By Alan Lucas
When the sun is hiding wind generators complement solar panels beautifully, presuming the wind continues to blow, of course. In adding them to our checklist the various types cannot be reviewed, but a common failing can certainly be looked at, which is the possibility of a blade flying off in a high wind.
The problem of blade loss introduces an oft-ignored facet of proactive maintenance, namely, the need to regularly scrutinise blade-hub marriage. If the blades (rotors) are secured to an aluminium hub with stainless-steel nuts and bolts, oxidisation of the hub places pressure on the blades, eventually cracking them around their boltholes. Ultimately, this causes them to fly off, threatening life and limb if you are unlucky enough to be hit.
It is imperative to regularly check all blades for hairline cracks around the hub area and for evidence of oxidisation of the hub itself. Don't push your luck with a suspect blade. Remove it immediately and wire-brush the aluminium hub free of oxidisation then fit a new one using a suitable coating to slow aluminium oxidisation.
For blade replacement the whole generator is best taken from its perch and repaired on deck, unless repairs in situ are possible. In either case, if your tool chest doesn't run to giant vices or multi-grips, the hub can be prevented from turning by fence-wiring it to its body while undoing its shaft nut.
It's true that most wind generators can be prevented from rotating using their reverse-magnet stop switch. However, this is more a stall-switch because strong gusts easily over-ride it when least expected. This dangerous possibility can be avoided by turning the generator downwind using a boathook hooked into its tail, then lashing the blades into final submission with small-diameter rope.
Whether under repair or not, trapping and lashing a wind generator's blades in this way is recommended practice for vessels connected to shore power or being abandoned for a lengthy time. Not only does it eliminate unnecessary wear and tear, it also silences it for the comfort of nearby neighbours.
It is not uncommon for a wind generator to become unbalanced when blades are replaced. Some say it pays to replace all blades regardless of how many throw off, others that re-arranging them can do the trick while fine-sanding rough spots off the blades is also declared a winner. A person facing this problem can only fiddle with all possibilities and hope for the best.