The Type of Wood to Use

The species of wood doesn’t matter as much as the mill cut. You should also consider the weight or the absence of knots. If the weight of the board is considerably more than the other boards, it might still be wet. Wet boards can twist and bow when they dry out. Some species obviously preform better than others in exterior uses. The straighter the grain is down the length of the blade the better strength it will have. A straight grain pattern will have the most strength.

The closer the grains are to one another indicates if the board is heartwood. Center cut wood, also known as heartwood, is the strongest. There can be no knots present. Knots will greatly reduce the strength of the blades.

Cedar and spruce are commonly used but any species will suffice. You will have to treat the wood anyway, since it’s exposed to the elements. Using wood sealants is preferable over paint and will make your blades last much longer.

Shaping the Blades

You want a good foil design and the blades should taper thinner to the tip. The blades should also taper in width and thickness as they get further from the hub. This will maximize rotational force and reduce friction. Leaving a thicker portion of the blade at the hub increases strength. The tapered end moves the fastest and doesn’t need to be as thick. The extra material can be removed and the efficiency of the blade will improve.

You want long thin tapered blades with a good foil design that runs the length of the blade.

Sealing the Wood

You can use exterior deck sealants. A better less expensive alternative would be linseed oil. You can purchase linseed oil for much less and achieve the same protection. Be careful storing rags covered in linseed oil in hot areas. Linseed oil is known to self combust and can easily catch fire. If storing the rags used place them in a metal container away from flammable materials and out of direct sunlight. Three coats of linseed oil or deck sealant is sufficient. Allow the blades to dry fully before mounting onto your wind generator.