aluminum with adhesive...

Discussion in 'Materials' started by tws, Aug 13, 2015.

  1. rwatson
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    rwatson Senior Member

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  2. Mr Efficiency
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    Mr Efficiency Senior Member

    rwatson, I've heard it said those rods that are just melted on with a propane torch are ideal for cosmetic repairs, easy as. Obviously not to be considered a fix where there are structural integrity issues, but above waterline should be OK to fill gouges.
     
  3. PAR
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    PAR Yacht Designer/Builder

    On the thin plate used in the OP'd boat, you'll make a whole lot of distortion using that brazing/soldering technique.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    I've never used it, but never heard of that happening from the fella who said it worked for him, and it was maybe 1.6mm or 2mm he was speaking about. But if you have had that experience, then it is a fair warning. It is a slightly "bodgie" way of doing things, anyway, certainly not to be trusted if the integrity of the boat has been compromised by the damage to it.
     
  5. Barry
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    Barry Senior Member

    The scratch does not look deep enough that it will impact the serviceability of the boat.

    You run the risk of a permanent distortion if you tig, mig or apply heat to this area if the aluminum is very thin. Thin large sheets can easily permanently warp with any heat application and when it is slightly prestressed it can happen pretty fast


    Tig can put more heat overall into a material because it is a slower welding process than mig. Note I said more heat, not temp, which affects distortion.

    I tried to find the thickness of a Westcoast fishing boat. This is an important factor in your decision

    I would be extremely careful taking a dremel to it in case you undercut the protrusions and end up with a larger surface area impacted which could show quite a bit

    IF the thickness is above .080, you might a find a qualified aluminum boat builder and
    mig the gouge but the process would be at an extremely low heat, and a series of short welds, AFTER EACH SAY 1/8 to 3/16 INCH LONG BEAD, YOU LET THE HULL COOL DOWN TO AMBIENT. Do not consider putting a cold wet rag on the back side as a heat sink or you most likely will blow through the sheet.

    Instead of pushing the bead as you normally would, after the first spot is applied, have the welder point the mig tip towards the first bead, and apply another, as this will let the first bead act as a slightly thicker heat sink. Again let the whole area cool down.

    This way the surrounding sheet will hold the shape. After that you would have to take a FLEXIBLE sanding pad to sand out the peaks. But note then the whole repair will show from the sanding process. If you grind it or use a rigid or semi rigid pad, you will probably flatten the plate and it will not look very good. It appears that the gouge is on an outside corner, convex and if you take a pad as stated above, you will change this curve and it will show up.


    If it were my boat I would carefully HAND sand the ridges so only the ridges see the grit and let everything stay as it is.

    If in the future a crack develops if you leave it , you have the option of welding up the crack.

    On the other hand, you could take a chance and have it tig welded. If you do send final picts as I am interested in seeing the result
     
  6. tws
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    tws Junior Member

    rwatson, mr. efficiency and barry,

    thank you so much for your detailed thoughts on this matter. i appreciate your valuable input. i think i will do as barry says and carefully hand sand the ridges... and keep an eye on the gouge as time progresses, for further spreading etc.
     
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  7. whitepointer23

    whitepointer23 Previous Member

    A quick fix would be just fill it with an epoxy stick like selleys knead it. Aluminum dinghys get scratched and scraped all the time. Its not normally a problem. .is it leaking ?.
     
  8. tws
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    tws Junior Member

    to true whitepointer,

    it's not leaking and not completely thru the hull - just a gouge...

    i'll check out the epoxy stick you mention. thanks!
     
  9. tws
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    tws Junior Member

    don't think selley's knead it can be had in the usa...

    maybe find and equivalent...
     
  10. sdowney717
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    sdowney717 Senior Member

    Simple cosmetic repair. You could use bondo, sand it and paint the outside and might get a reasonable match. You could fill it with a flexible polyurethane like 5200, Black PL polyurethane roof flashing from Home Depot, sand it and paint it.
    If you tape a piece of cereal bag over the polyurethane adhesive, it will come out smooth. The bag will not stick.
     
  11. whitepointer23

    whitepointer23 Previous Member

    The epoxy sticks are really strong and stick like the proverbial to a blanket. There are several brands on the market. They are an excellent addition to the boats toolkit for emergency repairs.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    I have seen some nasty poultice corrosion under epoxy repairs to alloy boats, might be avoidable with proper surface prep ?
     
  13. tws
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    tws Junior Member

    i do intend to fish this skiff in the salt... if i did epoxy to fill this gouge it would have to be the best marine grade and i'd definitely prep the surface first...

    thoughts?
     
  14. Ad Hoc
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    Ad Hoc Naval Architect

    You only get poultice corrosion when ally is in contact with a hygroscopic or wick like material..one that absorbs water..liek wood/rubber/foam etc.
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    May not have been poultice corrosion, then, but when the epoxy and glass was peeled away, there was a large amount of white corrosion product under there. It had been applied to areas of pitting and pin-holing. It may have been the surface wasn't clean to start with, and water infiltrated behind the patches.
     
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