Carving the Blades

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The blades are perhaps the most important part of our wind turbine - they are the 'engine'

that drives our generator. These wind turbine blades have a simple airfoil and when finished they'll look (and work) a bit like airplane wings. This design is a simple one. It's a compromise we made keeping the following things in mind: efficiency, strength, cost and availability of materials, and ease of construction.

Before you start a few terms should be defined. The 'tip' of the blade is the end that's at the very outer diameter - farthest away from the alternator. The 'front' of the blade is the surface that faces towards the wind, it's flat and angled a bit. The 'back' of the blade is facing away from the wind and it's rounded in shape. The 'Root' is the inside of the blade, closest to the hub and the alternator. The 'Leading Edge' is the edge of the blade that gets there first (if it were an airplane wing then the leading edge is the front of the wing). The 'trailing edge' is the edge is the edge of the blade that gets there last (if it were an airplane wing it would be the back edge of the wing). The 'Pitch' of the blade is the angle between the surface of the front of the blade, and the plane of the blade's rotation. It changes over the length of the blade. The Chord of the blade is the width (the distance between the leading edge and the trailing edge) and it gets less (the blade gets narrower) as the diameter gets larger. The thickness of the blade is the thickness at the

'fattest' point in the airfoil.

The simplest material to build your blades from is common pine, or fir 2 x 8 lumber. Typically a planed 2 x 8 is 7.5 inches wide and 1.5" thick, so the plan is based upon that. Pine and fir have good strength to weight characteristics. Very hard, or very soft woods should be avoided. The very best choice is probably clear (knot free) Sitka Spruce, but it's expensive and hard to find. Most lumber yards have perfectly acceptable material. Generally you should use conifers although the very lightest ones might be too weak. I would avoid Redwood. The wood should be dry and as knot free as possible. Often times we build ours from laminated Red Western Cedar 2 x4's, but that adds an extra step and it's not necessary - but it does make for a strong, lightweight blade. Whatever you find, you need 3 boards about 7.5 inches wide, 1.5 inches thick and 60 inches (5 feet) long.

There are a variety of tools you could use. A draw knife is almost a must have. Chisels, hammers, sand paper, planes and other wood working/carving tools are handy. Some of the work at the beginning of the project involves removing large pieces of the board and a band saw is very useful - but not necessary. A hand held power planer is nice but hand planes work almost as well and they're much quieter and more peaceful to work with. This whole project can be done fairly easily with hand tools only.

The instructions will describe how to carve a single blade. You need to make three of them. We suggest you make all three at one time rather than making one at a time. There are several operations involved, it's better to do one operation to each blade and work them all along together, they'll come out more alike that way. If you perform an operation on one blade... do it to the other two before you move along to the next step.

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Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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