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lllazar wrote:Ahh, so i'll need a generator and some probes as well? Thanks

And 1 last question, in a general way could you briefly explain what kind of design/material would produce more power and not just a fast rpm, like for example:

Would a balsa turbine that has the same rpm as a turbine made of playing cards produce more power?

There's a lot of factors to take into account there. First of all - would the balsa be longer than the playing cards? If not, you really only have a difference in mass of the blades. But I'd think you'd want something longer than playing cards.

The total power you can capture in the wind stream increases proportional to the square of the turbine radius:

However, rotational inertia and aerodynamic drag oppose the rotation of the turbine. If we assume the blades to be rods (fairly close) and use the radius r as the rod length, we find the rotational inertia of a single blade to be . So inertia also increases as a square of blade length.

You want to find the optimal length that maximizes your power captured.

Your generator will be the motor from a CD player. The probes should come with or be attached to your meter.

How did schools generate that much last year? like 1600?

We managed 600 total, and got 3rd at regionals. I just wish we had more than two weeks to test out designs. 1600 sounds pretty good to me.

OlympiadLover wrote:How did schools generate that much last year? like 1600?

The highest combined score at last year's nationals was 3361 mV. For just B division. The full scores are here.
Has anyone this year gotten above 100 mW?

Based on last year's rules, wouldn't Division B get higher combined voltages? Due to the fact that we had a smaller maximum diameter, the blades would be able to spin much faster. This year, I think its better to go for a slightly larger diameter.

In regards to construction, last year I used basswood instead of balsa for extra strength. This year, since I assume the assemblies will have a quite a bit more surface area, I would think that you might even need something sturdier than basswood.

Also, you do not need masses of technology to do well at this event--an X-acto knife worked fine for me.

illusionist wrote:Based on last year's rules, wouldn't Division B get higher combined voltages? Due to the fact that we had a smaller maximum diameter, the blades would be able to spin much faster. This year, I think its better to go for a slightly larger diameter.

Yes, that makes sense. Except at nationals, they had two completely different setups for for testing, so who knows.

I see a lot of people saying we need more surface area - is this to more efficiently capture wind and get past inertia?

Well, if your blades are just free-spinning, then you want really thin blades that won't create a lot of drag. If you hook up a load (resistor in this case), then I would think you would need blades that catch more air. To accomplish this, an increase in blade surface area might help. Of course, the load isn't that huge in this case so it may be that fairly thin blades is still best.

E Edgar wrote:In regards to construction, last year I used basswood instead of balsa for extra strength. This year, since I assume the assemblies will have a quite a bit more surface area, I would think that you might even need something sturdier than basswood.

Also, you do not need masses of technology to do well at this event--an X-acto knife worked fine for me.

So did you sand down the bass in order to get it at an acceptable weight? Cause I can only find 1/4 inch bass sheets...