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Rear Window second try

gkalin

Member
So I managed to crack my rear window during countersinking. Drilling went well, and I know what I did wrong......end of long day, tired, pushed on the curved portion while I was countersinking. Heard it crack. About an inch long toward the inside on one of the rollbar holes about half way up the rollbar.......you would see it every time you got in the airplane.

So I ordered a new window, but I am wondering how I am going to drill it, now that the rollbar is already drilled and tapped. Original construction has you drill the window AND the rollbar together, so naturally they are lined up perfect. So how am I going to do that now? Just eyeball it? Not going to get them all perfect, and there is bound to be some stress on the window from even slightly misaligned screws causing cracks in the future. The skins are not dimpled yet so I am good there.

Anybody have to replace the rear window and how did it go?
Thanks, Jerry

RV-14
SN140601
 
It happened to me, too. These photos show the problem you face and how I solved it. Be careful and you will be fine. To be clear, I drilled the center of a screw head, attached it to a piece of aluminum scrap, and used that as a guide to drill the new rear glass in the center of the dimpled hole.

Oops, I just reread your post and I guess I assumed you had already dimpled the skin. I don’t recall an issue drilling the rollbar holes, but I may have done those after attaching the window at the rear. As I said before, be careful and you will be fine.
 

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Sikaflex is your friend

I really cannot see any reason why one should battle with drilling of holes ad fitting screws if Sikaflex is so easy to do.

Please do yourselves a big favor and go the Sikaflex route.
 
Sika Flex

I used Sika on my -8. 400+ hrs. Lots of aerobatics. Banged my head against the canopy in clear air turbulence hard enough to see stars and dislodge the rear follower. No issues. I'll be using Sika on my -14a.
 
I used Sika on my -8. 400+ hrs. Lots of aerobatics. Banged my head against the canopy in clear air turbulence hard enough to see stars and dislodge the rear follower. No issues. I'll be using Sika on my -14a.

Be aware, the QB 14 has holes predrilled to mount the rear canopy glass. You will have to find an acceptable way to hide them.
 
So I ordered a new window, but I am wondering how I am going to drill it, now that the rollbar is already drilled and tapped. Original construction has you drill the window AND the rollbar together, so naturally they are lined up perfect. So how am I going to do that now? Just eyeball it? Not going to get them all perfect, and there is bound to be some stress on the window from even slightly misaligned screws causing cracks in the future. The skins are not dimpled yet so I am good there.

Anybody have to replace the rear window and how did it go?
Thanks, Jerry

RV-14
SN140601

These things happens so I wouldn't sweat it. You are on the correct path on replacing it.

I think you can still drill in the same way as the original way with that has been done with the pilot holes, perhaps with a bit more care to come closer.

Or possibly use set screws in the rollbar that protrude slightly above the surface and put a dab of paint or marker on the set screws. Install the canopy per instructions but in someway that transfer the markings to the canopy. Then drill from inside.

Good luck
Mehrdad
 
When match drilling holes on a radius, it is critical that the two surfaces stay in tight contact or later on during final assembly when the the fasteners are installed (which will pull the surfaces together) the holes will progressively go out of alignment.
So in a case where dimples already exist, I would recommend that only a few holes be drilled at a time, the window be removed, and machine countersunk so that it can be pulled flush to the skin with the clecos before moving on to additional holes.
 
Sikaflex on rear window

Has any 14 builder used only Sikaflex on their install of the rear window? Will the thickness of the Sikaflex effect the installation?
 
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