I thought I got off lucky with the rear window and drilling the screw holes. Completed this task back last fall and no sign of any cracks what so ever. Installed the canopy today to install the new side pins and while working in that area I noticed that most screw holes in the rear window are severely cracking. SO FAR none are cracking on the canopy, hope this stays that way. I thought perhaps I had over tightened the screws but two fingers on a screw driver can turn them. they are certainly not more than lightly snug. The only thing that changed is I have nothing to do in the hangar (waiting for the FWF kit) and turned down the heat to 5 degrees C (40 F). I'm also wandering if using the roll bar as a hand hold had anything to do with it?
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Acrylic crazing
- Thread starter Ron B.
- Start date
flyboy1963
Well Known Member
what to do?
Ron, we feel for ya!
I guess there's 2 things;
1. what happened
2. what to do
1. to troubleshoot, so you don't do it again...suggestions.
- use new acrylic ( not up to you, but I'll bet it's not aged & brittle)
- warmer is better
- use a sharp plexi bit with zero rake angle
- turn as slow as possible, with very light pressure
- support the BACK of the plexi...look closely at your cracks, are they only on the inside? you may have burst thru the last millimeter without knowing it.
- sealants can attack the plexi, check the ingredients, but not likely the smoking gun here, as would be the case with polycarb.
2. ok, other builders will likely have better ideas than I.....
- enlarge the hole to eliminate the cracks.
- 'deburr' the edges with a stone or countersink, very slowly to remove the stressed material...... sand, polish, etc.
- get out the magnifying glass to see if you've really taken out the cracks.
- last resort, get a new piece of acrylic, which could be tough, (not too many guys have messed up their tipper/windshield yet!...so no back halves to sell)
Ron, we feel for ya!
I guess there's 2 things;
1. what happened
2. what to do
1. to troubleshoot, so you don't do it again...suggestions.
- use new acrylic ( not up to you, but I'll bet it's not aged & brittle)
- warmer is better
- use a sharp plexi bit with zero rake angle
- turn as slow as possible, with very light pressure
- support the BACK of the plexi...look closely at your cracks, are they only on the inside? you may have burst thru the last millimeter without knowing it.
- sealants can attack the plexi, check the ingredients, but not likely the smoking gun here, as would be the case with polycarb.
2. ok, other builders will likely have better ideas than I.....
- enlarge the hole to eliminate the cracks.
- 'deburr' the edges with a stone or countersink, very slowly to remove the stressed material...... sand, polish, etc.
- get out the magnifying glass to see if you've really taken out the cracks.
- last resort, get a new piece of acrylic, which could be tough, (not too many guys have messed up their tipper/windshield yet!...so no back halves to sell)
Just a small dab as per instruction.
These cracks were not there for a couple months after install which surprised me. One would think they would appear right away if it was a drilling issue, I'm fairly sure it had something to do with drilling. The cracks are extending out too far to repair, I will need to replace eventually.
MS19087
Well Known Member
Loctite!
I'm really surprised that they said use a dab of loctite. That is the source of your crazing - without a doubt. You may want to call customer support . . .
I'm really surprised that they said use a dab of loctite. That is the source of your crazing - without a doubt. You may want to call customer support . . .
I could be mistaken, it was a while back, maybe it was silicone. I'll go out and check.
Posted in July 2015
http://www.vansairforce.com/community/showpost.php?p=995112&postcount=58
A plans update was issued shortly after that correcting the mistake.
The current Rev level of that drawing is 1.
http://www.vansairforce.com/community/showpost.php?p=995112&postcount=58
A plans update was issued shortly after that correcting the mistake.
The current Rev level of that drawing is 1.
Follow-up
The following notification was e-mailed to all builders after the plans correction was made......
BUILDER NOTIFICATION:
All RV-14 Finish kit builders require email notification.
BUILDER NOTIFICATION EMAIL:
The use of blue Loctite on the window installation screws called out on Page 38-04 is in error.
Blue Loctite will cause crazing when it comes into contact with the Window.
For window installation, builders should reference RV-14 Page 38-04 Revision 1 or higher, available on the Van's Website.
If you did not receive the notification, check with the office to confirm they have a correct e-mail address on file for you.
The following notification was e-mailed to all builders after the plans correction was made......
BUILDER NOTIFICATION:
All RV-14 Finish kit builders require email notification.
BUILDER NOTIFICATION EMAIL:
The use of blue Loctite on the window installation screws called out on Page 38-04 is in error.
Blue Loctite will cause crazing when it comes into contact with the Window.
For window installation, builders should reference RV-14 Page 38-04 Revision 1 or higher, available on the Van's Website.
If you did not receive the notification, check with the office to confirm they have a correct e-mail address on file for you.
Scott, I'm not blaming Van's, now that I know there was a correction. I'm glad to know where I went wrong, so hopefully it will not reappear on my next window. I have not had many reorders with both the 14 and the 10, it's just my turn now.
