Filling small holes in Aluminum

Discussion in 'Metal Boat Building' started by Katoh, Mar 12, 2011.

  1. Dean Smith

    Dean Smith Previous Member

    yes mate its fine, there are more than 10 ways to skin a cat
    My mate has just built ( from scratch) his own design a 7 cyl radial engine
    At peak power, that is cruise power, the heads were overheating, he had to extend every fin, there must be a dozens of em, he used a copper backing bar
    I am not saying use that for salt water situations
    Just for the reference , you can buy ceramic backing back in strip, they are rather like tiles, mainly used in steel seams and butts, never have tried on alu but will one day. Even with pulse , single sided welding still needs that backing medium
  2. Katoh
    Joined: May 2010
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    Katoh Senior Member

    Mate I hear you! My biggest problem I just don't have the experience and Knowledge in this field, that's why we ask the question's, to get the answer's and hopefully there right. If I knew I wouldn't ask, but you can very easily put all lthe equations together and get the big picture.
    I never even thought about ceramics, but s/s would still be easier to make something up.
    that salt water stuff, its real friendly is it not? Only if your a fish, mind you a salt water fish at that it might be Ok.
    Ad Hoc
    I would dearly love to get in contact with the builder, who apparently retired in the late 90's, He could answer so many questions that would make my life so much easier. I would not even know were to start looking for him, I have tried all the internet searches ect, even contacted a firm he used to have dealings with, but this is Oz and don't hold your breath for a reply , as blue is not a good shade for people to have.
  3. PSG-1
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    PSG-1 Junior Member

    I've heard of using copper as a backing plate. I also know that copper, if left in contact with aluminum, will cause horrible corrosion. Having said that, I'd use a thick piece of stainless, about 1/4" thick as my backing plate. And just FYI, stainless will also cause aluminum to corrode if left in contact with it.
  4. fishhawk
    Joined: Jan 2011
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    fishhawk Junior Member

    Ad Hoc, Yes aircraft are riveted, the primary alloys are 2024-t3 & 7075-t6 that should never be welded, there are a lot of other weldable alloys used, such as 3003,5052 5083 & 5086 that we call "work hardened" & 6061,6063 that must be heat treated after welding. I do not profess to be as knowledgeable as you in engineering matters. Back in the 90s, i built a 18" setback transom for my wellcraft, i used 1/2" 5086-h112 tig welded with 5356, painted with fluid resistant primer, and finished with imron,now 13 years later there is no signs of corrosion, not even a small bubble. I am not trying to win this argument, only to insure that KOTAH does a good repair that does not fail in the future. KOTAH, if you want to use stainless, go ahead, it will work as well as copper
  5. tazmann
    Joined: Aug 2005
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    tazmann Senior Member

    Clean steel works for temp backing allso if you dont have stainless available.
  6. Katoh
    Joined: May 2010
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    Katoh Senior Member

    I have plenty of everything, stainless, copper, mild steel. My father suffers from in the incurable "rusty iron disease", there is a pile of crap that would rival the very best of hoarders.
  7. alidesigner
    Joined: Nov 2006
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    alidesigner Senior Member

    It might be a bit late but if you havent done it yet have you thought of using alloy brazing rods.
    You can get them here
  8. hoytedow
    Joined: Sep 2009
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    hoytedow Carbon Based Life Form

    I agree. If it is only cosmetic and you are painting anyway, epoxy is best.
  9. Katoh
    Joined: May 2010
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    Katoh Senior Member

    Thanks for the suggestions,
    I have actually become very proficient at this hole filling business, with the mig and a spoolgun, takes me 5 seconds if that to fill the hole with a stainless backing plate and a quick grind with a flapper sander on both sides. You would never know the hole ever existed, or I defy anyone to pick were the hole was. I find this works perfectly up to 12mm or 1/2" hole with absolute minimal heat into the plate.
    I only use 5356 filling wire.
    Many Thanks to all!
  10. scott hightower
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    scott hightower Junior Member

    I have used copper as a backing plate. You may even consider putting the copper on the front side instead so you don't have as much clean up. If the back side is not exposed you can place a small dime sized patch over the hole.

    You probably already know this but you need 100% argon as a sheilding gas when welding aluminum.

  11. pwsf
    Joined: Oct 2011
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    pwsf New Member

    Aluminum CAN'T be clean enough to weld. I like to drill the holes out a size larger to get to fresh alum as well as grind both inside and out. I would weld them shut and then finish them by grinding and sanding them later.

  12. Katoh
    Joined: May 2010
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    Katoh Senior Member

    I like to use a a flap disk on a drill, sorry just cant think of the proper material name at present, drawn an absolute blank in my mind. The fingers penetrate the hole giving a clean alloy base to weld upon, I have made a a backing handle with a plate of 316Stainless you hold over one side of the hole and just fill from the other, works a treat!
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