Can you explain why the cooling fans have straight fins?

[Maxists The Baddist]

I though they would have a little curve in them like to draw air in. I realize they don't want to draw alot of power from the engine, but the fins are straight. I'm wondering why?

[BarracudaHockey]

Its cheaper to manufacture.

The Hirobo fans have more vanes and they are curved like an airfoil.

[WayneBrown]

MA fans have airfoil shaped fins too. You just are looking at a 'budget' machine's fan...

[flyinfool]

With centrifugal fans you can have the fins forward inclined straight or reverse incline depending on the airflow characteristics that you are after.
The way the fans are setup in most (not all) helies is very inefficient so blade shape ends up having very little effect.

The short course is;
If you look at the fan in your furnace/AC unit you will notice that the blades seem to be backwards, they look like they are trying to move air in the opposite direction of what it really move, this is forward inclined and it will move a high volume of air but it can not create much air pressure to over come obstacles in the air path, like cylinder head in the duct. straight blades will create higher pressure at lower volume.
Reverse inclined blades will generate the highest pressure but at the lowest volume.

The biggest single improvement to fan efficiency in our helies would be to have a the tops of the blades covered like on the TT metal fans, the fans that have the open tops can be helped by getting them as close as possible to the fan shroud so that air can not just leak over the top of the blade, air leaking over the top of the blade is called recirculation and just kills efficiency.

[Tintin]

I reckoned that fan didn't draw air in from the sides but sucks air up along the motor and then throw it out to the side. Air has weight so making it rotate like this fan does will throw it out to the sides by it's own weight, therefore straight blades are ok as the object of the blades is to make the air spin, then the air leaving to the side will suck new air into the center of the fan.

[WillJames]

Thnks for the info Jeff!!

[Pinecone]

Reverse curved fans are also quieter, and that's why they are used in house units.

Straight blades are used in places where there may be dust loading as they shed dust builup better. So you find them in industrial ventilation setups. Also cheaper to make, especially in small units.

They all move air. :)