Inspecting/Reinforcing External Lead Ballast

Discussion in 'Boat Design' started by Swiftsure33, Dec 21, 2017.

  1. Swiftsure33
    Joined: Oct 2017
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    Location: Tampa

    Swiftsure33 Junior Member

    My boat, a 1960 Rhodes Swiftsure 33, has external lead ballast that makes up about the forward 1/3 of the keel. It is secured with bronze bolts through the bottom of the hull and the nuts over these bolts were then glassed over by the factory/yard. This makes me think the yard never intended for the bolts to be replaced, but my concern is that if at some point the edge between the ballast and the hull were not sealed properly the bolts could have been at risk of corrosion. The only way to really inspect them is to grind away the glass over the nuts and build a cradle that can lower the ballast on jacks. My question is that if I do this and decide that the old bolts are no good, how do I remedy the problem? I would have to believe that the bolts are molded in to the ballast, so I can't easily replace them. I suppose the best solution in that case would be to grind out the old bolts, and set some new ones in and fill them over with new lead? Another thought I had is that I could possibly drill new holes from inside the boat and just tap in new bolts next to the originals. I may not even need to drop the ballast if I can get as many new ones in as there are already. I'm sure that this whole system was fairly overbuilt for obvious reasons, but losing my ballast is not something I want to ever be in the back of my mind. Maybe I'm even just being overly paranoid and this design was meant to last a lifetime. This project would be pretty far down the line, but I just wanted to get some feedback from people who know more than me on the subject given how crucial it is to the boat. Thanks.
     
  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The first thing to do is check the ballast/hull interface and see if the joint is opened up or there's any movement. If there is, chip off the laminate covering the bolts and inspect the nuts and washers, including tightening them down to the recommend torque. It's at this point you'll have to make decisions. Bronze holds up quite well, even at this age, so the usual procedure is to reef out the sealant along the parting line, squirt in fresh and tighten up the assembly with new nuts and washers. If the bolts seem spent, well the job gets a good bit harder and the ballast casting needs to be removed (jack the boat, lose the nuts and lower it down with a fork lift). You can drill and tap lead, but only if the casting was formulated with an appropriate amount of antimony. Pure lead isn't very strong, but with a 3% antimony mix it's 4 times better in tension and with 5% over 5.5 times stronger. The antimony also permits much better machining, which will be necessary for tapping the keel. I wouldn't tap it, I'd drill through bolt holes, insert custom length bolts, plug the bottom ends and jack it back up.
     
  3. Swiftsure33
    Joined: Oct 2017
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    Swiftsure33 Junior Member

    Thanks PAR for always being so quick to comment and sharing your knowledge with us amateurs. It has a good seal currently but the boat has undergone a few more minor restorations than what I'm doing so it's tough to determine how well the seal was kept during the boat's lifetime. I believe the yard that built her is still in operation so I've just emailed them to get their recommendations as well and see if they can confirm the antimony content. If I understand correctly, in this type of construction they typically use bolts with a u-shaped bend on the bottom end that is molded into the lead. I imagine the process of replacing these would be to drill out the full length of the bolt and set a new one in it's original spot, then pour new lead over the top. Do you lose strength in the mating surface between the old and new lead? Thanks again.
     
  4. Swiftsure33
    Joined: Oct 2017
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    Location: Tampa

    Swiftsure33 Junior Member

    Another thought I had is possibly drilling out the old bolts oversize, then sinking in a tapered rod, or a bolt with a large nut on the bottom, to provide horizontal surface area to counteract the downward force of the lead. I suspect this would be easier and cheaper than replacing with new j-shaped bolts. Of course I'm really just hoping the original bolts simply have no signs of corrosion, but if it needs to be done I plan to do it myself, as I am with the entire restoration, so the easier/cheaper the better (provided it remains as strong).
     
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I think you're correct about the J bolts, but you don't drill these puppies out, you drill near them or along side them for a new bolt. Unless there was some serious leaking in the life of the boat, I'll bet those bolts are fine. In the era that boat was built, they used just about any kind of lead they could for ballast castings. I'd be surprised if they have a clue about the alloy content, so tapping the lead is out (can't be trusted). Additionally pouring molten lead into a solid lead hole isn't going to work well either. The usual practice is to epoxy bond the bolt in place in an oversize hole.

    Does your boat still retain the origional bronze hardware? My memory of these old CCA lasses were they could use a little more ballast and later models did carry a little more. You casting should be around 3,500 pounds (again relying on memory), which isn't much for a hefty set of bolts to hold up. I mean look at what a single 1/2" bolt will hold up, compaired to what it actually has to hold up, then multiply by the number of bolts you have and you'll get a good idea.

    If it was me, I'd slack off all the nuts, with the ballast supported and the boat on stands. Then I'd lower the ballast an inch or so, to reef out the seam and have a look at the hull shell/ ballast casting interface. This is where the serious corrosion will happen. If necessary lower the ballast more, but still trying to keep the bolts partly in their holes (makes putting it back easier), then clean the faying surfaces, maybe even smoothing them out with some putty if necessary (usually is). With clean surfaces (yeah the tight gap is a pain, but doable) and a pass on the fastener inspection, butter her up with some polyurethane (3m-5200) and jack the ballast back up. Jack the ballast hard into the sealant and let this sit unmolested for a week or two, before you dog the nuts down to torque specs.
     
  6. Swiftsure33
    Joined: Oct 2017
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    Location: Tampa

    Swiftsure33 Junior Member

    Sounds like a plan. Now that you mention it, all of the centerboard hardware is bronze and appears to be original, and same with the rudder. Since I plan to inspect all of that anyway, I think I'll start by driving out the pin for the centerboard, which actually would have spent it's life in the water, and seeing what kind of condition it's in. And I do take comfort in the fact that there are a lot of bolts for the size of the ballast. I count at least six, with possibly more hidden in the integral bilge water tanks. Overall I doubt there will even be an issue, but I do feel a lot more confident now that I have a plan for moving forward if I find a problem. Additionally, I did notice that she has a fairly low ballast ratio, but the centerboard is 200 lb of solid bronze, and like I said she carries a good 60 gallons (according to sailboat data) of freshwater in her keel. Not to mention there are some exceptionally deep wells beneath the engine bed and cockpit that I could add more ballast or a second water tank to if she ends up being a little too tender for my taste. Anyway, once I get around to the ballast project I'll try to post some pictures of what I find, and see if I can find someone local who knows more than I to check it out.
     

  7. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I'm local(ish), Tampa is only an hour or two away.
     
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