  9. pogo
    Joined: Mar 2010
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    pogo ingenious dilletante

    Another one who wants to reinvent the wheel---his personal , excentric , rectangular wheel.

    pogo
     
  10. pogo
    Joined: Mar 2010
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    Location: Germany Northsea

    pogo ingenious dilletante

    Greg,
    u got it.








    http://www.cruiser-racer.com/0000000371/Sadler-Barracuda-45







    pogo
     

  11. Tanton
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    Tanton Senior Member

    Pogo.
    The compromise came from me, to offer 2 options towards the owner's goals.
    1).Spending a couple years in shallow waters with the ability to beach the boat. A ballasted aluminum 33' hull with a daggerboard and twin lifting rudders.
    2) then the ability to cross the Pacific in a safer manner by fitting a bulb at the bottom of the daggerboard.
     
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