Nitrovein

I´m new to this with flying, and have started to construct/build my first plane. It started with the end of my first ARF, sort of speak.

I have done someresearch andstudying to begin this endless task of knowingaerodynamic.
When I started to thinking of hove I wanted thehorizontaltail, I started to think about a airfoil shape instead of a "flat-balsa" tail.
That lead me to think about hove it would work if the theentire horizontal tail would be used like a "rear canard" (control surface).

Iguesssome one have tried this before, ore at least know hove it would work out..? Would I get "a hardlesson in gravitation"?

(Sorry for my badEnglish, hope u understand what I mean)

Villa

Hi Nitrovein
In the average (conventional configuration) model plane, the horizontal stabilizer is, in fact, a control surface, which pushes down. While many are flat, some do have an airfoil.

Nitrovein

Yes, I see your point. After reading through some of the treads hear I (luckily) saw that the main wing should have i slight up anglecompeered to the tail (think it´s calledlongitude dihedral).

But would it be over sensitive to elevator input if theentire horizontal tail would act as a elevator?
The way I have started to build this plane enables me to put (forexample) a aluminium-tube straight through the body with thelever on the inside.
So I can make it durable enough to both fix and control both sides,but will it becontrollable in the air with that?

I wasleaning towards NACA-0006as the airfoil to be used there, or maybe some-on has a better idea...

pimmnz

Many models do this, particularly soarers. Fast aerobatic models do, though only Matts Arrow comes immediately to mind. Keep the pivot forward of 25% MAC, gear the movement down to not much to start with, depending on the speed you expect to fly, of course. The fixed tail/elevator deal is much easier for beginners, and probably just as efficient, if not more so. But feel free to experiment.
Evan, WB #12.

BMatthews

Nitrovein, welcome to RCU!

The proper name for what you are describing is a "stabiliator" which is the combined names of stabilizer and elevator.  Or some just call them "all flying tails" to indicate that the whole surface moves.  It's not really right to call it a "canard" if it's on the rear.  The term "canard" refers to the forward control surface on a canard style of airplane.

Really other than on a sailplane where it has some slight drag advantages due to not having a hinge line and also because the airfoil is always oriented directly into the flight path other than the slight angle needed to lift up or down there's really no big advantage.  And on many models it makes building them more difficult to engineer and construct a truly slop free hinge so that the tail doesn't wobble.

On some models there's good reasons to make the tail with a proper airfoil shape.  But on simple sport models a flat plate actually works just fine.  Flat plates show up on many models and full size aircraft throughout the history of aviation.  The venerable J3 Cub uses a flat plate made from fabric covering a simple flat pattern of tubing bent and welded together.  And many, many other full size planes use this same easy to use method that produces a flat plate for the tail sections.  Unless your model will be used in some competition where the last bit of drag matters there is not that much to suggest that a flat plate is all that harmful to the flight of most models.

Nitrovein

Thank you all for the replies! Ireallyappreciate it!
I wasaware that the word canardwasn't right, butdidn't know the right word. Thank you for teaching me the right word.

I will do a simple flat stab instead, if there is no big advantage to an airfoil shape. The thought´s I had was that it might track a bit better, but I could try that out later and keep it simple for now.

The plane I´m building is something of an compromise. I do a lot of training in RealFlight-sim, and had a hard time to figure out what I liked the most.
So I started to fol around with different types of wings in Design-foil, and thentried them out in the Simulator as well.
I guess that it´s a combination of an aerobatic (like Extra 300) and a pattern. If it will work, I´m not so sure about, but failure will give me more learning thansuccess.

I will post some pics if it all works out.

Again, thank you for taking the time to help me out!

Franco2fly

It is difficult, but there are SUPER advantages to stabilator set ups


In this example the two halves are split.  Through some ingenious mixing, when the ailerons go up/down, the two stabilator halves mirror the movement.  The plane rolls like an arrow....  when up elevator is applied, the two ailerons droop down, and when down elevator is applied the two ailerons move upward.  This makes inside loops as well as outside loops extremely tight.

