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Old Jan 24, 2010, 11:07 AM
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I hope there is still time left before the "old F---" category is reached. I flew the Ringmasters both profile and full body versions plus many others- some with bladder tanks. Ambroid would grab,shrink and distort but Testors seemed better. I now love Elmers aliphatic resin water based which is very light weight. My favorite U control model was the Nobler but RC prevented me from building it.

Steve, Your version of the Goose looks good except for a couple of thoughts. First let me tell everyone that my thoughts are sometimes quickly given without research and are always subject to change. My hope is that every one's ideas can be taken as constructive efforts without causing friction or hurt feelings. Now back to Steve's Goose: Since the wing's LE has brought more area forward with less sweep back, the CG will move forward with it. It also brings the vertical fins forward which reduces their lever arm. They also "look" a bit small to me. If it were my model, a D shaped piece would be glued onto the rear of the fins like a rudder to correct the situation. My second thought is really a matter of preference: If the model weighs one pound, it should have 80 to 100 watts from the battery considering the great power to weight ratios we now have. The 500 mah battery with 3 cells would have to deliver 7.2 amps for 80 watts. With 4 cells it would use 5.4 amps which would be reasonable to me. I can see, Steve, why you build so light as I also do. Whatever, you seem to get great performance from that small battery. Fifteen years ago, I was operating on 50 or less watts per pound and concentrating on scale like performance with large wing spans. My largest model had a 63" span, weighed 2 pounds and was powered with a geared speed 400 driving a 10-8 prop. I have since gone to 274 watts per pound on one model. I saw a lipo battery recently claiming a 45C output rating.
Charles
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Old Jan 24, 2010, 04:39 PM
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I liked the Nobler too but I was more into combat than stunt. The Ringmaster got me started. The Flight Streak honed my skills and the Voodoo and Winder got me into fighting shape. there were a lot of others and some scratch built planes too.

Charles, You said:
Quote:
"First let me tell everyone that my thoughts are sometimes quickly given without research and are always subject to change. My hope is that every one's ideas can be taken as constructive efforts without causing friction or hurt feelings."
Any comments or suggestions you make are welcome. The help that you and others give on this thread is the reason it's so successful.

RE: The Gosling...
The fins are pinned on the Gosling at the moment and I could use external elevons and sweep the fins back and make them larger. To move the GC aft a bit. I want' to run some numbers through the Canard Calculator first.
Here is the latest Specs. Looks OK. Will try to hit around 5.5 oz/sq ft.

I, personally, appreciate the way you and others here share their experience and, while I can only speak for myself, I'm also sure that others feel the same as I do. I am becoming addicted to canards as you can probably tell and without this thread the learning curve would be a lot steeper.

Thanks to all of you,

I have good luck and less trouble with the BW motors and the smaller batteries. I'm pulling 10A and less on the 500/600mah 2C 3s cells I use. When I go to the 1300mah batts and use the BP21 or the 2822 I can get from 150 to just over 200 watts. the problem has been the batteries tend to puff on me and I've lost quite a few. I stopped using the Litemax. Rhino's seem to be a bit better but are heavier. The smaller planes seem to fly as well as the bigger ones for me and I have a field that has about 80m x 20m of decent landing space surrounded with trees. The parts are cheaper, the building time is less and I use less materials in the smaller planes. Also in the back of the microvan there isn't room for a wingspan bigger than 48".

I don't know why I like the full flying canards the best and a simple front-elevator/aileron ship should perform OK. I'll try that one of these days too.


Steve.
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Old Jan 24, 2010, 07:36 PM
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Canard CG Talk

Steve, You are kind. Thanks! It's a matter of give and take here and I must try to remember that the pictures in my mind about your model design are very often wrong and things are said which turn out wrong. For instance, you have a parallel battery which is something I have never owned. It doubles the amperage capability and quickly negated my concern.

My purpose here is to convey to all canard lovers how I see the CG purpose and how it's position is changed with wing areas.

The front, "canard" wing" has the job of controlling the lift of the main wing and must keep it from stalling. It controls the main wing's lift by rising off the ground first which adds angle of attack to the main wing which gives it permission to lift it's load. In order to protect the main wing from stalling, it must stall first. We must do two things to force the canard to stall first: 1, we raise the incidence of the canard by several degrees so that before the main wing can stall at 15 degrees AOA, the canard has already stalled several degrees before. 2: we must put the CG well forward of the main wing so that the central load is increased on the canard while the main wing is relieved. If the CG were to be placed in the position of the conventional plane at about 1/4 back of the main wing's LE, that wing would be in full control of itself and the model would be unstable with a tiny canard area. Our models do not need the small Reynolds number up front at slow speeds.

