Quote:
Originally Posted by Cd
How important is following a template to the function of a NACA duct ?
I plan on adding some to my car, but am limited on space.
I see some templates online that show a 10 to 6 ratio.
If I go with a 'fatter' 10 to 7.5, will it decrease the efficiency ?
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I've never used nor designed a NACA duct, so I don't have personal experience.
In my references, Tune to Win (Carroll Smith) has detailed diagrams showing what criteria a NACA duct needs to conform with to be effective.
He also states that for them to work:
- they must be made very closely to the design shown above
- they must be in attached flow
- the boundary layer needs to be thin
- they need to be located parallel to the local airflow
He also adds that:
- the angle of the ramp floor should be a max of 10 degrees
- the ratio of duct depth to duct width should be as high as practical (deep ducts)
- there must be a radiused lip at the rear of the skin opening
- the duct corners must be kept square