I just bought a Bell Northwoods, 18'6".   Until now, I've always paddled 17'  canoes.  

Are longer canoes inherently more stable?

prouboy

All the canoes in the Bell Northstar-Northwind-Northwoods line have tremendous secondary stability (stability when the canoe is in motion) so, comparing apples to apples, that is the Northstar (16-6) to the Northwoods (18-6), I don't think you'd find much difference in stability.  The bigger canoe will undoubtedly be a hair slower due to the load you'll be carrying (although the hull speed is actually higher) but, given its added length, should track a little better.
Congratulations on your new canoe.  If you haven't paddled a Bell before, you're going to love it.  Hang on to it, those Bells are getting rarer as we speak!

If you have two hulls of similar design/shape the longer hull will generally  be faster and track straighter. The Northwoods is a sweet tripping hull - moves well, can carry a load and handle difficult conditions. Nice find!

Thanks Solus.  Years ago I sold a Northwind black gold as it weighed 59 pounds. But I've missed the Bell. Now I'm back in the fold!