Aluminium Keel Ballast

Discussion in 'Metal Boat Building' started by Wynand N, Dec 18, 2004.

  1. Pavel

    Pavel Guest

    Good point, of course you pressure test it first to about 3psi and then fill it with oil (checked the plans again). Also checked the book 'boatbuilding with aluminium' by Stephen F. Pollard and he suggest to pressure test the keel to above mentioned preasure and seal it by welding (no mention of oil).
    Also when pooring lead, stronbacks about six inch appart are recommended to hold it together. Hope this helps.
     
  2. gonzo
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    gonzo Senior Member

    You can pressure test with air, oil will explode if you try to weld it. I don't know where you are, but check for environmental regulations, specially for transformer oil; it is toxic.
     
  3. Thunderhead19
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    Thunderhead19 Senior Member

    I would like to add a little point about moisture when pouring lead or or any other molten metal. Water expands around two thousand times it's volume when it vapourizes, and superheated steam can contain even more energy. Imagine heating an ounce of water to 800 degree superheated steam in less than half a second. BOOOMMM! all the water must be driven out prior to pouring.
     
  4. Pavel

    Pavel Guest

    yap right, of course you air pressure it, it comes without saying. Then fill it via that test ball-valve with oil and leave it as is. If transformer oil is not good enough, try Monini extra virgin olive oil, its rather good one. Its new to me that in US you guys do care about environment. Good.
     
  5. Dutch Peter
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    Dutch Peter Senior Member

    Although I have no actual experience with lead in alu keels, I have a lot of confidence in the yards that use the methode I described before. My notion is still, that a yard that builds 30-50 million euro yachts knows what it's doing and doesn't look at saving a couple of hundred bucks for not coating with epoxy or taking a chance of losing a keel due too corrosion.
     
  6. kapnD
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    kapnD Senior Member

    Alan, I'd hesitate to use epoxy as a medieum for the lead shot. Its bonding properties are severe overkill, its extremely expensive, and then the chemical hazard. I'd look for a glue on the lines of "Parabond" or similar. (I'm no chemist, but I think they're called polymer or aliphatic glues?) They cleanup with water when wet, and remain resilient when dry. In a deep sailboat keel, I'd suggest a small sump with a pipe up through the lead to monitor moisture and pump out if necessary.
     
  7. ted655
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    ted655 Senior Member

    I'm facing a similar delema. Reading these threads gave me an idea. I don't need every inch (mm) of space to achieve my ballast ratio. I'm going to use lead shot (hail) and pour it into short lengths of 6" PVC pipe. Plastic covered ingots. Then, after trim, pour a gravy of epoxy & thickining agent to seal everything tight. Thanks for having the discussion. I to was ready to "pour".
     
  8. MikeJohns
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    MikeJohns Senior Member

    Dont mix

    I have been a bit busy lately, been meaning to post these photo's.

    I had an insurance report on this very topic.

    Here is a photo of 8mm 6000 series plate that was hosting poured lead ballast. The plate has been cut out for replacement and is lying on concrete (visible through the holes).

    Overflow water from the chain locker sump had occasionally over the last 8 years made its what had been considered a dry bilge.
    The lead was on a thick film of aluminium oxide scale, the oxide layer was consistent and around 5 to 7mm thick the hull had corroded through in a number of small areas and while at sea the outer paint film failed and the water seeped slowly in.
    In reality the damage is minimal and the owner caused much damage ripping out the furniture to find the source of the new spring. She was taking around 5 litres per hour.

    The insurance will not cover either his damage nor the re-plating. The builders (lawyer) to whom we sent a very detailed report, claim normal established procedure although there was no barrier epoxy coat or barrier top coat.

    In the same vessel there were some trimmer lead pigs lying in a thick bed of epoxy under the engine in a damp bilge area. When they were finally jack hammered and prized free (on my insistance for inspection) the hull was pristine underneath.

    The Moral is if you pour molten lead into alloy then isolate the area somehow to keep it dry. Capping with a welded plate and ensuring an airtight seal would be sensible if there is any chance of moisture ingress.
     

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  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Look folks, if you pour molten lead into anything it will shrink a bit when it cools, so a tight fit isn't possible, cast ingots to fit the keel. They're removable and can be sufficiently coated to prevent any dissimilar metals contact issues from rising. The other option with lead is to use shot or ground up bits and embalm them in the goo of choice, before during or after the placement. I'd recommend you use the ingots (pigs) because they can be removed for repairs, or to lighten the load in a grounding, both very good reasons not to bond the stuff to the plating.
     
  10. AlexMorozov
    Joined: Jul 2004
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    AlexMorozov Custom yachts

    ballast

    Hi,
    as per my expirience, good way to use the lead gots, loaded in heavy primed/painted aluminum keel. The sides/bottom of the keel is heavy covered with PU paint/primer or sealant. Then loading the gots and pured with concret mixing. layer after layer. On top of last concrete layer, the epoxy is applied. And surely some crossbars are welded at top of ballst block.
    So, it is not expensive, take short time, good for fire protection (just3-5 mm of epoxy), no deformation and no problem while grounding as it is solid block with outer layer of sealant/promer+aluminum. Also possible to take out the balast, if required, but it take much more time then loading it.
    good luck
     
  11. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    Im curious:confused:
    Just how do you propose to take this "ballast block" out of the keel after being grounded?....start with the welded cross bars;) Another thing thought, I do not sail a bare hull and deck....
     
