Waterprothing all under waterlevel seams/rivets from inside Aluminum hull

Discussion in 'Metal Boat Building' started by the brain, Nov 13, 2017.

  1. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Most aluminum boats would tolerate moving a bunk to enable checking an area of concern. Typically bunks are longitudinal and could be modified to suit your needs. You could widen the bunk and split it over the rivets or move it some. But I am guessing without seeing. You have to be the judge, but a slight move to expose the rivets seems wise from here. I doubt if you move the bunk off the seam a half inch it'd be a problem. Sometimes bunks under al boats are transverse. You could also just split a bunk like that.

    The bit about the freeboard and hump stringer confused me. It sounds like you want to raise the sole? I would not support that idea unless you intend to add rails, but the details are foggy.

    The foam is a great idea, but how can you do a rivet repair or do you assume the foam will stop mechanical movement of the entire bottom? So foaming the entire hull?

    I'd leak test the whole boat first because you'll be sad if you have leakers. And I'd buy the best foam with the lowest water absorption possible if me.
     
  2. IronPrice
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    IronPrice Senior Member

    About 18 years ago I reconditioned and old (then) star craft dinghy. It had two leaking rivets at the seams, and leaking rivets securing the reinforcing ribs inside the hull. All of them were the older solid rivets.

    I did the following: -

    1) Drilled out all leaking rivets on the seams
    2) Driledl out all rivets on each ribs (one rib at a time)
    3) Re-riveted each rib with beads of modified silicon adhesive sealant under the mating surfaces
    4) Replaced rivets removed from the seams.
    5) Coated the inside of all seams with a paint-on rubber membrane - I used one called Duram 195.
    6) Replaced the transom ply.

    This worked very well , the boat was much more rigid and all those years later (now at a friend's beach house) is still water tight.

    I used blind/sealed rivets - the skinny end of these is closed. Traditional open ended rivets are not water tight.
     
  3. the brain
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    the brain Senior Member

    finally got her off the trailer for much needed rivets redo. decide for the revite redo and for observation/inspection purposes move the outside bunks in a couple inches.

    The orginale trailers bunks where not surporting the hull under this seam bottom/freeboard.

    the outside of these green treated 4" X 6" bunks are flakeing away feels like cardboard.
    1.will the bunks carpet protect the hull from contacting the green wood thus the associated corrision created w/ green wood on saltwater aluminim hulls?

    three days ago the State of Alabama was closed due to 6" of snow Gov declared state of emergency smart thing to do.

    yesterday I was wearing shorts, back in the back yard at boat/trailer restoration.

    will pull interior flooring/flotation and rerevite from outside in will smear the G2 on each revit. (holding off on Goop.)

    I'm anxious to see if the revits attaching my extra stringer are all intact. they have had a few a good beatings.
    this time when floor comes up I'll install the allready fabbed port extra stringer.

    I'm optimistic to have a primary fuel tank enclosure/step combo/leanback sjump seat.real inatation seadeck aft deck, then all the aft deck needs is washdown/livewell plumbling ect. rememeber the LW is built just needs plumb.

    the seam at midship where these three revits popped out will need reinforcing best I can come up w/ is fab small chins (knee braces) on each latitudale rib kindof like extending the ribup to the freeboars was planning the revit and glue to rib then glue to inside of freeboard.

    any suggestions on reinforcing is appreciated. TB

    I will initiate this type of bracing I attach image
    Cut radius at end of brace then slide over hump revite/glue to side of hump, flange out freaboard end also glue revit then floatation.
     

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    Last edited: Jan 23, 2018
  4. the brain
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    the brain Senior Member

    Update only one revit is completely gone the other two just the head remains

    So I’ll have to drill then replace.


    The rusted screw )replacing a vevit) is about ¼” in diameter I don’t have a blind revit bigger than 3/16” I know the proper method of repair is to braze however I’m wanting a quickie fix, I have 3 more days of of greater amberjack in the Gulf of Mexico federalwaters



    Maybe a stainless steel bolt covered in G2 to replace rusted screw? Then glue ontop.

