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-   -   Lord Adhesive vs. Weld-On Update (https://vansairforce.net/community/showthread.php?t=104739)

Bill.Peyton 10-06-2013 02:58 PM

I don't know of anyone who has done this. I doubt it would be any more difficult than the current method. There would be a small edge around the window, but so what if it fixes the cracking issue. I noticed at OSH last year that the Vans aircraft has cracks around the windows. The sika adhesive was designed for this application.

Unkgd 10-06-2013 09:20 PM

I will take a look
 
I will take a look and see what it will take. I think it will require reversing the flange, and coming up with a device to push/hold the window in place from the inside while the door is closed.

Will be interesting.

ppilotmike 10-07-2013 09:32 AM

Want to learn more.
 
I don't understand how mounting the windows from the inside, against an exterior flange would solve the problem of cracking. Wouldn't it just move the cracks to the inside? Also, if expansion/contraction is the culprit, there would still be cracks appearing on the outside flange to window interface, wouldn't there? I'm nowhere near the window install stage, but I'm interested in learning from those who have gone before...

rleffler 10-07-2013 11:01 AM

I used Lord adhesive and two layers of fiberglass tape over the seam. Although, I'm not quite flying yet, it has been ten months since painted and over a year since installed. No evidence of cracking yet. I was very careful not to sand into the glass when finishing.

rvator10 10-07-2013 11:59 AM

window cracks
 
From my experience, small cracks turn into larger cracks. I?m in the camp of a removable window from the inside.:)

Bill.Peyton 10-07-2013 05:19 PM

By mounting the window on the inside, you no longer have to paint the window. So there is no paint to crack! The cracking results from the dissimilar expansion rates. Bob, wait till it sits in the 100 degree sun a few times. I hope you are correct. I know Geoff used the lord adhesive and also has a small crack. The best part of mounting the window from the inside is the ease of replacement. I will admit, the sika adhesive is meant to expand and contract. That's why it works so well with bonding of materials with dissimilar coefficient of expansion. I initially did not intend to paint onto the window, but to create a pro seal bead around the edge of the window, just like the Cirrus guys do. I changed my mind, which was my mistake. I have considered fabricating a new door just to see how it would work.

Unkgd 10-07-2013 07:08 PM

Inside mounting of windows
 
Mounting the window inside and making it appear "seamless" on the outside while providing a robust attachment is going to be interesting. Currently envisioning the current window flange thickness sitting flush on the outside of the door, which means the window will be recessed by that anount. Could try match tapering both surfaces. It would minimally reduce the overall viewport size but would require some dedicated fixtures (male mold for window flange and taper transfer fixture for the window) and tooling.

Other ideas?

And if the cracks are non structural - is it worth the effort?

rleffler 10-07-2013 07:15 PM

Quote:

Originally Posted by Bill.Peyton (Post 814375)
Bob, wait till it sits in the 100 degree sun a few times. I hope you are correct. I know Geoff used the lord adhesive and also has a small crack.


It already has. We had a few of them this past summer. I've got my fingers crossed that since I've gone through four seasons already, that I may be lucky and not have any cracks.

I seem to recall that Geoff mention that he thought he may have sanded into the glass covering the crack. I also used a heavier cloth than some have used.

digidocs 10-07-2013 07:41 PM

Rudi Greyling used Sika to attach his windows. See this thread:
http://www.avcom.co.za/phpBB3/viewto...rt=255#p754392

Also, he sent me these additional details via PM:

The 10 is more difficult than a 7 cause of the side windows thickness almost exact fit with little Sika bond thickness.

So you have to get the minimum thickness around the edge. Cut your windows 3 mm smaller than the recess in the fuse all round, and bevel the window edge 45 degrees inward. smear Sika and stick it on with clecos. Most of the Sika will peal out, but make sure you have 3mm edge. The bevel and 3mm edge bond with the thin layer between is enough to hold the windows in place.

Fill the cleco holes with Sika.

Bill.Peyton 10-07-2013 08:07 PM

What I would do is to reduce the outer half door window opening by the amount of overlap needed for the glue joint. Fill in the current joggle with fg lay ups. This will leave the door skin bond flange around the window intact and not reduce the bond surface area. This will also leave an inside joggle in which to attach the window. I would use the Sika product for the adhesive. I would finish the edge of the glass by rounding the inside edge and finishing with a Sika filet. The Sika product uses an activator applied to both sides of the bonded surfaces that leaves the oposite side of the glass with a nice shiney black mask reveal.
The rear windows would be even easier.

I want to add that I did pull tests using the Sika adhesive. The substrate broke apart and the joint never failed In any of the test panels I created during the bonding process.


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