Steel Yacht Windows

Discussion in 'Metal Boat Building' started by cal_d_44, Mar 23, 2016.

  1. cal_d_44
    Joined: Jul 2008
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    cal_d_44 Junior Member

    Hi all, I am after some feedback, I have a Steel John Pugh Winsong Yacht, she is 25 yo and the original windows were 10mm lexan bolted to the hull from the inside. Obviously water penitrated the screw holes and caused rusting issues see picture attached. I have removed the rust, reinforced the window frames for strength and to assist in fit out. I also intend to use a 2400 mm x 300mm panel of 6mm tinted Acrilic/Lexan, fixing the windows from the outside covering 3 windows with the one panel. They will be bonding with 3M brand tape 'VHB 4991' and bedded on the painted hull with Dow Corning brand, silicone # 791. There will be no penetrating bolts through the hull.
    See Pictures attached.
    Is there anything I should be aware or concerned about?
     

    Attached Files:

  2. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    Try to find out why the ship initially had lexan10 mm and if the thickness and material if you want to place has the same properties or higher than de previous one. Do not experiment. Note also that a plate of, say, 1400 x 500, suffers much more deformation than three plates of 450x350
    The window frame, in addition to holding the glass, has to provide resistance that the hull has lost by making such big holes. Therefore, in my oponión, windows (3 windows, three frames) should carry metal frame, preferably stainless steel, and bolted.
    If the boat is obliged to comply with any structural standard, this is an issue (openings in the hull) that all regulatory agencies consider very important. See, if you think fit, any regulations.
     
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    By reinforcing do you mean welding plates over the damaged area?
     
  4. TANSL
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    TANSL Senior Member

    I do not know who you ask, but in general, weld something on a damaged area is very bad practice. Depending on the damage, it would be normal, first, clean up the damaged area and, if necessary, cut by "healthy part" and add new material.
     
  5. cal_d_44
    Joined: Jul 2008
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    cal_d_44 Junior Member

    Gonzo,The skin is 3mm mild steel I have cut all the rust affected areas out and re welded in new 3mm mild steel.

    TANSL Cheers
     
  6. waikikin
    Joined: Jan 2006
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    waikikin Senior Member

    "crop & renew"

    Great project, looks good especially with the return edge, would have been nice to retain the radius corners but still good.
    Only thing/s I would be concerned about is the huge amount of trust being shown in the VHB tape and the gooee combined with the 2400 long plastic panel. There may be significant scope for difference in rate of thermal expansion of the tinted lexan and the substrate. May be better to split your panel in three with a gap between. I would also back up with fasteners, you may not have liked the previous result but having the plastic on the outside is a better scenario than having fine metal edges exposed to outside along with fastening heads exposed at steel. If you trust your goo, trust it to seal the fastening interface. Also if you do fasten make sure not to use countersunk heads to plastic, better RH & washers or csk with screw cup style washers and give the fastenings some reasonable clearance for expansion.

    Jeff
     
  7. MikeJohns
    Joined: Aug 2004
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    MikeJohns Senior Member

    I'm with Jeff.
    The plastic should be in 3 parts due to the differing thermal expansion rates.
    Also I don't like adhesive only bonds they are not 100% reliable long term and I'd add some fasteners. Also the sealant Lexan bond will last longer if the Lexan is painted to block sunlight over the sealant, the sunlight degrades the bond over time. Some of the pre-prime compounds do this on the inside surface.

    Physical fastenings need not cause the same problem you are repairing, just make sure the sealant fills the bolt holes.
     
  8. cal_d_44
    Joined: Jul 2008
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    cal_d_44 Junior Member

    Cheers Jeff and Mike I am now going with separate windows :)
     
  9. cal_d_44
    Joined: Jul 2008
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    cal_d_44 Junior Member

    Now going with individual windows, Thanks for the replies.
     

    Attached Files:

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  10. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Nicely done.
     
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