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indigoonlatigo(at)msn.com Guest
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Posted: Tue Jun 17, 2008 8:55 am Post subject: window adhesives revisited. |
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I jumped the gun a while back and didn't carefully enough look at the instructions on the Sikaflex web site. If I hadn't already painted the interior of my canopy I would have added fiberglass to the inside of the window flange to thicken it so that I could deepen the flange to allow a greqater bond thickness Also, at initial trimming I would have als left the flange one inch wide not 3/4" wide.
The pros with the use of Sikaflex is the idea of a floating acrylic window which would allow for expansion and contraction. The thermal coefficient of expansion between the frame and the window is huge. Because of this, Sikaflex requires a 3/16'" thick bond thickness and an expansion gap at the edge of 1/4" to 3/8". Given all these requirements, my existing frame flange will need to be thinned by 1/16" and the window thinned by 1/16" whick would still leave the window proud of the outside contour. Also because the flange is only 3/4", and because we would need a minimum of 1/4" expansion gap, when the window contracts in the cold it will not have that much bond space
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Jim Berry
Joined: 10 Jan 2006 Posts: 237 Location: Denver
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Posted: Tue Jun 17, 2008 9:28 am Post subject: Re: window adhesives revisited. |
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Even if you use an adhesive that requires less bond thickness, you will have places where the window stands proud of the cabin surface. There will also be places where the door is proud of the top, and other places where the top is proud of the door. You should be very proud. All of this can be accommodated by contouring with micro or other lightweight filler.
Jim Berry
40482
Proud to be finished with fiberglass
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speckter(at)comcast.net Guest
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Posted: Tue Jun 17, 2008 9:49 am Post subject: window adhesives revisited. |
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I flew my Glasair III with ½” thick windshield for 15 years with it bonded into the frame with epoxy with no problems of cracking or crazing. With that thick of windshield there is no flexing of the acrylic to take up any differential in expansion either. There are many hundreds of Glasairs out there with the same proven record. You can tell from the above comment how I put my window in the 10.
Gary
40274 Flying
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Gonzalez
Sent: Tuesday, June 17, 2008 11:53 AM
To: rv10-list(at)matronics.com
Subject: window adhesives revisited.
I jumped the gun a while back and didn't carefully enough look at the instructions on the Sikaflex web site. If I hadn't already painted the interior of my canopy I would have added fiberglass to the inside of the window flange to thicken it so that I could deepen the flange to allow a greqater bond thickness Also, at initial trimming I would have als left the flange one inch wide not 3/4" wide.
The pros with the use of Sikaflex is the idea of a floating acrylic window which would allow for expansion and contraction. The thermal coefficient of expansion between the frame and the window is huge. Because of this, Sikaflex requires a 3/16'" thick bond thickness and an expansion gap at the edge of 1/4" to 3/8". Given all these requirements, my existing frame flange will need to be thinned by 1/16" and the window thinned by 1/16" whick would still leave the window proud of the outside contour. Also because the flange is only 3/4", and because we would need a minimum of 1/4" expansion gap, when the window contracts in the cold it will not have that much bond space.
I orderred the Weld on and will most likely do it that way and bond it and cover the gap and the edge of the window and the canopy with fiberglass for a smooth transition as I see on most fiberglass ships.
The thing that concerns me is that we are trying to contain/constrict the plexiglass during expansion and contraction and that just doesn't seem right. I suppose the Glasair guys with 10 year old ships should be able to put my concerns at ease.
Oh well, just the over analysing dentist in me.
JOhn G. #409 Quote: | http://www.matronics.com/Navigator?RV10-List | 0123456789
[quote][b]
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John Ackerman
Joined: 19 Jun 2006 Posts: 130 Location: Prescott, AZ
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Posted: Wed Jun 18, 2008 9:17 am Post subject: window adhesives revisited. |
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Quote: | On Jun 17, 2008, at 9:52 AM, John Gonzalez wrote:
.... If I hadn't already painted the interior of my canopy I would have added fiberglass to the inside of the window flange to thicken it so that I could deepen the flange to allow a greqater bond thickness Also, at initial trimming I would have als left the flange one inch wide not 3/4" wide... |
We went through this and decided not to post 2 months ago, but maybe the following will be of value to somebody.
