I used to use Titebond 3, but after I did a LOT of destructive testing (some of it actually on purpose
), I asked a friend of mine back in NC who builds boats for a living. For tough gluing operations where you need intense strength, flexibility, and all weather resistance, there's NO substitute for Resorcinol Glue.
I buy the 1 quart kit of Aerodux Resorcinol Resin from Amazon.com. It's a bit expensive at $62 per quart, but there's enough in there for about a dozen bows. (Make sure you mix it at a 5:1 ratio by weight, so a $20 digital scale is a must. I usually use 60g of liquid to 12g of powder for one bow. Oh, and don't use excessive clamping pressure... Just enough for squeezout is fine.)
Yeah, it's expensive, but where I've had Titebond 3 gluejoints fail, every destructive test that I've ever done with Resorcinol, the wood literally ripped apart where it was glued. There was never even one instance of a glue joint failue. That's why this stuff is used in boat building, as well as high strength industrial applications - it just works. It will even fill small gaps.