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  #1  
Old 05-02-2019, 02:35 PM
dwranda dwranda is offline
 
Join Date: Jan 2015
Location: Jamestown,NY
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Default canopy crack help needed

I just went to the garage to start taping the canopy for the fiberglass fairing and was absolutely disgusted to find this crack. After all the trouble I have had with the canopy part of me was going to be surprised if there was no crack when I was done. Well now what to do? I obviously have to stopdrill it and have read through a bunch of posts on others cracks. I have to get a plexi bit, but where do I get it and what size? I used sika so I haven't drilled any holes in the canopy. Any help or tips is mch appreciated.
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  #2  
Old 05-02-2019, 03:27 PM
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Vern Vern is offline
 
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Exclamation Drilling plexiglass

You want to drill it soon so it doesn't grow longer.

A small finishing nail or brad will work, or use a number 40 bit held against concrete to dull it.Try it first on a scrap.

Sorry!
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  #3  
Old 05-02-2019, 03:36 PM
lr172 lr172 is offline
 
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Default

I started all holes in my canopy with a #40 drill bit and never had a problem. A 1/16" bit would work even better for stop drilling. You can then put a bit of epoxy or silicone in the drilled hole. It doesn't look that bad, though it will be a constant reminder of your struggle.

For others reading this, It is important that spacers be used so that the plexi is not forced too hard to fit bends. The problem with the sika approach is the use of clamps. It is critical that the clamps are not used to force the plexi to make too aggressive of a bend without using heat or spacers to help it conform and not create too much stress. The sika is very strong and will easily hold the plexi in that stressed position, if held there with clamps as it cures.

Larry
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Last edited by lr172 : 05-02-2019 at 03:43 PM.
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  #4  
Old 05-02-2019, 03:50 PM
dwranda dwranda is offline
 
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Quote:
Originally Posted by lr172 View Post
I started all holes in my canopy with a #40 drill bit and never had a problem. A 1/16" bit would work even better for stop drilling. You can then put a bit of epoxy or silicone in the drilled hole. It doesn't look that bad, though it will be a constant reminder of your struggle.

For others reading this, It is important that spacers be used so that the plexi is not forced too hard to fit bends. The problem with the sika approach is the use of clamps. It is critical that the clamps are not used to force the plexi to make too aggressive of a bend without using heat or spacers to help it conform and not create too much stress. The sika is very strong and will easily hold the plexi in that stressed position, if held there with clamps as it cures.

Larry
Thanks! I don't know how I could have used spacers on the sides of the canopy because I had to pull the canopy in a fairly decent amount to get it to line up with the fuselage sides. After all is said and done the passenger side lines up almost perfectly with the fuselage but the pilot side sticks out about an eighth of an inch. I have a friend building a 14 and I can't wait to see his canopy go together.
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  #5  
Old 05-02-2019, 03:52 PM
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bkervaski bkervaski is offline
 
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Default

On the 14 a some of us had to cut relief points, kind of like a keyhole shape, to relieve stress points. You can’t tell after the layup.

Sorry to see that crack!
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  #6  
Old 05-02-2019, 04:05 PM
dwranda dwranda is offline
 
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I stop drilled it with a 1/16" regular bit. Hopefully that stops the crack. I may order a 1/8" plexi bit just in case. I saw many posts saying to use Weldon #3 in the crack. Is that still the preferred way to seal the crack?
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  #7  
Old 05-02-2019, 04:15 PM
lr172 lr172 is offline
 
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Quote:
Originally Posted by dwranda View Post
Thanks! I don't know how I could have used spacers on the sides of the canopy because I had to pull the canopy in a fairly decent amount to get it to line up with the fuselage sides. After all is said and done the passenger side lines up almost perfectly with the fuselage but the pilot side sticks out about an eighth of an inch. I have a friend building a 14 and I can't wait to see his canopy go together.
When the plexi wants to bend in one place, you use spacers further out from the bend to make the bending force more gradual and less concentrated in one area. Heat can also be used to relieve the stress, but it takes a bit of experience to keep from getting it too hot and creating visual distortions.

My 10 windshield had a bulge in an area similar to yours and I used a heat gun to get it back in without using force.

Larry
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  #8  
Old 05-02-2019, 04:48 PM
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Vern Vern is offline
 
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Default Heat

Careful on application of heat via heat gun or heat lights. A friend just melted his finished 8 canopy with 'just a little heat'.

A hot summer day is perfect heat!
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Last edited by Vern : 05-02-2019 at 07:35 PM.
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  #9  
Old 05-02-2019, 05:24 PM
Bavafa Bavafa is offline
 
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Sorry to hear it, tough luck.

I am thinking, would this stop at this point or is it going to grow eventually even with stop drilling a hole. If it needs to be replaced, this is the best time before the fiberglass lay up and paint has been applied.
I guess it will be tough call to make but it is worth spending a bit of time and research.
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  #10  
Old 05-02-2019, 05:51 PM
dwranda dwranda is offline
 
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Quote:
Originally Posted by Bavafa View Post
Sorry to hear it, tough luck.

I am thinking, would this stop at this point or is it going to grow eventually even with stop drilling a hole. If it needs to be replaced, this is the best time before the fiberglass lay up and paint has been applied.
I guess it will be tough call to make but it is worth spending a bit of time and research.
Oh man don't say that! I am praying to the canopy gods that it will stop there. If I had to replace the canopy at this point I would be tempted to push the plane into the back of my garage and take a couple years off! The thought of starting a new canopy takes ALL the wind out of my sails!
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