Dear Christine & Peter,
I think you might be interested in the ventilator locations we have
installed in G-BWRO europa #196. We have been flying since 1997 and have over
300 hours and although we are from the UK are temporarily based stateside
until the end of July 2000.
The 2 naca vents are adequate if you will only be operating in relatively
cooler temperatures - but if you plan to fly in heat and sunshine (my
favourite flying conditions) the cockpit turns into a small hothouse and the
standard vents are totally inadequate. After experiencing stifling heat on
numerous hot summers days we decided to rethink the ventilation system in our
aircraft.
We elected to place 3 extra vents and to clad the engine side of the
firewall with heat and sound insulating material. Cladding the firewall has
made a great difference in reducing the amount of radiated heat from the
engine entering the footwells (at a cost of $50 US and 2 lb weight).
We first placed 2 small "hinge" vents under the windscreen on pilot and
passenger side. These are opened with a small knob on the top edge of the
panel and provide a cold blast of air to the face.
Next we added an "extractor" vent in the middle of the cockpit roof as
far back as possible - this is just a reversed naca vent. We reasoned that
simply providing more input vents would not solve the problem which is akin
to holding an empty bottle with its neck pointing forwards out of a car
window while driving at speed - as you accelerate very little extra air gets
in until you provide it an escape route.
We now have 5 cockpit vents which can be opened in any combination
permitting comfortable cockpit conditions through a wide range of ambient
temperatures. The drag penalty is inconsequential - at 5000ft we cruise at
130 kts at 4600 rpm with our rotax 912ul sipping a mere 13 L/hr. The downside
is that they leak slightly in heavy rain - I carry a small roll of tape with
me just in case I have to park somewhere to sit out a storm.
I enclose a couple of pics,
Happy building,
James McDiarmid
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