Duct Placement

[Tomfox]

Thanks to all - the strap is now in back so there is no need for a notch. Also - thanks for the heads up on clearing the oil cooler lines - saved at least two fittings

[HighWing]

Not specific to the question, but reading this brought back some memories. Although I am hesitant to post this as I have lost contact with the owner of the airplane and have no knowledge as to the project’s success.
It was about seven years ago that I began helping a friend finish his Series V. His plan was to take the airplane up to Alaska where his flying heart has always been. He had purchased the Series 7 cowl and of course it came with the NACA duct for radiator air. He wanted to modify the duct for a couple or reasons. First, there were occasional reports of cooling issues with this set-up and Second, the challenge often found in cold temps of keeping engine temps up. When helping another friend finish a Lancair IV, there was frequent talk about cooling issues and one solution that seemed to help was to reduce internal cowl pressures by reducing inlet air duct size. Talk, at the time, mentioned that for maximum cooling the inlet size should be a fraction of the outlet size – can’t recall the exact ratio but something like 1-1/2 outlet to 1 inlet area.
With that in mind we decided to put a “door” on the NACA inlet or rather hinge the cut out portion of the cowl for the door. I had done it on the vent inlet on my IV, so the fundamentals were known, although on a much smaller scale.

NACA 3.jpg

The challenge was to make the door openable from the cockpit. We wanted to have the control knob work in the same way that the throttle or other engine control knobs work, Control Knob In - Full open, Out - Full closed. The mechanics were designed so the operation was a push rather than a pull at the firewall. This way, there was no need for a tool required connection at the firewall, but rather a rod and receptacle that could be easily mated and that a push from the fuselage side would result in a push on the cowl side. The default position of the door was open – full forward on the control knob, so the design resulted in a reversal so a pull at the control knob was reversed to a push at the connection. A spring would open the door in case of a control failure. I have been trying to contact my friend for a report, but no go – sorry about that.

NACA Cowl.jpg
Naca Duct 1.jpg
Naca connect 2.jpg
Naca Connect.jpg