Lead Keel Modification

Discussion in 'Boat Design' started by Dick Flower, Apr 25, 2007.

  1. Dick Flower
    Joined: Apr 2007
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    Location: S France

    Dick Flower Junior Member

    As my nearest lead foundry is over 200 miles away, guessing at the costs of getting a 3200 lb keel there and back plus the casting costs, I am going to forget the option of recasting the keel. I'm just a poor pensioner.
    Taking all comments so far into account, I have decided to reduce the depth of the hollow keel stub by about 4 to 6", and reattach the keel without modifying it, so the displacement will not change (except by the small weight of the GRP removed).
    The boat will actually float slightly lower, due to the loss of the buoyancy of the removed stub.
    Given that the ballast:displacement ratio is 25%, this should raise the CofG by 1 to 1.5", which I don't think will be any more noticeable than normal variations of boat loading.
    I have never succeeded in getting the rail under in up to F7-8 on the beam, so I don't think there is much more risk of a knock down with the slightly reduced righting moments. (Especially in a canal!)
    In any case, when I remove the mast for the canals, the CofG will be lowered, probably by a similar amount.

    Dick
     
    Last edited: May 4, 2007
  2. Dick Flower
    Joined: Apr 2007
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    Location: S France

    Dick Flower Junior Member

    Well, it’s a few months later, and I still haven’t done anything about reducing her draught.

    After measuring the depth at various places on the canal I decided we could get through OK, so took down the mast in September and tried, but ran aground before we even got 10 metres into it. I have since found that this build-up of silt at the entrance has now been dredged, but am told not to rely on more than 1m40 water depth.

    The boat is now ashore waiting for my decision on how to reduce the draught.

    If I cut down the keel stub and remount the keel casting higher up I have to drastically modify the fuel tank, I’m sure there will be difficulties to fair the keel casting to the larger section of stub to which it will have to fit, and I shall be moving the CG of the keel forward because of its rake.

    I think the best option is to cut off a section from the bottom of the casting and recast it as two bulbs to attach to the sides as has been suggested.

    If I cut it with a saw I will probably cut through the keel bolts, so I am wondering if it would be possible to use a cutting torch or similar to melt the lead from the bottom upwards, collecting it in a suitable container, so that I can cut off the bolts to a suitable length, put them through a drilled plate underneath, and put nuts on them.

    Any ideas out there please?
     
  3. barklymad
    Joined: Dec 2007
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    Location: Scotland

    barklymad Junior Member

    Dick , could you not just remove the keel , temporarily glass over the stub with something , and leave the keel in the south ; someone will be coming up with van or room to spare ! Sort out the mast if you want , Then , rebed the keel, add a staysail , try er out.
     
  4. Dick Flower
    Joined: Apr 2007
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    Location: S France

    Dick Flower Junior Member

    Thanks barklymad, and a very Merry Christmas to you and all on this Forum.

    When I hauled out I had decided to remove the keel and fit a steel plate under the stub before glassing it over, then add around 500kg of ballast.

    We have to go by sea about 10 miles to get to the canal, and I am concerned about stability in the open sea with no keel and the mast on deck. Although the hull should have considerable form stability, the mast is quite a lot of weight to carry so high – about 2 feet above the cabin top.

    I found lead for ballast, but it costs €3 ($4.30) per kg in 25kg ingots from the nearest foundry I have located (in Barcelona), which is more than I can afford. Dealers will pay only about €1 per kg for scrap lead, but I have found none who will sell it.

    I can get iron in large pieces much cheaper, but it takes up at least 70% more volume than lead, and having had one boat with pig iron ballast, which created a vile soup of rust, spilt oil and other debris in the bilge, I am loath to go that way again.

    However, if I could remove the lower half of the keel and add this material as a bulb on the bottom, I would decrease draft by 20cm, about the same depth as the skeg without major surgery on the stub.

    This should not alter the sailing stability drastically if I step the mast again, and would be less work and expense than other options.

    All I need to find is the best way to remove 20cm of keel without possibly damaging the bolts.
     
  5. Dick Flower
    Joined: Apr 2007
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    Location: S France

    Dick Flower Junior Member

    Does no-one have any ideas on cutting off part of a lead keel?
     
  6. Gilbert
    Joined: Aug 2004
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    Location: Cathlamet, WA

    Gilbert Senior Member

    Since you have arrived at the decision to cut off the keel I would say you should go head and use a saw. Of course that would mean you would need the boat cribbed up quite a ways. I don't know what type of saw to recommend as lead is famous for not standing up to a cutting edge. Trial and error is the approach, unless someone here can give you the correct answer. No doubt the bolts will be cut also. Fit a fairly heavy plate to the bottom of the keel made of the same material as the keel bolts. Cut a hole in the plate at the location of each keel bolt that is smaller that the diameter of the bolt and have a welder weld the plate to the keel bolts. At the fore and aft ends of the plate you may need a strap to fasten the ends of the plate to the lead to prevent the plate from bending down from some impact.
    I would suggest you try sailing the boat with the cut off keel to see if you feel going to any more trouble is necessary.
    Your boat would carry the downrigged mast fine with no ballast at all on the 10 miles of open sea. Of course it is always best to pick good weather.
     
