Hi John,
Brightly finished teak on a Commander is like gold in the sun. I know varnish well, so I'll limit my comments to that and hope someone who knows the two-part product from Awlgrip will chime in too.
Schooner 96 by Interlux, proved to be the best performing product I've used lately. I've used them all, Captains, Epifanes, Pettit, Interlux, whatever, I've used it on my wood boats and/or on the Commander in the past. It seems from my recent experience (and the recent formulas on the market in 2008) that Schooner 96 gassed out and left the nicest final finish (unthinned out of the can).
I was surprised and pleased to know Robert DaPron, a professional boat restoration expert and friend of the Forum, having contributed many of the scans and brochures we share world-wide here, also spoke of the Schooner 96 as his favorite. So you have a hands-on hobbiest and a professional restoration guy both agreeing on the Schooner 96 as the best varnish.
As for the two-part (polyurethane), first of all Awlgrip has a very good name in marine circles. I also put a huge amount of stock in Interlux, having used many of their products over the years, but never having used Awlgrip. Awlgrip seems to be more heavily in the two-part poly business than the traditional varnish business, and I would expect their products to be first class. I am wondering if their polyurethane can be put down over top of a traditional coating of varnish? I say that, because varnish is pretty friendly to wood when it comes time for refinishing; you can sand it reasonably well, work it, and not erode into the wood. The polyurethane may not be so friendly, I don't know because I have never used it, although I've been tempted to do so for the better part of 30 years when I saw my first polyurethane finished Chris Craft Capri. There was a concern back then that the poly may not be as pliable and might split between planks, but that was just us guys shooting the breeze back then. The boat looked great.
The polyurethane may not give the golden color of varnish. It may be clear. It would be much stronger for abraision resistance, but I don't know if it would peel faster or whether or not it has the same UV protection; certainly Awlgrip tech guys can answer those questions.
I am wondering if you could sand your teak down to the degree necessary, perhaps use a stripper and get it all off, clean the surface with acetone to get rid of any oils that migrated to the surface, and then put that traditional first coat of thinned varnish on. I would wonder about putting on a couple coats of varnish, and topping it with a couple coats of the two-part polyurethane.
Since there is a likelyhood of having to touch up or repair some places, I now wonder what it would be like to sand through the hard top layer into the softer varnish layer underneath, and how it would look once repaired. Since I have never done this, being a traditional varnish guy all the way, I just offer this for "whatever it's worth"..
I'll send Robert a note and ask him to comment on this, because this is the sort of thing many people can benefit from knowing. Anyone having first hand experience please feel free to chime in!
Regards,
All the best,
Paul