Today's Message Index:
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1. 01:26 AM - Re: Re: Slats (JC Gilpin)
2. 03:34 AM - Re: Re: Slats (Roy Szarafinski)
3. 03:52 AM - Re: Re: Slats (Roy Szarafinski)
Message 1
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Gday,
I regret being so slow to reply to this thread, but I=92ve been occupied
elsewhere. Not wanting to prolong it, and I do hope this is the last time
that I=92ll feel the need to post on this subject. But I feel that I must
respond to a series of mis-truths that are so often repeated without
basis. This is based only on real life flight testing and experience.
Sorry it=92s so long, but it needs to be said=85..
*=85Taking the slats off of the 701 wing makes a completely different
airfoil so you have become test pilots not experimental pilots=85*
Not so now. The Colombians who were the first to take their slats off were
the test pilots, but that was 24 years ago, and they=92ve been flying that
way ever since... I did the experimenting and evaluation 7 years ago, and
since then have 1000hrs of flying without slats, much of that touring
outback Australia, including countless STOL ops from rough off-field
locations, and never felt the need for slats. Hans now has 800hrs since
removing his slats, and three other aircraft at our airfield would have
about another 500hrs, with no one wanting to change back. Ron in Arizona
has many, many hours experience each way, and much prefers his 701 without
slats, as he has stated on this forum. J.S. in Mississippi, who=92s a high
time professional pilot in a wide variety of aircraft, and a very critical
test pilot, (he doesn=92t =91sugar coat=92 anything), was initially sceptic
al,
and set out to disprove my claims, but found out they were true, and now
his slats hang in the roof of his hangar. So we=92re now way past the test
pilot and experimental stage; this is now a proven and established
configuration.
*=85the basic airfoil has about a 1.3 coefficient of lift. It's the slats
that make the difference=85*
Have a look at this video of Hans taking off without slats, only a light
breeze and a warm day, (not like the frigid air at Valdez).
*http://www.youtube.com/watch?v=Y4_GsoN9hA8*<http://www.youtube.com/watch
?v=Y4_GsoN9hA8>
* *
To lift that weight at that speed, that=92s a whole lot more than 1.3 CofL
=85.
J.S. stated that his tests showed that slats gave him about 10% shorter T/O
roll, but then as he said, =93=85for a 701 that=92s a difference of about 6
-10
feet ' big deal=85=94.
Who needs a shorter take-off run than Hans just demonstrated??
*=85Slats double the lift of a given airfoil=85***
That is so for some wings, but careful, repeatable, flight testing shows
it=92s definitely not true for the 701! Let the writers of the books expla
in
why not=85. But there are observations I can make from personal experience
with other slatted aircraft including the Helio Courier, Rallye, and the
Pegastol wing for the 701. All of them have slim, low-camber wings that
are optimized for cruise when the slats are retracted. When those slats
are deployed they not only move forward to open the slot, but also move
considerably downwards, which has the effect of increasing the effective
camber of the wing, and thus greatly increasing the CofL. But the 701
starts with a highly cambered wing with an already high CofL, and the slats
are fixed directly in front of it, thus not increasing the effective camber
and CofL any further. (Actually, the 701 did originally have the slats
mounted with their leading edge below the wing, but that caused such
turbulence and instability at fast cruise that they were moved upwards to
where they are now). Fixed slats are a difficult compromise at best, and
experience and testing shows that very little CofL is lost in removing them
from a 701.
*=85Taking the slats off of the 701 wing make a completely different airfoi
l=85*
That=92s correct, but it=92s not an entirely unknown airfoil. We were flyi
ng
with very similar airfoils on ultralights 20+ years ago, and they had very
forgiving stall characteristics and good slow speed flight.
Who would have thought this airfoil would be so good for both stall and
cruise on the 701?? I certainly didn=92t expect that, so even before I fir
st
removed the slats I=92d made new nose ribs to match the contour including t
he
slats. But after closing over the slots temporarily and not liking the
result, and having tried the bare wing without slats and being impressed
with the flight characteristics, those ribs hung in my workshop for years
until they finally went for scrap
Some call it a =91blunt=92 leading edge, but it=92s not so, it=92s just =91
nice and
fully rounded=92 (like a good woman). That =91fully rounded=92 leading edg
e
gives excellent stall characteristics and a benign pitching moment, just
what you need for flying safely at minimum speed. The surprising part is
that it causes so little extra drag at cruise speed; about 1.5kts as
compared to a NACA 65018 leading edge. But the =91fully rounded=92 leading
edge gives a 2kts slower stall speed and a much more docile stall
characteristic, so I=92m happy to live with that for my purposes.