  7. Earl Boebert
    Joined: Dec 2005
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    Location: Albuquerque NM USA

    Earl Boebert Senior Member

    My experience in working lead is strictly in model yacht domain, but I've done quite a bit of it. Two things that work are freezing it (probably not practical here) and lubricating your cutting tools with copious quantities of mineral oil. The first thing I would try is chiselling a groove with a very sharp (google on "scary sharp") chisel. Even if you don't cut all the way through with that technique, it will reduce the amount of sawing, which is about the toughest thing to do with the stuff. And, of course, take precautions against accidental ingestion.

    Cheers,

    Earl
     
  8. Dick Flower
    Joined: Apr 2007
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    Location: S France

    Dick Flower Junior Member

    Where can I get some NC hot dip galvanizednuts?

    After many distractions this year, including ane eye operation which put me out of action for some time, I have returned to working on the keel.

    I wasted a lot of time during the winter attempting to find a lead foundry which would recast my keel. The only one expressing any interest, 300 miles away, did not reply after I sent photos and drawings. There is now only an answer machine there, and no-one replies to messages, so I assume they have lost interest – or gone out of business.

    I decided to cut off half the lead myself, so I can use the boat without the mast, and worry about recasting the material removed at a later date.
    I removed the keel and brought it home to my workshop, where I am better equipped to deal with problems such as hitting the “bolts”, which I found are cast-in studs.

    With the keel upright and two chain hoists to support it, I began to cut.

    After two days with a sabre saw / ”Sawzall” I had managed to get just beyond the first stud from the thinner end, maybe 5% of the total cutting required, but at least established that I was cutting below the studs.

    I then remembered I saved some information last year and found this article which I had forgotten about

    http://www.marsmetal.com/newpages/tek/articlecutkeel.html

    On Saturday, with some trepidation, I cranked up my trusty Mac. It cut through the lead like butter (well, almost). My arms were aching when I stopped, and I have about 6 inches left to cut today. The F1 GP and the golf yesterday were a good excuse for a day off.

    [​IMG]

    Now I have another, smaller, problem.

    The keel studs are steel, are still in good condition, but the steel nuts were badly corroded and are not reusable. There are 2 nuts on each of the 6 studs. The top nut on 3 of the studs was stainless steel, which I guess were the only NC nuts I could find in Spain when I replaced them in 1990.

    The exposed tips of the studs which had stainless nuts are more corroded than those with steel nuts, presumably due to galvanic action in the damp bilge.

    I want to replace all 12 nuts with hot dip galvanized nuts, but cannot find these in France or UK, where everything now seems to be metric. I have found them in the US, of course, but the minimum purchase is by the hundred or by the keg.

    Can anyone here help me to source 12 each ¾ x 10 NC (not Whitworth) hot dip galvanised nuts, please?
     
    Last edited: Jul 21, 2008
  9. Gilbert
    Joined: Aug 2004
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    Location: Cathlamet, WA

    Gilbert Senior Member

    Hi Dick,
    It looks like things are going pretty well with your project. I haven't looked yet, but I have quite an assortment of bolts and such and may have the nuts you need and if I do will let you know.
    It is great that you do not have to cut the bolts as they will be protected from galvanic action by the lead.
    I would like to encourage you to sail the boat with the downsized keel. I am pretty sure you will be surprised at how well it will sail and how stable it is. Of course it will not be as stable as before and so, as I mentioned before, you will need to be able to reef readily to compensate. Of course, you may already have that capability.
     
  10. Dick Flower
    Joined: Apr 2007
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    Location: S France

    Dick Flower Junior Member

    Hi Gilbert,

    I finally found a couple of places in UK selling the nuts, just waiting to hear if they will supply a small quantity. If not I'll get back to you, and thanks for the offer.

    I'd like to try sailing with the new keel, but I took all the rigging home for storage, and it's a lot of work to replace it and refit the roller reefing for such a short trip, plus paying for lifts to replace and remove the mast.

    I plan to cut down the mast and deck step it. I had a nice tabernacle made quite some time ago, copied from photos of my 8 ton Hillyard, and bought a good piece of teak for a base. I shall drop the mast stub inside the boat for now, and complete the work this winter.

    Carrying a mast on deck is not too handy in the canals, especially when negotiating locks

    [​IMG]

    so I shall store it near the canal, and plan a trip down to the sea again when I can raise and lower the mast in the tabernacle without a crane. I had a lot of practice doing this with the Hillyard, and could do it single handed in calm water, using a halyard from the anchor windlass and a stayed boom as a stiffleg.

    Now I just have to re-glass the keel bottom and put it back!
     

  11. diwebb
    Joined: Jun 2008
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    Location: New Zealand

    diwebb Senior Member

    Hi,
    just found this thread. Sorry to come in so late with an off the wall suggestion but it may help someone else later. One consideration that no one seems to have thought of is to revise the hull bouyancy down. This could be done quite easily by spray on foam which could then be faired and glassed over. I dont know what the weight per inch immersion is on your hull, but three or four inches of foam tapered out over the whole bottom to just above the waterline would bring her up by the required amount and would not compromise the stability and construction of the original design. This could also change the hull shape by softening the bilge curves and curing the hard motion of the boat. What do the experts think of this proposition??
    David
     
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