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Crack in Windshield

Pmoran

Member
I went to the hangar yesterday to take the RV-6A out after a cold winter's rest. After an extensive preflight, I pulled it out of the hangar and climbed in and started it up. As I was getting everything set up and slowly continuing through the checklist, I glanced up and notice a small crack in the windshield that I hadn't noticed before. I almost had a breakdown right then and there. The crack is about two (2) inches and it runs from the top left-center down and it is not noticeable while seated unless you intentionally search for it.

It just so happened that I ran into another RV owner on the airport that night that also experienced a crack in his canopy this cold winter; so I knew I wasn't the first person to experience the bad luck. Thankfully this website provides so much with regards to resources and information that the small donation requested is well worth the investment. I spent a lot of time researching to see if others may have experienced something similar and I wasn't disappointed.

I found a thread from 2014 from Gerry Julian who had a very similar experience. He drilled through his windshield with a 1/16 bit to stop the crack from continuing. Others suggested that one should use a drill bit exclusively for acrylic, however I could only locate a 1/8" bit from a local shop that develops plastic products. The person at the shop suggested that a 1/16 bit won’t grab enough to make a difference at that size.

My questions are: Should I use the 1/8 bit designed for this type of surface? This will create a little larger hole. Will the larger hole be significant enough to notice? Regardless of the size of the bit/hole, will this create a lot of noise and allow cold air to enter at a high rate of speed? Other than drilling a hole to stop the crack from spreading, is there anything else I should do and/or be aware of? Sorry for the big pictures. I'm still learning how to do this.
Any suggestions, advice or words of caution are welcome. Thanks in advance,
Pat Moran
(619) 994-3542

Windshield_crack_2_March_2018.jpg


Windshield_crack_1_March_2018.jpg
 
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I initially used a regular #40 drill for all of my holes in the plexi and that should be all you need stop drill this.

Larry
 
Just to give another thought, a larger hole may make sure it stops. If you worry about air, fill it with some glue or silicone. Make sure the glue is compatible with your canopy.
 
I'm getting ready to repair a similar canopy crack on my RV-7. I'm going to stop drill it with a #40 for acrylic. I don't think a 1/16" is big enough. That's a 1.59 mm diameter, and I don't think 0.80 mm is sufficient radius to relieve the crack stress.

After drilling, I'm going to fill the hole and the crack with Weld On #3. I bought a 1/4 pint can of Weld On 3 from Amazon for about $8. I also bought extra syringes with tiny little needles to help fill the crack and hole.

Good luck to as all! :eek:
 
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High RPM

If you want to reduce the chance of more cracking or chipping when drilling. Put the bit in a High Speed Dremel. the bit will then melt the plexi as it drills and the hole is no bigger but the surface is sealed from the melted plexi.

Steve
 
Pat,
I'll be taking my -4 to Pella tomorrow morning for the weekend. I have a new 1/8 acrylic bit you're welcome to use that I'll leave taped to my hanger door. Hanger A8. Compare the acrylic to the non-acrylic and you can see how the acrylic is designed to not grab. Keep it as long as you want. I'd leave it in my black truck but will be parking the truck in the hanger. Steve Schmitz
 
I had the best luck drilling holes in my canopy using a step drill bit with wide steps. A step drill has no tendency to draw the bit into the acrylic and you can keep the size of the hole to 1/8 inch.
 
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Please do not use a standard drill bit... Yes, many will report doing so without problems. A regular drill bit, just as it is starting to break through the far side, will "pull" itself through the rest of the way, making awful sounds. And, you may have much larger cracks to deal with. Someone offered the 1/8" plexi drill, good advice.
 
Thanks Steve,
I was able to get an (1/8") plexi bit from a local plastic shop in West Salem, but I really appreciate your very kind offer.
Pat
 
Jim, Larry, Rockwooddrv9, Karl, Steve B & Steve S, Mike, Bob and Alex thank you each for the advice, suggestions, and support.
I really appreciate the information and as I've said in the past, this website is an incredible source of information.

Karl - I'm unfamiliar with Weld On #3, however I understand that it is an acrylic cement but is it compatible with our canopy and windshield? I'd prefer to use that over the plastic fix used in the repair of the 8 canopy that was featured in the thread link that Mike provided.
My confidence is low using plasti fix, however the Weld-On #3 seems straight forward.

I appreciate all comments and suggestions.
Thanks,
Pat
 
In the Dallas area (McKinney) back in mid December we had a night that dropped to the mid teens.

Result was my slider canopy had a crack perpendicular to the mid-canopy tube radiating out about 7 or 8 inches each side running through the 4th pop rivet.

I stop drilled each end with a #30 acrylic bit and then applied bookbinder tape over the cracks on each side inside and out as smoothly and carefully as I could, and tried to avoid air pockets in the tape.

No one notices it unless I tell. I don?t notice it too much because my Koger shade covers it, but it makes odd shadows on the shade...

Still, I know it?s there and I had that miserable feeling when I first saw it, and I continually monitor it and fret over it.