When we considered Sikaflex, I did the differential thermal expansion (actually contraction is critical) calculations in the attached spread sheet, which assumes free movement of the plexi relative to the fiberglass. The results are appended as text below in case the attachment can't be posted.
It's clear that even a stretchy Sikaflex glue line cannot accommodate the necessary movement unless it is _very_ thick. For example, the door glue line would have to be uniformly 1/8" thick to accept the contraction of 0.07" (on the diagonal) that would result from cooling to - 35 °F from a fabrication temperature of 75 °F. In that situation the glue would have to stretch 15%. I think that would be near the limit, and it might break or become un-bonded if it were thinner anywhere. The flange is nowhere near deep enough to give that kind of thickness, and of course the flange depth and plexi thickness are not completely uniform.
Sikaflex tech support briefly reviewed the situation with me and agreed. Apparently more than a few tens of percent stretch is not tolerable. My expectation is that the allowable stretch might be less at low temperatures, but I didn't ask them.
After talking to Van's engineering about the situation, it finally dawned on me that the RV10 design approach was to hard bond (very little flexibility) the plexi to the fiberglass and let the expansion forces be taken by deformation of the structure. This puts tremendous forces on the adhesive. For that reason, we elected to stay with Van's design and materials.
As pointed out in other posts, this is essentially the same approach as epoxying the window in place and making a glass flange around its periphery, a la Glasair, et al. Quite a change from the free-floating windows in Cessna, et al, huh?
John Ackerman 40458
Assume: Zero stress at fabrication
Plexi and GRP expand and contract as "free bodies" - bond stretches
No deformation of acrylic or GRP (as opposed to expansion)
Acrylic free to expand and contract in flange "joggle"
Perfect fit of window in flange "joggle"
Expansion coeff's from:
http://www.edl-inc.com/Plastic%20expansion%20rates.htm
3.80E-05 Thermal expansion coefficient, acrylic, per °F
2.00E-05 Thermal expansion coefficient, epoxy GRP, per °F
1.80E-05 Differential thermal expansion coefficient, per °F
145 Max temp, °F (Phoenix Summer in sun)
-35 Min temp °F (North Dakota winter in hangar)
75 Fabrication temp °
110 Max temp swing from zero stress state, °F
36 Max length of door window (diagonal), inch
0.071 Max length change of door window, inch
0.036 Max bond point movement, inch
27.5 Max length of rear window (diagonal), inch
0.054 Max length change of rear window, inch
0.027 Max bond point movement, inch
Elongation ratio is the stretched length of a section of adhesive between the fiberglass and the plexi, divided by its unstretched length.
Door Cabin
elongation, in 0.071 0.027
Bond thickness, in Elongation Ratio
1/8 1.15 1.02
1/16 1.52 1.09
3/64 1.82 1.16
1/32 2.49 1.33
1/64 4.67 2.01
Bond thickness, in % elongation
1/8 15% 2%
1/16 52% 9%
3/64 82% 16%
1/32 149% 33%
1/64 367% 101%
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indigoonlatigo(at)msn.com Guest
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Posted: Wed Jun 18, 2008 9:54 am Post subject: window adhesives revisited. |
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This was an awesome email. Thank you for truly educating me and making my decision an easier one.
Anyone want to buy five tubes of Sikaflex, cleaner and primer. Darn, I could have filled up my F250 diesel one time with the money I spent on that stuff or my Prius six or seven times. Oh , need to figure the hazardous waste disposal fee also.
John G.
[quote] From: johnag5b(at)cableone.net
To: rv10-list(at)matronics.com
Subject: Re: window adhesives revisited.
Date: Wed, 18 Jun 2008 10:13:09 -0700
Quote: | On Jun 17, 2008, at 9:52 AM, John Gonzalez wrote:
.... If I hadn't already painted the interior of my canopy I would have added fiberglass to the inside of the window flange to thicken it so that I could deepen the flange to allow a greqater bond thickness Also, at initial trimming I would have als left the flange one inch wide not 3/4" wide... |
We went through this and decided not to post 2 months ago, but maybe the following will be of value to somebody.
