> As noted by several on this site there are some concerns and possibly desired
> mods to the XS cowl. Personally we're looking at fitting the 40 A Rotax
> alternator to a 914, needing space for a landing light, the on ground cooling
> capability, space and airflow for intercooler and improved aerodynamics (go
> faster!). Bruce & Suzy have also expressed these concerns. We would be
> willing to partner with other Europa owners / builders to investigate
> improvements to the cowl. My idea is to inquire of LoPreste to initially
> look at the Europa and see if he thinks these objectives can be achieved. If
> so the next step would be to find out how much $$ he would charge. If we
> spread the cost over several of us, it may be manageable. Any body else
> interested of have ideas? Bruce & Suzy have volunteered to take their 914 to
> LoPreste as the evaluation aircraft.
>
> Jim & Heather A185
FWIW, on the aerodynamics aspect, the substance in Hoerner's "Fluid
Dynamic Drag" re cowlings is this. Once you have the problem of a
propeller, aerodynamics aren't much more than the least wetted area,
limited by "practical considerations" of what's inside. The shape is
a transition to the fuselage with curves of decreasing radii. Thus,
whether an alternator "bump" is worse than a larger cowling is a
matter of experimentation, or just aesthetics at a possible price.
Biggest issue is cooling drag, meaning smallest, most efficient inlets
to still do the job. Whether a NACA scoop is better for the
intercooler, or larger central duct and split the flow, or totally new
arrangement would involve expert opinion. But I suspect it still
reduces to trial and error even for Lopresti. It's curious also that
Lopresti obtains the biggest gains on the faster aircraft, which I
guess is the "velocity squared" phenomenon: only 5 MPH on the Arrow
and no cowl kit for the slower but bigger market PA-28 fixed-gear
versions. In comparison, the XS cowl appears to have the type of
cleanups the aftermarket guys do.
For landing lights, I have small halogens, 35W to 75W with narrow-beam
reflectors that are tiny and only $4 each, to play with. Besides room
to fit, having 2 small lamps means less heat each to deal with the
heat issues, and more focused light pattern to maybe make up for the
lower candlepower compared to the short-life aircraft lamp.
Regards,
Fred F.
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