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I searched. Nuthin. Just wondering if I could buy a Givi for $112 and cut the duct myself, saving me $88 in the process.

Would anybody be kind enough to make a rubbing of their NACA duct and scan it with a ruler in the picture for scale? or, if you were really clever, list the dimensions?
 

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Is the angle of the windshield really ideal for use with a NACA duct?

I thought these were intended for relatively shallow angles of attack. (If I recall correctly, the shape causes vortrices to go into the duct and cause very little interuption of the airflow behind the duct.)

Is there any benefit at the steep angle of a windshield?

..Tom
 

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This should be of help...if not helpful, it is pretty interesting. It got me thinking of heading for the garage and giving my Dremel a little exercise.

http://www.chris-longhurst.com/nacavents/


I searched. Nuthin. Just wondering if I could buy a Givi for $112 and cut the duct myself, saving me $88 in the process.

Would anybody be kind enough to make a rubbing of their NACA duct and scan it with a ruler in the picture for scale? or, if you were really clever, list the dimensions?
 

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Not really

All the NACA ducts I've seen (admittedly, in cars and airplanes) operate at very shallow angles of attack, which is to say that the incident airflow is nearly parallel to the surface in which the ducts are placed. The idea was to induct air through the surface (usually for cooling) without disturbing the relatively laminar flow along the surface, and thus increasing drag. Except for the very thin boundary layer, this is not true of a windshield. So the whole idea of a NACA duct becomes a hole in the windshield, I'd expect. Probably better to enlarge the vent at the base of the windshield, so the fairing directs the air up the back side of the windshield. The 'NACA ducts' shown are vents from the high pressure side of the windshield to the low-pressure side, and are unlikely to generate much flow up the backside, as the sharp edges will separate the airflow from the back surface. Of course, I could be wrong. Anyone got yarn-tuft pictures at speed? Of course, you could add deflectors behind the 'ducts' to attach the incoming air to the back surface.
 

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All the NACA ducts I've seen (admittedly, in cars and airplanes) operate at very shallow angles of attack, which is to say that the incident airflow is nearly parallel to the surface in which the ducts are placed.
I agree. Givi screens don't have a NACA duct on them, all they have is a NACA-duct-shaped-hole. It could be square or round or anything else and accomplish basically the same thing since nothing is being ducted.
 
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