rebedding windshieds

Discussion in 'Boat Design' started by gabriel, Apr 13, 2015.

  1. gabriel
    Joined: Jan 2012
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    gabriel Junior Member

    Hi guys

    I am having water coming in from the windshield on my Bertram 58 ft 1983.
    That boat is designed with all aluminum frames. The windshields are bedded over aluminum frames and held in place in with external aluminum frames too and screws.
    I want to replace all the old caulking I between . the question is what caulking products would you recommend for best performance and ease of application. ?
    Do I need to use gaskets too or would the caulking be enough?

    Thanks
    Gabriel
     
  2. Petros
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    Petros Senior Member

    caulking should be enough. You might consider what all the modern automobiles are using Polyurethane adhesive caulk. It is flexible and very strong, weather proof and will add strength to the installation. Most auto glass shops can show you how they install it: large heavy bead around the clean frame, and the glass set in it and allowed to cure.

    It is tought to remove when a replacement is required, but again the auto glass installers know how to do that. there are many Youtube clips showing how it is installed.

    You can buy polyurethane adhesive caulk at most hardware stores. I have used it in many marine applications, and it makes a tough and reliable bond.
     
  3. gabriel
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    gabriel Junior Member

    rebedding winshields

    Hi, I found a Marine sikaflex 291 in west marine catalog, but although it is polyurethane base it does not mention windows in the list of applications. Will this product work to re bed the Windshields on their aluminum frames? If not can you please give me a product name that I can search for.

    Thanks again
    gabriel
     
  4. kapnD
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    kapnD Senior Member

    As Petros said, the stuff is available in any hardware or auto parts store.
    Don't feel compelled to use only products bearing the dreaded "marine" label!
     
  5. Petros
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    Petros Senior Member

    Automotive windshields (or winds screens for those of you across the pond) use only the polyurethane adhesive to hold the glass in place. In your installation you have screw down trim strips that actually capture the glass between the trim strip and the frame, so even if the bond is not as strong I do not see why the sika flex would not work fine.

    Personally I would locate the type used on automotive windshields, it is designed to bond to both metal and the glass, and take weather, sunlight and vibrations and often even structural loads. If it holds auto glass in place without leaking it will certain hold your boat's windshield in place. It is far more common than marine adhesives, so it should cost less too.
     
  6. PAR
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    PAR Yacht Designer/Builder

    The real key with automotive windshield polyurethane is is exceptionally clean glass and frame. Many require a special primer on the metal and the glass is typically buffed with acetone. Don't touch the contact areas, before applying the goo.
     
  7. CDK
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    CDK retired engineer

    If you use Sika 291 it will be extremely difficult to remove the glass later, so make sure the seal is perfect.
    I had leaks in the windows of my Draco from the same era; the cause turned out to be the seal between aluminum and grp.
     
  8. gabriel
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    gabriel Junior Member

    sika flex 291

    Thank you CDK

    let me ask you something, I have not yet taken the windshield apart. do this windows have gaskets or seal? Do I have to make new ones or can I go only with a Silicone caulking ?
    What kind of sealing should I use I am getting confused .

    Thanks
    Gabriel
     
  9. Petros
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    Petros Senior Member

    No one said anything about silicone, that is a sealant and not an adhesive, it likely will not last very long (but it is a lot easier to remove when you have to replace it). Polyurethane windshield adhesive does both and is very durable and should make a permanent seal that will last the life of the boat.
     

  10. CDK
    Joined: Aug 2007
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    CDK retired engineer

    The Draco had 2-part aluminum frames with a rubber gasket between glass and frame and stainless screws on the interior side.
    Because the gaskets suffered badly after 30+ years and I was unable to locate a supplier I used silicone compound instead when one window pane was replaced. There crept some water between the frame and the polyester, also under the port window I did not replace.

    Because several heads snapped when I removed the stainless screws I decided not to remove the port window and in the end sold the boat with leaking windows.
     
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