patternman

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I jsut added Side Force Generators on my trusty Sig Fazer, and they make a world of difference. Added 133 sq. in. in side area. Tracks much better, less speed needed for knife edge, and makes rudder authority about twice as effective.
Ever try to sail a sailboat without the centerboard? Even if you have a good tiller, it will not steer. It needs something to pivot on. The SFG gives the anchor to pivoit with. Post is on profile and funfly planes/Fazer with SFG
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rmh

They are great little aids
to clear up a point - they are not a pivot point
Your original design has a huge lateral area--aft of the center of geavity and of course the center of pressure
So adding the SFG's really re distributed the lateral area -moving the effective area forward
Also -and quite importantly, the plates change the air flow on the wings by essentially trapping air that is sliding toward the tips
Maybe one of the guys who likes formulas will chip in - but essentially that is what is going on
nice job . Makes the hobby interesting when you can try something and actually see how it works

ArmedZagi

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I agree completly...mine are 112in^2. I added them only 2 weeks ago. They make a world of difference. Pics
[link=http://image.rcuniverse.com/forum/upfiles/178084/Sn42409.jpg]Pic 1[/link]
[link=http://image.rcuniverse.com/forum/upfiles/178084/Ge95874.jpg]Pic 2[/link]

Thread [link=http://www.rcuniverse.com/forum/m_4455276/tm.htm]Winglets on Extra300[/link]

Edit: Just wondering, but does all lateral area foward of the CoG work basicly like the counter-ballence on a rudder or elevator? Maybe a bad comparison..but just curious...

rmh

no -- the counterbalance reduces forces need to swing the rudder against the airstream
The really act like making the fuselage much deeper and taller - forward -over the wing -- they also control the spanwise airflow
the current crop of 3D thingy models (lots of fun) have the area all at the back -to make em easier to hover .

redcommander

side force generators are de-stabilizing directionally. The neat thing is that, with SF generators, you can destabilize the aircraft directionally without affecting the longitudinal stability. For example, you could increase rudder sensitivity, or make a plane knife edge better by sending the cg aft, but this would simultaniously result in poor longitudinal stability.

I am interested in why people are seeing better tracking. I find this hard to believe. A sideforce (crosswind) should have a tendency to blow the entire airplane off-track, instead of yawing the airplane and allowing it to crab, thus staying on track.

rmh

well - they little buggers work quite well and -- you can't blow the plane sideways -unless it is setting on the ground
also has no effect on lateral drift - (relative to ground path)
crabbing the plane --will still allow it to drift with the wind
setting the crab angle is actually easier as the increase in forward area negates the (usually)excessive area aft the CP
But you are right on the tracking - the plane is destabilized in yaw.

redcommander

Dick, I'm having trouble following you. The airplane can be blown sideways. It just takes wind.
When crabbing, you are aiming a component of force (propulsion system) to oppose the wind force. How would you do this on a neutrally stable airplane?? first you would have to input rudder to set the crab angle. A directionally stable airplane will set the crab angle for you.

How do you determine "excesive" area aft of the c.p. ? What does this mean? how is it easier?...are you refering to the a.c. comprised of the wing and h. tail, or are you refering to the ac comprised of the V.tail and the fuselage (pimary directional components)?

redcommander

one more thing, I believe you that those little buggers work well. my question is...what do they work well at accomplishing? 1, destabilizing the airplane directionally 2, decreasing the sideforce loading (kinda like wings decrease wing loading). This would allow knife edge flight at lower power setting or lower Beta (angle of sideslip--AoA for knife edge)

What I'm asking about is tracking? Do they improve tracking? and how? Maybe my first question should be...what is tracking (ground track, appearance of no yaw disturbances)?

mesae

A crab angle is the difference between an airplane's heading and it's ground track. Normally, crab angles are set with normals turns until the desired ground track is acheived. A crab is NOT holding rudder continuously against a crosswind.