*=85VGs only make a poor performing airfoil work better=85*
Not so. VGs don=92t improve a wing, they just improve the airflow over any
wing. They keep the air flowing in a contiguous sheet, close to the wing
surface, and help prevent disturbances from spreading. This helps any wing
perform to it=92s best. The =91fully rounded=92 701 wing is already an exc
ellent
airfoil for STOL purposes even without VGs, but they do help control the
airflow to make it hang on even slower.
*=85why any of the "Slat Removal Group=94 bothered to build the 701 in the
first place=85*
That=92s really easy ' because the 701 is such an excellent little aircra
ft!
(other than the slats) Great performance from an excellent wing, excellent
controls, and excellent landing gear. That all-metal construction is
rugged and durable, and so easy to work with. It would have to be the
easiest aircraft to build from kit or plans, so it=92s quite affordable.
It=92s not sleek and sexy, but it=92s durable and practical, like a good ol
d
4WD, and that=92s just the sort of aircraft I want. I wouldn=92t want any
of
those delicate and fragile fabric or plastic aircraft. I consider the
original 701 with slats to equate to a WW2 Willys Jeep, a brilliant new
concept for it=92s purpose at that time, but tedious on the highway these
days. Without the slats, and with a couple of other improvement mods, that
old =91Willys=92 701 now equates to a modern day Suzuki 4WD, fine on the
highway and still just as good off-road. That=92s what I want in an
aircraft, and I just love it!
What=92s with you guys who object so strongly to removing slats, when you
have no real experience of the comparison?? Keep them on yourself by all
means, but please don=92t try to inhibit others the freedom to make their o
wn
choices based on the considerable experience that so many of us have
already demonstrated. It=92s evolution in action, and that=92s what makes
progress. If a fella like Ernest can get the cruise capability that he=92s
wanting, without having to sell his good little aircraft and buy another,
(at much hassle and probably at a loss), then he should be encouraged to
try the easy and proven option first=85
As my old Dad used to say, =93=85Take everybody=92s advice, then do as you
darn
well please=85=94
JG
Message 2
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JG,
Thanks for the good work and posting real life results.
I would like your considered opinion in regards to using the full 65018 nose
rib and leading edge.
The CG range being 20-35% in the original configuration, from front edge of s
lat to rear edge of flaperon. Does or did you notice any aft CG tendencies w
ithout the slat?
My reason for asking is that my firewall forward weight will exceed 200 poun
ds and I do not want to create a compounding situation running slatless.
Roy Szarafinski
www.roysgarage.com
roy@roysgarage.com
rvickski@yahoo.com
On May 11, 2013, at 4:25 AM, JC Gilpin <j.gilpin@bigpond.com> wrote:
> Gday,
> I regret being so slow to reply to this thread, but I=99ve been occu
pied elsewhere. Not wanting to prolong it, and I do hope this is the last t
ime that I=99ll feel the need to post on this subject. But I feel tha
t I must respond to a series of mis-truths that are so often repeated withou
t basis. This is based only on real life flight testing and experience. So
rry it=99s so long, but it needs to be said..
>
> Taking the slats off of the 701 wing makes a completely differen
t airfoil so you have become test pilots not experimental pilots
> Not so now. The Colombians who were the first to take their slats off wer
e the test pilots, but that was 24 years ago, and they=99ve been flyin
g that way ever since... I did the experimenting and evaluation 7 years ago
, and since then have 1000hrs of flying without slats, much of that touring o
utback Australia, including countless STOL ops from rough off-field location
s, and never felt the need for slats. Hans now has 800hrs since removing hi
s slats, and three other aircraft at our airfield would have about another 5
00hrs, with no one wanting to change back. Ron in Arizona has many, many ho
urs experience each way, and much prefers his 701 without slats, as he has s
tated on this forum. J.S. in Mississippi, who=99s a high time profess
ional pilot in a wide variety of aircraft, and a very critical test pilot, (
he doesn=99t =98sugar coat=99 anything), was initially sce
ptical, and set out to disprove my claims, but found out they were true, and
now his slats hang in the roof of his hangar. So we=99re now way pas
t the test pilot and experimental stage; this is now a proven and establishe
d configuration.
>
> the basic airfoil has about a 1.3 coefficient of lift. It's the s
lats that make the difference
> Have a look at this video of Hans taking off without slats, only a light b
reeze and a warm day, (not like the frigid air at Valdez).
> http://www.youtube.com/watch?v=Y4_GsoN9hA8
> To lift that weight at that speed, that=99s a whole lot more than 1.
3 CofL. J.S. stated that his tests showed that slats gave him abou
t 10% shorter T/O roll, but then as he said, =9Cfor a 701 tha
t=99s a difference of about 6-10 feet =93 big deal
=9D.
> Who needs a shorter take-off run than Hans just demonstrated??
