On 10/04/2012 01:34 PM, Paul McAllister wrote:
> As to cooling. I have extensively modified my cooling with cowl flaps,
> lamovia heat exchanger, diffused inlets, intercooler and internal
> ducting. I have spent 12 months over 3 winters and countless hours on
> this and although I am close, its still not right. I would encourage
> you to think carefully before getting into complex modifications.
Well, at least we can now tell what won't work.
The main thing we found is that no matter what you try, the original
coolant radiator is just to thick to get both a decent low drag and
efficient air flow through it. Replace it with a thin radiator (as in
*every* commercial Rotax application I have seen) and from there you can
just optimize the cooling system by recycling the exit air for cowling
and turbo cooling and applying an adjustable cowl flap for temperature
regulation, and optimizing inlet and outlet for minimal drag. It will
give you superb cooling and add some knots to your airspeed at the same
time.
> It you really want to get into this then don't do what I did, take a
> look at Fran's solution, but plan on adding 6 months to your build.
Thanks! Well, 6 months is a little bit exaggarated once you know how to
do it, but of course you need to extensively modify the cowling, and
depending on your skills and experience this will take more or less
time. I had no prior experience in modelling and building shapes, but
once I got the hang of it I could work pretty fast. Before I got it
right I built a dozen or so diffusing air inlets (in fruitless attempts
to get sufficient airflow through the thick radiator). The end result
with a thin radiator in line with the cowling belly is surprisingly
easy, much easier to build than all the carefully calculated and shaped
diffusers. Take a look at the Rotax equipped Diamond airplanes (super
Dimona, Katana) to get some inspiration.
I used a Laminova heat exchanger so I only had to care about cooling of
the coolant.
Frans
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