Today's Message Index:
----------------------
1. 02:13 AM - Re: KIS TR-1 Airfoil (Propellerjan)
2. 04:12 AM - Re: 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: KIS TR-1 Airfoil |
Yes it give more drag with the cuff at speeds higher then the CL 0,3 as I wrote
in previous post. and I realize it is not for Scott's light and fast plane.
To the "pure" CL given from weight, speed and density alt, we have to ad 0,02-
0,03 due to tail down force. (about 10%)
There is 2 NACA 63-215 airfoils, the one with a A is the one used on the KIS-1
this is the one without cusp, straight or almost straight upper and lower rear
surface. said to have 0,0002 Cd more then the cusp'd airfoil, (like a mosquito
shit on the LE) but simpler, more structure and more effective ailerons with
the A model. this is the basic airfoil I used in this example.
The related Riblett airfoil would be GA 35A215, it is using Ribletts mean line
and NACA 63A015 thickness distubution.
I am curious how much drag the modified wing with cuff will make, say at WOT 8000I0-240,
1450 lb, My Propeller software say 179 mph 155kts TAS, thats what you
guys say too, CL 0,25+0,02 = 0,27
The total drag will be 80 kg/ 176 lb.
the delta drag coefficient from the cuff is at CL. 0,27 = 0,000857 if the X-foil
program is correct.
with the exposed wing area this give a Fo of 0,00594 m2 (sorry for using metric
system) the q is 314,3 kg/m2 and then delta drag is 1,86 kg
at 175 mph q is 300,4 = drag is 1,78 kg
so new speed will be 174-175mph/151-152 kts
BUT at that speed CL is 0,27 + 0,02 = 0,29 where the drag penalty is less then
half of what it is at CL 0,27, so real slow down 1,5-2 kts.
At faster speeds the drag penalty will be higher!
The goal with the cuff isn't to reduce drag but enhance handling, slower stall
speed, better climb, less erratic moment coefficient,
It is a quick fix for a faulty airfoil. if it paying off?
Flying slower than 150 mph IAS it will, maybe a cuff with half the LE drop will
be better? I just used the example in the book. realising the concave spot under
the nose where the cuff fair into the original airfoil would create drag at
small alpha. and sure it did.
This have to be seen in relationship to the drag with VG's on the wing, any one
with real numbers?
Jan
--------
www.jcpropellerdesign.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=393078#393078
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: | Re: KIS TR-1 Airfoil |
Okay, always goes faster second time.
Riblett talks about his mean line have 0,3% nose drop on the CL 0,2 mean line,
so I used that, and it is half of the first one.
Very interesting result.
I used single Re Nr. 2 and 6 million. 47,5 & 143 kts SL to make the graph clear,
and zoomed in the interesting parts at the speeds
at 2 mill the original and the full cuff airfoils polar curve just stop at CL 1,2
and 1,4 but not the half cuff, why i don't know. maybe the half cuff is good?
at Re 6 mill the half cuff have half the drag penalty of the full cuff at CL 0,15
and brake even at 0,25 with original airfoil.
at CL 0,6 the half cuff is better.
Higher CLmax at higher alpha, and Cm curve more even.
Okay good exercise.
Jan
--------
www.jcpropellerdesign.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=393079#393079
Attachments:
http://forums.matronics.com//files/half_cuff_992.jpg
http://forums.matronics.com//files/close_up_at_re_6mil_410.jpg
http://forums.matronics.com//files/cuff_at_re_6mil_538.jpg
http://forums.matronics.com//files/cuff_at_re_2mil_193.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! --
|