Official Luthiers Forum!

Are kerfing angled on arch-back guitars?

Yes. This is most easily achieved with a radius dish lined with sandpaper.

Are they? Sometimes at least not I believe.
From this webpage - http://chandlerbryan.com/BuildArchtop1.html

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Colin, I thought he was talking about a normal acoustic guitar with a radiused back. Yes, an arch-TOP guitar is usually built with a flat connection between the rims and the plates (at least the ones I have built). Perhaps the OP can tell us which guitar he is asking about.

That would be a good idea.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Are y'all suggesting most arched-back guitars/ukuleles are flat enough on the outer edge to not need angled kerfing?

Depends on how you build it. If you make the back with a full radius then you need angled kerfing. But, if you make a back by carving from a thick piece of wood (like a traditional arch top guitar), or you form a back like in your photo, which shows a complex curve and re-curve resulting in a flat area along the perimeter, then you would leave the kerfing flat.

So, regardless of the style, the kerfing needs to be flush/glued with the back-board.

Of course. You normally want joints to close up with little pressure before you glue them. Unless you have a specific reason to make a "spring joint" where you want some added tension.