Subsequently, when we had some really cold nights and days (for North Texas) early in January, I left a 40 watt bulb plugged in for several days, dangled in the cockpit more or less, hung from the canopy handle. Also covered the canopy with a heavy moving blanket and an old bedspread. Not sure if that was useful, but no more cracks developed.
 
I found myself in almost the same boat as you described last winter, discovering a 2" crack during preflight. I immediately stop drilled it and it's remained the same ever since. I've been waiting on warmer temperatures so I can repair it.
I just checked out the "Weld On #3" product as suggested and from what I can gather, it's very thin liquid. The reviews on Amazon boast it's great for welding/gluing pieces together but I couldn't find any info to suggest how it would be for filling a #40 or 1/8" hole.
Watching intently hoping some with experience will chime in. 👍🏻
 
I haven't used the Weld On #3 yet, but the brain trust at the airport here says it's the right stuff to use on these cracks. I'm told it's very "watery", so be sure to tape underneath during application.
 
My -8 had a stop-drilled 1" crack in the rear area of the canopy edge when I bought it. During the 3rd winter of my ownership it cracked another inch beyond the stop drill, so I had it stop-drilled again. I was going to glue it with Weld-On 3 when I noticed that the crack widens slightly at the edge in cold weather and narrows again in warmer weather. I've read that these canopies have stresses in places that can't be predicted because of the way they are manufactured. A photo on this site showed a crack that started and ended well away from the canopy edges. So, I'm considering leaving the crack as it is and covering the area with my EAA or AOPA decal, which is how it was originally covered.
 
I'm told it's very "watery", so be sure to tape underneath during application.

I would recommend against doing that.

The best application method is to use a syringe with a small needle.
Apply small amounts at the top working your way along the crack.
Because it is about the same viscosity as water, it will wick into the crack via capillary action. You can see when the crack is filled in an area because it changes the light reflection properties when the crack is filled.

It shouldn't drip if you only apply enough to fill the crack.

If you tape the bottom of the crack, depending on how resistant the tape and adhesive is to the chemicals in the weldon-3, it may wick out of the bottom of the crack and under the surface of the tape.
 
Have stop drilled plexiglass cracks at least 20 times. Never had a problem. Always used a 1/16" bit. Drill past the visible end of the crack 1.5 time the bit diameter. Use something like the end of a wood dowel rod on the opposite side to back up as you drill and drill with very light pressure. I have used silicone to fill the hole,but prefer super glue or thick gap filling version of super glue.

Be careful not to drill at the visible end of the crack, because the crack can continue as you start drilling and go past where you are, so that you would not be at the end of the crack.
 
Thanks for the advice Scott. You make a very good point! I will do it like you describe.
 
I would recommend against doing that.

The best application method is to use a syringe with a small needle.
Apply small amounts at the top working your way along the crack.
Because it is about the same viscosity as water, it will wick into the crack via capillary action. You can see when the crack is filled in an area because it changes the light reflection properties when the crack is filled.

It shouldn't drip if you only apply enough to fill the crack.

If you tape the bottom of the crack, depending on how resistant the tape and adhesive is to the chemicals in the weldon-3, it may wick out of the bottom of the crack and under the surface of the tape.

I wholeheartedly agree! It will be a mess under that tape...
 
Pics of the hole after drilling to stop crack

After practicing on a piece of acrylic, I finally had to the courage to drill into the windshield to stop drill the crack. I used the 1/8" acrylic bit and I drilled very slowly. It appeared to have gone well and I'm waiting for the weather to warm up before I attempt to use Weld-On #3. In addition, I'm planning on using silicone to plug the hole.

I've never used this before and I'm wondering what temperature I need the hangar to be prior to attempting repair with Weld-On #3. Any suggestions?
Any suggestions or warning about using silicone to plug the drilled out hole? I read one post that the person preferred to use super glue; any thoughts on super glue compared to silicone?

Until the temperatures warm up in Southwestern Wisconsin, I was planning on using tape over the crack and 1/8" hole. Is this an acceptable interim fix? Any concerns that I need to be aware of?

As always, any comments are welcome.
Thanks,
Pat Moran

Stop_Drilled_Crack_1.jpg


Stop_Drilled_Crack_2.jpg
 
Nice work on the drill job Pat. Stick a little clear tape on there for now and go fly. Once the temp picks up to the level of sticky in your area you have what you need to apply the goo. Go grab some air!
 
some light reading

surely you've seen this;

http://www.vansaircraft.com/pdf/Acrylic_Canopy_and_Lexan_Window_Hints.pdf

another note; the curing agents in silicone, and there may be quite a wide variety among brands, but I would never allow this to come in contact with the raw edge ( like a crack or drilled hole) in my $1000 canopy. The acrylic may tolerate it, but why risk it?
it will DEFINITELY attack polycarbonate, and craze and crack it eventually.
A speck of Weld-On #16 ( thickened 'glue') will fill and bond to the acrylic, unlike silicone......
 
