Keel to hull attachment strength

Discussion in 'Fiberglass and Composite Boat Building' started by melamphyrum, Feb 2, 2014.

  1. melamphyrum
    Joined: Jan 2014
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Switzerland

    melamphyrum Junior Member

    I have recently bought a 1975 custom IOR 3/4 Tonner sailboat. The boat was designed by Ben Lexcen (aka Bob Miller) and built by Custom Yacth Services, Australia using c-flex and vinylester. (LOA:34.3, BMAX:10.6, Draft: 6.0, Displ:12600). She is currently on the hard and I am fitting her out for offshore cruising.

    My previous boats all had long keels (Folksong 25, Marieholm 32, Golden Hind 31), so I have little experience with fin keels. I heard the horror stories of keels falling off boats, and the infamous 'Catalina smile' which makes me a bit concerned about the attachment of the keel on my boat. While the keel is unlike the thin blade that I can see on most modern cruiser/racers and it is relatively wide at its root (about 1 foot) it is simply bolted to the skin with 12 3/4 inch SS bolts arranged in two rows. Please look at the attached picture showing the bilges. The thickness of the hull is around 7/8" at the bilge.

    I think the bolts should go through full length floors that extend as far athwartship as possible, but at least to the first pair of stringers (you can see these stringers on the attached picture, the partial floors are bonded the these 1.5-foot-wide stringers). I am considering to strengthen this area. My idea is either to glass-in additional floors or replace the washers with big backing plates extending 1 foot athwartship on each side.

    My questions are:

    1. Is it common practice to bolt the keel directly to the skin of the boat? Is this acceptable?
    2. Does the current arrangement give sufficient strength or some reinforcement would be a good idea?
    3. What would be the best reinforcement method?
    4. Can I do this while the boat is on the hard? While on the hard, the whole weight of the boat is on the keel, certainly causing some deformation of this area. This deformation will disappear as soon as the boat is in the water stressing the newly glassed-in components possibly causing delamination.

    Thanks in advance.
    Den
     

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  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 488, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Yep, you're fine and it's a common practice, so don't worry. The bolts should be checked for tightness (they have a torque setting) periodically and inspected for corrosion. A '74 boat should consider it's bolts suspect, just from age, which generally means replacement, which can be a daunting task in some boats.

    The horror stories usually have a common theme, such as bashing into something, hard racing for years and not inspecting the bolts, corrosion, etc. Those bolts look pretty good after 40 years, so they may have been replaced at some point.
     
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