Lord Adhesive vs. Weld-On Update

I don't know if you guys remember, but we attached the pilot side door window on our plane with Weld-On and the other windows with Lord Adhesive as a little experiment. Some builders feel that the Weld-On is responsible for the small cracks that form around the window over time. Personally, I was sold on ANY alternative after working with Weld-On for the first time; what a huge mess!  Note that, for all windows, we left the appropriate (and same) size gap around them and then filled in this gap with filler as instructed in the plans.

Flash back to OSH 2012... at around 55 hours, a friend pointed out a "ridge" forming around our Weld-On window. It was pretty nasty looking and would have definitely caused some paint issues if the plane would have been painted already. Since then, this "ridge" has covered more ground around the window but has not really changed in height. Here's a photo of the Weld-On "ridge" when we first discovered it.

Yesterday, our painter, Don, pointed out some cracks around the rear windows and doors in which we had used the Lord Adhesive! Granted, they are NOWHERE near the size of the strange "ridge" that formed on the Weld-On window but, they're still there. We're now at about 270 hours and I've never noticed these cracks before so I don't know how long they've been there. They're pretty small so it isn't something that you'd see on an unpainted plane unless you were, say, prepping the cabin cover for paint. It might not even be something that would have shown up through paint already; I have no experience in this area. Below are photos of the cracks found in the Lord Adhesive rear and door windows, respectively. You can click them to open the full size image and get a better view of the cracks.


I find it very interesting that the cracked areas don't always occur at the edge of the window. A few spots are actually at the cabin cover, on the other side of the gap.

I still think Lord Adhesive is the better option but, it's not the ultimate solution. I'm not sure there is one short of masking the cracks by putting a few layers of glass around the seams. It seems cracks are inevitable when you have two different materials expanding and contracting at different rates.  

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