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Builder's Tip - JB Weld's ClearWeld Epoxy

By Ian Brown, Editor - Bits and Pieces, EAA 657159

Having worked on more than one crack in plexiglass, I was always on the lookout for a new product to help stabilize the crack, and hopefully do it with the lowest visual impact. The bulletin boards on the topic seem to agree that Weld-On #3 is the ideal product. It's runny like water, and really bonds plexiglass well, and the best source seems to be Amazon.com.

The J-B Weld steel epoxy has always been a staple in most aircraft builders' shops and right next to it, in my local Canadian Tire, I noticed a new (to me) product called ClearWeld. It sets in five minutes and cures in an hour. It also comes with a new cap which forms a cleaner, more secure cap than the previous version, without the need to cut off just that right amount of tip. The cap has a foolproof "only one way" fitting and a simple turn 90 degrees securely closes the tubes.

iPhone screen protectors have a very flat, clean surface which serve well to flatten out the pool of epoxy while it is hardening, but it's difficult to control how widely the epoxy will spread. In my very quick testing of this product, I found that it was really clear at the outset but then I managed to induce air bubbles in it by working with it too much, so mix a very moderate amount.

It's probably a good idea to apply the ClearWeld when it's very runny in the first 30 seconds if you want it to flow into a crack, and maybe flex the crack a little to aid the flow, and of course, you'll want to read AC 43-13B for a full description of temporary and permanent repairs in plexiglass. You will find the appropriate pages in Section 4, subsection 3-40. A syringe is recommended in the text, plus filling the stop-drilled hole with a piece of acrylic rod, which is then cut off flush. I haven't tried this, but I'm tempted to suggest a good way to fill a crack might be to create a vacuum on the opposite side to which the ClearWeld is applied. A shop vac might do the trick, but if you did this, you might want to tape a piece of absorbent material over the crack, so any excess didn't mess up your vac.

Whether you're fixing a crack in a windshield or pottering about with some other hobby, ClearWeld might be a useful product to have in your arsenal. Having ordered some "Weld-on #3" I'll present a comparison next month


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