Cutting Scarf Joints?

I have a new project boat, an MRE, that needs some gunwale work, it’s at the ends on the inside only where the old decks were. My plan is to take off the inner wales and cut a scarf joint to make it all good again. I plan on using G-Flex on the joint as I think this is better than Gorilla Glue as I’ve used both.

I did find a plan on line to make a jig for cutting the joint. Is it necessary to use a jig or can one do it freehand? (Hmm, dougd, freehand, sharp tools, could be questionable!) Also, any recommendations about adhesives would be appreciated. Many thanks for any insight.


A jig is the only way I know to
get your angles to match exactly. You might be able to cobble together a simple shooting board for use with a hand plane that wouldn’t necessitate complete removal of the inwales.

Scarf joints
Look on the WCHA website. there was a recent discussion on gunwale scarf joints. Basicly the easiest way is to use a clamp on homemade jig.

Good luck

J Curtis

Wow. Nice job. Thanks!

I noticed Thurlow’s weren’t quite as long.

without a jig
I’ve done it without a jig. I clamp the new stock to the old boat, then cut them both at the same time. It just depends on what you feel comfortable with. A better alternative would be to bring me the ME and I’ll swap you a boat that doesn’t need any work.

There was a short time
When we had to scarf wood for Bell’s 17.5 and 18.5 hulls. with screw spacing of 6" we made sure the scarfs were 9" long and had two screws securing the joint.

We used West Systems Epoxy to bond the joint.


– Last Updated: Feb-14-12 8:22 PM EST –

I've glued gun'l scarfs on two kayaks using Urac 185. It's a urea/formaldehyde glue (2 parts, resin + powdered hardener) that is waterproof and very strong, and doesn't creep like many glues. It can be mixed by weight (more accurate) or volume (easier with very small plastic measuring cups). It's typically regarded as "the glue" for building laminated wood and wood/bamboo longbows (ie; a very high stress application with the limbs bending under tremendous strain). It's a thick glue and a good gap filler that tolerates sloppy joints. (Score the gluing surfaces and don't overclamp.) It's actually inexpensive, even shipped, when bought online directly from Nelson Paint Company.

Use The Jig

– Last Updated: Feb-16-12 11:11 AM EST –

The only way to make a good joint is with a jig. You can match cut or rough cut to get rid of the bulk of the material, and then plane on the jig for the finish glue joints. You will see recommendations of 4:1 glue joints, but that is minimal and a weaker joint. Go with a longer joint, at least 6:1,especially if using oily or resinous woods. In spar building, they use scarf joints of 12:1, so don't be nervous about making a longer joint. It will pay in the longevity of the job. As to wood choice, for example, Northern cherry (like New York or New England) is a dry, stronger wood, while South American rain forest cherry currently found on the market commercially is a softer, more resinous, less rot resistant wood and would need a longer joint. You'll find such variations in many woods, like Thai teak versus South American "teak". Try to locate scarf joints in areas with minimal curve (less stress) even if it means losing a little material. Keep protected (oil, paint, varnish) to keep moisture out of the joints. Use a thicker, gap filling epoxy, not a thin saturating epoxy like for fiberglassing. Some will specify gluing or filling in their name or description.

Scarf jointed gunwales
I’ve repaired and made segmented inwales and outwales including those on a Wenonah Itasca that had three joints per gunwale. I use a 7:1 scarf joint with Titebond III glue. I have a taper jig for my table saw but I think you could prepare a good scarf joint with hand tools.