[benz]

Thanks Brian--after posting that question I saw several pictures of pole spars that seem simply riddled with knots, and some even with longitudinal cracks (!). Trouble is, I'm an inveterate worrier, and I know I'll fixate obsessively on even a modest knot, as long as the night is dark and the wind strong.
As for aluminum tubing, all over the interenet I can find 20-foot lengths of suitable dimensions ( I need 6' OD, with a 3/16" wall thickness), but I need a forty-foot piece. The flagpole companies I've asked only go to 35 feet (anything longer they join two pieces with a sleeve), and their poles are generally tapered, which I don't want.
If anyone knows of an aluminum tubing source, I'd sure be keen to know it.
By the way, d-sv-taz, if you skin a pole with fiberglass, it will have to be very thick in order for the wood beneath not to compress and then pull away where things press on it--I tried that once on some oars when I couldn't get leathers, and it was a terrible idea.
ben