Paul puts a good bit of this success down to his new cowling.
It gets most radical underneath with twin oil coolers positioned way back inside the fuselage and fed by NACA ducts. As you already know I'm a big believer in getting drag further back on the airframe if at all possible. Whilst this is not the same as my setup it does share the same principles.
Also note the sawtooth edge on the main outlet. The only time I've seen it before is on jet engine exhausts where it has a silencing effect. See the Dreamliner's engine nacelle below. Incidentally this idea came from the mind of Robert Westley, who worked at RAE Bedford - just up the road from me.
After doing a bit of research I see that the sawtooth also has a effect on reducing the amount of turbulence when two airstreams are meeting - such as we have with the cold fast air outside the cowl meeting the hot slow(er) air exiting the cowl.
I see this part is also removable - as is the inlets. I guess this allows for a change to smaller or larger areas when the ambient temperature changes. It may be as cold as 15 degrees in some races and as hot as 40 in others. I will be doing a similar thing with my exhaust outlet fairing but my inlets will be fixed.
A couple of other things I noticed about Paul's cowl is the very long spinner and the air intake for the injectors that is angled upwards. I'm not sure why they do this but I am guessing there must be a downwash component coming off the prop which changes the angle of the air going into this intake.
BTW the genius behind this cowl is Paulo Iscold, a Brazillian who was also partly responsible for the CEA308 world record plane I posted about way back in November 2012.
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| 787 nacelle with sawtooth edge |
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| Bonhomme cowl underneath. NACA ducts for oil coolers and sawtooth edged outlet. |
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| Interchangeable Inlet. Note the tiny gap between spinner and cowl! |
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| Very long spinner and upward angled air intake for the injectors. |
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