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Old 07-19-2013, 03:55 PM   #1
liposucker
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Default Fiesler Storch flight characteristic..would be grateful for some advice/suggestions

Hi all

Today I gave my Fiesler Storch its maiden flight after months of enjoyable work. It is a built from a Dennis Bryant plan, originally for I.C. but I converted it to electric. The model is 70" span. The wing loading is 24 oz/sqft and the wing cube loading is 11.

If I can give you some information about the first flight, hopefully the more experienced builders/fliers can advise on my thoughts.... No flaps for first flight.

The take off was faultless....full throttle at the end of the take off run, a little up elevator and away she went. Aileron, elevator and rudder response were excellent.

The trimming out circuit...throttle reduced to about half. There was a noticeable reduction in response from the control surfaces...not dire but just not as crisp. Quite a bit of up elevator trim was needed for straight and level.

The landing approach...steady reduction in throttle after the last corner becoming quarter throttle as the ground approached. Ready for the flare. FULL up elevator was needed, over half an inch, only just enough. I was expecting just the usual small touch of up...but she was down safely.

Basically, the lower the speed, the less effective are the surfaces.

Also the level flight characteristics in the mid range throttle settings. I was really expecting her to float around on medium or slightly less throttle, but there is a definite nose down tendency.

So I have thought of 3 possibilities...

C of G. the plan shows a range of between 53mm to 60mm from the leading edge. I went for 53mm and just slightly nose heavy. Would a slightly further forward position...say 45mm improve low speed sensitivity?
Wing Incidence. There is no actual number of degrees given on the plan, but it looks like about 2 degrees positive. I was wondering if an extra degree of positive might improve the flight attitude in both medium and low throttle settings?
Motor Thrust. The plan says no side or down thrust. Would a degree of up thrust on the motor improve medium and low speed flight attitudes.

Sorry the thread is so long..and thanks in advance for taking a look
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Old 07-19-2013, 04:10 PM   #2
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Check this link, it may have related info:

http://www.wattflyer.com/forums/showthread.php?t=62627

AMA 928214
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Old 07-19-2013, 04:26 PM   #3
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Originally Posted by pizzano View Post
Check this link, it may have related info:

http://www.wattflyer.com/forums/showthread.php?t=62627

Thanks for the link. That is the plane, the Dennis Bryant one.

Mine came out to 7 lbs ready to fly, and at present she won't cruise around a quarter throttle. Need half throttle and some up elevator.
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Old 07-19-2013, 05:16 PM   #4
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If it needs full up elevator to flare there must be a question that the CofG is pretty far forward.
However it is very likely that when the flaps are deployed there will be a definite nose up tendency so perhaps the CofG position on the plan is a bit forward to allow for this.

I would try the flaps before changing anything.
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Old 07-19-2013, 05:21 PM   #5
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I'm sure there are several options you can try before modifying the wing incidence or thrust angle of the motor........I don't fly craft that large, but the the performance principals still apply.

A little nose heavy is normally good for better stability in wind and slower flight control.

Increasing the surface control (clevis and servo horn) deflection on the elevator may balance your trim and provide more snap to it's response.

1/2 to 3/4 throttle power for decent slow fly seems a bit much....but that could be due to the planes designed characteristics..........she's pretty heavy, (slow) glides are different for all models due to wing and tail sizes, pitch, dihedral, ect.....

There are many guys here that fly large planes that may chime in on this......stay patient. I'm sure a few helfpful respones are on the way!

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Old 07-19-2013, 05:39 PM   #6
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Originally Posted by quorneng View Post
If it needs full up elevator to flare there must be a question that the CofG is pretty far forward.
However it is very likely that when the flaps are deployed there will be a definite nose up tendency so perhaps the CofG position on the plan is a bit forward to allow for this.

I would try the flaps before changing anything.
Hi quorneng

Thanks for the reply.

I also expect a nose up tendency on deployment of flaps...not tried it them yet.

However, there is a designers note on the plan and I quote

"Application of full flap causes the model to assume a marked nose down attitude until re-trimmed. Only apply full flap when at a sufficient height to carry out trimming"

So the designer expects nose down which I though was a little odd.
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Old 07-19-2013, 07:37 PM   #7
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Sounds nose-heavy. Move the CG back slowly.

It is common for the CG recommendation to be nose heavy to give the best chance of a successful test flight. Once the plane is trimmed in roll and yaw, so you aren't fighting 3 axis of untrimmed flight at once you can start moving the CG to get best performance.

