keel filled with concrete

Discussion in 'Metal Boat Building' started by Lexluthor, Jul 18, 2010.

  1. Lexluthor
    Joined: Jul 2010
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Lexluthor Junior Member

    Hi all,

    I've purchased a steel ketch which i plan to strip completely and make a new interior, the long keel is filled with scrap iron, steel punchings and concrete,
    I'm thinking of chiseling out the concrete & scrap iron and replace that with lead and a layer of poured in expoxy.

    Anyone has any thoughts about such a project, should i weigh every bit of concrete and iron and put in the same weight of lead?

    with kind regards,

    Tom
     
  2. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 121, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    Whether or not to replace the concrete/punchings with lead depends on her current sailing characteristics. If the boat sails well now, why do it?
    It was probably designed for concrete. Changing to lead will change roll period and possibly adversely affect seakindliness/comfort.
    The insertion of the lead will be a mite tricky, or did you remove the cabin top?
    If you do trade for lead, it should weigh the same unless you are correcting a design flaw such as waterlines being too high/low.
     
  3. Lexluthor
    Joined: Jul 2010
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Lexluthor Junior Member

    thanks for the info allan,

    the concrete has a large crack in the middle, i plan do dril/hammer this out
    to see how far the crack runs. I'm not quite comfortable with this because it
    can let seepage trough. I know cement is quite a good rust preventer because of the caustic qualities it has but with cracks in it i suspect there is something lurking underneath.

    As for the lead, i about casting nice bricks of lead, cleaning out the keel, putting on a layer of owatrol CIP or 2, then a coat of tar-expoxy, putting in the bricks and topping/filling it up with epoxy.
     
  4. gonzo
    Joined: Aug 2002
    Posts: 14,338
    Likes: 618, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    You may make the boat too stiff which will stress the hull and rigging. Also, the ballast is spread out on a big area, lead will concentrate the stress in a smaller area of the keel. There are structural issues to consider. If it works now, why try to change it?
     
  5. Lexluthor
    Joined: Jul 2010
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Lexluthor Junior Member

    you've made a very valuable point, thanks ;) i thought lowering the center of gravity she would be a bit stiffer but then again point taken, an amateur shouldn't change the design specs without a good reason.

    i think i'll just investigate the crack and refill it with concrete and put a layer of epoxy tar on it to make it smooth& clean.
     
  6. MikeJohns
    Joined: Aug 2004
    Posts: 3,192
    Likes: 206, Points: 63, Legacy Rep: 2054
    Location: Australia

    MikeJohns Senior Member

    Usually you will find its the steel ballast closest to the surface that has expanded. Sometimes though it's all kaput since they just laid it in the keel and capped it.

    Borrow or buy an electric chisel hammer or get a pneumatic one and be prepared to make some noise !

    Now is the time to determine if the boat lacks the ability to stand to its sail some pictures of it out of the water or the hull lines would be interesting to see. What's the heel angle like going to windward in a stiff breeze and what's the size of the boat?

    But is the designer still around? If so go and ask him, if not and it's a common design then ask what others have used as ballast.

    Here it's common for steel boats from the same designer to have either lead or cement and steel ballast, the lead is usually the better option since it's easy to raise a COG even with relatively small amounts of weight but you can't correct a 'lazy' boat without major surgery, such as a deeper keel or lead instead of concrete.
     

  7. Lexluthor
    Joined: Jul 2010
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Belgium

    Lexluthor Junior Member

    i'll post a few pictures when she's out of the water. I'll take full measurments also. She's hard chine, long keel, ketch rigged.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.