I used to fly this on a Nitro .09 but recently converted to electric.  Now if I can just get a break in the weather.


KKKKFL

Nitrovein

Thats cool! I like the idea that with an R/C-plane you don´t have to fit in it after it´s done, that opens up some new dimensions!

Instead of building astructure of balsa and thenapply film to it, I´m building my backwards... If it will work I don´t know, but I sure will try!
Toclarify what I mean. I have turn my wreck (with some modifications) in to a plug that I have molded a thin and light fiberglass shell from.
I have made some balsa cheats with fiberglass on both sides that I´m going to create an X from. The shape I take from the plug.
In the front I will do a box for fuel tank and engine, that I will fit with-in the X.
This way I have a strongstructure to attach servos, wing and stab to that goes through the entire plane, but without having tosacrifice weight where I don´t want it.
The vertical tail will have it´s core from the same cheat that goes through (almost) the entire plane.

If it works out I can post some pics later on, that willprobably make more sens then me trying to explain it...

Franco2fly

The picture I posted is the result of a contest between me and some Aero-engineers.

We all started with a fiberglass tube, and then cut identical wing and Stab cores. I elected to use a fiberglass rod in the main wing for the spar. Black "low-heat" covering over the main foam wing. The Stab cores were balsa sheeted and two aluminum tubes glued into the foam. Steel rods go through the fuselage andthe front steel rod goes into each of thtwo inverted "L's". The back steel rod is screwed into the associated side. Since each L is independant of the other, the associated Stab side can move independantly. This means that the Stabs can move with each aileron... ie on the left side, the aileron goes down, that side stab leading edge moves up.... Right side does just the opposite.(real life F-14 TomCats did this) A mechanical mixer is used up front to mix aileron/elevator. Further mixing in the receiver produces the Flap/elevator mix. Winding up with axial mix and elevator/aileron/flap output.

As for the contest, first flight demo, everybody else quit....


heheheh


KKKKFL

Nitrovein

Nice! You know you´ve done something right if the other throw in thetowel.

I know that most people use a foam core with balsa cheat and then fiberglass, and I do see that it would make it more easy.
But I like the way CollinChapman constructed things, with every partbeing apart of the wholestructural integrity.
Therefore I havedecided to try this out, if I willsucceed is yet unknown.

The reason I wasconsidering to use an airfoil instead of a "simple" flat profile was that Iconsidered it to make the plane track better. That lead me to start thinking aboutmaking the whole horizontal tail in one piece.
I guess that I don´t have to make thatdecision right now.
First I have to see if I can get all the other piecestogether...

Ireally appreciate all the help, thank you!

ron ward

that's the beuty of this hobbyand this site. a guy can build a complete "experiment" unkown asto whether it will work or not and not, ask a question and not hear, "you're crazy" or, " you're wasting your time". just informative answers and advice from people have been there also.
i am doing the same thing...building an experiment, that is, and getting tons of positive help from one small, simple question.

Rodney

A very large and serious problem in trying to make a flying tail for a model is the hinge. There is a great deal of stress at that point so you need a rather substantial type hinge or pivot that will not bind under high G loads yet not succumb to flutter under some flight conditions. Getting the hinge or pivot point at the best for/aft location is also a necessity. For slow and not so aerobatic models it can usually be done but at much greater effort and expense in weight and effort than the conventional elevator/stabilizer set up.

Nitrovein

Yes, I´ve found out that people that flytheir R/C-models are a bit morehelpfulthenthose who stay on the ground.
Maybe it´sbecause "gravity based problems" tends to make themistakesmoresevere... (For the record, I do both so I don´t know how I am...)


To make the hinge bothstable and light would be anissue.
My thoughts were to use a aluminium tube in about 6-8mmdiameter to hinge and connect them with. Then using 2 small ball-bearings with flange (or bushing) CA-glued to somebrackets made ofcarbon-fiber.
A rod couldbe attached to the tube on the inside of thefuselage to control them.