When we considered Sikaflex, I did the differential thermal expansion (actually contraction is critical) calculations in the attached spread sheet, which assumes free movement of the plexi relative to the fiberglass. The results are appended as text below in case the attachment can't be posted.
[b]
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ricksked(at)embarqmail.co Guest
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Posted: Wed Jun 18, 2008 2:42 pm Post subject: window adhesives revisited. |
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Since I'm going the Silpruf method and it is also a silicone based product I have to consider those ratio's also but, I have the video from the Glasair folk on how to install using the Silpruf adhesive and there is a gap left around the window to be filled after paint with Silpruf...this should eliminate the contraction space problem. Given the different expansion and contraction rates for the plexi vs. fiberglass, it seems that no matter what you did the only time the glass would not be either under negative or positive compression would be at the exact temperature that occurred during installation. This would explain the cracks around the windows installed with Weldon since the Weldon creates an ungiving, solid bond between both materials. If you allow for expansion and the material used in the expansion/contraction joint is flexible I think this would present a better option than the Weldon. Filling the areas around the windows with flox/epoxy and covering with glass cloth gives brute strength to the gap hopefully preventing the cracks. I talked to two Glasair builders with 10 plus years on their aircraft with glass installed with Silpruf or similar silicone and they had no problems...This is kinda getting like primer wars in a way. If you get a chance to look at a Cirrus up close you will see their windows are installed with a defined gap around the plexi to cabin flange, the gap is filled with a material either like proseal or silicone...maybe anyone with experience on the Cirrus windows may be able to shed more light on that install. Till then...I'm sticking (literally) to Silpruf install.
Rick Sked
40185
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n212pj(at)gmail.com Guest
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Posted: Thu Jun 19, 2008 7:45 am Post subject: window adhesives revisited. |
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Is this a discussion about the use of the windshield as a structural component? I've not paid much attention to the windshield debate, but if structural, then Weldon, I would think.
John Jessen
40328
[quote] From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Rick Sked
Sent: Wednesday, June 18, 2008 3:40 PM
To: rv10-list(at)matronics.com
Subject: Re: window adhesives revisited.
Since I'm going the Silpruf method and it is also a silicone based product I have to consider those ratio's also but, I have the video from the Glasair folk on how to install using the Silpruf adhesive and there is a gap left around the window to be filled after paint with Silpruf...this should eliminate the contraction space problem. Given the different expansion and contraction rates for the plexi vs. fiberglass, it seems that no matter what you did the only time the glass would not be either under negative or positive compression would be at the exact temperature that occurred during installation. This would explain the cracks around the windows installed with Weldon since the Weldon creates an ungiving, solid bond between both materials. If you allow for expansion and the material used in the expansion/contraction joint is flexible I think this would present a better option than the Weldon. Filling the areas around the windows with flox/epoxy and covering with glass cloth gives brute strength to the gap hopefully preventing the cracks. I talked to two Glasair builders with 10 plus years on their aircraft with glass installed with Silpruf or similar silicone and they had no problems...This is kinda getting like primer wars in a way. If you get a chance to look at a Cirrus up close you will see their windows are installed with a defined gap around the plexi to cabin flange, the gap is filled with a material either like proseal or silicone...maybe anyone with experience on the Cirrus windows may be able to shed more light on that install. Till then...I'm sticking (literally) to Silpruf install.
Rick Sked
40185
---
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ricksked(at)embarqmail.co Guest
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Posted: Thu Jun 19, 2008 8:17 am Post subject: window adhesives revisited. |
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Good point, I have not heard the "are the windows structural?" point come up as far as I can recall.
Rick Sked
40185
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msausen
Joined: 25 Oct 2007 Posts: 559 Location: Appleton, WI USA
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Posted: Thu Jun 19, 2008 8:18 am Post subject: window adhesives revisited. |
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I don’t believe so. I believe the discussion is just for the side and door windows.
Michael
Do not archive
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Jessen
Sent: Thursday, June 19, 2008 10:40 AM
To: rv10-list(at)matronics.com
Subject: RE: window adhesives revisited.
Is this a discussion about the use of the windshield as a structural component? I've not paid much attention to the windshield debate, but if structural, then Weldon, I would think.
