w1nd6urfa

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Hi all,
I got my hands on an ESM Storch, partially assembled.
Initially it looks a nice kit with machined aluminum parts to form the wing and LG mounts, fairly accurate outline and full-featured wing with slats and slotted flaps.

w1nd6urfa

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Thing is ...

This kit has been discontinued due to "high production cost" and there are very few if any flight reports, most are disasters:

1. Crash on maiden take-off (aileron reversed?)
https://www.youtube.com/watch?v=WuXVjJm0qnY 2. Awful maiden flight, crash landing
https://www.youtube.com/watch?v=28hSADk5aW4

w1nd6urfa

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A few old threads exist, but it seems the projects were abandoned / planes never flew or (worse) crashed on maiden

http://www.rcuniverse.com/forum/rc-w...rch-build.html

http://www.rcuniverse.com/forum/rc-w...sm-storch.html

http://www.rcuniverse.com/forum/rc-w...storch-vq.html

w1nd6urfa

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In some rare cases they did fly, not very Storch-like though ...

https://www.youtube.com/watch?v=ZWhru_rccu8 https://www.youtube.com/watch?v=Ebiz-Bcw9sM https://www.youtube.com/watch?v=-dQ3L8HbEPw

w1nd6urfa

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So from the research I did the problems are:

1. Wing geometry
Slats in wrong place, gap too big
Flaps not hinged correctly to work as slotted flaps

2. Weight
Needs a lot of nose weight to balance, plane ends up too heavy

3. Landing gear
Needs reinforcement or re-engineering, too flimsy My plan is to fix the wing first and find a way to "wind-tunnel" test it, if it doesn't work then I'll hang it from the ceiling or pass it on to someone else.
Same with CG, if it goes over 7 - 7.1kg then no-goIf anyone has any experience with this model, please chime in

If all works well until maiden, it will get a nice Afrika Korps paint scheme (that;s the easy stuff!)

w1nd6urfa

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To address the above issues I studied a few builder's kits:

1. Svenson 1/6 scale 95" old European kit, flies well and can be built light under 12 lbs
Free plan here: http://www.outerzone.co.uk/plan_details.asp?ID=5945

2. Dennis Bryant 1/6 93", more complicated kit, plan from Traplet: http://gb.trapletshop.com/copy-of-fi...-156-storch-93

3. The amazing Paolo Severin 1/4 112" kit very much based on the original with steel tube fuse: http://www.paoloseverin.it/download/index.html

w1nd6urfa

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Starting with the slats, I can see 2 problems:

1- The slats gap must be correct: as I received the kit partially assembled the stand-offs make quite a wide gap

w1nd6urfa

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2- The slat airfoil is not exactly right - especially the trailing edge is missing

The slat jig was made from the Svenson and Severin plans:

Joespeeder

Hi W1nd6urfa,

Looks like you are on a good path to success!! Looking at the Storch I would suggest setting the ailerons up so they are not reversed.... and adding 50% differential to them as a starting point. If the travel calls for 1 inch up defection then you should have only 1/2inch in the down aileron. DIfferential will give you much more positive low speed control and help stay away from adverse yaw.

I would add a Mix that was switchable on your TX of Aileron to Rudder...... I would guess about 50% but would begin with about 40% as a test..... With your Tx switches set to normal for the maiden no mix would be active..... Flip the mode switch and add the Aileron to Rudder mix. See how you like it. But you can bail out of it if needed. I'd guess you'd like it at low speeds and flip it off at cruise.

Then I would prop it like a 3D plane. Big disk and low pitch.....


I believe the Storch flew on both fixed Slats and movable slats. Seems like I saw the ailerons were used as flaps also someplace. I'd have to look again. But as I remember they ailerons were flaperons moving down about 1/2 of thier travel with the flaps being deployed fully at the same time.



Looking at those vids the ESM looks a little heavy.... Save all the weight you can and you'll be dog fighting L-4's in no time !!!



