Duct Placement

[Tomfox]

Reading the instructions on duct placement in the lower cowling has me confused.

1 -have a constant gap between its aft edges and the front face of the radiator
2 - fit around the center radiator support

Does this mean that the bottom of the duct extends under the radiator? I don't understand the "fit around the center radiator support".

I have an oil cooler, so it would obviously have to fit around those pieces also?

Thanks
Tom Livermore
SS7 - Rotax 912

[jiott]

Ignore the statement about the center radiator support; it is on the bottom of the radiator and is no factor. I think some earlier versions had the support on the top of the radiator and the instructions just need some updating. You will need to notch the upper edge of the duct to fit around the oil cooler hoses/fittings.

[Dave S]

Tomfox,

We have an early S7 which had the center radiator mounting strap coming down from the engine mount. Check the two attached photos. I don't know when the mounting changed, but in our case, a notch had to be cut into the top of the NACA duct to clear the strap. We had the old model radiator at the time....possibly mounted a little closer to the firewall than the newer aluminum radiator.

Sincerely,

Dave S
KF 7 Trigear
912ULS Warp Drive

[TJay]

I really like that setup anybody think it would work on the early Foxes with the 582 without the round cowl? I don't care for the radiator under the belly of the plane.

[Dusty]

The 582 radiator setup is less than ideal but due to the exhaust location,moving to within the cowl would be a bit of a mission.
A streamlined radiator cowl used to be available,I don't know how effective these are.In some climates the radiator size could be reduced, especially if the hot air dumping Off the muffler could be redirected to avoid flowing through.
I considered making a radiator to fit at the front of the round cowl but it would
have been a tight fit and with the speeds we fly at possibly only a small gain.

[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.

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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.

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