Sealing side windows

I have the new window trimmed, foam tape around the edge and ready to seal and install. I have the Bostik sealant from LP Aero. My question is…Do I put a bead all the way around the window on top of the tape? How big of a bead? Do I leave it a bead or brush it? Thanks for any tips.


  • Or do you put the bead of sealant around the inside window frame?

  • Hi and thanks for writing. I'm away from my office until Tuesday, March 14. If you haven't resolved the issue by then please contact me and I'll get you in touch with my mechanic who did my LPAero windows 2 years ago.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Piper Owner Society Forum Moderator and Pipers Author.

    Need help? Let me know!

  • edited March 2023

    I recently replaced all of the side windows in my -161.

    1. Make sure the windows fit into the space without binding with the foam wrapped around the edges.
    2. Clean the inside surface of the airframe, removing all of the old adhesive. It's not necessary to remove OEM primer or chromate down to clean aluminum.
    3. Deleted.
    4. Apply a bead of the Bostik about 3/16" thick around the inside surface of the airframe window frame.
    5. Put the window into position and press firmly around the edges to squeeze the sealant to a uniform thickness around the perimeter.
    6. Install the retainers.

    The sealant will ooze out for several months, so don't bother trying to make it pretty immediately after installation.

    Installing the windows is meticulous, not difficult.


  • Thanks Scott. Re read your article several times and saw your pictures. Looks like you mechanic put sealant on the window. Others say the window frame. I think it comes down to what is easiest. First thought, I don't see an advantage either way. I'll probably put in the first window tomorrow.

  • Why would it ooze out over several months? I thought it would cure in a day or two

  • Sorry, in looking back I realized I misspoke in my use of Bostik. I actually used a 3M strip caulk that never actually hardens, but stays pliable for years. Thus the oozing. I was thinking Bostik was a similar product, but it is not. Bostik cures and hardens.

    One other tip toward successful installation. Don't remove the protective paper from the window until completely finished with the installation. Only fold it back about an inch around the perimeter of the window on both sides to keep the adhesive and scratches off the plastic.

  • Update...2 sides windows in. It's was not bad at all. I think I'm a professional installer now. 😀 I'm waiting for the interior to come in to do the left side. I had a crack that needed to be repaired now. Much rather take off window trim once. I elected to put the sealant on the window frame instead of the window. I think it was easier and less potential for messes.

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