How to install acrylic windows reliably ??

Discussion in 'Materials' started by MikeJohns, Dec 12, 2006.

  1. MikeJohns
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    MikeJohns Senior Member

    How do you install acrylic windows panes when they are simply bolted proud on the outer surface so that they stay water tight for a long time .

    Any expertise here or good guides that anyone can point me to would be appreciated.

    Thanks
     
  2. jehardiman
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    jehardiman Senior Member

    Here is a technique that I have used.

    Cut the inner opening in the shell.

    Drill/set the mounting holes/studs such that they are outside the gasket/sealent that will ring the opening.

    Cut the acrylic so that there is an additional margin of 2x the mounting bolt/stud diameter + the acrylic thickness outside the bolting centerline Add any additional margin for edge finish/calk relief or make the bolting ring 1/8" larger than the arcylic. The bolting ring is drilled to match the mounting bolts/studs .... NOT oversized.

    Drill the mounting holes throught the acrylic 2x the diameter of the mounting bolt/studs. Use the proper drill bit point shape and go slow.... see this website http://www.plasticsmag.com/features.asp?fIssue=Sep/Oct-01.

    Mount the arcylic, taking extreme care that the mounting bolts/studs are centered in the oversized holes and that the gasket/sealent is continuious and not touching the mounting bolts/studs. DO NOT FILL THE OVERSIZE HOLES WITH ANYTHING. You may calk the outer shell to arcylic join after you are through bolting up

    Bolt the arcylic in place either using the bolting ring or large cup washers. If using through bolts, seal the interior side only.

    I've used this method on acrylic windows up to ~2.5 m x ~.75 m x ~16mm using Sikaflex as a sealent and calk. After 5 years when I sold the boat, there were no leaks around the acrylic, and just occasionally a little weeping around a few of the bolts when taking green water and working heavily.
     
    Last edited: Dec 13, 2006
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  3. SmithCraft64
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    SmithCraft64 Junior Member

    Thank You Jehardiman

    I was looking for different applications for installing a windshield on my SmithCraft. I'll keep this one on file until I get to that point. Which shouldn't be to long from now.
    If it will work for Windshields also? Am I off base on this for windshield applications?
    If nothing else maybe some the techniques could be applied? By the way the windshield is not curved its a flat surface 5 piece windshield. The center panel opens to the bow.Just clarifying its design so you don't think I'm losing it. lol Hey I've lost it before and it's not that bad. ha I found it again without to much effort. ha
    Do you have any pics of your work? That would be great. You know the old saying; "A picture is worth a thousand words." Thanks again, SmithCraft64 :cool:
     
  4. jehardiman
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    jehardiman Senior Member

    Not up in digital right now, and we are in a remodel so the photos are packed away. I don't know if my case was the same as yours. What I had was a Ranger 26 sailboat that a previous owner had tried to "fix" the failing "plate in extrusion" type window and mangled it. With a 7' long opening down each side of the cabintop, the cabin was flexing a lot and thin acrylic they used sandwiched between the cabintop and liner just wouldn't handle it. Ended up using 5/8" acrylic on the outside with hardwood doublers on the inside to get the strength back up and so you could step without worring about going through something. There was maybe 2" of bow along the length and maybe a very slight twist.
     
  5. Frosty

    Frosty Previous Member

    Jehardiman-- Exellent post there about the acrylic sheet. Do you over size the holes to stop any misallignment cracking the acrylic.
     
  6. MikeJohns
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    MikeJohns Senior Member

    Jehardiman

    Thanks for the page on working the stuff. What do you use as the gasket or goo?

    Has anyone tried the Sika 295 product? Heres the Sika how-to link that they emailed me after I enquired.

    http://www.sikaindustry.com/ipd-marine-window-295

    Dont like the idea of just glueing it, I have seen a few loose windows (just about able to push them out ) that used that method. A combination of goo and fasteners, but do you use dome headed fasteners or rebated heads?

    As an aside
    They used to use acrylic to show stress fields, eg a spanner cut out of acrylic sheet when applied to a bolt and viewed through a polarising sheet you can see how the stresses run. (That was back in the slide rule days these days we use an FEA package ). So maybe with your polaroids on you could see how much stress you have induced after it is mounted. (Don't quote me on this it may have been a specail light too)


    Cheers
    Mike
     
  7. Crag Cay
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    Crag Cay Senior Member

    I've used Sikaflex to bond Lexan windows which have never given any problems, including Antartic cruising.

    However I have always recessed the opening which gives good local stiffening, have always used generous overlaps, and used a dark edge tint to give enhanced UV protection.
     
  8. MikeJohns
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    MikeJohns Senior Member

    Thanks Crag

    You specified the 392 ? No fastenings other than the 392 ?

    Cheers
     
  9. Willallison
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    Willallison Senior Member

    Mike - I have a fairly comprehensive paper on bonding 'windows'. I'll have a look tonight and see if I can find where it came from....
     

  10. catmando2
    Joined: Sep 2006
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    catmando2 Malaysia bound....soon

    Here is an artical from the Coastal Passage, a free boaty paper published in Australia.

    Forget drilling holes, who wants bolts in their boat.

    Forget sikaflex, it has expansion problems in the tropics.

    http://www.thecoastalpassage.com.au/windows.html

    Have done windows over the years the same way with exellent results using 3M double sided tape made for the job.

    Have tried to get same windows of a boat later on and pulled fiberglass.

    Go to the home page afterwards and check out the rest of the mag.

    Also use Lexan or Shinkolite, acrylic is a poor second to these materials

    Dave
     
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