****

Flaps affect planes in different ways based on the airspeed, CG and the % chord of the flap surfaces.
If deployed at speed you could see "ballooning" with the plane potentially nosing up.
The drag of the flaps can cause the plane to pitch down due to sudden loss of airspeed.
You can get both of these results from the same airplane depending on deployment rate and airspeed when you deploy the flaps.
Use of computer radio "servo slow", programmable servos or a device to slow the servo response rate can help dealing with the effect of deploying flaps.

Note that sudden flap deployment at high speed can rip the flaps off of many aircraft. This is not as common with models as full scale. Full scale will have a notation of maximum speed for any given flap setting.
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Old 07-19-2013, 08:36 PM   #8
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Hi fhhuber

Thanks for the reply. I'm taking everything onboard.
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Old 07-19-2013, 08:50 PM   #9
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All the symptoms point to the model being very nose heavy. If it were mine I'd put the CG close to 60mm. Flap effects on trim can be trimmed out with an elevator mix
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Old 07-23-2013, 08:10 AM   #10
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Originally Posted by JetPlaneFlyer View Post
All the symptoms point to the model being very nose heavy. If it were mine I'd put the CG close to 60mm. Flap effects on trim can be trimmed out with an elevator mix
+1

I think I need a signature.
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Old 07-24-2013, 03:56 AM   #11
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This was and is a STOL design intended for a virtual float around the race track
except when it is butt high nose down on the step with the CG where specificed.

Landings will typically have to be forced touch down because of ground effect. I
would get used to a 20 degree flap position and not exceed that until you have
gotten bored with doing touch n goes... something this design will do easily.

Won't need to have more power once you work the CG location out.

Good luck!!

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Old 07-26-2013, 05:54 PM   #12
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The trim control on the full size Storch changes the angle of incidence on
the entire STABILIZER which is huge, something to think about.
Storch is on my "someday" list.
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Old 07-26-2013, 06:24 PM   #13
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Default Full Size Fi-156 VS Models

Originally Posted by 1geo1 View Post
The trim control on the full size Storch changes the angle of incidence on the entire
STABILIZER which is huge, something to think about. Storch is on my "someday" list.
Horz Stab trim aka incidence is not adjustable on any of the ARF, kits, or plansets I am aware of...I have
built two Svenson's and have a 1/4 scale planset I will have laser cut.

The reason for the 1:1 incidence change was to accommodate CG effect of onboard load.

The Fi-156 was capable of taking off within 15 feet, rising vertically to an altitude of 2k feet then descending
to the orinial point of take off. This was the intended purpose for sake of recon and direction of artillary.

Don't believe you will find an rc need, nor without a gyro be capable of doing this. Remember this was
performed in normal flight attitude, level.

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Old 07-26-2013, 06:41 PM   #14
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was just thinking that a little "up trim" on the entire Stab would be the same
as a lot on elevator and wanted to throw it out there.
How my mind remembered something I read in 1983 behooves me anyway...oops,
make that 93
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Old 07-26-2013, 07:00 PM   #15
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Default Effects Of Deflection

Originally Posted by 1geo1 View Post
was just thinking that a little "up trim" on the entire Stab would be the same
as a lot on elevator and wanted to throw it out there. How my mind remembered something I read in
1983 behooves me anyway...oops, make that 93
Did you mean to say raising or lowering the leading edge to adjust for changes in level flight.

In order for this to work as Dr. Fieseler intended you would have to place flaps at proper angle after
taking off to compensate for conditions as the aircraft rises. These will be adjusted constantly, as
will the elevator and tail plane incidence.

Lets see now...left hand and arm...right hand and arm...left leg and foot...right leg and foot....and

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Old 07-26-2013, 08:59 PM   #16
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Thank goodness for computer radios right ?
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Old 07-26-2013, 09:57 PM   #17
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Flite-Metal
"taking off within 15 feet, rising vertically to an altitude of 2k feet then descending to the original point of take off."

As a STOL aircraft the Storch was well ahead of anything the allies used but I think you are endowing it with characteristics it did not really have.

Its stalling speed was given as 32 mph so it would require a pretty substantial wind of at least that strength to achieve a true 'vertical' flight.
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Old 07-26-2013, 10:11 PM   #18
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Originally Posted by quorneng View Post
Flite-Metal
"taking off within 15 feet, rising vertically to an altitude of 2k feet then descending to the original point of take off."

As a STOL aircraft the Storch was well ahead of anything the allies used but I think you are endowing it with characteristics it did not really have.

Its stalling speed was given as 32 mph so it would require a pretty substantial wind of at least that strength to achieve a true 'vertical' flight.
They forgot to mention the circle around the traffic pattern...

