Hi DanG,
Like topspeed says, "the weather and elements just take a toll"
The thing is that plywood on that failed Turbine had been used for 7 years, and yes it got re-painted every year or so, with an Industrial Oil based primer and oil based top coat.
The wind turbine is a dynamic structure with every bit of it handling stress, flex, gravitational forces and centrifugal forces.
I sealed every screw hole and overpainted, i also mastic sealed around the 5off 12mm/1/2 inch main blade to hub bolts, but still the water got in.
I see it like this, ..... There is a fine line between getting it working and producing Power, and making it stand the elements of the weather. ie, I could make it and seal it and re-design everything so not a drop of water ingress, I hope. But then the cost the weight and the work involved just makes wind power at this scale absolutely not cost effective.
Hugh Piggotts design is fantastic. Its the blades and the hub that are stressed and at the rotational speed of a 12 footer/3.7m diameter, any imbalance is soon seen and causes the issues.
Well that's my opinion with 3off, after nearly 14 years flying.
Remember that my No2, has My design and made fiberglass blades, has only a little vibration after 5 years of flying, so by No3 i think i got it about correct. I hope?