>
> Slats double the lift of a given airfoil
> That is so for some wings, but careful, repeatable, flight testing shows i
t=99s definitely not true for the 701! Let the writers of the books e
xplain why not. But there are observations I can make from persona
l experience with other slatted aircraft including the Helio Courier, Rallye
, and the Pegastol wing for the 701. All of them have slim, low-camber wing
s that are optimized for cruise when the slats are retracted. When those sl
ats are deployed they not only move forward to open the slot, but also move c
onsiderably downwards, which has the effect of increasing the effective camb
er of the wing, and thus greatly increasing the CofL. But the 701 starts wi
th a highly cambered wing with an already high CofL, and the slats are fixed
directly in front of it, thus not increasing the effective camber and CofL a
ny further. (Actually, the 701 did originally have the slats mounted with t
heir leading edge below the wing, but that caused such turbulence and instab
ility at fast cruise that they were moved upwards to where they are now). Fi
xed slats are a difficult compromise at best, and experience and testing sho
ws that very little CofL is lost in removing them from a 701.
>
> Taking the slats off of the 701 wing make a completely different a
irfoil
> That=99s correct, but it=99s not an entirely unknown airfoil.
We were flying with very similar airfoils on ultralights 20+ years ago, and
they had very forgiving stall characteristics and good slow speed flight.
> Who would have thought this airfoil would be so good for both stall and cr
uise on the 701?? I certainly didn=99t expect that, so even before I f
irst removed the slats I=99d made new nose ribs to match the contour i
ncluding the slats. But after closing over the slots temporarily and not li
king the result, and having tried the bare wing without slats and being impr
essed with the flight characteristics, those ribs hung in my workshop for ye
ars until they finally went for scrap
> Some call it a =98blunt=99 leading edge, but it=99s not s
o, it=99s just =98nice and fully rounded=99 (like a good w
oman). That =98fully rounded=99 leading edge gives excellent st
all characteristics and a benign pitching moment, just what you need for fly
ing safely at minimum speed. The surprising part is that it causes so littl
e extra drag at cruise speed; about 1.5kts as compared to a NACA 65018 leadi
ng edge. But the =98fully rounded=99 leading edge gives a 2kts s
lower stall speed and a much more docile stall characteristic, so I=99
m happy to live with that for my purposes.
>
> VGs only make a poor performing airfoil work better
> Not so. VGs don=99t improve a wing, they just improve the airflow o
ver any wing. They keep the air flowing in a contiguous sheet, close to the
wing surface, and help prevent disturbances from spreading. This helps any
wing perform to it=99s best. The =98fully rounded=99 701
wing is already an excellent airfoil for STOL purposes even without VGs, bu
t they do help control the airflow to make it hang on even slower.
>
> why any of the "Slat Removal Group=9D bothered to build the
701 in the first place
> That=99s really easy =93 because the 701 is such an excellent l
ittle aircraft! (other than the slats) Great performance from an excellent w
ing, excellent controls, and excellent landing gear. That all-metal constru
ction is rugged and durable, and so easy to work with. It would have to be t
he easiest aircraft to build from kit or plans, so it=99s quite afford
able. It=99s not sleek and sexy, but it=99s durable and practic
al, like a good old 4WD, and that=99s just the sort of aircraft I want
. I wouldn=99t want any of those delicate and fragile fabric or plast
ic aircraft. I consider the original 701 with slats to equate to a WW2 Will
ys Jeep, a brilliant new concept for it=99s purpose at that time, but t
edious on the highway these days. Without the slats, and with a couple of o
ther improvement mods, that old =98Willys=99 701 now equates to a
modern day Suzuki 4WD, fine on the highway and still just as good off-road.
That=99s what I want in an aircraft, and I just love it!
> What=99s with you guys who object so strongly to removing slats, whe
n you have no real experience of the comparison?? Keep them on yourself by a
ll means, but please don=99t try to inhibit others the freedom to make
their own choices based on the considerable experience that so many of us h
ave already demonstrated. It=99s evolution in action, and that=99
s what makes progress. If a fella like Ernest can get the cruise capability
that he=99s wanting, without having to sell his good little aircraft a
nd buy another, (at much hassle and probably at a loss), then he should be e
ncouraged to try the easy and proven option first
> As my old Dad used to say, =9CTake everybody=99s advi
ce, then do as you darn well please=9D
> JG
>
>
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>
Message 3
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Correction, should read; did you notice any forward CG tendencies?
Sorry about that, my brain got in front of my thinker.
Roy Szarafinski
www.roysgarage.com
roy@roysgarage.com
rvickski@yahoo.com
On May 11, 2013, at 6:33 AM, Roy Szarafinski <rvickski@yahoo.com> wrote:
> JG,
> Thanks for the good work and posting real life results.
>
> I would like your considered opinion in regards to using the full 65018 nose
rib and leading edge.
> The CG range being 20-35% in the original configuration, from front edge of slat
to rear edge of flaperon. Does or did you notice any aft CG tendencies without
the slat?
>
>
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