Welding polyurethane foam and such...

Discussion in 'Boatbuilding' started by jprev, Dec 17, 2004.

  1. jprev
    Joined: May 2003
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    jprev Junior Member

    Well sorta... I want to build a kite board for my son. I figure with the abuse a kite board gets it should be a perfect match. And I want to fill it with 2 part polyurethane foam. The good stuff.

    Besides the technical problems if putting the foam INSIDE the board, which I think I just about have figured out, I have a problem of somewhere sometime having to weld some aluminum (1/8" 5052) that has polyurethane foam jammed up to its back side. I see a serious OSHA investigation here. I see a horrible death from inhaling the fumes associated with this operation. I see smoke, fire and explosions only slightly less intense than a nuclear event. But I also see two part foam in almost every aluminum hull and I know somewhere someone is having to do the same thing.

    Does anyone have any experience with this? Any comments or suggestions would be apprciated!

    Thanks,

    Joe
     
  2. tschienque
    Joined: Feb 2004
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    tschienque Junior Member

    Make sure you get it all on film! Americas funniest videos could be interested (as long as no one is seriously harmed).

    There was a surfboard builder in the yard I spent a season or two in and I was surprised how lightly they were built/reinforced. 2-4oz glass over basic foam blank

    Normally the foam blank gets built first and then covered / reinforced with some glass cloth

    Q1 - Why would you want to reverse this process?
    Q2 - Why do do think pourable foam would be better?

    Epoxying the aluminum would be more than effective. Presumably the ali would be attached to the board's glass surface, rather than to the foam (as you state). I would have thought any shear forces on the ali would tear the foam apart.

    Is a kite board's construction necessarily that radically different?
     
  3. jprev
    Joined: May 2003
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    jprev Junior Member

    I just don't have much command of the English language. I don't want to put aluminum around a kite board. I want to build a kite board out of aluminum and inject in some 4-6 lb (or higher) foam. Somewhere along the line I was going to have to weld the 1/8" 5052 with the foam behind it. I was worried that I might cause some sort of nuclear type meltdown inside the board from the heat of the weld.

    Sorry for the misunderstanding but damn I appreciate someone replying!

    Thanks,

    Joe
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    At the temperature the aluminum is going to be, insuring a good weld, you'll have well cooked the foam. It'll likely not be foam anymore.
     
  5. tschienque
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    tschienque Junior Member

    Agreed! And aluminum being the excellent conductor that it is, the foam will be cooked pretty well throughout the board.

    Why an aluminum kiteboard in the first place?
    1. I would think it might be dangerous (injury wise) to your son and other kite boarders (due to it being heavier and harder material)
    2. Always going to be heavier than foam & glass board (for similar size), requiring a bigger and more expensive kite

    Is it that you have easy, cheap access to aluminium and you have welding skills but not fibreglass skills?

    I've done a bit of welding in steel but have stayed away from aluminium welding as skills required are much higher.
     
  6. Ssor
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    Ssor Senior Member

    I don't see how you could expect to get the proper shape for a kite board in 1/8" aluminum. Shape it up in 4" pink styrofoan and sheath it with epoxy and fiberglass. I have used that method to make outrigger pontoons for a sailing canoe and for fun boards for paddling down small rivers in the summer time. BUT if you insist on foam filled aluminum shape and weld the thing complete and leave two holes in it at opposite ends. Pour the foam into one end and let it fill to the otherend and the excess push out the second hole. Then poprivit a plate over the hole.
    Ross in Bel Air
     
  7. D'ARTOIS
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    D'ARTOIS Senior Member

    Although I didnot follow the discussion completely I just want o check the following: No1: why do you want to weld? Constructional parts you may glue and rivet using Cherry aircraft type water-and gastight rivets. Even the thinnest alusheets that you cannot weld, you can still rivet.

    Just an idea.
     
  8. jprev
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    jprev Junior Member

    I guess the real question here is what happens when you have a joint of aluminum, say a interior side meeting flooring that has polyurethane underneath. I see photos of boat construction done this way all the time. But it seems that bad things could happen to the polyurthane floatation if right under the weld. Bad things such as noxious fumes and explosions and flames. Am I incorrect in assuming this. How else could a aluminum boatbuilder get around this problem?

    Thanks,

    Joe
     
  9. Ssor
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    Ssor Senior Member

    All welding is completed before the urethane is introducded to the hull.
    Put a match to a SMALL piece of urethane foam OUTSIDE, Away from buildings and watch what happens. It burns with all the intensity of liquid fuel and with very nasty smoke.
     
  10. Thunderhead19
    Joined: Sep 2003
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    Thunderhead19 Senior Member

    Boat builders get around this problem by doing the foaming LAST. In cases where this is impossible, I've heard that the foam will put up with a bit of welding heat as long as it is in a sealed, oxygen-depleted area. I've also heard of boats being destroyed completely when air suddenly finds it's way into the hot foam. Give LORD automotive structural adhesive, Loctite H8000 or SikaFast 3000 series a try. They're amazingly strong and in a lap joint of the right dimensions, they're stronger than a weld.
     
  11. jprev
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    jprev Junior Member

    Thanks! Great info. I'll check into expoxies etc. Also anyone have a source on those Cherry aircraft rivets.

    Thanks,

    Joe
     

  12. Ssor
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    Ssor Senior Member

    Try McMaster-Carr in Chicago they have everything look under rivets there are more kinds than you need to know about, but what the heck, grow a little. Seriously there are rivets that are liquid tight and they are great if you are not planning to fill the assembly with foam but with something that will stay liquid and you will utilise later.
     
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