I’m starting a new 3 foot wooden blade to test out using a higher blade twist. This one should hypothetically have a 24 degree highest angle of attack for the airfoil at the base of the blade. The starting block of wood is constructed by gluing 2 2×8′s together and then I plan on chiseling and sanding it down to the correctly twisted airfoil. I think it will be easier in the future to start from a bunch of jig saw cut 1×8′s glued on top of each other so I have to chisel out less wood. I also plan on buying a draw knife tomorrow, which should make my work much easier as I try and build smarter blades quicker.
I started reading “Developing Wind Power Projects: Theory and Practice”by Tore Wizelius, yesterday on the train and it has done a quickly done a good job of educating me on wind power. As I read and work I have started keeping a little bit of a journal. In later days, I will probably scan some of these pages to show diagrams and such.
This book does a good job of making me think critically about design and has taught me important things like how the airfoil at the tip of the blade can be imperfect in order to increase the swept area of the turbine, because increasing the swept area is more important, as weight is the decisive factor in blade design.
I’m also starting to think critically about how to get an appropriate twist along with an appropriate combination of airfoils to vary the stall speeds along the blade and allow the blade to start up in lower winds and perform well in high winds, while keeping the nominal wind speed low. Testing will be required…
If you want a little bit more information on the type of turbine I am designing here it is: I am planning on finally building a ten foot diameter 3 bladed turbine that runs on a direct drive(meaning no gearbox) synchronous generator to a frequency converter to a transformer to a series of batteries probably. The rotor will be kept facing into the wind by a tail made of a welded metal frame a wood tail. I want to figure out some sort of system to remotely send information such as wind speeds and energy production either by text messages or have it all recorded on sight. The tower will be some sort of a guyed tower with a concrete base. I am also trying to design some sort of a remotely controlled mechanical break to stop the turbine in inclement weather or freeze it during repairs.
Here are some photos of the test blade I was constructing earlier tonight. As it got late I started to switch to hand tools because of noise issues. It would be more efficient to wait until tomorrow to do lots of the airfoil construction because I plan on buying a drawknife, but I really enjoy chiseling, so chisel I did.
It’s very relaxing working in the garage and it was nice to get to stand up for awhile, after spending much of the day sitting and scanning 4×5″ negatives for my photoblog. I listened to a lot of The Mountain Goats and a Leonard Cohen Best Of CD.
While I was in Rhode Island the past two days they bought an electric heater for the garage! too bad it was 60 today.
Clamps are very important. You can never have too many clamps.
Here is me working away!
The mallet on the left is Stephen’s homemade one, I decided to stop using it because I was afraid I would break it… so I switched to the one on the right.
Chiseling may be slow, but it is a great way to slow see and visualize the blade in the wood and you get to watch it emerge, in a way that a band saw can’t.
If anybody has any experiences building homemade fiberglass wind turbine blades off of a plaster mold, let me know, because I am soon embarking on that adventure!
