Curious about Wooden Canoes
on my chestnut canoe the keel has come apart from the hull dose this need to be looked after right away, or can it be left for a year or two. when i recanvise it has opened up aprox 1/8 inch for about a foot

I would think you would want to fix the loose keel, as the screws which hold it in place (or are supposed to) make holes in the canvas, which are potential leaks. If the troublesome spot is at the bow or stern it should be a relatively easy matter to work some bedding compound or other goo under the keel and fasten it back onto the stem where it belongs, probably using new or renewed screw holes. If the loose area is amidships you might be able to do the same, but screwing through ribs from the inside into the keel. I would make sure there is plenty of bedding compound in the holes and under screw heads. The real question may be why this has happened - rot in keel or stems so fasteners let go? Undoubtedly you will find out at re-canvasing time.

Don in Vermont
If not leaking then I wouldnt worry about it.If leaking smear some goop along the crack just dont use anything silicone based in the goop.(Been there done that) Adhesion problems later on something that has been siliconed.
On the inside in the area that has lifted/ check those little "cup" washers to see if the have been sucked into the ribs...then check the ribs to see if they might be getting "spongy".....I am currently re-vanvasing my Chestnut and so far have replaced 3 ribs...I noticed that those cups can suck down into the wood if "Superman" set the screws. good substitute bedding that can be squeezed in that area is "plumbers putty" If it is leaking...stays flexible and wont adhere to the keel or ribs when replacment time comes.
Good luck