ELECTRIC FANS: Curved Blade v Straight Blade

[Guest]

Hello.

 

I'm probably opening up a science debate here, but in brief - are curved blades better than straight blades on radiator electric fans ?? 

 

Is it down to preference OR the difference is so slight that it's hardly noticeable ??

 

My understanding is that curved blades are less noisy when running.

 

This is question specific rather than vehicle specific.

 

Many thanks.

 

Richard.  

[Clive]

I am like you, undecided. Or rather, suspect there is little if any difference.

I would be looking at the fan quality rather than design, if that makes sense. You can't go wrong with SPAL fans, or indeed most of eh OEM stuff pilfered off a tintop.

 

FWIW the fan on my Spit is an ancient Golf GTI bit of kit. It is unfashionably small diameter, and has just 4 rather thick blades. Looks like a boat prop! But is not overly loud, and extremely efficient (largely down to using the OEM shrouding setup)

 

On a Vitesse the difficulty is space. I used a fan off a RF GT turbo, lovely thin bosch fan that had wire mountings that usefully worked out well  for the Vitesse. But they will be a bit harder to find these days. 

[Guest]

Clive.

 

I did some additional research yesterday and came up with this info which is succinct:

 

The straight blade fans provide maximum cooling for their size.  The curved blade fans sacrifice a small amount of performance in return for a much quieter fan. If noise is an issue, go with the curved blade fans.  If ultimate performance is the objective, use the straight blade fans.

 

Additionally, the initial amp draw is slightly higher with straight blades than curved - why, I do not know.

 

Thanks for your info and agreed.

 

Best wishes.

 

Richard.

[Clive]

Higher initial drawn will be because they take a fraction longer to get up to speed (because they shift more air)

In that case there will be less back EMF, meaning a higher initial current draw, or rather for longer. But we are talking a second or so....until the fan is up to speed.

 

The other problem is that unless the motor is identical they can't be compared. So a slightly more powerful motor with curved blades should be as efficient at cooling, but hopefully quieter. At the expense of overall higher current draw...but not for the initial startup!

 

Head hurts now.

[TomL]

My thoughts are that a simply constructed fan would have flat blades.  Curved blades would only, I guess, be introduced as a measure of sophistication, presumably for either greater efficiency or reduction in noise, or both.  It appears from your research that it is to make it quieter.  I imagine the extra current draw at start-up (of the flat blade type) is because it's shifting more air, as Clive says.  I suspect that the extra draw is negligible. 

 

Are you planning to change your fan?

 

Tom

[Guest]

Hello Tom / Clive.

 

I changed over to a curved blade fan on the Vitesse prior to going to France last year and it has been one of the best of many mods I've undertaken.

 

Thought I'd flag the thread as it gives other Forum members a better insight to the different fans prior to going down that route. We all understand the benefit of shrouds and the necessity of the fan being adjacent to the rad itself; but blade shape is often overlooked.

 

All the best. 

 

Richard.