securing Ballast

Discussion in 'Boat Design' started by ytquest, Aug 24, 2012.

  1. ytquest
    Joined: Oct 2005
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    Location: Hendersonville,Tn.

    ytquest Junior Member

    I am working on a Bombay 26' center board. After replacing the pig-iron ingots with lead I am not sure what kind of medium to re-secure the lead around the center board trunk. I am not sure if concrete will give me a moisture problem. Any help in this or suggestions for different materials would be appreciated.
     
  2. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    You haven't given us much to work with here. How much of it? All 2500#? a bunch of photos would be nice. Was yours built by Island Packet?
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    In many cases you don't want to "fix" the ballast, but rather hold them down, but have them also removable, so you can adjust trim issues. I'll second Phil's comments and ask how much of the 2,500 pounds is in the board. As a rule, you'll probably fix 50% of the trim ballast, with the remaining left movable, though locked down.
     
  4. ytquest
    Joined: Oct 2005
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    ytquest Junior Member

    Secure Ballast

    Yes it has been awhile since I have logged on! To answer the weight question, I have 2,096 lbs of lead in place where the iron ingots were (encased in a concrete or mortar type medium ). This boat was built before Bombay was sold to Island packet. It is a shoal draft centerboard with fixed ballast. I am hesitant to use concrete because of moisture issues with this medium. What came out of the bilge area was a white chalky (VERY hard) material.
    She has been sailed many times to balance the ballast and behaves great. I have estimated that it would take around 400 lbs of fill to secure the lead in the bilge. It has a floor glassed on top of this to lock down the centerboard trunk to keep it from flexing. Thanks for any suggestions you can give. I will head to the marina and take some pic's this afternoon.
     
  5. ytquest
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    ytquest Junior Member

    Sorry, I did not answer the CB question. Roughly 100 lbs, it was made very light with heavy lamination, no weight on the tip or any of the norm. It also has no lock down in the trunk. (PUZZLING)
     
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    You generally don't lock down a centerboard, which permits it to bounce over bottom strikes or other impacts. Concrete wouldn't harm the ballast or the hull, if you elect to use this to secure the lead. This said, it might be a lot easier to just coat each brick with straight epoxy, then place a layer of these where they need to be, touching each other as they will. Contact areas will bond to each other and the bottoms will bond to the hull, locking them in place. Of course the area they'll live should be cleaned and scuffed up with no finer then 100 grit. If it was me, I'd pour a slightly thickened mixture (milled fibers and silica) over the whole shooting match to further bond them to each other and the hull shell. They could be removed with some effort, but would remain in place under all sailing conditions, including capsize.
     
  7. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    I'll expand a little on PAR's response about the centerboard. The Bombay 26 is a centerboard boat with the ballast for increased stability. The primary function of the centerboard when down is to increase lateral resistance so the boat sails better. The centerboard can be lifted to decrease draft in shoal water. It can also be lifted to increase speed when going downwind since the increased lateral resistance isn't needed then.

    There are also boats, sometimes call "swing keel" boats, which have an appendage which swings like a centerboard but is heavily ballasted. In addition to increasing lateral resistance the ballast in it significantly increases stability. Swing keels are able to be locked down so that the swing keel becomes effectively the same (almost) as a fixed keel. Swing keel boats are generally not intended to be sailed in other than light breeze with the swing keel up. Compared to an unballasted centerboard the much heavier swing keel should have a stronger case, pivot and lifting gear.
     
  8. ytquest
    Joined: Oct 2005
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    ytquest Junior Member

    Secure Ballast

    Thank you, David and Par for giving me some insight to the differences between the two types (CB-SK). I was worried that my CB would start to jump up and down in heavy seas and damage the trunk if not locked down. This makes more sense with the cat rig and twin running back stays and block and tackle sys. on the CB. I obtained the boat disassembled and have had a difficult time finding info. on it. I still not sure if I should use the high strength mortar we put under columns to be able to lock the lead in the keel.
     

  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The board will not jump up and down if properly designed. The case isn't designed to tolerate strikes and impacts if it's locked down, you'll just rip out the pin and/or smash the case to leaking bits. High PSI mortar will do, though it's not especially strong, nor does it grip 'glass very well, which is the whole point. Epoxy will work and the bond will be great.
     
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