BONDING CHINES AND BATTENS

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BruceB
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BONDING CHINES AND BATTENS

Post by BruceB » Fri Mar 22, 2019 3:02 pm

When you are bonding scarfs, should you use filler with the epoxy?

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Bill Edmundson
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Re: BONDING CHINES AND BATTENS

Post by Bill Edmundson » Fri Mar 22, 2019 3:16 pm

Bruce

Right or wrong, I use micro-fibers. I make it about like a wet applesauce.

Bill
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JimmY
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Re: BONDING CHINES AND BATTENS

Post by JimmY » Fri Mar 22, 2019 4:23 pm

If you are using an already thickened epoxy, like Poxy-Grip, you should not need to add fillers or fibers.

On a few joints I was out of Poxy-Grip, and used the much thinner System 3 Silver Tip with micro balloons to help it stay in place and span any gaps. Like Bill, I mixed it like wet applesauce, just enough to help it stay put but not too much to compromise the strength. In this case, I would apply some un-thickened epoxy to both halves of the joint, then add the filler to the pot and mix it in, apply the thickened epoxy, and then clamp the joint.
-Jim
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hoodman
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Re: BONDING CHINES AND BATTENS

Post by hoodman » Sat Mar 23, 2019 5:12 am

Wood flour also works great for thickening epoxy.
Matt

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Moeregaard
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Re: BONDING CHINES AND BATTENS

Post by Moeregaard » Sat Mar 23, 2019 7:43 am

I prime the bare wood with epoxy to gain penetration, and then make the actual joint with cotton flocking added to the epoxy. As Jimmy says, a consistency of applesauce works well. The flocking is a bear to sand, so be sure to wipe away as much excess as possible. The wood flour is a great filler in this application as well. Micro-balloons are a wonderful filler, but they don't contribute to the strength of a joint. Just my two cents.

-Mark Shipley
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JimmY
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Re: BONDING CHINES AND BATTENS

Post by JimmY » Sun Mar 24, 2019 3:48 am

Hi Mark,

I was hesitant to mention "flocking" which is just cotton fibers. I wasn't sure if it was a good idea in boat building, since exposed fibers might absorb water and promote rot. I've used flocking elsewhere, and it is great for filets on joints, and adds to the strength of the epoxy. I'm not sure if my concerns are valid or not.
-Jim
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Re: BONDING CHINES AND BATTENS

Post by PeterG » Wed Mar 27, 2019 8:24 pm

I'm a bit late to this but will offer up what I did with scarf joints. I prime the mating surfaces of the joint with neat epoxy (no filler or thickeners) using thin coats and letting it "soak in". Epoxy doesn't really penetrate much at all but the neat mix will usually go further into ithe wood than the thickened stuff. Then I add the thickener (microfibers made from milled fiberglass) to the same batch of epoxy to make an applesauce or mayonnaise consistency. I apply it to one side of the joint and clamp it up. I have used this for solid wood and plywood and have not had any joints fail yet.
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