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Rotor Blade

Overview

RotorBladeSubstractive_Description

In this section we focus on carving the Rotor Blade by hand from a piece of wood. Use the CAD file to gain a better understanding of the diamensions as long as we didn't put numbers on the renderings.

This method is heavily inspired by Performance analysis and improvement of a small locally produced wind turbine for developing countries, section "Blade manufacturing manual for the new rotor design", p.111, by Nienke Hosman.

Following variables are used:

Variables mm
blade length R 900
wood length L 1000
blade width W 80
minimum wood thickness H 25
chord C 80
M 200
N 140
B 67
A 33
D 10
E 13
airfoil thickness T 10
a1 10
a2 3
a3 24
blade angle θ 7°

Materials

See pos. 1 in the BOM, not all materials listed there may be required at this point.

Build

1. Define up- and downwind side of the blade

RotorBladeSubstractiveView: Perspective RotorBladeSubstractive_10View: Looking from blade tip to root

2. Carving the windward face

RotorBladeSubstractive_1View: Perspective RotorBladeSubstractive_11View: Looking from blade tip to root RotorBladeSubstractive_2View: Perspective

3. Carving the downwind side and blade thickness

RotorBladeSubstractive_3View: Perspective RotorBladeSubstractive_12View: Looking from blade tip to root RotorBladeSubstractive_4View: Perspective upwind side RotorBladeSubstractive_5View: Perspective downwind side

4. Carving the airfoil shape

RotorBladeSubstractive_6View: Perspective upwind side RotorBladeSubstractive_13View: Looking from blade tip to root RotorBladeSubstractive_14View: Looking from blade tip to root RotorBladeSubstractive_15View: Looking from blade tip to root RotorBladeSubstractive_16View: Looking from blade tip to root RotorBladeSubstractive_7View: Perspective upwind side

5. Cut the edges of the root

RotorBladeSubstractive_8View: Perspective upwind side RotorBladeSubstractive_17View: Perspective blade root RotorBladeSubstractive_18View: Perspective blade root RotorBladeSubstractive_9View: Perspective upwind side

6. Create changeover from airfoil shape to root

RotorBladeSubstractive_19View: Perspective upwind side RotorBladeSubstractive_20View: Perspective upwind side

7. Drill root holes

Uses the Rotor Front Mounting Plate as a template to drill the holes in the root.

8. Surface treatement

Use sand paper to smoothen the surface. Start with graining 80, then 150, then 240, then 320. Moistening the surface with a sponge or rag. The remaining wood fibre will stand up. Wait till the surface is dry. Sand it one more time with graining 320.

Apply boiled linseed oil with a brush or sponge. Wait 20 to 30 min. Clean off the surface of remaining oil with a rag. Repead the process at least two more times.