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Preventing cracks around windows

D

dwilson

Well Known Member
Just about ready to glue in my rear windows.

Have read much on the forum and Matatronics list about the issue.

It seems to me like a logical solution to the cracks that develop around the windows would be to leave a gap between the Plexiglass and the fiberglass when gluing the window in. Then when the glue has cured fill the gap with Proseal.

Proseal is tenacious, flexible and paintable.

What are the down sides?

Thanks,
 
The weld-on will ooz out and fill the gap anyway. I don't see much of a way preserve a gap.

I sanded the ooz down, laid 3 layers of 3oz cloth over the top, then laid balloons down over that to blend it in. The cloth was there just to provide support to the balloons so they hopefully don't crack.

BTW-Putting Weld-On down with a cake decorating bag was really clean and easy.
 
I only put one layer of over the seam and my paint is cracking. I would definitly put more knowing this.
Ron
 
I also read all the posts about weld-on & over glassing and decided I didn't want to deal with the lump or all the fix up if I had to replace a window. I figured the cracking wouldn't be too bad, just like fillets on most big planes. They usually crack too. So, I followed the plans exactly. Then I painted and all the joints were perfect and invisible. Four months later the cracking started. Last Friday at about zero degrees I took my roadie Jake for a ride. 20 minutes in the cold & I felt a draft. We looked all over, checked vents etc. and couldn't find it. I landed and discovered the right door window popped loose with the lower front corner scooping air. Grrrr!. I took the door to my hangar, routed the joint with a dremel and started carefully prying. I almost got it out without cracking, and this is what I found. The stupid weld-on was adhered to the acrylic, but popped off the fiberglass almost clean. The bond sucked big time. The weld-on was going brittle and if you crushed a piece it went powdery. I've ranted in the past about Vans glass attachment methods, so I won't do it again right now. These cracks aren't just cosmetic. I'm getting the nasty feeling that when you see cracks they are an indication of debonding all throught the joint. I'm also afraid that over-glassing may just hide the problem and that the debonding is happening underneath anyway. I fear the differing expansion rates between acrylic and fiberglass are just too much for the rigid weld-on joint. So, instead of sitting here pointlessly posting I started doing homework on weld-on and every other glue/adhesive I could think of. Now that I've done that, I can't fathom why Vans chose weld-on in the first place. The whole theory is just wrong. So, I've got the new window fitted and I'm waiting for some 3M 5200 to show up. It's white, has 3 times the tensile of Sika, 900% elongation and is supposed to be compatible. I'll try it on scrap and if it looks good I'll rout a fillet bevel in the joint and glue that sucker in there. Wish me luck.
I'd recommend that all you 10 guys do a little "push testing" on your glass and if anyone else had or has a window coming loose, I'd like to hear about it.
 
aerhed said:
I'd recommend that all you 10 guys do a little "push testing" on your glass and if anyone else had or has a window coming loose, I'd like to hear about it.
Click to expand...

Me too.:rolleyes:

I don't know of a weld-on window that has failed. There have been some alternative methods that have though, I'll have to look them up and post later.
 
Here is one of the reports....


Back when I was building my -10 in 2006-7, there was a lot of discussion on this newsgroup about alternatives to Weld-On #10, and one of the epoxy adhesives highly recommended by the Glasair builder community and some RV10 builders was FE6026, because of its ability to bond materials with dissimilar expansion coefficients, including fiberglass, lexan and acrylic. (see: http://www.matronics.com/forums/viewtopic.php?p=138148&sid=753e5e6cc22788dd55bfd58fbdfc75f5 ). That?s what a I chose for my windows.

Fast forward 420 flight hours TTSN to Friday, 5 Nov 2010 when I was enroute in N104LD from Nashville to Orlando, happy as the proverbial clam cruising above the undercast in blue skies at 13,000 ft. Atlanta Center called and said I either had to go up to 15K or take an amended route around their very large airspace, so I elected to climb to 15K, where the outside air temp was -20C/-4F. Was ripping along at a TAS of 177kts and groundspeed > 200kts, with both cabin heaters going strong. Suddenly there was a large thump and a lot of wind noise from behind the pilot seat, and I looked back to see the left rear window had departed the plane. A few tense minutes ensued while I determined that other than the noise and a new cool breeze in the cockpit, all was well in terms of controllability. In fact, the window blow-out only took a couple of knots off the TAS. I was able to complete the trip safely with an appreciation that an RV10 would make a fine air-to-air camera ship if you happen to remove a rear window. J Luckily, it missed the empennage on its way back and down somewhere over northwestern Georgia.

Pictures of the damage are here:

http://160.129.203.138/rv10/RV10_lostwin_frontview.jpg
http://160.129.203.138/rv10/RV10_lostwind_rearview.jpg

A close examination showed a clean separation between the epoxy glue and the coarse sanded inside surface of the window. Since I have flown the bird a lot at 15-17K I think the difference this day was the exceptionally cold air outside and very hot air coming from the rear heater vents, augmented perhaps by some pressure differential of a tight cabin with all vents closed and both heaters pumping air in to the cabin.

