Today's Message Index:
----------------------
1. 05:34 AM - Re: Cruiser wing chord (William Schertz)
2. 02:36 PM - KIS TR-1 Airfoil (Propellerjan)
Message 1
INDEX | Back to Main INDEX |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Cruiser wing chord |
56=9D is what I have it at.
Bill Schertz
From: Scott Stearns
Sent: Thursday, January 10, 2013 9:59 PM
Subject: KIS-List: Cruiser wing chord
Can someone tell me what the correct wing chord for the Cruiser is?
I think it is about 56".
Thanks,
Scott
From: mark_trickel <marktrickel@gmail.com>
Sent: Thursday, January 10, 2013 8:41 AM
Subject: KIS-List: Re: Current TR-4 Cruiser Builders
Graham Brighton,
I tried to send the list file out to the address listed on your post but
it comes back as undeliverable. Can you check that and see if it is
correct?
Mark Trickel
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=391984#391984
Message 2
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | KIS TR-1 Airfoil |
KIS TR-1 Airfoil
In the search for information to calculate an optimum propeller for the KIS I0-240
I found a lot of information and thoughts about its handling especially during
landing.
When picking an airfoil for a airplane project that is about the last thing to
do before the design is set in stone. The wing area is determined in respect of
stall speed with flap arrangement.
When having MTOW, wing aspect ratio and wing area, we can calculate speed and lift
coefficient, CL
The speed we use for this will be where we spend most of the time, not stall speed
and not top speed, but climb and normal cruise speed. So in this range the
airfoil should have the lowest drag, if it was an airliner that spend most of
its time climbing and cruising at high altitude at low indicated speed it will
be at similar CL most of the time (but Mach Nr will play its roll)
All aircrafts that see any production see an increase in installed power and weight.
If this was in the design of the KIS from start I dont know, but the prototype
had a Limbach from start if understand it correctly, and several hundred
lbs less weight.
Most seem to have the I0-240B engine installed now and a MTOW of 1450 lb or so.
And it is cruising at around 140 kts. This give an lift coefficient, of around
CL 0.3 at cruise, it mean that an airfoil with higher camber would have been
better then the current N-63A215, where the 3:d last digit tell the designed
CL So it have an airfoil designed for higher speeds, but no meaning to have that,
no one cruise at WOT at SL, but most cruise at 65-75% power from 2000 to 8000
or 12000
The NACA 6x- series isnt the best with today standard, rumour says that the NACA
screwed up when publishing these new airfoils with a faulty design that they
could not take back.
An Harry Riblett GA-37A315 would be a better choice, it have gentler stall, and
will show less drag at both cruise and climb, The difference between Riblett
and NACA is that the nose radii is placed correctly on the Riblett. The Riblett
will have about 7-8% higher CLmax.
I draw up both airfoils for evaluation and when aligning the portion where main
and after spar will be, it is a different of 1 degree at the chord line. (From
nose radii to trailing edge)
The NACA is in Green
>From the main spar and back there is very little difference in shape, meaning
the lift at same angle will be about the same with this difference in angle
The chord line is just a reference line that is convenient to draw and measure,
but aerodynamically it is almost a fictive line, the important line or angle
of an airfoil is the zero lift angle, from this line the lift is generated if
it is given an angle to the relative wind, think of an symmetric airfoil where
the zero lift line and chord line is the same, and at alpha zero it will not
produce any lift.
An airfoil with camber will produce lift even if the chord line is at alpha zero,
or slightly negative, because the zero lift line will have a positive alpha
to the wind.
To make a cambered airfoil to produce zero lift, the nose have to be lowered until
the zero lift line is parallel to the wind, so an cambered airfoil is said
to have a zero lift angle of minus some degree depending of the camber, it can
be -1 to -6 degree on common airfoils and camber.
The NACA 63A-215 have a zero lift angle of -1.64 degree, and the Riblett GA-37A315
-2.14 degree.
A difference of 0.50 degree.
The lift slope Cl alpha is depending on the wing aspect ratio, for a AR of 6, the
slope of the lift curve is CL = 2Phi / 1+2/A2 = 2Phi / 1 + 2 / 6 = 4.71239
per radian
Or 4.71239 / 57.3 = 0.08224 per degree
The original wing is 3 degree up from chord line to fuselage reference line, so
if we fly it with the reference line horizontal the wing CL is 3 - -1.64 =
4.64 degree a 0,08224 = 0,38 CL.
The GA-37A315 will be 1 degree less measured at the chord line, so 2 - -2.14 =
4.14. so CL with fuselage level will be 0.34
It means that at higher speeds the nose down angle will be 0.5 degree less.
Lets say we cruse at 165 MPH TAS @ 8000 and 1450 Lb the CL will be 0.30 plus the
fact that the wing have to carry the down force from tail plane. Both airfoils
have a negative pitch moment of 0.05, the Riblett just a little more then the
NACA due to more camber.
The load at the tail is its moment times the wing chord and area, times dynamic
pressure.
Divided with tail length.
It will be about 84-85 lb down force at cruise if CG is at 25% chord
So the wing then will carry 1535 lb or CL 0.32
A CG further back will reduce negative lift and then reduce induced drag. (And
reversed.)
1450 lb at after limit will reduce down force at the tail with 10 lb
at forward limit it will ad 35 lb to a total lift the wing have to do of 1570 lb
or CL 0.33
A CG to forward and the elevator will not be able to hold the nose up with flaps,
to far back and it will be sensitive on the stick. Then we come into:
Nose drop at landing, sounds like ground effect, when closer to ground the down
wash from wing is flattened out, meaning the tail will have less down force.
With a horizontal stab area of just a bit over 17% of the wing area, seems small,
even if the tail arm is long.
One reason for the elevator not be up to the job can also be the tail incidence,
0.5 - 0.75 degree down might help. (but hard to fix that now)
Seems like, longer elevators chords is a good thing, 1,75 longer chord move the
hinge line to 60% chord/40% elevator. (about normal)
And VG's, seems to help, it means something is wrong from start, to small elevator
or wrong incidence. Or to small H.- tail area or all three.
The Wing Fuselage fairing should be expanding and 10% of the chord at the trailing
edge, according to Raymer, It mean in my eyes it should be 10% of the local
chord, so mid chord it is 5% of the total chord length.
I dont see anyone on Matronics talks about if they sealed the control surface hinge
gaps with tape. That will make a big difference. Tape them with Tesa fabric
tape on the bottom side of the Hinge line, inside the elevator, inside the
rudder, inside the aileron, and bottom of the flap hinge line.
Having them unsealed is like driving with the parking brake on.
On a Kitfox it is the difference of being able to make a 3-point or not with or
without sealing the elevator gap.
Jan Carlsson
JC Propeller Design
Ps. Sorry to say, I have never been onboard a KIS.
--------
www.jcpropellerdesign.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=392088#392088
Attachments:
http://forums.matronics.com//files/63a215_37a315_le_rad_133.jpg
http://forums.matronics.com//files/63a215_37a315_184.jpg
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|