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-   -   Star cracks around canopy hole (https://vansairforce.net/community/showthread.php?t=74150)

pwhaley6347 07-11-2011 08:02 PM

Star cracks around canopy hole
 
I have a problem with one of my holes (1/8) in my canopy. It has very small cracks all the way around it. The longest one is about 1/2". Anyone have an idea how to repair this problem. Thanks in advance.


cjensen 07-11-2011 09:11 PM

My first thought was to get some Weld-on and use the dropper to wick it in to the cracks...

apkp777 07-12-2011 05:10 AM

Chad's suggestion looks like a good one. You may also want to look into and possibly try Ethylene dichloride. I am not sure where you get that stuff. Perhaps a nail salon or pet store (fish tank repair). There are lot's of cracked canopies out there. Someone must have found a fix for this.

Rick6a 07-12-2011 05:14 AM

If I determined the fractures emanating from around that hole are relatively shallow surface defects, and based upon your photo it *appears* to my eye they may be, using Micromesh or similar, I'd likely blend em away.

terrykohler 07-12-2011 06:35 AM

Fix the problem before putting the bandaid on
 
Looks like a lot of chatter marks in the hole. First, make sure the hole isn't undersize. If the screw touches anywhere in the cylinder, you need to enlarge. Next, take a chamfer bit in your fingers or in a hand brace and gently turn it to smooth out the chamfer. You might also use an intermediate drill size for one turn to break the corner between the chamfer and the hole. Look closely. You may want to fix other holes before they start to show cracks. Any sharp corner or stress riser can be A problem in acrylics.
Terry

mv031161 07-12-2011 06:45 AM

what you have is the typical result of using a drill bit not designed for plexiglass grabing to much material as it cuts through creating micro cracks and stressed points. it appears by your picture that the cracks are coming from the results of the tapered tool and not as much from the hole itself therefore giving you the appearance of surface cracks and not all the way across.

Chapter 9 of AC43.13-1A has the approved procedures as to how to deal with repairs. you may need to use the Surface or Plug patch procedure. good luck..make sure you use a Plexiglass designed drill bit or some of the pointers given by builders in this forum

rv6ehguy 07-12-2011 12:32 PM

Leave it alone
 
Leave it alone and don't atempt to repair this problem. These are stress fractures and may or may not grow beyond what you have here. I guarantee if you add any kind of liquid, chemical or glue to these fractures you are inviting them to grow into a crack. These fractures are micro in nature and many of them are not even on the surface. With the exception of water, all thin viscosity liguids and glues will be drawn into the fractures via capillary action and in most case expand in the fracture, making the problem even worse. I pesonally would not attempt to fix this problem until you have an actual crack. At that time, I would stop drill the crack and then introduce with a sryinge, an acrylic/plexi glue such as "Rez-n-Bond" 'Hope this helps.
John Van Lieshout
Toronto, Ontario
RV6A 80%

pwhaley6347 07-12-2011 08:02 PM

Thanks for the input
 
I appreciate all the input on this issue. I also consulted with Vans and this is what their reply was...

"Those look like they were maybe caused by the countersink chattering in the hole. Or possibly the pressure of the cleco was enough to cause some stress cracks - this happens if a fastener exerts too much clamping pressure on the plastic. I don't think there's any way to fix it, but it doesn't look like they go all the way through the plastic, so I doubt they will spread further."

I think I will go with RV6ehguy suggestion and leave it alone.

Thanks again.

vickruis 07-12-2011 10:59 PM

I would consider using a drop of chloroform, you can buy this in a pharmacy. Chloroform is used to glue plexiglass, and it has extremely high viscosity, so you can probably fill in the cracks and prevent further tearing.

BTW, I glued my canopy completely, but had a stress crack aroud the infamous 'ears'. Yep, cut them off!

Av8torTom 07-13-2011 09:44 AM

Chloroform
 
I second the chloroform idea. We used to use it to "weld" plexiglass parts together. The joints were often stronger than the material itself.

I would first try and reproduce your cracks in a scrap piece and give it a try.
In my opinion, chloroform is very LOW viscosity and will wick into those cracks via capillary action and weld everything nice and tight.

Bavafa 07-13-2011 12:45 PM

Weld-on #3 is also a great liquid that is used for plexiglass and it does wonders. I have tested Weld-on and it wicks in any small crack if there is a physical access to the crack.


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