John Jessen
40328 Quote: |
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Rick Sked
Sent: Wednesday, June 18, 2008 3:40 PM
To: rv10-list(at)matronics.com
Subject: Re: window adhesives revisited.
Since I'm going the Silpruf method and it is also a silicone based product I have to consider those ratio's also but, I have the video from the Glasair folk on how to install using the Silpruf adhesive and there is a gap left around the window to be filled after paint with Silpruf...this should eliminate the contraction space problem. Given the different expansion and contraction rates for the plexi vs. fiberglass, it seems that no matter what you did the only time the glass would not be either under negative or positive compression would be at the exact temperature that occurred during installation. This would explain the cracks around the windows installed with Weldon since the Weldon creates an ungiving, solid bond between both materials. If you allow for expansion and the material used in the expansion/contraction joint is flexible I think this would present a better option than the Weldon. Filling the areas around the windows with flox/epoxy and covering with glass cloth gives brute strength to the gap hopefully preventing the cracks. I talked to two Glasair builders with 10 plus years on their aircraft with glass installed with Silpruf or similar silicone and they had no problems...This is kinda getting like primer wars in a way. If you get a chance to look at a Cirrus up close you will see their windows are installed with a defined gap around the plexi to cabin flange, the gap is filled with a material either like proseal or silicone...maybe anyone with experience on the Cirrus windows may be able to shed more light on that install. Till then...I'm sticking (literally) to Silpruf install.
Rick Sked
40185
----- Original Message -----
From: "John Ackerman" <johnag5b(at)cableone.net>
To: rv10-list(at)matronics.com
Sent: Wednesday, June 18, 2008 10:13:09 AM (GMT-0800) America/Los_Angeles
Subject: Re: window adhesives revisited.
Quote: |
On Jun 17, 2008, at 9:52 AM, John Gonzalez wrote:
.... If I hadn't already painted the interior of my canopy I would have added fiberglass to the inside of the window flange to thicken it so that I could deepen the flange to allow a greqater bond thickness Also, at initial trimming I would have als left the flange one inch wide not 3/4" wide... |
We went through this and decided not to post 2 months ago, but maybe the following will be of value to somebody.
When we considered Sikaflex, I did the differential thermal expansion (actually contraction is critical) calculations in the attached spread sheet, which assumes free movement of the plexi relative to the fiberglass. The results are appended as text below in case the attachment can't be posted.
Quote: | href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-Listhref="http://forums.matronics.com">http://forums.matronics.comhref="http://www.matronics.com/contribution">http://www.matronics.com/c | | 0123456789 Quote: | href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List | 0 Quote: | href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List | 1 Quote: | href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List | 2 Quote: | href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List | 3 Quote: | href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List | 4
[quote][b]
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indigoonlatigo(at)msn.com Guest
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Posted: Thu Jun 19, 2008 8:45 am Post subject: window adhesives revisited. |
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I have been discussing the side and the door windows.
John G.
[quote] From: rvbuilder(at)sausen.net
To: rv10-list(at)matronics.com
Date: Thu, 19 Jun 2008 11:15:33 -0500
Subject: RE: window adhesives revisited.
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I don’t believe so. I believe the discussion is just for the side and door windows.
Michael
Do not archive
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Jessen
Sent: Thursday, June 19, 2008 10:40 AM
To: rv10-list(at)matronics.com
Subject: RE: window adhesives revisited.
Is this a discussion about the use of the windshield as a structural component? I've not paid much attention to the windshield debate, but if structural, then Weldon, I would think.
John Jessen
40328 [quote]
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Rick Sked
Sent: Wednesday, June 18, 2008 3:40 PM
To: rv10-list(at)matronics.com
Subject: Re: window adhesives revisited. Since I'm going the Silpruf method and it is also a silicone based product I have to consider those ratio's also but, I have the video from the Glasair folk on how to install using the Silpruf adhesive and there is a gap left around the window to be filled after paint with Silpruf...this should eliminate the contraction space problem. Given the different expansion and contraction rates for the plexi vs. fiberglass, it seems that no matter what you did the only time the glass would not be either under negative or positive compression would be at the exact temperature that occurred during installation. This would explain the cracks around the windows installed with Weldon since the Weldon creates an ungiving, solid bond between both materials. If you allow for expansion and the material used in the expansion/contraction joint is flexible I think this would present a better option than the Weldon. Filling the areas around the windows with flox/epoxy and covering with glass cloth gives brute strength to the gap hopefully preventing the cracks. I talked to two Glasair builders with 10 plus years on their aircraft with glass installed with Silpruf or similar silicone and they had no problems...This is kinda getting like primer wars in a way. If you get a chance to look at a Cirrus up close you will see their windows are installed with a defined gap around the plexi to cabin flange, the gap is filled with a material either like proseal or silicone...maybe anyone with experience on the Cirrus windows may be able to shed more light on that install. Till then...I'm sticking (literally) to Silpruf install.
