How to Build a Replacement Wind Turbine Blade
A wind turbine blade is probably one of the parts of wind turbine that can easily get broken. If you find that your wind turbine blade's life is coming to an end, you may opt to build a replacement on your own. It is highly suggested to go for wooden blades, as they tend to be more durable and last longer. Continue reading below to find out how to build a replacement wind turbine blade for a 3-bladed wind turbine all on your own. Note that this project is for a turbine blade with 90 inches in diameter and a tip speed ratio of 5.5. First, prepare the tools and materials needed for this project.
Step 1 – Choosing Wood
For the wooden blades, a lightweight softwood is recommended. If you don't mind the price, the most suitable for the job would be an imported Oregon pine. Just choose pieces of wood that are close grain, well seasoned and straight.
Step 2 – Marking the Pieces of Wood
Once your materials are ready, it's time to mark your wood. Take the three pieces of wood with the 1150 mm in length. Divide them into 5 sections along the length of the blade with each section 230 mm each. Mark the position of each section and draw a line around the piece using your square. The left most part would be the root of the blade, and the right most hand or fifth section would be the tip.
Step 3 – Tapering the Wood
Now it's time to taper the blade such that the tip must be narrower than the root. Thus, the right most section would be narrower than the left most section. At each line you marked earlier, measure the width and mark such that the first section starting from the left measures 145 mm, the next line will measure 131 mm, third will be 117 mm, fourth line will be 104 mm ,and the last or the tip will be 90 mm. Once you've marked the width, cut using a band saw. You may also use a saw and chisel to cut the width by sections.
Step 4 – Planing the Blade
Using a plane, smoothen the surface. It must also lay flat, so make sure it is straight, flat and square. Use a spirit level across your wood piece to make sure it is flat and no twists have risen.
Step 5 – Creating a Twist
Now it's time to create a deliberate twist. When you were laying the blade flat, the left most section is the widest, and the right most has the narrowest width. When you tapered the wood on one side, there's a leading edge on the side closest to you. This side is straight and leveled in all sections. The other side where you tapered the wood will be called the trailing edge. Turn the blade around such that the trailing edge is now closest to you and the narrowest tip would now be on the left. Now it's time to mark the thickness of the wood. From the tip, mark a point on each line from the front face going down with these measurements: 5 mm, 10 mm, 17 mm, 35 mm and 50 mm drop. Join the dots to draw the line of the trailing edge. On the root side, draw a line that goes up to the front face at a steep angle. Now carve the wood by following the jotted line you just made, creating a twist into the blade. Now you'll have a slightly tapered wood with a twisted face.
Step 6 – Reduce Thickness
The correct thickness of each station from the root to the tip are as follows: 25, 20, 18, 15 and 11 mm. Measure, mark and draw a line following this measurement unto the leading edge and on the opposite side, which is the trailing edge. Turn the piece so that the front face is facing the ground and start cutting away the waste. Use calipers to check the actual thickness of each station as you go along cutting it.
Step 7 – Create an Airfoil Section
The last step to carving a blade would be to feather off the trailing edge. Plane off the wood from the back such that there is less than a millimeter wide in the trailing edge.
Step 8 – Smooth into a Wing Shape
Not it's time to give it a wing shape. At the back of the blade, draw a line 25% back from the leading edge. Do not cut the line. Remove corners with the use of spokeshave. Alternately you may use a sand paper.
Step 9 – Cut a Point
For each blade, cut to a point at the root. This will allow the blade to fit perfectly at the hub. To do this, mark the exact center of the root and draw lines toward the edges at a 60-degree angle. Do it at the front and at the back and cut along the lines.
Step 10 – Paint the Blades
Before you connect the blades to the hub, prime the wood by applying stain or coats of glossy paint. Sand before the final coat. It's ideal to apply resin for added protection. Let it dry.
Step 11 – Installing the Blades
Once ready, connect the blades into the hub and drill holes into the blades that will allow it to be screwed to the hub disc.