naca airvents

does anyone know if the old style naca airvents are still availabile this vent was on my 4 when it was finished in 1989
these are not the same ones that vans offer.
they have a small knob that opens the vent ....theres three pics in the attachment
thanks

http://www.seehere.com/badflyr/rv-4_vent

Stuck in the 80's

Rob,

Those vents were all the rage back in the late 80's early 90's, Aircraft Spruce still sells them. I too installed a set like yours on my 4's canopy skirt (back in the 80's) that weren't effective as it's a low pressure area (chapter one in my "I wish I'd done that different" book). Finally after alot of trial and error I attached a pair of VG's out in front of them, really improved airflow. Later I added a pair of Larry Vetterman's flip out vents on the fuselage side which worked well.
Good luck!

Smokey
HR2

NACA-duct look-alike

Actually, those are only a look-alike NACA ducts, whose true nomenclature is a curved-divergent submerged duct or inlet. There was also a parallel-wall submerged duct and a straight divergent duct. A true NACA duct is much longer when made by the original x-y coordinates with a 7 degree ramp and the inverted airfoil leading edge at the outside of the aperture. Many of these look-alikes that you see have a sharp edge at the outside, and their pressure recovery is not as good. They also do not perform well as an outlet. See NACA RM # A7I30

Does anybody know if these are available? My knob is missing and I'd like to get a new one

i checked with spruce and they said to company went out of business a couple years ago... i was going to wait till osh to see what i come up there other wise il have to go with a Larry Vetterman's flip out vents on the opposite side with a ugly cover plate in the old vent or replace the whole skirt....

NACA Vent

It's not hard to make your own vent. Inside you need an expansion chamber to work optimally, then an eyeball outlet and you have a nice vent. I put one under my wing (canard) and it blows out the GIB. Without the expansion it should still move air only not as forcefully. Some Aero Engineers could advise you better on that.
Spruce and maybe Wicks still have a NACA that will work with an eyeball I think?
Those old ones were OK until they got really cold and you tried to work them with gloves and snapped off the plastic threaded rod. Then they didn't work so good.....