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Sikaflex window (or canopy) bond

Good day,

Trying to understand how to bond transparencies using Sikaflex 295UV. I read a 2019 Kitplanes article on the subject but could not understand why using both the 205 activator plus the 209D primer before applying the Sikaflex itself.

Attached is a screenshot of a webinar from a Sika senior product engineer clearly mentioning not to use activator on acrylic glass.

My conclusion are that only a thin layer of primer 209D should be used before applying Sikaflex 295UV.

Thanks in advance for any comments for or against this option...
 

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The 209 primer will work fine on both the acrylic and the steel frame. Make sure you mask off the areas where you don't want any primer as it is almost impossible to remove without damaging the underlying surface.

Use spacers (about1/8", 2-3mm, small pieces of split garden hose work well), and scuff the surfaces to be glued, dulling the acrylic surface is sufficient. Also sand down to bare metal on the frame and apply the primer straight away.

Apply enough Sika to secure the canopy and once cured remove the spacers and apply the rest of the Sika within the next day or so to fill in gaps and form a nice fillet. The Sika will adhere to itself if done within this timeframe.

Like anything preparation is key. Use the primer on all surfaces to be glued. The Sika will not adhere properly if this is not done. If the process is followed correctly the acrylic will break before the Sika lets go.

Clive Whittfield
Auckland
New Zealand
 
And forget the spacers - not needed... Pipe the triangular fillet of Sika and sit it down, just like the auto glass guys do :D

Hey, this is like Primer Wars - Yummy !!!
 
And after more research it appears that activator must effectively be used before primer on the fiberglass or aluminum parts (not on the acrylic).
 
Sika website

If you go to the sika website, they have nice PDF files you can print that has the steps listed. I hung one from my shop wall. Although we don't use the exact primer since we are a combo of plexi, alum and fiberglass, the wait times are all there.
 
Sika

And forget the spacers - not needed... Pipe the triangular fillet of Sika and sit it down, just like the auto glass guys do :D

Hey, this is like Primer Wars - Yummy !!!

What he ^ said.
It allows the plexi to settle into a natural curve. No stress points.
Just a data point, but I used the Aktivator on all parts before Primer and Sika. She hasn't flown yet.
I recommend testing before bonding a canopy without using Aktivator. There's plenty of scrap cut off to test. I suspect it will be fine. The necessary component is the Primer. No Primer, No Sticky. You can literally rub the Sika off. It's pretty important. If you don't want Sika to stick, mask carefully so Primer isn't applied to the part.
 
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