Rick Sked
40185
---
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rv10(at)sinkrate.com Guest
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Posted: Thu Jun 19, 2008 9:02 am Post subject: window adhesives revisited. |
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Rick and all,
I asked Van personally at a gathering of like minded plane nuts a while ago if the windows provided any structural strength. He said “oh a little, not much but a little”. I then said “So did you engineers say – We should add a window there for strength”. He sorta chuckled and said they did provide some strength but not much. One thing he did say was the windows were installed when they did the drop test but he couldn’t remember if they blew out or cracked. I always wondered if anyone has dropped one on its back (hopefully in test). I assumed the results were good but I didn’t ask.
-Ben
#40579
PDX
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Rick Sked
Sent: Thursday, June 19, 2008 9:15 AM
To: rv10-list(at)matronics.com
Subject: Re: window adhesives revisited.
Good point, I have not heard the "are the windows structural?" point come up as far as I can recall.
Rick Sked
40185
---
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AV8ORJWC
Joined: 13 Jul 2006 Posts: 1149 Location: Aurora, Oregon "Home of VANS"
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Posted: Thu Jun 19, 2008 8:19 pm Post subject: window adhesives revisited. |
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They are no more structural that the steel tube installed from the glareshield to the canopy.
John Cox.
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Gonzalez
Sent: Thursday, June 19, 2008 9:43 AM
To: rv10-list(at)matronics.com
Subject: RE: window adhesives revisited.
I have been discussing the side and the door windows.
John G.
From: rvbuilder(at)sausen.net
To: rv10-list(at)matronics.com
Date: Thu, 19 Jun 2008 11:15:33 -0500
Subject: RE: window adhesives revisited.
I don’t believe so. I believe the discussion is just for the side and door windows.
Michael
Do not archive
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Jessen
Sent: Thursday, June 19, 2008 10:40 AM
To: rv10-list(at)matronics.com
Subject: RE: window adhesives revisited.
Is this a discussion about the use of the windshield as a structural component? I've not paid much attention to the windshield debate, but if structural, then Weldon, I would think.
John Jessen
40328 [quote]
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Rick Sked
Sent: Wednesday, June 18, 2008 3:40 PM
To: rv10-list(at)matronics.com
Subject: Re: window adhesives revisited.
Since I'm going the Silpruf method and it is also a silicone based product I have to consider those ratio's also but, I have the video from the Glasair folk on how to install using the Silpruf adhesive and there is a gap left around the window to be filled after paint with Silpruf...this should eliminate the contraction space problem. Given the different expansion and contraction rates for the plexi vs. fiberglass, it seems that no matter what you did the only time the glass would not be either under negative or positive compression would be at the exact temperature that occurred during installation. This would explain the cracks around the windows installed with Weldon since the Weldon creates an ungiving, solid bond between both materials. If you allow for expansion and the material used in the expansion/contraction joint is flexible I think this would present a better option than the Weldon. Filling the areas around the windows with flox/epoxy and covering with glass cloth gives brute strength to the gap hopefully preventing the cracks. I talked to two Glasair builders with 10 plus years on their aircraft with glass installed with Silpruf or similar silicone and they had no problems...This is kinda getting like primer wars in a way. If you get a chance to look at a Cirrus up close you will see their windows are installed with a defined gap around the plexi to cabin flange, the gap is filled with a material either like proseal or silicone...maybe anyone with experience on the Cirrus windows may be able to shed more light on that install. Till then...I'm sticking (literally) to Silpruf install.
Rick Sked
40185
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