I do get notifications from Van's so I probably forgot about this one.
I do get notifications from Van's so I probably forgot about this one.
Warning: remove canopy material to clear the F-01474A-L & -R Stiffener Angles
I emailed Vans support as this issue as it was not mentioned in kit steps and I wanted to confirm cutting of the Windows needs to be done. Looks like it may cause the rear Window to crack at the screws if some of you missed this. And changes in the ambient temperature could make the cracks even worse.
Here's the email I sent to Vans support:
We are at the stage of fitting our rear RV-14A Window, I have trimmed the window to fit the roll bar brace brackets as per page 38-02 steps 1 to 6.
When I looked closer I noticed that the Window will not site tight to the roll bar as its hitting the F-01474A-L & -R Stiffener Angles (yes we have already riveted the F-01474A-L & -R Stiffener Angles).
It looks like we will need to remove 3-5mm of canopy from each side to clear the F-01474A-L & -R Stiffener Angles, is it ok to remove this much of the rear Window in this area please?
I have not drilled the window yet and want to confirm this before I ruin the Window by cutting it, thanks.
And here's Vans reply (I hope they don't mind me posting this as it was very helpful):
Yes, just trim it in the affected area until the window is able to fit tight to the roll bar. The windows will vary in size, they will change noticeably with temperature so make sure you leave a gap for expansion. The canopies will err on the side of being too big – it’s easier to trim it than to try to add material.
Vans
I emailed Vans support as this issue as it was not mentioned in kit steps and I wanted to confirm cutting of the Windows needs to be done. Looks like it may cause the rear Window to crack at the screws if some of you missed this. And changes in the ambient temperature could make the cracks even worse.
Here's the email I sent to Vans support:
We are at the stage of fitting our rear RV-14A Window, I have trimmed the window to fit the roll bar brace brackets as per page 38-02 steps 1 to 6.
When I looked closer I noticed that the Window will not site tight to the roll bar as its hitting the F-01474A-L & -R Stiffener Angles (yes we have already riveted the F-01474A-L & -R Stiffener Angles).
It looks like we will need to remove 3-5mm of canopy from each side to clear the F-01474A-L & -R Stiffener Angles, is it ok to remove this much of the rear Window in this area please?
I have not drilled the window yet and want to confirm this before I ruin the Window by cutting it, thanks.
And here's Vans reply (I hope they don't mind me posting this as it was very helpful):
Yes, just trim it in the affected area until the window is able to fit tight to the roll bar. The windows will vary in size, they will change noticeably with temperature so make sure you leave a gap for expansion. The canopies will err on the side of being too big – it’s easier to trim it than to try to add material.
Vans
Larry DeCamp
Well Known Member
Blue loctite testimony
Blue locktite also strips Stewart systems paint near fastener holes where primer is accessible to locktite on fasteners. I am going to use 2K primer from now on.
Blue locktite also strips Stewart systems paint near fastener holes where primer is accessible to locktite on fasteners. I am going to use 2K primer from now on.
Lycosaurus
Well Known Member
Sorry Ron, but I don't think alcohol is an approved chemical to use on our 'glass'. My understanding is that it can cause crazing as well.
I have a very short memory, but I do remember using what Van's recommended as I did not want this to re-occur. The alcohol was not used on the "glass" it was a new window, it was used to clean the Loctite out of the threads. Apparently I did not do a good job, now I'm faced with not knowing how to clean properly and having the next one do the same.
az_gila
Well Known Member
Not correct....
Isopropyl alcohol, aka rubbing alcohol, is approved by Vans as a cleaning agent.
https://www.vansaircraft.com/pdf/Acrylic_Canopy_and_Lexan_Window_Hints.pdf
AlexPeterson
Well Known Member
Are the tapped holes in the plexi? Posts subsequent to the above would seem to indicate that. Bad idea, it would seem, if it is so.
In an effort to assist the high percentage of builders that have difficulty taping holes straight, particularly on a curved surface like the roll bar, the construction manual directs the builder to tap the holes with the rear window in place.
This provides an alignment guide for the tap so that all of the screws will thread in aligned correctly. One all of the holes are tapped, the window is removed and all of the tapped holes are final drilled and deburred, to remove the threads and leave a smooth I.D. in the holes.
Per Scott's post, I was perplexed as I first read the plans and it called for tapping the plexi, however after fully understanding that this was temporary, I found the process very straight forward,
It worked well, left a nicely aligned hole and a nicely tapped hole in the roll structure.
It worked well, left a nicely aligned hole and a nicely tapped hole in the roll structure.
How much space did you leave between canopy and back glass where it closes?
Between 1/32 and 1/16 inch I would say. I the area the five screw holes have cracked this time I would be safe to say it's a bit over 1/16" gap.
