Which wood would be good?

I'm very lucky in that Chertsey has a lot left about it that's original, and more that, while not original, is pretty old and traceable to its working history. Even if this wasn't the case, of course I'd want to restore it sympathetically and make it look right; the fact that it is makes me feel even more keenly the responsibility to make sure, as far as practically possible, that it not only looks right, but is right.

So, the gunnels will be wood. At present it doesn't have any, but the hull sides are dead straight and there's no structural need to put steel ones on, so from the start I was determined that they would be made of wood.

The question is, what sort of wood. Originally they would have been oak. Everyone seems to want to warn me off using oak though. Mainly this seems to be on the grounds that the tannin in oak reacts with the steel mounting (what is the proper name for that?) and the bolts. What I haven't established yet is whether this reaction merely causes discolouration (not really a problem as the whole lot will be tarred or otherwise blacked) or whether it actually contributes to the corrosion of the steel. Or maybe it makes some compound that attacks the wood. Even if the latter, I'm wondering can they not be isolated from each other? The wooden gunnel will in any case be bedded into some suitable waterproof compound, and it must be possible to sheathe the bolts (or use stainless ones, except Jim already has a hundred otherwise suitable bolts left over from a job where the building inspector changed his mind, as they so often do).

Bath with its kerouing gunnels, fitted in 1982

Many people seemed to have successfully used tropical hardwoods - kerouing is one that frequently pops up in conversation, and apparently goes by other names according to where it's grown. I know this is what Dave and Izzy used on Bath and their gunnels still look fine after more than twenty five years, but... Firstly... tropical hardwood... no matter how sustainably grown (and we haven't yet tracked down a source of sustainable kerouing) still has to travel a long way; and I would always have doubts about claims to sustainablity anyway; it's such a complex area. And secondly, my heart tells me it should be oak, for authenticity, unless there's a really good reason for it not to be.

Is it cost perhaps? Oak certainly isn't cheap. Jim was researching this at the weekend and good quality English or European oak is going to work out at around £600 for the quantity we'd need. Now, to be honest, that doesn't sound too bad to me, in the scheme of things. Maybe the tropical stuff would work out cheaper? But I don't think I want to know. Is it durability? How long would oak, properly maintained, last?

So, if you know something about oak that I don't, a really good reason for avoiding it, please do let me know....