An airplane flying with a steady crosswind component will have a ground track that is downwind of it's heading. A steady crosswind does not cause the airplane to turn, so no rudder or aileron pressure is required against a wind. If the airplane's true airspeed, and the windspeed are constant, the airplane's resultant path over the ground will be straight (or would be if the world was flat - actually it's a geodesic, but we'll ignore that).

rmh

The best thing you could do to answer and permanently imprint the effects of side force generators, would be to buy one of th funny little electric biplanes George Hicks designed a couple of years ago .the TENSOR 4D
These had huge innerplane struts and a wildly exaggerated fuselage section between the wings
In flying these - it becomes instantly apparant that sidewise tilting of the wings changes nothing-- banking does not cause a turn
Effectively the plane is a crucifix design.
same lift in knife edge as in level flight
further - the fore/aft lateral area is well balanced - - the plane does knife edge flight by simply rolling to knife
IF the cg is too far forward -it dives - too far aft it climbs -- all, in knife edge.
a picture is worth a million words in this instance .
much of the accepted theory of conventional aircraft seems to go goes right out the window after flying this type design.
The addition of the force generators to otherwise connon designs, simply makes a hybrid , of the conventional and a unconventional approach
the true rules of flying don't change -but your understanding of them will likely become so

Baron Johnson

I was under the impression that the very purpose of these devices was to increase the side force capability without affecting the directional stability. Hence, they are placed essentially on the CG.

BMatthews

I'm surprised that no one jumped on you for this already.

The plane is NOT blown sideways since it's already drifting with the wind such that it only sees a direct on headwind at all times. The only times it'll see any side force is when the rudder is moved or for a moment when it moves into a volume of air where the velocity or direction or both is dffernet from the last volume (turbulence don'cha know). At that point it'll see a small side wind until the model is once again in direct headwind equilibrium.

IE: a dandelion seed drifing with the wind sees NO apparent wind force other than from below since it is always falling even if it IS a very slow fall.

mesae

Three or so posts up from yours.

rmh

post 5--
you guys who have not flown one of the Tensors (Baron????) just can't appreciate how they work-
George Hicks did a bang up job on this toy!
He did not ruin the directional stability just changed the overall program

Baron Johnson

I have several Tensors and do appreciate how they work. Like indicated in my earlier post, I believe side force generators (by definition) are not intended to affect the directional stability one way or the other. As you mentioned earlier, though, they make it easier to obtain a directionally unstable aircraft by moving the CG a little too far aft (which is not as far aft as one would be accustomed to with typical aircraft).

redcommander

ok, to clear up...the term destabilizing does not imply "ruin" the stability, but just make it less stable. I don't think anyone here argues that SF generators do this. Less stable is often good, as in 3D airplanes for long and dir stability. I am also not stating that SF generators make the airplane UNSTABLE. This term would imply that a side force increases beta (angle of sideslip). This would be bad !! since this increase in beta would result in higher sideforces, which would increase beta further, until the airplane is in a spin.

uhh, yes, I do know, its called a wind perturbation. And and this very term is the basis for stability analysis. If everything was always in equilibrium, we would have no need for stability now would we? more specifically, directional stability is a measure of the airplanes ability reduce its angle-of-sideslip WITHOUT CONTROL INPUTS. Every airplane that flies sees perturbations in every axis every second, and its stability is DEFINED by how it responds to these perturbations.

BTW, if a dandelion sees no forces, how did it get moving??? F=ma...it sees forces every time it accelerates and decelerates!

no, They would have to be placed at the knife edge equivelant to the aerodynamic center (predominately made up of fuselage and Vtail) for them to have no effect on dir stability. for ALL dirctionally stable airplanes (this only excludes exotics like B-2) this is considerably aft of the cg.


no it doesn't! and these are not a new concept, just new to the hobby world.

again, we aren't talking steady state here...or else we wouldn't be talking stability. a side perturbation (or side gust) can turn a directionally stable airplane (in the direction to reduce beta), while it won't turn a neutrally stable airplane, and it will turn a directionally unstable airplane the wrong way (increase beta)

mesae

The wording of the post I responded to seemed to imply not the case of a perturbation, but a steady state, since you were discussing crab angles, with are useful over relatively long time periods, not during perturbations.

