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Window Sealant (Weld On #10 vs Sika Flex)

What adhesive works best on RV-10 side windows

  • Weld-On #10

    Votes: 1 9.1%
  • Sika Flex

    Votes: 3 27.3%
  • Something Else

    Votes: 7 63.6%

  • Total voters
    11

mulde35d

Well Known Member
Friend
I am tracking that a few RV-10's have had issues with windows separating in flight as a result of the Lord adhesive that was once used. Now it looks like Van's recommend Weld On #10 to install the windows. However, on the RV-14A we used Sika Flex with great success. Curious your opinions on Weld On #10 vs Sika Flex or something else to install the RV-10 side windows.
 
I am tracking that a few RV-10's have had issues with windows separating in flight as a result of the Lord adhesive that was once used. Now it looks like Van's recommend Weld On #10 to install the windows. However, on the RV-14A we used Sika Flex with great success. Curious your opinions on Weld On #10 vs Sika Flex or something else to install the RV-10 side windows.

Do a search for people using Silpruf as well. It's a very interesting method.
 
Here is a data point on the Sika.

I used Sikaflex on all windows. I created 2 test coupons for each window to save and to test after application. When the test coupons were subjected to a pull test, the surrounding material tore before the actual joint. This was 10 years ago and 1300+ hours. My only complaint is that the Sika does flex and around the sharp corners of both back windows, in spite of a layer of fiberglass over the joint, paint cracks started to show immediately in hot weather. The cracks in the paint have not changed over the life of the aircraft. The Glare shield and door windows have not flexed enough to crack the paint and look fine.
 
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Why wouldnt you use Lord adhesive as one of the options? I’m guessing that will be up there as many folks have built according to the plan.
 
I am tracking that a few RV-10's have had issues with windows separating in flight as a result of the Lord adhesive that was once used. Now it looks like Van's recommend Weld On #10 to install the windows. However, on the RV-14A we used Sika Flex with great success. Curious your opinions on Weld On #10 vs Sika Flex or something else to install the RV-10 side windows.

Are you sure? I think Vans has used Weld On for a long time. A decade ago people were saying don't use the weld on. I used Lord adhesive and have been very happy.

Only complaint is that the Lord adhesive is an off white in color...you can get it in black but the work time is only like 8 minutes, which isn't enough.

If I did it again, I would likely look at sika flex...
 
All good points, I appreciate the discussion. I am a bit biased towards Sika Flex but plan to look harder into Silpruf.

I may be wrong about the Lord adhesive as it was many months ago, but I really thought that's what people who had windows pop out had used when mentioned on this forum.
 
Here is a data point on the Sika.

I used Sikaflex on all windows. I created 2 test coupons for each window to save and to test after application. When the test coupons were subjected to a pull test, the surrounding material tore before the actual joint. This was 10 years ago and 1300+ hours. My only complaint is that the Sika does flex and around the sharp corners of both back windows, in spite of a layer of fiberglass over the joint, paint cracks started to show immediately in hot weather. The cracks in the paint have not changed over the life of the aircraft. The Glare shield and door windows have not flexed enough to crack the paint and look fine.

Same experience. Very strong. However it goes from concave to convex with the temp swings (-10 to 100 in my case). It has 300% elongation, which is what makes it the perfect adhesive for acrylic. My paint also cracked in the corner area, where the acrylic movement is most pronounced.

If I did it again, I would do the same. Not sure how lord or weldon would hold up to the extremes that I see, but I have heard the lord holds up well. You couldn't pay me enough to use the weldon that Van's recommends. Even the weldon tech reps say it is the wrong adhesive for that application - it is VERY rigid with 0 elongation. There is a reason that sikeflex 295UV is the gold standard for adhering acrylic to fiberglass. Nothing else is used in the marine area, as only sika can deal with the elongation requirements and the UV exposure. As we paint over it, UV is not as large of a concern.

Larry
 
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