Scarf Joint and G-Flex

My teak cap rails are due for wooding and refinish. I have a few scarf joints that have opened over the years. I've tried cleaning the edges and filling the joint with liquid polysulfide caulk. I varnish over it and it seems to last a couple of years, but it still cracks, water ingress, downhill from there. Repair at refresh time becomes almost impossible.



This time I'm using Awlwood, and I'm contemplating using West System GFlex thickened epoxy to prep the spreading scarf joints. I can tint it to match, or black, but wondering if anyone has used it on a scarf joint and could offer any tips.

How big is the crack? I have used a syringe to inject somewhat thickened epoxy into larger cracks. You can’t get really thick epoxy to go through the syringe but I have had some success with partially thickened. I have not used G-Flex epoxy. Have you contacted West Systems, I have found their support team to be very responsive.

I've used GFlex and basic WEST epoxy on crack repairs. The only repairs I would call "mistakes" are where the wood shrunk and cracked, I filled the cracks, then the wood expanded again in high moisture. Even though GFlex is said to adhere well and provide some flexation - it's not like a soft caulk and you have to make sure there is no expansion of the wood expected.

Comodave said:

How big is the crack? I have used a syringe to inject somewhat thickened epoxy into larger cracks. You can’t get really thick epoxy to go through the syringe but I have had some success with partially thickened. I have not used G-Flex epoxy. Have you contacted West Systems, I have found their support team to be very responsive.

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I’ll contact West, the gap stays pretty consistent, but there must be some movement or the varnish & caulk wouldn’t separate from the teak. Scarf joints are the hemorrhoids on finished bright work.

If there is some movement then G-Flex may be the way to go.

Maerin - is that a scarf or butt joint? I guess I'm just unable to see the scarf from the photo. My thought is to fill it with something that remains flexible. From this angle, that joint does not seem to need strength to perform. If I'm looking at that picture wrong and it really is a scarf and is weakened by the crack - they I agree that GFlex is the best of the common options.

Bkay said:

Maerin - is that a scarf or butt joint? I guess I'm just unable to see the scarf from the photo. My thought is to fill it with something that remains flexible. From this angle, that joint does not seem to need strength to perform. If I'm looking at that picture wrong and it really is a scarf and is weakened by the crack - they I agree that GFlex is the best of the common options.

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Yes, that one is a butt it's the miter on the corner; the scarf joints aren't pictured, and the gap's not as wide. A couple of the scarf joints are perfect, others not so much. Always a source of trouble to keep the varnish intact.

At some point it might be worth finding a local shop/worker that could craft a replacement for the problematic section. Maybe a separate piece that moved the joint. Might be worth the price to get it done once and avoid the on-going hassle.

I tried G-Flex on mine. I cleared a 1/8-inch gap to fill and tinted it with graphite. It didn't work on any of the perpendicularly butted scarf joints (perpendicular ones), but it did work on the fancy forward rail scarfs that aren't directly perpendicular to the grain. Next time I'll clear a full 1/4-inch, awlwood, then fill with black 3m 4000 or SIS 440.

I like the 440. It would be easy on the butt joint to open it up to 1/4” and fill it with 440. The true scarf joint would be tough if not impossible to open up.

Maerin said:

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I’ll contact West, the gap stays pretty consistent, but there must be some movement or the varnish & caulk wouldn’t separate from the teak. Scarf joints are the hemorrhoids on finished bright work.

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May I suggest, creating a piece to fill that sizable area and then, pick your poison, secure it with some sort of marine adhesive. Let's hope you pick one that will accept tint and varnish.

I had this problem also ,especially at the curved corners. I cut stainless plate to match the curve from one stand to the next and mounted them under the rail.I used the existing holes in the top mounting plates to attach them making them continuous and unmovable and safe. I had an incident where someone nearly fell thru the upper deck rail when they leaned on it so this was my solution.