Today's Message Index:
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1. 03:34 AM - Re: KIS TR-1 Airfoil (Propellerjan)
2. 10:04 AM - Re: Re: KIS TR-1 Airfoil (Mark Kettering)
3. 01:02 PM - Re: KIS TR-1 Airfoil (Propellerjan)
Message 1
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Subject: | Re: KIS TR-1 Airfoil |
I made a "final" test with original NACA 63A215, Half-Cuff on the same airfoil
and the Riblett GA 35A215, all these have the same basic symmetric airfoil, except
the Half-Cuff that is modified under the LE, The NACA and the Half-Cuff have
the same mean line, except at the nose of the Half-Cuff, the GA have the Riblett
GA-2 mean line.
It is seen that the Riblett will have a "softer" stall, seen on the more rounded
polar curve at stall, meaning the stall will be more like a mush then a sharp
stall.
The Half-Cuff will have almost as low stall speed as the Riblett, but little sharper
stall, but what happens to the N-63 at low speed? laminar bubble that burst?
The Half-Cuff will be like a in-plant for the KIS, and VG's will be more like a
band-aid.
Nothing wrong with the KIS-TR1 that can't be fixed.
Why did I do this? because I read that so many if not all have issues with landings
and it have to be landed precise at a almost constant angle at approach.
Please correct me if I am wrong, I have not flown the KIS
--------
www.jcpropellerdesign.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=393120#393120
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Message 2
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Subject: | Re: KIS TR-1 Airfoil |
Hello Jan,
As far as I know there are 3 issues with landing the TR-1. The pitch control is
very light. I think the best two fixes for this are increase the cord of the
elevator by adding 1 to 2 inches to the trailing edge and maybe changing the
control ratio. The second is lack of control power when at or near forward CG.
Adding to the elevator cord helps and and slightly increasing the travel helps.
The travel can be increased via changing the control ratio. The third
landing issue is the nose slamming down after touchdown. This is due to the main
gear being too far aft and is simple to correct by slightly angling the main
gear legs forward. This also helps to solve 2 other problems, the over rotation
on liftoff and the high loads on the nose gear.
Anytime you reduce the stall and landing speed it is good. But any time you reduce
the cruise speed and the VNO it is bad. It is less simple to change the
good without changing the bad at the same time when using fixed aerodynamic changes.
Of course to some the slow speed numbers are more important but at least
for me the high speed numbers are more important as long as the low end meets
my minimums.
What other landing issue have others had with the TR-1 and TR-4?
Thanks,
Mark
-----Original Message-----
>From: Propellerjan <propellerdesign@tele2.se>
>Sent: Jan 27, 2013 6:34 AM
>To: kis-list@matronics.com
>Subject: KIS-List: Re: KIS TR-1 Airfoil
>
>
>I made a "final" test with original NACA 63A215, Half-Cuff on the same airfoil
and the Riblett GA 35A215, all these have the same basic symmetric airfoil, except
the Half-Cuff that is modified under the LE, The NACA and the Half-Cuff
have the same mean line, except at the nose of the Half-Cuff, the GA have the
Riblett GA-2 mean line.
>
>It is seen that the Riblett will have a "softer" stall, seen on the more rounded
polar curve at stall, meaning the stall will be more like a mush then a sharp
stall.
>
>The Half-Cuff will have almost as low stall speed as the Riblett, but little sharper
stall, but what happens to the N-63 at low speed? laminar bubble that burst?
>
>The Half-Cuff will be like a in-plant for the KIS, and VG's will be more like
a band-aid.
>
>Nothing wrong with the KIS-TR1 that can't be fixed.
>
>Why did I do this? because I read that so many if not all have issues with landings
and it have to be landed precise at a almost constant angle at approach.
>Please correct me if I am wrong, I have not flown the KIS
>
>--------
>www.jcpropellerdesign.com
>
>
>Read this topic online here:
>
>http://forums.matronics.com/viewtopic.php?p=393120#393120
>
>
>Attachments:
>
>http://forums.matronics.com//files/final_re_6_650.jpg
>http://forums.matronics.com//files/final_re_2_101.jpg
>
>
Message 3
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Subject: | Re: KIS TR-1 Airfoil |
Hi Mark,
I see you know a lot on this and about the KIS, I am new to this forum, so I don't
know your background so please fill me in a little.
I hope I didn't step on anyones toes here.
When I write, I try to make it understandable for all, pilots, homebuilders or
engineers.
Some things is obvious for some people, but news for others.
I fully understand the need for speed, designing optimal propellers as I am.
As in the example with the full first cuff, loosing 2 kts might not seen much but
1-1,5% speed is the same as 3-4,5% thrust power.
(and the other way around)
On the other hand 1 kts might be within reading and instrument error.
I understand there is issues with horizontal tail volume, as I wrote in the first
posts in this thread, where the original tailplane and elevator is to small,
with a TV of 0,49 -0,50 depending on CG.
elevator is recommended to be 35-45% of chord, and original is 36%
and recommended TV would be 0,6 in a 2 place with flaps.
but TV is not any absolute numbers, NP and stability margin say more.
More elevator area will move the forward cg limit forward, or some nose down on
the stab, but the same time we want the elevator to be in line with stab in cruise.
Larger stab and elevator will move the rear cg limit back, or increase stick force
gradient. so making the elevator larger is a good thing, nothing new there.
2,5" extra will make the elevator 42% of total chord. and increase tail area
with 10% and a TV of 0,55.
Even a larger H-tail area seems to be needed, those changes above move the cg limit
maybe one % each direction, but a larger area will ad drag too.
But we had covered that before.
What I read between the lines when it comes to deployed flaps, is that they hardly
make any difference in stall speed? is that right? and don't change the moment
either, until VG's is installed on the wing?
That make me think there is something fishy with the original airfoil, if that
can be fixed without adding drag like VG's will do I think it is a good thing,
I understand that higher CL will lower stall speed as well as Va and Vno, but
the change will be small,
Today is the Vno calculated from real world stall speed or theoretical? if the
latter, a correction of the airfoil will probably not change anything.
The biggest change will be in stall speed with flaps, and that will not change
Vno nor Va.
What I can read in this forum is that most pilots would like to have a better handling
and a honest airplane that behave the same every time.
I am not saying it is the single problem, but as seen in the "wind tunnel" test
the 63A215 change its Cm rapidly at 4-5 deg alpha, meaning something is happening
there, I understand all 3 airfoils goes from laminar to turbulent about this
angle too. but if there is a bubble that form and burst it will probably give
the result that the flap don't work as a flap but as a air brake only.
The GA-35A215 isn't the same airfoil of the GA-family I tested, this seems to be
no more draggy at any speed compared to the original, top speed will more likely
be the same, but climb speed and stall speed better up.
But all airplanes is a number of compromises, so somewhere we have to chose between
good handling and speed.
Sincerely
Jan
--------
www.jcpropellerdesign.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=393148#393148
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