To move the CG forward, the canard area must be increased to carry the load. If the area of the main wing is increased, the CG or load will be moved rearward to balance the load. Please think of the converse of this. A long nose adds to stability just as the long rear fuselage adds to the stable control of the conventional plane.

The short nosed canard needs elevons at the rear but the long nosed one does well with ailerons.

I believe in these thoughts but if you disagree, we can discuss some alterations.
Charles
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Old Jan 25, 2010, 12:54 PM
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The stall speed is only affected by the wing loading not the AOA. The higher incidence on the canard is a necessity of the higher wing loading.
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Old Jan 25, 2010, 04:42 PM
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Originally Posted by canard addict View Post
Steve, You are kind. Thanks! It's a matter of give and take here and I must try to remember that the pictures in my mind about your model design are very often wrong and things are said which turn out wrong. For instance, you have a parallel battery which is something I have never owned. It doubles the amperage capability and quickly negated my concern.

My purpose here is to convey to all canard lovers how I see the CG purpose and how it's position is changed with wing areas.

The front, "canard" wing" has the job of controlling the lift of the main wing and must keep it from stalling. It controls the main wing's lift by rising off the ground first which adds angle of attack to the main wing which gives it permission to lift it's load. In order to protect the main wing from stalling, it must stall first. We must do two things to force the canard to stall first: 1, we raise the incidence of the canard by several degrees so that before the main wing can stall at 15 degrees AOA, the canard has already stalled several degrees before. 2: we must put the CG well forward of the main wing so that the central load is increased on the canard while the main wing is relieved. If the CG were to be placed in the position of the conventional plane at about 1/4 back of the main wing's LE, that wing would be in full control of itself and the model would be unstable with a tiny canard area. Our models do not need the small Reynolds number up front at slow speeds.

To move the CG forward, the canard area must be increased to carry the load. If the area of the main wing is increased, the CG or load will be moved rearward to balance the load. Please think of the converse of this. A long nose adds to stability just as the long rear fuselage adds to the stable control of the conventional plane.

The short nosed canard needs elevons at the rear but the long nosed one does well with ailerons.

I believe in these thoughts but if you disagree, we can discuss some alterations.
Charles
Your points make sense to me, Charles... You are saying the short fuselaged canard benefits from elevon and canard mix while the longer fusleaged canard doesn't need it. The size of the front wing and the leverage gained from the extra length is enough for good pitch control. A more forward CG and a bit of positive incidence load the canard more than the main wing and insure the canard will stall first and keep the plane more flyable.

In your experience, what do you see as "good" numbers for the average canard? I'm thinking in terms of a general layout. Ratio of main wing to canard areas, Canard incidence angle relative to main wing, and distance between the two wings? Aspect ratios of the wings for good average flying that will allow for some aerobatics but retain good stability etc. I know there is no magic formula for this but there must be a general range that seems to work well in most cases.
What do you think?

I would like to eventually get into the 3D canards but for now I have to be content with something a little more sedate so my skill level can catch up. Here's a DeltaStorm X-41 that I like and would like to design and build something with similar performance some day.
X-41 Deltastorm (2 min 30 sec)


This plane is what gave me the idea for the elevon/canard mix I have been using on my experimental planes.

Steve.
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Old Jan 25, 2010, 04:49 PM
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TechDad even mentioned once the canard on the Deltastorm is not for normal canard work, but for extreme maneuvering.
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Old Jan 25, 2010, 05:09 PM
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Originally Posted by DreamArcher View Post
The stall speed is only affected by the wing loading not the AOA. The higher incidence on the canard is a necessity of the higher wing loading.
Interesting point...
There is angle of attack relative to the ground and angle of attack relative to the air-stream. As long as the wings are not stalled the plane is flying on the wing/wings, even when going vertical.

Seems like higher incidence also means higher drag. This is one reason I like a full-flying canard. You vary the incidence of the whole wing, which is both good and bad. It allows for minimum drag but will more easily allow the main wing to stall before the canard if not handled well.

Most conventional flying is done with the wing/wings bearing the weight. 3D flight is done with the wing/wings stalled and the thrust bearing the weight.

I want my Canards capable of both!

Steve.