@Pmoran In my previous live I used to specify holes in bits of Perspex and such like to be dragged through the air at over twice the speed of sound. I have very little experience of light aircraft. But that hole looks to have quite a rough finish including some small cracks. If that was my canopy I would be trying very hard to get rid of any roughness and any visible imperfections.
 
Crack club! -:(

I'm devistated, I've joined the cracked canopy club!!., had my bird 3 months, found a 1&1/2" crack going vertical from the skirt towards the rear of the canopy about opposite where the rear seat luggage access is, it feels like a death in the family, am very upset:(
No idea how it got there but I'll have to stop drill it if I can find a plexiglass/Lexan drill bit....sob sob sob
 
Sorry to hear about the Crack

I'm devistated, I've joined the cracked canopy club!!., had my bird 3 months, found a 1&1/2" crack going vertical from the skirt towards the rear of the canopy about opposite where the rear seat luggage access is, it feels like a death in the family, am very upset:(
No idea how it got there but I'll have to stop drill it if I can find a plexiglass/Lexan drill bit....sob sob sob

I completely understand how you feel. It's been a little while since I discovered my cracked windshield, but since I've stopped drilled the crack it has been no issue. I took advice from a previous post and placed clear book tape over the hole and crack. I intend to use Weld On #3 to fill the crack, and Weld On #16 for the hole, but until then, I am flying.

Best of luck!
 
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when I installed my canopy, I started every hole in the canopy with a standard #40 drill bit and had no issues. Go slow and let the heat build up at the tip of the bit.
 
Like many of the previous posters, I experienced a 2 inch crack in my canopy back in April of 2013 and about 450hrs ago. My repair is a bit different so I am passing it along as another option. I drilled out the crack with a 3/16 inch Plexiglas bit. I then cut and measured a piece of 3/16 clear plastic rod and cut it to fit the thickness and shape of the curved canopy. I then used #3 Weldon like many have suggested. Finally finished the repair by using a Plexiglas scratch repair kit to sand smooth the outside and inside exposed portion of the plastic rod. Maybe a bit more work then some of the other techniques, but it has proven strong and sound over the years. (plastic tube and Weldon purchased form the same company after searching the internet for Weldon #3 suppliers in my area) PS temp in April was in upper 60's.

Steve Koziol
RV9A Approaching the 800hour mark.
 
Well stop drilled the crack today out in the sun so the canopy was warm. Got a drill bit that I blunted off in concrete and with the aid of a magnifying glass drill a 2mm hole right at the end of the crack. Looked great, debured the hole either side gently with a larger twist drill by hand only, jobs done..........well so I thought! Cleaned my tools came back to check it after a few mins and I noticed a very small (about 1-2mm long) crack starting upward again from the top of the whole!! Not my day🙁🙁 I'll leave it for now to see if the crack travels any further🙁
 
I just joined the Lexan Canopy Crack Club (LCCC)...having t-shirt made. Good thread!

Talked to mothership and discussed technique and options ($$$). Will attempt fix first.
 
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15 months now since I stop drilled my small crack, the very tiny one that started beyond the filled hole has not progressed any further, am glad it's not in my view!
Welcome to the club TomVal, it's something you accpet and live wth, hurts though at first! -:(
 
I just joined the Lexan Canopy Crack Club (LCCC)...having t-shirt made. Good thread!

Talked to mothership and discussed technique and options ($$$). Will attempt fix first.

Tom, where did it crack? Did Van's have any suggestions about how to prevent the problem?

Thanks,
 
Tom, where did it crack? Did Van's have any suggestions about how to prevent the problem?

Thanks,

The crack is about 1.5 inches long and started about two inches above the trailing edge of the canopy skirt. The crack does not penetrate completely through the Lexan but has an internal void appearance like an elongated air bubble was trapped inside. The crack is near the fuel filler side of the canopy.

The best prevention is keeping the canopy free of contamination, particularly from fuel, and be sure to use only cleaning solutions approved for Lexan. I've been careful during the fueling process so my best guess is that my failure was related to stress and/or vibration.

On Van's website you can find some guidance on the proper care and feeding of your canopy.

https://www.vansaircraft.com/faq/acrylic-canopy-and-lexan-window-hints/
 
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Today I stop drilled and applied two applications of Weld-On #3 to the crack.

For filling the ⅛" holes, I purchased a 4 oz tube of Weld-On #16. I don't particularly like the applicator tip that came with the adhesive. I practiced with a scrap piece of lexan. The tip can easily slip off the nozzle of the tube and make a mess.

The applicator needle that came with #3 was too thin of a needle for use with #16. What size applicator needle or syringe should be used with this grade of adhesive? Also, what technique did you use fill the drilled holes without using tape on the underside?
 
I used the applicator that came with the Weld On #16 for the hole, but was not as smooth as I would have preferred.

It?s been a while since I made my repairs and thankfully the crack is not immediately in my view, but I haven?t had any issues with it and don?t even notice it until I clean my windshield after my flights.

Good luck!
 
plexiglass stop drillfrom the rear.

A glass or ceramic tile drill bit can be successfully used as a plexiglass drill bit. It has no flutes to further stress cracks, Go slow and support the plastic from the rear.
 
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