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1. 05:55 AM - Re: Slats & vgs (dcstrng)
2. 09:29 AM - Re: Slats (ronlee)
Message 1
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John and the STOLSPEED folks have done a herculean job of taking the unknowns and
mystery out of the slatless Zenith wing for us mere mortals -- albeit primarily
substituting VGs and often in company with a more symmetrical HZ stab foil.
There was a pretty thoughtful discussion over on the Zenair Aero forum on
the issue of slat v. slatless pops up every few months, so it remains a provoking
topic with numerous debaters Since mine is still years (decades???) away
from flight I have little personal experience other than a pleasant 30-45 minute
flight with Roger in the fully slatted CH750.
Nonetheless, my observations from reading a gazillion posts on the subject (and
just about anything I can find over many years in the NACA digital libraries
on slats and VGs) are that the slatless wing is particularly attractive to those
who want longer cross-country legs, a bit more economical and typically 5-10mph
faster at equivalent throttle settings extending the flight envelop beyond
its original design. One may recall the original wing and foil were largely
designed (optimized?) for a Rotax 503/532 with little hope of a 100mph cruise
or even achieving it all, except with a conspicuous vertical component.
The few folks who have articulated their reasons for retaining their slats indicated
the actual angle of climb and decent is higher (I believe STOLSPEED commentary
questions this conclusion, but a recent builder noted rather emphatically
that the issue of short, high-altitude field with high obstructions prompted
him to retain them -- partly to one-up the Kitfox fliers as I recall). So,
esthetics aside (always a very personal/subjective issue) my synthesis is the
slated v. slatless issue boils down to which end of the flight envelop is the
builder/flier trying to optimize. It is unfortunate that the PegaStol effort
went AWOL, because that had the potential to have it all in my opinion.
All debates aside, the slatted wing seems to remain dominant indeed Ive never
seen a slatless one in the flesh although thanks to the internet there is documentation
aplenty. A minor issue for me is my own personal bias although a disappointingly
low-time pilot and not a graduate engineer, Ive been entranced with
the technical side of aerodynamics since my days as a part of the SST and
TF-39 design teams (that would be in the mid-late 60s) and Ive rarely (hardly
ever) seen VGs permanently used except when the design just missed expectations
altogether, or an older airframe was being readapted for use outside its original
design envelop (as occasionally occurs in high-performance aircraft when
a aerial combat bird is redesigned to extend its useful life as a ground attack
bird, with accompanying external stores and the requirements for better low-speed
control).
As I said esthetics is a personal issue what one builder sees as innovation, my
eye sees as a band-aid. My guess is were both correct. The better way (for
me) to attack the issue if I were planning to build a slatless 701/750/801 would
be to extend the foil out to its proper profile and/or try to figure out the
Pegestol system or perhaps use a drooping LE ala the Wittman/Luce Buttercup
I started to build one and still like the design However, for pure simplicity,
the Zenith fixed slats or the STOLSPEED adaptation of VGs have to be the most
elegant solutions (assuming a solution is actually needed).
-- Larry
:?
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-- Larry
Virginia, USA
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397836#397836
Message 2
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The answer to the question about how to land a 701 with slats or with no slats
and VG's with no power is. One just has to be close enough to the runway, pattern
altitude (1000 feet above runway) and turn base quite quickly.I do a military
numbers to final (a steady 180). Of course keep the nose down enough to maintain
flying airspeed, I keep it about 60mph. Don't try to flair from very high
as it will slow very quickly and drop in. I takes some guts to not flair too
soon as it has to maintain flying speed to near touch down. Don't mush it in
as there will not be enough speed, inertia, to do a flair.
One thing I have never mentioned before is that the angle of attack in level flight
at 10000 feet is much less with vg's then with slats. I have no idea why.
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Ron Lee
Tucson, Arizona
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=397854#397854
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