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Our Experiment: Lord Adhesive vs. Weld-On

Brandi

Brandi

Well Known Member
On our -10 we have one door window installed with Weld-On and all other windows installed with Lord adhesive. We've noticed a few areas around the weld-on window where the surface is raised at the window gap. (the Lord adhesive windows are all fine) This gap was sanded real well before I applied the filler (no glass) and was smooth at first flight. I have some speculation that it was caused by a quick change from hot temps on the ground to pretty cool temps at altitude.





 
I had the right one pop loose and suck air in that same spot (weld-on). Got the old window "almost" out and cracked it. Nothing 20 hours and a couple hundred bucks won't fix.
 
With the flimsy doors, curvature mismatch, coefficent of expansion and one support strut it does not help. I used weld-on 45. No delamination yet, but plenty of cracking. Are you noticing any cracking yet?
 
I used sika adhesive, probably a mistake. It has too much elasticity. It looks good now, but I suspect when it sees some really hot temps it will show. When I had it in the paint booth, we took it to 140 degrees and saw one area of flex. It appears the lord adhesive, along with a couple of layers of glass cloth, seems to be the ticket
 
Bill.Peyton said:
It appears the lord adhesive, along with a couple of layers of glass cloth, seems to be the ticket
Click to expand...

That's what I did, but since I'm just going to the paint shop, it's too early to tell if I made the correct decision. I also didn't attempt to sand the fiberglass down to a feather edge either so that it would retain as much strength as possible to resist the cracking. The 1/32" - 1/16" step may not win me any awards at OSH, but I know my windows are firmly secured. :D

bob
 
Stock + fabric

I used the Weld-on per the plans, but added a ~1" wide layer of 3 oz fiberglass over the joint. After finishing and sanding, I don't think there was much of the fiberglass left, but it was still visible. After paint, no visible joint at all. Now, after 200 hours since February and temperatures from below 0 to 105 deg F, I see a little "gap" if you look at it in the correct light. It actually looks like a little bump or sag perhaps in the paint right at the joint. But you have to look hard and at the right angle to see it and the paint has not cracked. I'll be watching it but fairly happy so far. If I did it again I'd probably go with the Lord, though.
 
fabric?

Is the point of the transition strips to cover the gap from the window to the cabin top, or is the glass being used as a structural piece to help hold the window in place?

If the transition strips are just for covering the gap, I'm curious if anyone has ever used/considered using strips of polyfiber or similar to cover the transition. The polyfiber system has a much larger flex factor than fiberglass. Thoughts?
 
Structure

Maybe a little of both as I understand it. The fabric provides a substrate for the paint to adhere to that is less likely to stretch when the differential expansion of the plexi and fiberglass occurs. The gap seems to still appear but the paint hasn't cracked - so far.
 
Another data point....

When the rollover structure static tests were done to failure, side windows were literally shattered and blown out (there is a small dent in the side of Van's airport car to prove it :eek:)
Post test examination showed that anyplace the windows were attached to the door frame or cabin top, it was still bonded, with just the center portion fractured/shattered. The only way to remove the bonded area was to grind it off.
 
So, going by the results of the vans test the only purpose for glassing over the transition is cosmetic and to some extent aerodynamic.
 
Oops

When I said the fabric is somewhat structural, I meant with regard to protecting the joint, not the strength of the airframe. So in that context I guess you could say it is cosmetic...
 
Some builders were/are glassing over the seam of the windows for cosmetic reasons, but also perhaps to stave off the possibility of cracks developing in the paint later down the road. We have seen at least 1 RV-10 that has had cracks develop despite having put fiberglass on the seam. Most[?] people never experience the cracks so its not quite clear (to me at least) what leads to some cracking and some not. Just wanted to point out that our findings seem to indicate that the weldon has potential to swell, where lord adhesive did not. This could possibly be one factor that contributes to cracking in the paint.

Any other -10 owners out there who have experienced cracking that care to share the details?

IMG6397-L.jpg
 
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