Edit:
Dream Archer,
We cross-posted.
I have problems thinking of a small full-flying canard as a weight bearing surface. I think of it in terms of "Pitch Control"...
The, usually larger, fixed Canard with elevators is more of a wing to my way of thinking. I think this may be one reason Charles and I sometimes seem to disagree on points but the front wing is both a weight bearing surface and a control surface, as proven by the fact that adding even the smallest canard will effect the CG position.
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Old Jan 25, 2010, 05:14 PM
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That's a good point on the higher drag.
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Old Jan 25, 2010, 06:21 PM
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DreamArcher, Mike
Quote:
The stall speed is only affected by the wing loading not the AOA. The higher incidence on the canard is a necessity of the higher wing loading.

Mike, I tried but cannot agree with your quote. If you will look at a plot of alpha, which I see as AOA of the airfoil in a wind tunnel, vs coefficient of lift, it generally shows that stall occurs at alpha 9 to 14 plus or minus. The CL is 1 to 1.3 on the charts in Lennon's book. My belief is that if the canard is mounted at 14 degrees incidence or runway AOA, the canard will only mush and develop no lift. Lets say that my canard has 4 degrees canard incidence and zero degrees wing incidence. If I do a slow fly with nose up and cannot gain altitude, the model will be moving forward with the wings experiencing wind tunnel type AOA. When the thrust line reaches 10 degrees, the canard stalls at 14 degrees while the wing is flying at 10 degrees. This is what I believe happens when I hold full UP elevator and watch the oscillations at low power.


Cybernaught Steve
Quote:
Your points make sense to me, Charles... You are saying the short fuselaged canard benefits from elevon and canard mix while the longer fusleaged canard doesn't need it. The size of the front wing and the leverage gained from the extra length is enough for good pitch control. A more forward CG and a bit of positive incidence load the canard more than the main wing and insure the canard will stall first and keep the plane more flyable.
Sounds right to me



Steve
Quote:
In your experience, what do you see as "good" numbers for the average canard? I'm thinking in terms of a general layout. Ratio of main wing to canard areas, Canard incidence angle relative to main wing, and distance between the two wings? Aspect ratios of the wings for good average flying that will allow for some aerobatics but retain good stability etc. I know there is no magic formula for this but there must be a general range that seems to work well in most cases.
What do you think?

Regarding area ratios, I use canard area divided by wing area equals 30% at my moderate flying speeds.
The canard incidence is 3.5 degrees greater than the wing incidence. I measure the difference between the flat bottoms of the wings and usually put the main wing at zero or minus one.

The distance between Mean aerodynamic chord 25% balance points should be 2 to 3 times the main wing's MAC. The Goose has a MAC of 8.25. Three times 8.25 is 24.75. Since the wings are similar, I used 25" between LE's.

Aspect ratio is the wing's length divided by it's chord. A high aspect ratio will stall faster which is why, I believe, Rutan used a high aspect constant chord canard wing on the Long EZ. I tried that on my original Goose style and it would not raise the nose from the ground before the main wing lifted. I added 10 sq. inches of chord area to the canard and dropped the main wing's LE by one degree to get canard control.
Charles
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Old Jan 25, 2010, 10:59 PM
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Originally Posted by Cybernaught View Post
Interesting point...
There is angle of attack relative to the ground and angle of attack relative to the air-stream. As long as the wings are not stalled the plane is flying on the wing/wings, even when going vertical.
I'm not sure what "flying on the wing" means here. If the airplane is on a vertical line, the wings cannot contribute to holding the airplane up. In fact, to hold a straight vertical line, the airplane must be in ballistic flight, with zero lift. Only thrust and momentum are making the airplane go up, it is not different from a wingless rocket ascending vertically.

Quote:
Originally Posted by Cybernaught View Post
Seems like higher incidence also means higher drag. This is one reason I like a full-flying canard. You vary the incidence of the whole wing, which is both good and bad. It allows for minimum drag but will more easily allow the main wing to stall before the canard if not handled well.
No, that's not minimum drag. It is almost always more drag to get to a given lift coefficient by increasing angle of attack of a flat surface than by increasing camber (e.g. deflecting a trailing edge surface). I think the main motivator for an all-flying canard is that, if you're interested in achieving very high pitch rates, you can eliminate some of the pitch damping that would be created by a fixed canard.
RE
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Old Jan 26, 2010, 01:54 AM
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Okay, good stuff. Here's a question about canards and reynold numbers.

Charles says:
Quote:
Regarding area ratios, I use canard area divided by wing area equals 30% at my moderate flying speeds.
Quite right for a model, but if you're trying to scale a full size plane, you often end up with as little as 12 -15% and, with the typical model sizes of 3ft - 5ft ws, the scale canard chord can be as little as 3". You do usually get a pretty reasonable long nose, ie moment for the pitch control.

