Cardboard Savonius Wind Turbine

Step 3 Cut the top and bottom disks of the turbine

You will need to cut two disks 10 inches in diameter. Since I flunked kindergarten, I found this somewhat of a challenge. Trying to draw a true circle without a decent compass is tricky. Then after you have drawn it and cut it, finding the true center is also difficult. Here's an easy way to do it.

1. Cut a 10x10 inch square of cardboard.

2. On all four sides make a mark half way between the edges. That mark will be 5 inches from the corners on each side.

3. Use a ruler to draw lines that connect opposing 5 inch marks through the center of the square. Where these lines intersect, that's will be the center of the circle.

4. Use a compass if you have one and jab it into the center and expand it out to end of one of the radius lines. Now draw a full circle with the compass. I'm not sure school compasses are big enough to do this. An alternative might be to get a ten-inch bowl or something like that and lay it over the square and trace the lines. You can also simply eye-ball it and make an arc from the center of one side the the center of the next. You may not get a perfect circle but I don't think this is too critical for the model we are making. In the real thing it may throw off the ballance.

5. Now cut the circle.

Comments

[itsnotthenetwork]

An easier way to get a good circle is to put a tumbtack in the center and tie a small string (dental floss would work good) and stretch it out to the end of the cardboard and tie a pencil to it.

[Sky Woulf]

we used to call that a "carpenters compass" exept we used a small nail and a scrap of paper from the edge of a sheetrock bundle. (useful for cutting curved radiuses in a peice of wood with a saw.)

[nutsandbolts_64]

good idea, ill try it!