As requested!
[ The pictures won't carry onto the forum,of course. I will put them on the
list
support site tomorrow, - JFC ]
On Monday, June 03, 2002 9:44 PM, Erich D Trombley
[SMTP:erichdtrombley@juno.com]
wrote:
> Duncan, any pictures? Did you use the XS oil cooler or the classic's?
>
> Thanks Erich
>
> <ami@mcfadyean.freeserve.co.uk> writes:
> > Also for what its worth, testing of the Lo-mcfadyean-sti XS cowls has
> > just
> > been completed. These are comprised XS cowls with the underslung
> > portacabin
> > removed. The radiator sits in a new duct under the cowls. The duct
> > is much
> > slimmer and curvier, set further back from prop blade interference
> > and has
> > about half of the inlet area of the XS. The oil cooler is removed
> > from
> > behind the water radiator and is now smaller and placed behind the
> > port
> > nostril.
> >
> > In terms of cooling, it all works rather well.
> > In terms of aesthetics, it looks loads better (IMHO).
> > In terms of overall drag, I have no idea whether they are any better
> > or
> > not. A throttle -closed VNE dive with the former BMW cowls (not too
> > dissimilar to the Std. XS) lost about 4000fpm; now its about 3000
> > fpm
> > (although to confuse matters, prop pitch is now coarser).
> >
> > For good measure and to reduce wetted area(!) the cowls were also
> > reduced
> > in length by about 2" (because the Classic engine mount has been
> > used). The
> > secret to the cooling success is a new outlet duct at the base of
> > the
> > firewall through the area that the monowheel likes to occupy (or is
> > occupied by the nose gear stuff on the Tri). The inlet duct is also
> > "properly" dimensioned and shaped so that it isn't running in a
> > stalled or
> > 'vena-contracta' condition. You too can make this mod., but you may
> > first
> > have to change to fixed conventional gear to create the opportunity
> > for
> > the additional exit duct.
> >
> > Duncan McFadyean
> >
> > PS does anyone have a NACA duct splash mold I could borrow?
> >
> >
> >
> >
> > On Saturday, May 18, 2002 9:40 PM, Fred Fillinger
> > [SMTP:fillinger@ameritech.net] wrote:
> > >> 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.
> > >
> > > The Europa Forum is supported by Aviators Network UK
> > <info@avnet.co.uk>
> > The Europa Forum is supported by Aviators Network UK
> > <info@avnet.co.uk>
>
>
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