Patch My Leaky Aluminium With Fibreglass?

Discussion in 'Materials' started by abrogard, Apr 24, 2012.

  1. abrogard
    Joined: Apr 2012
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    Location: australia

    abrogard Junior Member

    I have an old aluminium dinghy. The seats and the keel are rivetted on and it is leaky.

    I have drilled out some rivets and put new pop rivets in and I've bogged up holes with epoxy resin type stuff.

    Not sure how good this kind of fix is.

    Seems to me a good fix would be to coat the whole bottom - or the bands across the boat where the seats have been rivetted on and the long band along the keel where it was rivetted on - with fibreglass.

    But is that a good idea?

    The boat is very old and thickly painted with at least three coats of paint.
  2. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    It really depends how extensive the 'holes' are, their locations and the causes of the leaks too. Got any piccies to show and tell?

    BTW..sikaflex is great...seals everything :D
  3. tunnels

    tunnels Previous Member

    West system make a semi flexable epoxy specially for what you are talking about !! Sticks like nothing else on earth and is semi flexable so wont crack / flake and fall off when the panel moves !!
    Have a look on there web site !!!!. there was even a short video last time i looked !!!
  4. Saildude
    Joined: Jun 2011
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    Saildude Junior Member

    I think the name is G-Flex that you want - extra flexible - I think they have sheets on both Alum boat repair and some sort of molded kayak repair
  5. abrogard
    Joined: Apr 2012
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    Location: australia

    abrogard Junior Member

    Thanks for the replies, guys.

    I do have some pics up on Photobucket.

    You can see there's four bands of rivets crossing the hull. And there's a few little pics of rivet holes and whatnot.

    I have used sikaflex along with these metal expoxy things.

    This G-Flex sounds good but it is an epoxy again. So would that be the consensus - that I should be satisfied with an epoxy and there's no need to go fibreglass?

    Does anyone have first hand knowledge of fibreglass repairs to aluminium?

    I ask because googling around I ran across a lot of posts saying that you can't fibreglass aluminium. (with or without the aluminium being already painted I don't know).

    But I found one post by some old timer who claimed to have fibreglassed his old aluminium dinghy in a few places and it was still going strong umpteen years afterwards.

    Can't find that post again. Don't know where that forum was. That's the trouble with googling and browsing too quick I guess.
  6. tunnels

    tunnels Previous Member

    Glass on any kind of metal surface is never going to stay there and will get ripped off real quick !!
    It does have its limitations and is nothing magical !!!
    The G flex epoxy is whats made for what you are doing !!!
    not sikaflex its almost a bad as putting on silicone !! use whats specially made for that purpose !!!!:)
  7. abrogard
    Joined: Apr 2012
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    Location: australia

    abrogard Junior Member

    Well this G-Flex certainly seems to be good. I've just been googling and reading up about it.

    It seems especially good when used with glass:

    Quite reasonably priced in the USA, it seems. Here in Aus. they seem to be doubling the price up. Pretty usual, that.

    I like the handling time, that's a plus.

    Probably I'll give it a go. Right now I shouldn't need much - filling the boat with water it doesn't leak at all, maybe a drip somewhere. Three days later the water was still in the boat, it's that good.

    But what worries me, of course, is all my epoxy and rivet 'fixes' popping out of place when the boat is in use.

    I've been casting around for something to turn to if that happens. G-flex with glass seems to be the go. Though it would certainly cost a bit to do the whole boat the way I've been thinking... but no hurry...

    Thanks everyone for their help.

  8. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Agreed on Epoxy, G-flex is good, but most good epoxy would work. I have even fixed individual holes with 5200. All will work for a few years, eventually you might have to fix a couple here and there,
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Regular laminating epoxy as well as the elongation formulations, like G-Flex will work, but only if the surfaces are prepped properly. In thin applications (like this) you'll see fastener hole "circle out" in time, if not wholesale delamination if the surface isn't prepped right on aluminum, especially old, well oxidized aluminum. The prep includes the overlapping portions of the sheets for best results. Log onto: and look up aluminum prep.
  10. bntii
    Joined: Jun 2006
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    bntii Senior Member

    Boy- strip off all that paint for sure.
    I would use some alumiprep after mechanically cleaning the plate:

    I use it to prep Al spars & can tell you it is more a wash for clean metal & will not strip off deep pitted oxides.

    Perhaps look into the sealants designed for aircraft fueltanks- they will absolutely seal up rivets though best used when installing new rivets:

    Trying to seal a loose rivet is tough.

    I think I would be going the route of removing & up sizing the rivets.
    So drill & seal with new rivets & sealant as installed.
  11. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    I fixed one with Gitrot and 10 oz cloth years ago for a commercial crabber. He got a couple of years of work out of it.
  12. whitepointer23

    whitepointer23 Previous Member

    i had a 12 ft tinny full of corrosion holes, i cleaned and roughed up the bottom and put on a layer of left over cloth and poly resin. it lasted 4 or 5 years of hard beaching and thumping through chop with an 18 on the back. i did cover the whole bottom so that probably helped it stay on.
  13. afteryou
    Joined: May 2012
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    Location: Southeast Alaska

    afteryou Junior Member

    First post here. would like to say hi. i am not sure how great of an idea it is in terms of longevity but a few guys around here have had the bottoms of their aluminum boat sprayed with rhino liner. they were happy at first anyway any thoughts?
  14. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Thick polyurethane coatings can work, but will have the same issues as 'glass or other coatings, which is surface prep and physical working of the separate elements. Holes will tend to circle out, panel edges will tend to slice the coatings, etc., unless the surface is well prepped and the structural issues attended.

  15. midnitmike
    Joined: Apr 2012
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    midnitmike Senior Member

    It's been a while since you responded to this thread, so I was wondering if you've fixed the problem?

    Leaky rivets aren't new, some guys take their boats to a shop and have them welded over, but this only stops those rivets from leaking and does not address the ones that are going to leak later on.

    About 20 years ago a friend of mine had 16' jon boat that was leaking so bad he was ready to scrap it rather then try and fix the damage. I convinced him to let me have the boat for a few days because I wanted to try something different. I flipped the boat over and proceded to grind down the bottom removing the old paint and cleaning up all the scratches and grooves left after many years of abuse as best I could. Once the aluminum surface was cleaned I cabosiled over the dents and holes and faired any imperfections that might interfere with my glass.

    Now I'd probably use different material but at the time this was an experiment, so I spared every expense.

    I then proceded to glass two layers of 1 1/2 oz. matte over the entire bottom and up the sides a few inches ending just under the first longitudinal rib pressed into the side panel. I ribbed rolled the surface until it was as smooth as possible, but left it plain ie. no paint or gel coat since I wanted to monitor it's progress. Here it is all these years later and although the boat is wore out in every way imaginable that bottom is still intact.

    To be sure high speed impacts have occured over the years, but the damage to the glass was minimal, and if they were bad enough they were easily repaired by him without my help.

    Would I do this again? You bet! Would I recommend this as a way to prolong the life of another riveted skiff...Yes again.

    I can probably think of a few ways to improve finish, but in the end it proved to my satisfaction that this procedure was both cost effective and extremely durable.

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