    TB
     
  5. the brain
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    the brain Senior Member

    Update was able to replace 3 of the 4 broken revits dipped in G2. will need another small revit tool for the fourth.

    smeared G2 on the few fingernail gap revits.

    fabbed the first midship/freeboard brace the wood represents the latitudinal hump.

    will fine tune brace.

    TB
     

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    Last edited: Jan 25, 2018
  6. the brain
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    the brain Senior Member

    Update was able to replace 3 of the 4 broken revits dipped in G2 then covered w/ G2.

    reattached bunks/removed forth jackstand tinding up trailer then out for a splash.
     

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    Last edited: Feb 6, 2018
  7. dinoa
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    dinoa Senior Member

    Do you have the spec for this low temp braze. Most stuff I see has 750F melting point.
     
  8. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The lowest melting point of the two products I use is 350 degrees (177 C) and has a bond strength of 20,000 psi, (138 MPa). The other primary stuff I use melts at 600 f (316 C) and has a bond strength of 30,000 psi (207 MPa). I also use (occasionally) other products from this same outfit for cast iron and a silver solder for refrigeration work. Have a look at muggyweld.com . . .
     
  9. the brain
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    the brain Senior Member

    I am impressed w/the bonding strenght of G2.

    the opposite side same midship all revitos intact not even a fingnail sized gap.

    its strange that all 4 broken revitos where in the middle row.will fab a couple braces.

    I will glue w/G2 a brace inplace to see how stronge G2 is.
     
  10. the brain
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    the brain Senior Member

    replaced loose rivets w/ blind type one size larger in diameter then covered w/ G2 shes still taking on water.

    I suspect the two lower though hull POD mount bolts they are under water line remember this POD is designed to takeon water I believe I saw speepage inbtween knee brace and transome plywood.

    my transome skin is completely welded sean sealed w/ G2. will redo the lower bolts goob on the 5200 shove bolt in then pull out another goob for good seal.
     

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  11. the brain
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    the brain Senior Member

    please suggest what to fill the two lower though hull POD mount bolts they are under water line I believe there is seepage include name and brand glue.
     
  12. IronPrice
    Joined: Jul 2017
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    IronPrice Senior Member

    3M 5200. Google it.
     
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  13. the brain
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    the brain Senior Member

    yes I used 5200 first time of POD install I did goob it on.

    now the second time I goobed it on again covered bolts and inserted into each hole then goobed again.

    I inserted the bolts Saturday and just snugged them down I didn't want to completely tighten in fear of squeezing out majority of glue.
    did the same thing first time around if I remember correctly I waited 2 days before I seriously tightened the temps where kindof warm and even after 2 days the glue was still kindof soft.

    I used the 5200 that takes 7 days to cure how long should I wait till I tighten bolts?

    only redid the two lower holes.
    Thanks TB
     
  14. IronPrice
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    IronPrice Senior Member

    When I'm applying 5200 to fasteners below the waterline on my aluminium boat I use washers under the bolt and nut and apply it liberally around the inside of the holes, around the outside of the holes on both surfaces, under the washers and around bolt shafts. Then I tighten up the fastening, clean up the excess that squeezes out and let it cure.

    You can't really squeeze sealant out of a fastening hole it will expand in all direction as you tighten up the fittings, including into the hole. Just use plenty and clean up the excess later.

    If it says 7 days, leave it seven days. It's an underwater fitting so you don't wan't to take any chances.
     

  15. the brain
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    the brain Senior Member

    yes I also used washers.first time I actualley waited 10 days for glue to cure before hanging engine.

    are you saying to tighten right away and not wait a few days? I bet the glue is still soft after applying 30 hours ago.

    after tightening bolts and glue cured was planning to goob more inside POD over bolts nut
    TB
     
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