Joe

w1nd6urfa

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Hey Joe,
You're right on all points.
I discovered the original Fieseler Storch Handbuch, a very interesting read!

The full size had 2:1 differential ailerons (28 degrees up, 14 down)
The ailerons became flaperons when flaps extended past 20 degrees. I will do that after maidening, to start with I might trim both ailerons to be slightly up at neutral as a countermeasure to the 0 washout

Extract from the Handbuch:

w1nd6urfa

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More stuff from the Fieseler Operation Manual:

The Storch was probably the first 3D plane in history just look at those huge fins, and the recommended elevator throw: 45 degrees up when the plane is Kopflastigkeit (nose-heavy)!

Also note the differential elevator: 45 up - 15 down (nose-heavy), 40 up - 20 down (tail heavy). The stab incidence was also variable to cater for different loads and CG positions

A very interesting machine!

Joespeeder

Hi W1nd6urfa,

Cool..... This looks like a careful set would reap large rewards..... Ahh..... You're going to get pages and pages of discussion on "washout" created by raising the ailerons.

That would be something I would think about the entire time I was building it and then only add it after I flew it and tested how I liked it.... You will have Aileron Differential, and Flaperons, so when landing the ailerons will be set as a minor flap and working as spoiler for roll control. I'm not sure setting fake wash out would help..... I guess the question would be would it help in normal flight ?? I'm guessing no again.

I've read lots of arguments on "aileron washout" and have used it. However, I have lots of planes set up without it. Depends on the plane. I'm guessing on the Storch but i think I'd leave it off to begin.


If you've flown any sailplanes with an electric motor up front you'll recognize the feel of a high lift wing while under power.

When we launch it's not uncommon to hold about 80% down elevator as the sailplane climbs. Lots of people think its a tail heavy airplane. When in reality it's the high lift wing that has the CG set for power off flying. Once you shut the motor down the sailplane settles out to a balanced flight and shows it is not tail heavy.

I would pay careful attention to the CG on the Storch and think of it as ALMOST a glider in my set up. It should climb so that you have to hold down elevator when you are at high throttle settings. When you are at lower settings it should fly trimmed and with a neutral stick. Only flying it will tell you what it wants. Unlike a typical warbird don't be afraid to move the CG back slowly after the maiden.

It is a weird and yet awesome plane

Keep posting pics and updates. It will be fun to watch your progress and thought on the ESM.

Joe

w1nd6urfa

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Joe I hear you
What I meant about fake washout was that I'll have 2 channels for ailerons so I can setup airbrake and flaperon mix in switches to be able to experiment. It will be off at maiden ofcourse

I fly warbirds mostly and am fairly competent at 3D too. Flying the Storch high-alpha harrier style and rudder turns will be no problem.

I have never flown sailplanes though, is the down-elev when climbing due to stabiliser positive incidence? I would imagine the high-lift wing produces a nose-down moment that needs positive stab & up-elev to balance it?

Joespeeder

Hi W1nd6urfa,

Cool,,,, I think you have things well under control. I mentioned the Sailplane set ups just to say it looks like the Storch was flown with a standard forwardish warbird CG. But to get the more scale flight you may find moving reward a bit which will mean the plane will trim with down trim at higher speeds. Maybe even holding forward on the stick at those speeds. Holding the stick forward (down) is a very normal sensation in flying gliders but is very strange in warbird flying.

In the bad maiden video it looks like they didn't have Aileron differential dialed in and the pilot was fighting with adverse yaw plus all the other jitters of a maiden. He has to really bank the storch to get it to turn and when he trys to do a normal turn it pitches away from him in a way that feels unnatural and feels like a tail heavy unstable plane. In that same video there is a shot with the flaps down. The amount of flap deflection shown is a brake, not a flap, and the ailerons are not down acting as flaperons. If you deployed the flaps like that the Storch is going to come down fast !!

