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Old 02-25-2019, 06:21 AM
Reilly Reilly is offline
Join Date: Oct 2008
Location: South Africa
Posts: 51
Default Sikaflex back lexan window

Hi Guys

Any merit in using sikaflex to fit the back lexan window?

I know there is a plexi window but I have an old kit and already have the lexan window.

Does the potential fuel issue and all the skin and window holes pose a problem or can these be easily resolved.

Just busy assessing which is best route to go. Screws or Sika.


Last edited by Reilly : 02-25-2019 at 08:42 AM.
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Old 02-25-2019, 07:09 AM
John-G John-G is offline
Join Date: Jan 2012
Location: Northeast Ohio
Posts: 582


From what I've read the Lexan will likely eventually need to be replaced at some point in the future ... no matter how careful one is about not getting fuel or chemicals on it. The Lexan seemingly eventually takes a toll from the stress created by the bends required to fit the shape of the RV-12. There are many threads here on VAF about the Lexan developing cracks. Granted, most are seemingly fuel related ... but not all.

My kit didn't come with the new plexiglass window but it had just been introduced .... so I didn't even bother with sealing the Lexan window with proseal during install knowing at some point in the future, I'll just make the switch to the plexiglass window and be glad I did.

My suggestion ... DO NOT use the Sikaflex because it will likely make replacing the Lexan window a real bear of a job when you need to replace it .... and it is very likely that you will need to do so years down the runway.

Happy building,
RV-12 Wings, Empennage, Fuselage, Finishing, Avionics and Powerplant kits all completed
Now Flying!!

Dues paid until September 2019
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Old 02-25-2019, 08:07 AM
DaleB's Avatar
DaleB DaleB is offline
Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,092

I used Sika on the new acrylic window, and am very happy with it. The biggest challenge was holding it in place while the adhesive cured. We did that with an inflatable exercise ball and some foam. Have not put the new canopy on yet, but we'll use Sika for that as well. It should be quite a bit easier to clamp.

If I were building new, I would probably use screws if I were going E-LSA. Honestly, though, I'd probably toss the Lexan window and install acrylic. It's a little pricey, but worth it IMHO to only have to do it once.

Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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Old 02-25-2019, 08:32 AM
DHeal DHeal is offline
Join Date: Sep 2006
Location: Windsor, California
Posts: 817

One data point: The original Lexan back window in my 2014 RV-12 (750+ hours) remains in excellent condition with only one barely visible crack at one screw hole that I drilled poorly. I use mogas 91 with 10% ethanol (I hate ethanol fuel) about 90% of the time being careful not to spill. The screw holes, screws, and cut aft edges of the Lexan are sealed with Proseal per Van's instructions. In light of others' experience with Lexan crazing, I would use the plexiglas version if given the option. If you want to experiment, try the Silaflex method. IMHO, the screw method works well and is a proven installation.
David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 (circa 1965) - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B 2020) - N124DH flying since March 2014 - 815+ hours (as of Aug 2019)!
VAF donation through June 2020.
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