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09-26-2013, 10:51 AM
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Join Date: Mar 2011
Location: Marietta, GA (KRYY)
Posts: 110
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Lord Adhesive vs. Weld-On Update
I don't know if you guys remember, but we attached the pilot side door window on our plane with Weld-On and the other windows with Lord Adhesive as a little experiment. Some builders feel that the Weld-On is responsible for the small cracks that form around the window over time. Personally, I was sold on ANY alternative after working with Weld-On for the first time; what a huge mess! Note that, for all windows, we left the appropriate (and same) size gap around them and then filled in this gap with filler as instructed in the plans.
Flash back to OSH 2012... at around 55 hours, a friend pointed out a "ridge" forming around our Weld-On window. It was pretty nasty looking and would have definitely caused some paint issues if the plane would have been painted already. Since then, this "ridge" has covered more ground around the window but has not really changed in height. Here's a photo of the Weld-On "ridge" when we first discovered it.
Yesterday, our painter, Don, pointed out some cracks around the rear windows and doors in which we had used the Lord Adhesive! Granted, they are NOWHERE near the size of the strange "ridge" that formed on the Weld-On window but, they're still there. We're now at about 270 hours and I've never noticed these cracks before so I don't know how long they've been there. They're pretty small so it isn't something that you'd see on an unpainted plane unless you were, say, prepping the cabin cover for paint. It might not even be something that would have shown up through paint already; I have no experience in this area. Below are photos of the cracks found in the Lord Adhesive rear and door windows, respectively. You can click them to open the full size image and get a better view of the cracks.
I find it very interesting that the cracked areas don't always occur at the edge of the window. A few spots are actually at the cabin cover, on the other side of the gap.
I still think Lord Adhesive is the better option but, it's not the ultimate solution. I'm not sure there is one short of masking the cracks by putting a few layers of glass around the seams. It seems cracks are inevitable when you have two different materials expanding and contracting at different rates. Anyways, just thought I would share more findings on our experiment.
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09-26-2013, 08:13 PM
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Join Date: Mar 2008
Location: Guelph Ontario
Posts: 267
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Weld On 10
I used Weld On 10 to glue all my windows in place and after 440 hours of flight time I have zero evidence of any cracking or ridges or any kind. now I hasten to add that I did apply a 1" strip of 3 Oz. (I believe) FG cloth all around each window and feathered it in with epoxy filler.
The gap between the edge of the glass and the joggle in the FG top was not filled with Weld On but rather with flox and then the cloth strip on top of that.
__________________
Ivan Kristensen
Guelph, ON. Canada
RV-10 (C-GMDV) 1355hrs.
Dual GRT 8.4" HXr EFIS, VP-200, TT A/P, Avidyne IFD440, uAvionixX ADS-B out, Sky Radar WX and Traffic, Dual EI's (one Lightspeed & one SDS CPI)
RV-14A under construction.
Link to my build site:
https://ivankristensen.smugmug.com/B...ENTAL-aircraft
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09-26-2013, 11:38 PM
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Join Date: Apr 2009
Location: USA
Posts: 1,499
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We used the thicker Weld-On 45, 410 filler, light fg cloth. Ridging/cracking showed up after first hot summer. If it gets too bad, black trim paint may get applied.
__________________
Good judgment comes from experience, and a lot of that comes from bad judgment.
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09-27-2013, 07:29 AM
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Join Date: Sep 2009
Location: St. Louis, MO
Posts: 1,788
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I used Sika adhesive and this summer I have seen cracks show up in the corners of the rear windows. I used the same method as Ivan, with 3 oz cloth all the way around each window. If I were to build another -10 I would fix this by installing the windows from the inside. It would take a little work to modify the window frames, but in the end would yield a better looking installation and would allow for re-installation/replacement of a window without having to paint the entire airframe or door! IMHO the engineering of the fiberglass structure took second seat in the design process, especially when you consider the door attachment and structure.
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Bill Peyton
RV-10 - 1125 hrs
N37CP
First Flight Oct 2012
Aviation Partners, LLC
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09-27-2013, 10:45 AM
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Join Date: Feb 2007
Location: San Antonio
Posts: 171
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I also used sika flex on my windows followed up with fiberglass around the windows. No cracks yet. I really think the fiberglass is the main reason I have not had cracks.
