I need some wood for my wood turbine. The measurements needed for one blade are 50mm x 200mm x 1500mm.
So i started collecting scrap wood from everywhere and i made some huge mistakes which you can learn from. For one, the wood should have been dry or at least approximately the same dryness. Some of the wood i found was drying in a shed for 10 years. Some was intended as firewood and quite wet. This makes balancing the blades later on very difficult as the wood dries or becomes more moist unevenly.
As i didn’t have enough good wood, i used firewood and removed the parts with broken nails using a saw. Afterwards, i glued in some good wood and ran the individual parts through my stationary power planer.
I distributed the wood evenly and prepared it for gluing. Unfortunately, i didn’t have enough wood after planing and i had to do some quick fixes with even worse scrap wood.
And i didn’t use enough wood glue. Nor the right glue. The glue should be water resistant which is the class “D4” in Germany. Mine is labelled as “water resistant”, but the fine print identifies it as “D3”. So it could be that my wind turbine delaminates as soon as things get moist on the inside. The right glue would have been Poly-Urethane-glue, or PU-glue. This one is absolutely water resistant and even stops being carcinogen after drying.
This is what happens if you don’t use enough glue and not enough evenly distributed clamping force. I managed to fix this, but a fine gap remains. You can fill those gaps and other little mistakes with a mixture of wood glue and saw dust.
Those are my three blades after tapering and ready to get a aerodynamic profile.
Thoughts to take away from this part:
- always have more than enough wood to proceed. I think 150% is a good number
- obtain wood of the some quality (dryness, hard/soft wood)
- this is really hard work. Unless you need specific features in your wood, just buy it
- buy the right glue, i.e. Poly-Urethane-glue
- place the harder and better wood parts in the front and back