[Low n Slow]

The RV-4 my partner and I just bought was built and flown in the Seattle area. The air from the two existing vents comes from the rear of the air box baffling and is heated by the cylinders before it enters the cockpit. This may have been advantageous in the frozen north, but here in sunny California, we?re sweating like proverbial pigs.

We?d like to add two NACA ducts on each side of the fuselage like we?ve seen on many other RV?s, but have two questions;

1 ? How much (if any) of a drag penalty do you pay for each NACA duct, or is it a non-issue?

2 - I read about adding a NACA duct mounted backwards under the tail cone behind the baggage compartment in another thread. Does anyone know how effective this is and if it?s worth the effort?

Thanks
Tom
RV-4

 

[dougweil]

Ventilation

I too originally set up a mixing valve to regulate between hot cabin air and "cool" air from the rear baffle. Not a good idea (and I live in northern Wisconsin!!). The "cool" air was probably 40 degrees warmer than ambient.

In the winter, we need as much heat as possible and Larry Vetterman suggested the reverse NACA vent to "suck" hot air through the cabin to increase heat to the rear seat. I did install the reverse NACA venter just ahead of the tailwheel and frankly I could not tell any difference. So I am not sure if that was a great idea.

In the search for more fresh air I installed one of Van's simple air vents from the RV-10 kit on the right cabin wall just below the cowl cheek. Works great!!! All the air one could ask for. In the rear I have one of Larry Vetterman's small one-inch diameter fresh air vents which works fine.

 

[Low n Slow]

I too originally set up a mixing valve to regulate between hot cabin air and "cool" air from the rear baffle. Not a good idea (and I live in northern Wisconsin!!). The "cool" air was probably 40 degrees warmer than ambient.

In the winter, we need as much heat as possible and Larry Vetterman suggested the reverse NACA vent to "suck" hot air through the cabin to increase heat to the rear seat. I did install the reverse NACA venter just ahead of the tailwheel and frankly I could not tell any difference. So I am not sure if that was a great idea.

In the search for more fresh air I installed one of Van's simple air vents from the RV-10 kit on the right cabin wall just below the cowl cheek. Works great!!! All the air one could ask for. In the rear I have one of Larry Vetterman's small one-inch diameter fresh air vents which works fine.

Thanks Doug!