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Old May 14, 2013, 04:04 PM
Registered User
Germany, RP, Waldorf
Joined Sep 2012
38 Posts
Discussion
Problem with KIS Midi DLG

A big hello to the community,

I came across DLG's a while back and fell in love with this type of plane in an instant. Because of my small budget and location (germany) i decided to buy myself a pre-build (handmade) KIS Midi from a seller in Austria. The builder and seller is pretty known here in the german region and is a repected DLG builder and flyer.

The Midi arrived a couple of days later in prefekt condition. After putting everything together (attach wings, servos, etc.) I was quite happy with the looks of the plane and the build.

Data:
Model: KIS MIDI
Wingspan: 1.2 Meters
Weight: 370 gramms
Servos: 4* 9g
Lipo: 2s 350mah
RX: Spektrum 6ch

Well, last week was maiden time. Since I had no idea what I was doing I decided to give it a couple of normal throws without a discus launch. Just a good runup and a toss. Here I noticed that it was a little nose heavy and added 5 grams a bit rearward of the CG.

After another couple of tosses I was happy that the CG was fine. TIme for a first "Discus Launch". Well, here come my first problem.

I cant get the plane straight into the air. It always tips extremely to the left thus losing a ton of speed. Well, to counter this problem I decided to add some right aileron on a switch .Before the launch I flip the switch to on, and when it gets into the air I flip the switch to off to go into a glide. Well, thats were the second problem comes into play.

The plane wont go any higher than 15 meters... no matter how many times I try to launch the thing. At max height it then goes over into a really bad nose dive for about 10 meters and only then can I get it under control. The 5 meters leftover from launch results in flight times of max 20 seconds.

And ideas what could be wrong with the plane? Here is the strange thing:

My dad has a binary 900 from HobbyKing. When I launch that plane it goes perfectly sraight into the air. I dont need any right aileron on launch. I can get the Binary 900 easily 40-50 metres into the air. No hassel.

What could be wrong with my KIS Midi? Its so frustrating to see my dad launch his DLG to 50 meters while I cant get mine about 15, and then the nose tip.

Any ideas would be super welcome!! =)

Thank you!

-Meik
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Old May 14, 2013, 05:19 PM
F3B and F3K
RetoF3X's Avatar
United States, TX, Dallas
Joined Mar 2009
1,458 Posts
Hi Meik

I saw some KIS DLGs in action and they did not launch as good as moulded or bagged planes

The KIS DLGs have full balsa wings and thus a high moment of inertia due to the higher specific weight. Therefore the yaw oscillations are much higher and more launch energy is dissipated. It also looked like the vertical tail is rather small and as it is just a balsa plate it might be less effective in damping the yaw oscillations than a larger tail with a proper airfoil.

You really have to try to release the plane as cleanly as you can.

Concerning the stall: this is a consequence of the high wing loading, when you stall, it needs more altitude to recover. Try not to stall the KIS, else it costs you a lot of altitude.
For the throw, you need to push over earlier (apply downelevator) then you might be used from the Binary. Check also the CG again, a rearward CG might favor the nasty stall you experiencing. A little bit more forward might help to stabilize the pushover at the end of the throw.

With all that said, the owners of a KIS that I know are happy with them. The all wood wings are durable and easy to fix.

Best,
Reto
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Old May 14, 2013, 05:36 PM
Registered User
Germany, RP, Waldorf
Joined Sep 2012
38 Posts
Hi Reto,

thanx for your reply. So basically I have to try to launch the KIS more cleanly. Dang, I was hoping there was a more simple solution. I guess the perfect launch comes with tons of practise. I can feel my wrist bend at release and I already had the thought that this was causing the extreme left yaw at launch. It sometimes launches at 90 degrees angle to the left (left wingtip facing the ground). It has even happened that the KIS turned on its back on a couple of launches. ;-)

I'm really gonna have to force myself to keep my wrist straight on launch. Maybe I'm gonna even buy me some sort of bangage to keep the wrist stiff.

I'm gonna give your tipp a try to push over more early and check the CG again. Hopefully this will get rid of that nasty nasty stall.

What do you think about the weight? Should I try and reduce it? Meaning smaller Lipo, smaller servos etc? I guessing I could save about 40 gramms with these measures.

I really want this baby to fly...but at the moment its only frustrating me. I guess the really frustrating part is knowing that 90% of the bad flight performance is coming from the pilot, me. ;-)
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Old May 14, 2013, 06:15 PM
a.k.a. Bob Parks
Glendale, AZ
Joined Jun 2008
2,087 Posts
You may also look for warped wings.

I am not familiar with this plane but usually DLG wings 'should' lay with the bottom flat on a table, and the trailing edges straight. Some may have a bit of washout at the tips.

It may also be the weight of the plane is sticking to your fingers more than your Dad's plane. Do not try to flick it with your wrist.

BP
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Old May 17, 2013, 05:41 PM
Registered User
Germany, RP, Waldorf
Joined Sep 2012
38 Posts
Hi BP,

I just checked the wings for warping... nope, they are very level. I really do think it has to do with my launch technique and the weight of the plane. I'm gonna replace the 4 9g servos with 4 5.5g servos and see if that brings any improvment. I'm also gonna be using a lighter lipo and reciever. All in all a weight saving of 40 grams. =)
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