redcommander

Yes, I was invisioning, for example, flying into a headwind, then making a turn such that now you are in a crosswind and your airplane now has some crab angle (since you aren't holding any rudder). This would not happen on a neutrally stable (directionally) airplane. If that crosswind then dissappeared, a stable airplane will then return to zero crab (again witout inouts from pilot)

another way to think of it is by applying a rudder singlet. an unstable airplane will spin as a result of a rudder singlet, while a stable vehicle will recover and resume with the pointy end forward. These cases are not steady state.

mesae

Respectfully, I'm not sure I follow you. Crab angles have nothing to do with stability. Are you sure you don't mean sideslip, or skid, instead of crab? A crab is only relevant with respect to an airplane's path over the ground - something the airplane has no "knowledge" of, unless in contact with it.

Also, I had to look up singlet, and I have not found a definition that seems to fit the context above. One defition is tank top, or sleeveless undershirt, and the other has to do with atomic physics and particle spin. There is some mention of particulate angular velocity, but I wasn't smart enough to apply it in a straighforward way to a rudder. Care to elucidate? I suppose if I tossed up a tank-top just as the airplane was flying overhead, and it caught on the rudder, it might enter a spin. (showing my ignorance). I'm sure I just missed a general enough definition to be able to understand it in the way you mentioned it.

rmh

Oh oh
the plane does not know anything about headwind or cross wind
it senses neither .
If you try to change over the ground path or relative speed to a point on the ground-then you deal with the wind
I read and read your last post - it seemsyou believe the wind (a steady wind) affects the angle of the crarft -as it flies .
It does not.
Only YOU trieng to orient to a ground point - will affect needed positions or recovery to a previousposition
A neutral plane simply keeps on going where it is pointed
a as- stable plane -requires constant inputs
a self stabilizing design - of course - given time- will correct to a level flight attitude-all on it's own hook- if it doesn't smack something first.
I have built all three types and they all have good reasons for existing

mesae

Errr, you weren't replying to me, were you? Cuz I'm right with you on this. Your post says "in reply to mesae" but you didn't quote anyone.

8178

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Dick,

I’m a big fan of your Tiporare design that has the tallest part of the fuselage along the wing and in front of the CG and I love they way it flies. http://www.rcuniverse.com/forum/m_2827386/tm.htm I think it is one of the most attractive looking pattern aircraft ever designed. Do you have any insight on why the current fad in pattern aircraft design has the tallest part of the fuselage further aft.

rmh

No -was to red -I hope I read him correctly -

rmh

Current stuff - -as far as I can see - the fuselage "look" is just that- a look
some of em are nice looking and some are not
It's like trying to assess new cars- some of the new hot sellers are as ugly as a sack full of festered butts.
The sales guys ran out of practical improvements so now it's all just change for change sake -
just like skirt hemlines --
The chopped top look from Chrysler -looks like a bad Barris Kustom copy from 1954
The large front ends on new pattern models is supposed to cause slower downlines
anyone who really accepts that - has no idea what is going on.
but they come up with an off the wall idea and present it as as fact.

redcommander

no, the plane does know something about headwind and crosswind...it reacts to changes in these parameters (i though I already said this) Again, airplane s&c is NOT all steady state although the world would be simpler if it were.

ok, when doing system identification of aircraft (not to be confused with parameter identification), one of the simplest inputs is a singlet. The pilot will input a control deflection and then release, the dynamics will then be recorded (inertial and control input will be logged). This is a simple way to MEASURE (not calculate or estimate) damping characteristics for example. Doublets are also used, commonly to measure lateral stability. These doublets and siglets are also used to measure control power derivatives. These measurements can be taken throughout the input frequency range until the response attenuates at high frequencies.


yeah, I understand crab. Tastes good too. We were talking about TRACKING, and this is how I am relating stability to tracking. I'll say it again, crabbing allows for the airplane to compensate for drift by adding a propulsion component to counter the wind. a neutrally stable airplane will have to point itself (with a control input) in the direction of the wind to maintain a ground track, while a stable vehicle will orient itself such that beta damps to zero without control input.

wrong. any preturbation will change its direction, and it will not return (or even damp) without control input. A stable airplane has the ability to stabilize these preturbations...hence the name stability.