lancevos-
Since i have never used the NACA i will chime in.
Quite a few new Ezes show up with a NACA inlet, but few new ones hatch now with the male inlet.
My understanding is the benefit of the NACA inlet is the
potential for improving the fuselage/gear leg intersection. But that may not be automatic. It does appear that eleminating the many intersecting elements of the gear legs and male inlet is obvious. But several experienced Eze folks have opined that there is little drag reduction (speed) benefit of changing from the male inlet to the NACA inlet, which may be why there haven't been many responses to this question.
We are often better at voicing opinions than accurately documenting the actual benefit of our mods. My list of improvements includes many 5 knot gains, with the plane now up to 300 knots, on paper
Of course there could be dozens of NACA installations with dozens of degrees of success, based on how well the gear leg intersection is handled, and what else is going on related to actual overall drag reduction on the plane, or not.
If it helps you any, my experience with the NACA inlet was to help a friend remove his, which included 3 or 4 inches of wall foam buildup under the gear legs, with the "floor" of the inlet being the original fuselage belly. The NACA inlet area was fairly near the the same area as the male inlet, with the lower lip about 3 or 4 inches below the firewall. I believe some folks have reduced the size of the NACA inlet with success, and hope you get a knowledgeable response from some of them here.
Adding material between the gear legs was counter to my interest in having the smoothest, most gradual slope from the belly up to the prop as possible. My cowl mates to the firewall with a constant curve to the prop.
Since my residuals are so profitable, i will mention the various successes of downdraft cooling making the circuits, particularly Scott Carter's Extra Eze Oshkosh winner. There are a couple of good inlet stories on his plane which i will save for Oshkosh
After all this, my suggestion from personal experience is to get the plane sound and in the air quickly, and unless you have already spent enough time on the flight line of Eze flyins, make the rounds this and next summer and see first person what the fast folks are doing. There also might be something worth hearing from folks that fly a lot. Then the lower cowl situation can hopefully be addressed more knowledgeably.
One friend switched from the male inlet to a boat tail with a claim of a 5 knot benefit, but showed me an area where there was still swirling air under the cowl. With such a short length for tapering down the firewall to prop area, we have to be real good or real lucky to optimize that area enough for a real benefit. However if someone is just looking make a big speed
difference, it is extremely easy to l
ose a lot of speed back there.
But if we do gain some ground, like always, that stubborn pool of swirling air would just go around the corner and "hang out" somewhere else, keeping us in the drag hunt for another go-around
Hopefully we are flying during the majority of the hunt.
Good flying-