A new window is on order. Suffice it to say, it will be installed with Weld-On #10.
Click to expand...
 
I would highly recommend Lord 7545A/E urethane. This is as strong of bond
as you will get going between fiberglass and acrylic. The Sikaflex material
is a single air cured sealant. Epoxy is not great with adhesion to acrylic. The Lord material is not a haz mat material. I used this for all my windows. It cleans up with PPG DT870 reducer or equivalant and will not hurt the windows. This material is hard when cured but not as hard as Weld-on or epoxy. The little amount of flex which is very little is good because of the expansion and contraction between 2 different types of materials.
I did a test with this material before using and it was the strongest of anything.

FWIW
Geoff
 
Geoff, Did you determine if you were going to sell the Lord adhesive in 'RV-10 friendly' packaging and quantities? Thx, -Jim
 
Bob,

My painters sanded down my fiberglass tape and filler transition too much. They went crazy with the sanding. Shortly after flying in cold and hot temps the expansion and contraction of dissimilar materials caused the seam to show through the paint. The painters stated it was the paint proseal gassing but it was only weld-on underneath the tape. The proseal went on later to make the transition from the paint to the plexi. Jets have the proseal transition and I would recommend it. It keeps the paint from chipping later due to rain/sleet relative wind, etc.
Anyway, the painters will be re-doing my fuselage blue and fixing my windows with me there to help during the crappy months this winter.:)
 
Geoff, any place to get Lord epoxy? I'm trying to find it for the other assembly you recommend as well (overhead console, etc...)
 
I bought LORD 7545A/E 50ml cartridges from http://www.krayden.com/. I also purchased the $2 50ml to caulkgun converter kit. It was a breeze to apply. We haven't glued the front or back windows yet but it took ~ 100ml to attach to the door window.
 
5200

Aerhead,

I did a test a couple of years ago with plexi pieces cut off from the corner of the windshield, and a piece of remnant fiberglass from the door. Here is the result I posted back then. http://www.vansairforce.com/community/showpost.php?p=321725&postcount=22

5200 did not work. Popped off the plexi very easily.

Sikaflex with it's own primer was the strongest of the few adhesives I tried. It's actually engineered to glue plexi windows to fiberglass boats. I tore up the fiberglass and still could not remove the plexi from it.

Lenny
 
sikaflex

The Sika test was with primer. Both on the fiberglass and the plexi. Both were first sanded with 8 grit sandpaper, cleaned with Sika cleaner, and the primed with Sika primer.

Used Sika Cleaner 226, Sika Primer 209D and Sikaflex 295UV.

Just looking at the container and it says it contains diisocyanate, which is the same nasty stuff that hurts you in polyuretane paint. Wish I knew that back then... wear at least a fresh charcoal mask when using this stuff.

Lenny
 
Lenny Iszak said:
Just looking at the container and it says it contains diisocyanate, which is the same nasty stuff that hurts you in polyuretane paint. Wish I knew that back then... wear at least a fresh charcoal mask when using this stuff.

Lenny
Click to expand...

A charcoal mask will NOT catch isocyanates! I know from experience. I ignored the MSDS once and was rewarded with 3 days of instant onset bronchitis after spraying polyurethane. (Maybe a little dain bramage too?) Fresh supplied air at a minimum when working with isocyanates!
 
To glue in my windows, I used Lord Fusor 127EZ. You can get it an an automotive paint supply store. It's designed for bonding GM plastic panels on Corvettes and the above number has 60 minutes working time. It stays flexible and is paintable.

I have lots of zero degree temp flights with no cracks, and my 10 has close to 200 hours on it. I did do 3 adhesion tests - fiberglass to the window material, fiberglass to fiberglass and fiberglass to epoxy primed aluminum. I was very happy with the results.
 
Welcome to VAF!!!!

Bob, from one RV 10 flying ex Stinson 108 owner to another, welcome to VAF.

How about some photos of the RV??

I assume your Stinson has a 220hp Franklin----what a sweet plane that setup is.
 
Hi Mike : Thanks for the welcome, as soon as my wife figures out how to post pictures, I'll post some. The stinson is a great moutain plane
 
Just as another data point. We also tested the Sika adhesive on several samples and ended up breaking the plexiglass. The joint never failed. I am using the 226 cleaner, 209D primer and 295UV epoxy. It cleans up with mineral spirits for about the first hour after application. Then its there for good.
 
Lord 7545 A/E urethane

I would like to let everyone know that Aerosport Products will be
stocking the Lord 7545 A/E urethane adhesive for gluing in the windows.
I will over it in a packaged kit of 3 200ML cartridges and 3 extra tips for
$130.00 plus shipping. You can by separate 200ML cartriges for $45.00.
3 packages should be plenty to do all windows and a little more. Extra tips will
be 1.75 each.
I will also have to dispensing guns available for rent for $10.00.
This adhesive is also good for glueing the cabin top door frame to the
aluminum fuselage. It will be available thru direct order only no online
ordering at this time. We have material in stock.

http://www.aerosportproducts.com
Geoff
 
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That's great Geoff. That's on par with bulk discount prices I found with LARGE minimum quantities. Thanks again for making this possible.
 
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