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Chad Holladay
Heritage Airpark TE86
RV-8 N769CE Sold
RV-10 N529W flying
RV -8 Building
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09-27-2013, 12:31 PM
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Join Date: Feb 2007
Location: Mpumalanga, South Africa
Posts: 1,065
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Quote:
Originally Posted by Bill.Peyton
I used Sika adhesive and this summer I have seen cracks show up in the corners of the rear windows. I used the same method as Ivan, with 3 oz cloth all the way around each window. If I were to build another -10 I would fix this by installing the windows from the inside. It would take a little work to modify the window frames, but in the end would yield a better looking installation and would allow for re-installation/replacement of a window without having to paint the entire airframe or door! IMHO the engineering of the fiberglass structure took second seat in the design process, especially when you consider the door attachment and structure.
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I love the idea of the window being fixed from the inside - a much better engineering solution. The only issue I can see is having to feather the flange to get a reasonable edge height. Couldn't agree more about the fiberglass quality - a real shame when the rest of the kit is so good.
I have used the Weld On 10 and laid up glass over the join. Even so, I am resigned to having cracks in the future.
__________________
Paul
Mercy Air, White River FAWV
RV-10 ZU-IIZ - "Zeus"
Building Bearhawk Bravo - RV-18 not available
2019 Donation Made
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09-27-2013, 01:36 PM
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Join Date: Apr 2009
Location: USA
Posts: 1,499
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Quote:
Originally Posted by paul330
I have used the Weld On 10 and laid up glass over the join. Even so, I am resigned to having cracks in the future.
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Now you are in the right frame of mind. Cracks are okay. I don't see them when I am flying over the beautiful clouds and landscapes. I don't pay any attention to them anymore.
__________________
Good judgment comes from experience, and a lot of that comes from bad judgment.
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09-28-2013, 07:31 PM
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Join Date: May 2007
Location: Canal Winchester, Ohio
Posts: 417
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If no fiberglass is used over the joint it will crack no matter what it is glued with.
As Ivan said you need at least a total of 3 oz of cloth minimum. Also very important is to fill the gap between the window and the fiberglass top with epoxy and flox or fiberglass chopped glass as the filler between the two. The other
thing to watch for is if you fiberglass over the window joint you must not sand back thru it when blending it in to the cabin top. If you sand partially thru the let's say 4 oz cloth it will probably crack around the joint sometime.
The big advantage of the Lord adhesive is that it is a little stronger bond than the Weldon and much easier to use. It cleans up easier and is much more forgiving and a longer work time.
Geoff
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Geoff Combs
RV-10 N829GW 865hrs
1940 Piper J3 Cub
Rans S21
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09-28-2013, 08:10 PM
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Join Date: May 2005
Location: X35 - Ocala, FL
Posts: 3,679
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Quote:
Originally Posted by Wayne Gillispie
Now you are in the right frame of mind. Cracks are okay. I don't see them when I am flying over the beautiful clouds and landscapes. I don't pay any attention to them anymore.
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I'm with Wayne also. The cracks look much better unjust the paint than through cloth, so if laying up over the edge, make sure to do it well. Installing from the inside gives a much less smooth exterior, which would be a shame on such a smooth plane. Still quite possibly cracks would appear with different expansion coefficients.
We have used epoxy resin with micro to fill the gap with quite good results till some hairline cracks, but that's kind of the nature of the beast.
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Jesse Saint
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10-06-2013, 12:46 PM
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Join Date: Jul 2008
Location: Central Coast,Ca
Posts: 87
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Topic Change - Interior installation of Windows
Quote:
Originally Posted by Bill.Peyton
I used Sika adhesive and this summer I have seen cracks show up in the corners of the rear windows. I used the same method as Ivan, with 3 oz cloth all the way around each window. If I were to build another -10 I would fix this by installing the windows from the inside. It would take a little work to modify the window frames, but in the end would yield a better looking installation and would allow for re-installation/replacement of a window without having to paint the entire airframe or door! IMHO the engineering of the fiberglass structure took second seat in the design process, especially when you consider the door attachment and structure.
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I did a briedf search for installing the RV10 windows with this method and did not find examples or a "how to".
Has this approach actually been performed? Or is this still in the theoretical stage?
Thanks,
Bill
__________________
Finally starting on the RV10 wings!
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