The full scale Storch could take off on an extremely short distance and it could land and have very little roll-out.
The models of it can do the essentially vertical performance with a modest headwind.
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Old 07-26-2013, 10:18 PM   #19
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Originally Posted by quorneng View Post
Flite-Metal

"taking off within 15 feet, rising vertically to an altitude of 2k feet then descending to the original point of take off."

As a STOL aircraft the Storch was well ahead of anything the allies used but I think you are endowing
it with characteristics it did not really have. Its stalling speed was given as 32 mph so it would require
a pretty substantial wind of at least that strength to achieve a true 'vertical' flight.
The Fi-167 and the Fi-156 were flown in this manner. Hanna Reitsch flew the Fi-156 in this manner...
I believe at the '39 Olympics...

Dr. Fieseler flew his Fi-167 this way to demonstrate its bombing accuracy capability.

There is a huge power:weight differential between the two. The Fi-167 was designed to deliver torpedos.
Every model of the Fi-156 can take off within two~three feet with a very light breeze. Our normal Texas
5~6 mph constant is plenty to do it. My Svenson's were OS61 powered and had no problem doing it.

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Old 08-01-2013, 11:23 PM   #20
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If this where mine I'd forget the flaps for now and concentrate on getting the CG moved back until the plane flies comfortably!!
It is obviously nose heavy!! I'd move it back to 60mm now, and recheck its characteristics.
Don't be afraid to go even further if needed. You should have easy level flight at something around 1/2 throttle, touchdowns should be like waiting for something to happen, when its right the plane will not want to settle.
From there, use the ele/flap mix to control decents by trying it up way high.
Some require elev down with flaps, others require up. I have a Twin Otter that needs down elev at 1/2 flap, and lots of up with full flaps along with 35-40% power to tug it thru the air. flying barely
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Old 08-02-2013, 01:15 AM   #21
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Default CG Is A Precise Location...Not A Kinda Sorta Location

Liposucker...

Its interesting to read people having you move CG here there everywhere but exactly where it should be.
CG is easy to calculate. Especially on simple rectangle wing planform.

http://www.scaleaero.com/CG_Calculator.htm

Click the above link and enter your data to determine exactly where your CG is if you don't have the plans.
CG is usually shown on plans with a cross hairs with a circle darkened every other quadrant within it.

The CG location of ALL Fi-156's is exactly the same, regardless of size! I found the CG listing for the Black
Horse Fi-156. That location is 115mm back from the leading edge. This is way more forward than I recall
the CG being. This location is virtually at the rear of the leading edge slats.

The balance point is located 115mm back from the leading edge. This is the balance point at which your
model should balance for your first flights. Later, you may wish to experiment by shifting balance
up to 10mm
forward or back to change the flying characteristics. Moving the balance forward may
improve the smoothness
and arrow- like tracking, but it may then require more speed for take off and
make it more difficult to slow down
for landing. Moving the balance aft makes the model more agile
with a lighter and snappier ”feel”. In any case,
please start at the location werecommend.


With the wing attached to the fuselage, all parts of the model installed ( ready to fly), and empty fuel tanks, hold
the model at the marked balance point with the stabilizer level. Lift the model. If the tail drops when you lift, the
model is “tail heavy” and you must add weigh* to the nose. If the nose drops, it is “nose
heavy” and you must add
weight* to the tail to balance.
*If possible, first attempt to balance the model by changing the position of the receiver
battery and receiver.
If you are unable to obtain good balance by doing so, then it will be necessary to add weight
to the nose or
tail to achieve the proper balance point.

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Old 08-02-2013, 01:31 AM   #22
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Flite-Metal
"The CG location of ALL Fi-156's is exactly the same, regardless of size!"

Surely only true if they are all built with exactly the same aerodynamic geometry.
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Old 08-02-2013, 01:52 AM   #23
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Default Its Either A Scale Fi-156 Or Its Not

Quo,

The latitude given the equal chord aka non-tapered wing and long moment of the Storch pretty well
defines there will be no difference unless of course someone were to use a radically different airfoil,
etc. Get real, its either a scale Fi-156 or its not!

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Old 08-03-2013, 02:04 AM   #24
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Hmmm.
The decalage (longitudinal dihedral) can have a huge effect on the CofG position of an otherwise perfect scale plane.
After all the tailplane of the Storch had adjustable incidence specifically to allow for a wide CofG variation.
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Old 08-03-2013, 05:06 AM   #25
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Isn't the wing loading rather high for a STOL aircraft?I would have thought something in the 14-15 oz. range would have been better.The Storch was a very lightweight aircraft,which is what gave it the short field capability.If you've built it to the plan,I feel it should have been lighter.
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