Sealing plexiglass, stop-holes?

Hi,

While removing some caulk, a 3/8" crack formed from the edge. I stop drilled it only to find a smaller, hair line crack formed from the stop-hole. A second stop hole and the part is stable. Fortunately this is just the wing tip cover for the navigation light so I only need a water-tight seal clear enough to pass light.

Is there consensus on how to seal the stop-hole and/or water seal the crack?

I did find an article using Acryfix to repair a canopy. But the article addresses canopy repair by laying up layers of UV cured, clear plastic. For a canopy that makes sense and it would work for the wing-tip cover.

I've also seen references to using "Weld-On #4" and acetone dissolved plexiglass. Mostly looking for recommendations.

I'm planning to use clear, GE silicon to replace the mold-growing, caulk.

Bob Wilson

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Originally Posted by bwilson4web

I'm planning to use clear, GE silicon to replace the mold-growing, caulk.

Bob Wilson

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that'd be my choice, too.

T-88 works quite well.

There is a product called Lexcel which is designed for use with lexan and/or plexi. I've found it in the caulk section at Lowes before.

'Mornin' all. I have done a number of things depending on the installation. In this case you might either use a bit of the sealant you are caulking with to just get it water tight OR or remember that a good bonding agent for joining (and patching) Plexi or Lexan is to melt shavings of the same materiel in MEK. Mask around the repair so you don't accidentaly make a bigger mess (I LEARN from my mistakes... sometimes)... When you get a melt that is smooth and just thin enough to 'spoon' in fill the hole. IF it won't stay or wants to drip you can put a little tin foil over it and tape it tight...both sides if you can't position it to get gravity to help.. i. e. a vertical piece being repaired in place. You can ultimately even use sand paper and a Micro Mesh kit to return the spot to transparent. BUT!! This does still leave a stress riser so if it's in a real windshield or a stressed piece (or God forbid a pressure vessel) I'd watch it carefully over time. This wants AT LEAST 24+ hrs to cure or it isn't fully bonded. Good luck. I have successfully bonded the edges of a Lexan guard that was about 8" long. The customer didn't trust it so I showed him a block wall to throw it against while I reached for my lunch... I won... :-))

There is a glue used in RC airplane assembly for attaching clear plastic canopies. It is called RC 56 canopy glue and comes in a plastic squeeze bottle. It is milk white and dries to crystal clear when hard and is flexible after hardening. I have used this in place of silicon rubber as a sealant as well and works great. Find it at your local airplane hobby shop.

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Originally Posted by fmworth

There is a glue used in RC airplane assembly for attaching clear plastic canopies. It is called RC 56 canopy glue and comes in a plastic squeeze bottle. It is milk white and dries to crystal clear when hard and is flexible after hardening. I have used this in place of silicon rubber as a sealant as well and works great. Find it at your local airplane hobby shop.

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THANK YOU! This sounds like just the stuff I need. Bob Wilson

Try Acrifix, a UV cured acrylic product.
A drop in the hole will seal it and also this stuff will fix the crack as well.
Google it.
I fixed several cracks in my motorglider canopy with it. Not invisible, but acceptable.
I bought mine from Knauff and Grove in Pennsylvania. About $50.00 a tube, but worth the money.
Carefully grind out v grooves on one side and fill with acrifix on one side.
Then grind the vee groove on the other side slightly into the glued (and cured) side to help eliminate the crack line.
After cure (in direct sunlight) I scraped the slightly raised plastic glue line with a single edge razor and then sand with increasing number grit until ready to polish out with fine compound.
Google other guys processes as well to make up yout mind how to proceed.

JDB

Use of silicone may pose problems when painting now or in the future...use extreme care around areas that will need to be painted as paint will never adhere. A polyurethane sealant may be a better choice depending on location and whether or not the area is already painted.

Quote:

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Originally Posted by redbarron55

Try Acrifix, a UV cured acrylic product.
A drop in the hole will seal it and also this stuff will fix the crack as well.
Google it.
I fixed several cracks in my motorglider canopy with it. Not invisible, but acceptable.
I bought mine from Knauff and Grove in Pennsylvania. About $50.00 a tube, but worth the money.
. . .

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I bought a 4 oz. tube of Acrifix IR 0192, the UV cured, cement, $19+9 shipping. I figured this would give the strongest, most permanent fix.

Thanks,
Bob Wilson

Quote:

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Originally Posted by redbarron55

Try Acrifix, a UV cured acrylic product.
A drop in the hole will seal it and also this stuff will fix the crack as well.
Google it.
I fixed several cracks in my motorglider canopy with it. Not invisible, but acceptable.
I bought mine from Knauff and Grove in Pennsylvania. About $50.00 a tube, but worth the money.
Carefully grind out v grooves on one side and fill with acrifix on one side.
Then grind the vee groove on the other side slightly into the glued (and cured) side to help eliminate the crack line.
After cure (in direct sunlight) I scraped the slightly raised plastic glue line with a single edge razor and then sand with increasing number grit until ready to polish out with fine compound.
Google other guys processes as well to make up yout mind how to proceed.

JDB

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I need to fill a number of quarter inch holes in a sheet of plexiglass, what is the best way to do this? I've done some research and found Weld-on 16 acrylic cement might work but I am wondering if the holes would be too big for that. Would polyurethane do the job?

Thanks for the feedback!