  12. MikeJohns
    Joined: Aug 2004
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    MikeJohns Senior Member


    Here's an email I just received on this subject I consider worth answering here. I'd also like any one else's suggestions.



    To Quote:


    Sorry for bothering you in this way but the thread I was reading is long closed.
    By accident I found your very interesting comment on lead filled aluminium keels.

    I fear I have encountered the problem you described with my 15 year old 44ft aluminium sailboat.
    When preparing for the season I found a tiny hole in the keel surface leaking moisture. Further examination of the interior found a crack in the sealed keel cover. The lead was sealed by the yard with resin (probably polyesther) . I imagine the occasional bilge water finding a way through this crack between the poured lead and the 8 mm aluminium plating.

    I had a marine surveyor do a sonic thickness test on the keel plating and he found 2 other spots also approx 3 cm below the “lead – level”. He advises to open up these three spots and weld 3 new plates of 10 x 10 cm in them. Then dry the boat (heat the keel for a couple of days) reseal the interior bilge.

    My question is if you think this will solve the problem. How can I be sure no other “weak spots” exist ? What method of repair did you use ?

    Your help is highly appreciated.

    Jop Dutilh
    Rotterdam,



    Jop

    Remedial work is always a compromise in these situation.
    You have a highly reactive metal in contact with a much more noble one with a small void and if you introduce an electrolyte there is unfortunately no cheap simple solution .

    In the case I posted about Initially we thought it would be a few small patches….
    Lots of drain holes were drilled down to the keel base several of which weeped, compressed air was blown in some of the holes which drove water out of others, it also blew some new small holes but it tended to balloon the plating slightly and care was required .
    It was washed as well as possible with fresh water and then by forcing ethyl alcohol through and heating with an electric heat gun.
    Alcohol mixes readily with water and the mix evaporates much more easily and is a common partial drying process, follow with heat .It was heated until vapor stopped venting out of the drilled holes.


    In the end more and more plate was cut away as the extent became apparent , in fact nearly 1/2 of the entire keel plate was removed on one side, All the bad parts looked like the photo I posted in this thread with lots of grey paste and white powder with numerous pits. The only way to stop the process is to replace the plate since the corrosion products trap too much electrolyte. Injecting epoxy and similar gap filling mechanisms would have no remedial effect once the corrosion has started and the moisture and ions and corroded alloy are all nicely mixed into a paste in full contact. Local corrosion cells form in this goop and the whole lot corrodes quite rapidly.

    The trick is getting rid of the moisture, but it is very hard to do when trapped in such expansive voids.

    When you have wet corrosion products trapped in the interface it will carry on self corroding . Unfortunately the first repair will probably only slow the problem down, stopping further ingress of water from inside and try and catch any thin bits before they pit right through and re-introduce more electrolyte. If you can do this eventually it should peter out, the full extent of the problem will become more apparent when the first effected areas are cut out.



    I'm sorry I cannot give you a magic bullet. I'd really like builders and designers to understand that this can be a significant problem.

    cheers

     
  13. flying dutchman
    Joined: Apr 2009
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    flying dutchman New Member

    thanks for the quick reply. One more question: you talked about replating the keel surface. Can this be done in a safe manner with the ballast in place ? In our situation the keel has 5 or 6 sections each of which are filled with lead. Welding from the inside sounds difficult.

    Regards,
    Jop
     
  14. Guest62110524

    Guest62110524 Previous Member

    what I usually do is throw in as big a pieces as possible, some up 20 30kg, then pour molten around it then seal then TEST USING NOTHING OTHER than manometre If the keel is properly constructed designed and built and welded there will never be a problem But if you have overlooked a pin hole and you say crack a plug weld, then you are introuble, because then you would have to cut open one side, flush with fresh water and dry , the slightest and I mean slightest hint of moisture and alloy will not weld
    In 30 years I have not had a prob, but saw Taberlys Pen Duick, with spent uranium or was in plutonium waste, was cracked in 78 Whitbread in AK , IMPOSSIBLE to fix in that short time
    To reiterate the manometre is the only test that is failsure
     

  15. MikeJohns
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    MikeJohns Senior Member

    Yes Stu this is the best solution; to cap and pressure test the welds.

    Jop

    Yes you re-weld with the lead in place. I'm not an alloy welder and whoever you use should have enough knowledge to accomplish this.

    With 8mm the plate welded form one side only the edges are prepped with a Y shape the first root weld is onto the base of the Y and should only just penetrate through then the remaining V is welded multiple run, the lead will melt if it comes in contact with the weld, if there is any room a thin stainless steel plate can be pushed down behind the joint as it is welded to isolate the joint from the lead, it's pulled out after welding.


    Any comments Stu ?
     
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