Lead Keel Bulb to Aluminum Hull

Discussion in 'Metal Boat Building' started by Vizy, Jan 22, 2022.

  1. Vizy
    Joined: Jan 2022
    Posts: 2
    Likes: 0, Points: 1
    Location: UK

    Vizy New Member

    Good day all. I'll keep this short and sweet.
    Looking for your aluminum yacht building expertise: I am considering the idea of casting a lead bulb, hydrodynamically fair and bolt it to an aluminum fin shaped keel.

    Seeking advise regarding if this concept of attaching a lead bulb to an aluminum hull is common in yacht building (similar to a cast lead keel attached to a composite fibre hull) or just not good practice for fear of galvanic corrosion.?

    Appreciate in advance your time and knowledgeable comments on the topic.
    Cheers
     
  2. bajansailor
    Joined: Oct 2007
    Posts: 2,666
    Likes: 991, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum Vizy.

    Aluminium is anodic relative to lead, as per the table in this link, so you will need to have anodes (but you would need to have them anyway) -
    Metal Compatibility | Galvanic Corrosion Scale https://www.mfcp.com/technical-info/galvanic-corrosion

    Note though that lead is much closer to aluminium on the scale than stainless steel - and stainless steel is commonly used for fastening to aluminium (think of S/S bolts securing an aluminium toerail - but you will want to have a suitable sealant in between them).

    Rather than bolting the lead keel to the aluminium hull, would it be feasible to put the lead inside the alumnium fin keel? .
     
  3. Vizy
    Joined: Jan 2022
    Posts: 2
    Likes: 0, Points: 1
    Location: UK

    Vizy New Member

    Hi Bajansailor
    Thanks for the welcome and your input.

    My go-to option is to fill the fin keel with lead bars. I also want as low as possible CG with a bulb shape to increase the volume/weight. My skills in shaping aluminum plate into a hydrodynamically fair curve is highly doubtful, thus considering a bolt on option to a standard fin keel.

    I was wondering if this is perhaps a common option in practice, taking into account sufficient epoxy sealant between lead, aluminum and S/S bolts, with all surfaces coated and antifouled. Would I still run the risk of galvanic corrosion or one should just avoid that option.

    Cheers
     

  4. bajansailor
    Joined: Oct 2007
    Posts: 2,666
    Likes: 991, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    Righty ho - can you tell us a bit more about your aluminium hull please?
    Is it an existing hull that that you are now modifying, or are you in the process of building it?
    If an existing hull, can you post a photo or two of it please?
    And if it is a new construction, and you have not started building yet, can you post a drawing of the boat showing the proposed keel arrangement?
     
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.