Good question about the incidence. I don't know, I think it's the lift form the wing, since some of the slopers we fly are flying wings and some of the traditional sailplanes are full flying tails. I was just thinking that the Storch may feel the same at higher throttle settings and need forward stick to achieve more scale like Storch flight at lower throttle.



As an aside.... If you get a chance to fly sailplanes be sure to try it. It is a very different style of RC than warbirds and 3D. Both Thermal flying and Slope Soaring have taught me bunches about set up and flying techniques that I would never have even thought about in powered flight. I bet you have Slopes in Greece that would be great flying sites. It is soooo very cool to fly a plane BELOW the level you are standing and look down on it !! When we go sloping we try to pick days that will be high winds of 15+mph. In those conditions you are holding about 1/2 down to keep the plane on the same alittude, pushing to about 90% down to fly below yourself, and by just releasing the stick to neutral the plane will pop up rocketing past were you are standing and higher..... Way cool. Thermaling I tend to think of as more like fishing than rc flying...... I go look for a thermal in one part of the sky, if nothing is there I go to another part of the sky and look there. Once in a thermal I work it till the plane is a dot in my vision, get out of it, and let the plane come down to try it all over again. 20 minute flights are common and 45 minutes are the goal !! It's addictive to fly that long with no power, but it is a very relaxed pace and more like fishing than rc flying... lol But in both cases you'll find yourself building muscle memory and creating aircraft set ups that transfer into builds like the Storch.

Here are some videos where holding forward stick was the norm. You'd never know it from looking at the plane but I'm controlling my pitch/altitude by releasing the forward pressure on the stick. In the Grob video I cruise around a bit as it's a shake out flight at 1/2ish throttle. But on launch and when at high throttle settings I'm holding down stick. In the Sleeping Bear video we were at a location were you had to walk a mile carrying your gear through the woods and over sand dunes.... So it was foam that ruled the day that day. The last video is of a scale Minimoa 2 seater that was used a trainer for fighter pilots in WWII.... That wing has a big under cambered airfoil and I have to hold LOTS of down when it's being launched under the power of the prop. It would loop if left to it's own. All of these planes fly very well, stable, and balanced at low power or with no power.

https://youtu.be/xt2Urt7EwGg?t=8m39s

https://youtu.be/-zsPLbT5b7o

https://youtu.be/kQLA_m2KPLQ



I'm looking forward to seeing your project in the air!! You've done lots of research and will have the best set up example that I think anyone has seen. Keep posting the pics as you go!

Joe

w1nd6urfa

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Cool videos!

I might try thermalling some time, my problem with slope gliding is that when its windy ... w1nd6urfa goes windsurfing

w1nd6urfa

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Continuing with the slats, if setup correctly they don;t exactly produce lify but rather they delay the stall (which occurs at a lower speed and higher AoA)



This is achieved by a high-speed boundary layer that attaches to the top of the wing:



There are 2 important details:

- The slat should be close to the wing
- the exit gap must be 1/3 the entry gap

w1nd6urfa

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Stripped the covering off the slats, and sanded them to improve the airfoil as per Severin/Svenson:

w1nd6urfa

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Covered the slats with Fliteskin to form a perfectly smooth surface, sharp leading and trailing edges

w1nd6urfa

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The result

w1nd6urfa

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Inner side

w1nd6urfa

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Leading edge

peruse12

Hi w1nd6urfa , I am in the process of building a Dennis Bryant Storch and thought you may be interested in his slat shape .

Gary

w1nd6urfa

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Hi Gary
Thanks for the pics, any information is appreciated.

Looking closely at the Bryant slat I notice the venturi (slot gap) is more parallel to the wing, compared to the Severin and Svenson plans that have the 3:1 entry-exit ratio.

How is your build going? Have you finished the wings?

w1nd6urfa

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After the slats I made some improvements to the wing and control surface trailing edges by adding a strip of Fliteskin

Lifted the covering and planed off 0.5 mm of balsa

w1nd6urfa

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0.010" Fliteskin strip