Methacrylate Structural Adhesive

Discussion in 'Boatbuilding' started by Thunderhead19, Sep 10, 2004.

  1. Thunderhead19
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    Thunderhead19 Senior Member

    I need some pointers on the use of Methacrylate structural adhesive. We have been playing with MA820, but we need some advice w/r/t applying technique. There is an enormous potential to use this stuff where welding is difficult or impossible.
     
  2. Darren
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    Darren Junior Member

    By the number MA820 I suppose this is made by Plexus.
    We tend to use a large amount of this, please confirm & I will answer any questions that I can
    Darren
     
  3. Thunderhead19
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    Thunderhead19 Senior Member

    That's the stuff! ITW Plexus MA820. I have many questions. The decks of our boats are installed over a gridwork of framing comprised of 1 X 2 aluminum channel. Now, we know that the adhesive has a minimum required thickness of .03in. in order to work properly. We know that we have a 2" wide piece of channel to put it on. We're trying to figure out a way of applying a consistently thick bead of the stuff, of securing the decking while it cures (still allowing .03" thickness), and what kind of bead we should have (wide and flat, round, several beads, narrow "s" shaped bead. What will give us the best results consistently? We're doing our testing using the 380ml cartriges. There will be more questions when I can remember them :)
     
  4. Darren
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    Darren Junior Member

    Hiya
    Hope the following helps

    1) To maintain a certain thickness (ie so that the deck doesn't push all the plexus out) you can glue some S/Steel waswhers onto the frame every 200mm or you can even use self adhesive sticky bumpers (like fitted to the inside of kitchen cabinet doors, this is the method that we use on smaller boats of up approx 38ft. Above that we use the washer (up to 108 ft so far)

    2) The cartridges should come with an approriate mixing nozzle that mixes the glue as it is applied. We tend to Zig Zag in one continual line.

    3) Ensure that you abraid the two surfaces with approx 100 grit, then you need to clean the two surfaces using acetone.

    4) Don't bother cleaning up any excess glue (just use the old gld glove and smooth the glue out) as it all helps

    5) Not too sure if I can help with how you secure the deck down during curing time but you could try Ratchet Straps around the whole structure. Let me know sizes etc and will let you know if I can help

    Anyway enogh babable.............what are you making............who are you.........and good luck

    Regards
    Darren
     
  5. Thunderhead19
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    Thunderhead19 Senior Member

    The boats we make are of this type, fully welded, aluminium. The decking is not accessible from behind, so we either have to plug-weld, or use methacrylate. We specifically requested that this be a no-prep product (other than a quick cleaning with solvent), and that's what they promised. As you an see, the decking is in the cockpit, and we have little choice but to throw sand bags on it. I like the idea of using spacers, but this might create a minor alignment problem for us (easy to fix). working time for this stiff is 4-6 minutes, and cure time is 15-25 minutes.

    What about using blobs, as opposed to continuous beads?

    http://www.boatdesign.net/gallery/showgallery.php/cat/500/ppuser/1708
     
  6. Darren
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    Darren Junior Member

    They also make MA320 (I think thats the number) which has a working time of about 20 mins. They also make a Low Odour variant which is much better, it is blue in colour
    I wouldn't recommend that you scrimp using blobs as the loadings on the plexus and the deck wouldn't be spread over a very big area
    If you need to use vast quantities they can also supply it in 50 lt drums. They have supplied us with a special air gun that mixes it as it goes but we tend to use lots

    Regards
    Darren
     
  7. Thunderhead19
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    Thunderhead19 Senior Member

    One cartridge costs us $60. We can plug-weld the decks for only slightly more. This was supposed to be a real cost savings. The people from Sika are coming to visit on thursday to try to sell us their product. Maybe it will be cheaper. I'll let you know how that works out.
     
  8. Darren
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    Darren Junior Member

    We use Sika for many applications, some would be relevant
    Run this past the sika boys

    Abrade the ally and then apply sika primer prior to any oxidization
    Use sika 252 structurall adhesive with a 3-4mm spacer.
    We use the kitchen door bumpers

    Regards
    Darren
     
  9. Thunderhead19
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    Thunderhead19 Senior Member

    SikaFast

    They gave me a sample of a new product they launched this spring called SikaFast. It's a methacrylate like Plexus MA820, and it looks pretty good, (it's taking a long time to cure). They told me that instead of washers or kitchen bumpers that I could buy a bag of glass beads to sprinkle on the adhesive. I'll let you know what happens when we test the stuff tomorrow. We have determined that we're subjecting the product to a lot of heat from adjacent welding. We shall see what the makers say about that. They also suggested that if I wanted to go back to the moisture-cure urethane products that I could mist the glue with water before putting the pieces together. This would reduce the cure time and help us out with another consistent problem where we have to move the part before it's cured.
     
  10. Dutch Peter
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    Dutch Peter Senior Member

    Daren, JDF,

    Would appriciate comments on this question:

     
  11. Thunderhead19
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    Thunderhead19 Senior Member

    My local Plexus rep gave as an example a manufacturer of sailing trimarans. I'll find out who. They have been attaching their hulls to the...arms?...and the arms to the centreal hull with this stuff, I believe without anything else. Also Freightliner trucks get assembled with this stuff, as well as various Bombardier products. I think there are more than one boat yard who merely glues. This stuff is actually stronger than fiberglass tabbing and in some cases much stronger than screws because the bond covers the entire lap-joint. I'll get some info from my local rep.
     
  12. Dutch Peter
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    Dutch Peter Senior Member

    Will be highly aprreciated!
     
  13. AVMan
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    AVMan Junior Member

    Structural Adhesives

    I know of at least several builders who use Plexus or other MMA adhesives to bond their molded stringer systems into the hulls (no mechanical fastening), and I know there was an article in Professional Boatbuilder on this subject (I believe #41, the one with the molded stiffener system on the cover)..
     

  14. Thunderhead19
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    Thunderhead19 Senior Member

    Okay, Now I've tried Plexus MMA, SikaFast MMA, Sikaflex urethane, Powerseal urethane, Epoxy, the guy from Loctite is coming in a week, and a supply house is hunting down some different stuff for us.
     
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