How small can we go? I've got down to 20% and 4" chord without needing any elevon mixing. I built the stabiliser : control surface ratio 60 : 40. Seems to work. By using a swept canard, I believe I'm getting more chord in terms of the air flowing over the surface, even with a smaller perpendicular width to the canard wing. Am I right?

Nick
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Old Jan 26, 2010, 03:26 AM
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I'm not sure what "flying on the wing" means here. If the airplane is on a vertical line, the wings cannot contribute to holding the airplane up. In fact, to hold a straight vertical line, the airplane must be in ballistic flight, with zero lift. Only thrust and momentum are making the airplane go up, it is not different from a wingless rocket ascending vertically.
What you say is correct and indicates that my explanation did not express what I wanted to convey.
Please see picture to clarify.

Also, Technically, I can't agree with your last statement either but I know what you mean and I get your point. A wingless flying object and a winged flying object have to react differently when subject to the same forces and conditions due to differences in shape etc, regardless of direction. I know I'm being "nit-picky" here.
Sorry!


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Originally Posted by Edmonds View Post
No, that's not minimum drag. It is almost always more drag to get to a given lift coefficient by increasing angle of attack of a flat surface than by increasing camber (e.g. deflecting a trailing edge surface). I think the main motivator for an all-flying canard is that, if you're interested in achieving very high pitch rates, you can eliminate some of the pitch damping that would be created by a fixed canard.
RE
Good point! I see canards more as directional surfaces than as weight bearing surfaces. My approach to canards is based on a non-technical view of high alpha parkjet type planes not easy flying, more sedate floaters. I don't know why I'm so fixed on the full flying canard. Maybe because I'm a bit enamored with planes like the J-10 and Gripen...


Charles,
Thanks for the insights on canard/main-wing area-ratios and separation distances. I'll have to cut and paste that into a text file so I have it for handy reference.

I also have an idea for a fuselage that will allow the easy swapping of noses and wings to make experimenting easier.

BTW: How aerobatic is the GG???

Steve.

PS.
Gale force winds and rain here. Hope all of you are getting in some flying time.
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Old Jan 26, 2010, 06:43 AM
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...
The canard incidence is 3.5 degrees greater than the wing incidence. I measure the difference between the flat bottoms of the wings and usually put the main wing at zero or minus one.
...
There is a fixed definition for these angles:
http://en.wikipedia.org/wiki/Chord_(aircraft)
http://en.wikipedia.org/wiki/Airfoil

To get the "real" incidence difference you need to measure the difference between the chords(!) of the canard and the wing. That is the standard definition nowadays.
For example, if you measure a high cambered airfoil for the canard and a more symmetrical Airfoil for the main wing with your method, that can make a big difference to the "real" incidence difference.
If you use a computer program (they were mentioned somewhere and usually use the standard definitions and rules) to get the incidence difference (and CoG for example) and use the method from your description above for measuring them, you might get problems during flight, because you don't fly with the incidence difference from the program.

This is just meant as a friendly hint, that there could be problems because there are other definitions than the standard ones used.


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...
A high aspect ratio will stall faster.....
...
Why?

Uli
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Old Jan 26, 2010, 10:47 AM
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WOW! Lots of input here for thought. All the responses to questions are gratefully appreciated.

Geronimo Uli
Quote:

Quote:
Originally Posted by canard addict
...
A high aspect ratio will stall faster..... WHY?

The Reynolds number, which IMO, Seems to be a factor of lift in air is directly proportion to speed and chord of the wing. Tests show that high aspect ratios [lower chords] reduce the stalling angle and the Reynolds number especially at lower speeds. In models, which usually fly at slow speeds, it has been said to keep chords to no less than 5 inches. This is why the wing loading must be drastically reduced in our micro models. I apply these thoughts to my sedan sized models of 3 to 5 ft. spans.
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Old Jan 26, 2010, 11:31 AM
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My belief is that if the canard is mounted at 14 degrees incidence or runway AOA, the canard will only mush and develop no lift.
Yes there is a limit to the effectiveness of too much AOA and the lift goes down. But will it be absolutely zero lift. You can put your palm out the car window at 30 deg and see the result.

I think you have a great mind for understanding these things so I'm not going to suggest you're wrong. I'd just like to add something, look at how they work at different speeds. While something might be true at low speed it could be completely false at mid or higher speeds.

On the 2 subjects of AOA (or incidence) and wing loading. It's not that AOA does A, and wing loading does B. They're intermixed, they affect each other, and it's a moving target.
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