I dont know how they will stand up to rot being made out of beech, mine were made out of mahogany, with a threequarter inch stainless capping strip and they work great, they are also 3 inches thick for the real world of granite docks and old harbour walls, if your boat has a lot of curve in the topsides keep the strips of wood fairly thin 3/8 or so should do it and build the rail up in layers its suprising how much of a compound curve you will have to put in the timber, my rail was screwed and glued to the hull using 5200 and i am extremely pleased with it. ps a big heavy rub rail acts like an external stringer and does reduce flex in the hull.
Any wood that is of lesser durability can be improved by using a saturating epoxy preservative such as International's everdure. This would work well if you decided to make the toerails by laminating up with smaller pieces as suggested by a previous poster.
International stockists should hold literature on the product.
Beech is very porous and not classed as a durable timber - thats why its commonest use is for furniture. Much better material would be iroko or maybe British Colombian Pine /Douglas Fir.