But, thats only themechanicalissue, then theaerodynamic has to be right to.I shouldprobably try it on a later model and keep this one simple.
I still have many other thing to figure out, so I am keptbusy as it is anyhow.
It sure is a great hobby if you want to make some new gray hair!

Franco2fly

Mine is a steel rod, at 25% back from the LE.  The second movable aft rod is about 3 inches back.  The bottom of the inverted "L" (picture an upside down L with two steel rods one is the pivot  and the back of the short leg is a screwed in steel rod.  This allows each side to be moved independent of the other.  My "L's" have an angle at the top for additional rigidness.

Here's a shot up the rear where you can see the control rods going forward down at the bottom.  Look closely and you can also see where the aft rod is threaded:



As you look across the stab and in the upper left the left aileron is visible.


KKKKFL

Nitrovein

Clever solution! That should make it quietstableas well. Thats a bit trickyfuselage to build in to, not much room to get all thepieces to movefreely.

The thought of getting them to moveindependentlydidn't even cross my mind. Hmm.... I might take a swing at this anyway, but I will see how the rest goes first.
I guess that it´s better to failmiserably and have tried it all, then to make something half intended and played it safe. Sooner or later I will crash it anyway!

I´m still waiting for my wings.
There is a guy that could help me cut foam in a CNC-cutter that he made, I had planed to make a mold from that. But haven´t herd from him in a month or so, should look in to that.
Otherwise it´s back to the drawing board again...

BMatthews

Franco, you need to wash the mud out more often...

Nitrovein, if this will be your first actual flying model be aware that the RC flying simulators are only good up to a point. They do not model a lot of the real stuff all that faithfully. And even the best that I've tried, while pretty good, still did not stall and spin like a any real model that I've flown. The simulators are just a little too "clean" in their modelling I guess.

The point of this is to lean more towards a model that is trainer like. You may be OK with flying a sport model in the simulator but trust me, you'd have your hands very full trying to fly the same model in real life and at the end of your day abag of pieces is more likely than not if you were to base your first actual model on what you have "mastered" in the sim

This isn't to suggest that sims are no good for anything. They are excellent for teaching a lot of aspects of RC flying. But they also lead one intoa false sense of flying ability by not being able to faithfully model ALL the things you'll find in the real world.

So for your first design and build I strongly suggest you keep it simple. There's nothing at all wrong with the Colin Chapman approach. A favroutie saying of mine that butchers English grammar is "light is right and lighter is righter". But equally important is KISS (Keep it Simple Stupid - that's the original version which for political and social correctness has been tempered down by switching the last S for other words... ) in a design.

By the way, flat doesn't mean that it has to be solid sheet. In smaller models you can make the tail out of sheet stock. But you can use less wood to build up a flat surface of twice the thickness that uses the leading and trailing edges as spars along with a few ribs and it will use half the volume of wood. So flat does not have to mean you can't make it built up for lightness. And sometimes even "flat" can end up with an easy to produce airfoil shape. It just depends on what you want to do with your model and how you want it to look.

Here's a quick sketch of some options that have been used in the past by a variety of designs.

Nitrovein

I have toremember KISS, thats funny!

I have crashed my first model, it´s that one I´m using for a template. Well, actually I have done some modifications to the fuselage, but it was a ground that I started from to make the plug.
I agree that the simulator is a bit more forgiving, even if I have tried to make it as hard as possible.
But as a friend of mine told me (he has experience of both R/C and 1:1 scale flying) I´maggressive when flying, so I don´t loose mynervesthat easy.
First time up I tried hovering, knife-edge, inverted, loops etc. (And I was all alone flying at home)
But... at another time I was flying at dusk, when I did a flatspin at 30 fot it tipped over and... Now I building a new one!
(However, in that point the simulator wasaccurate, it ends the same way there!)

I know that I can build a flat stab with ribs, thats the way the one thats... was built. (I got a good look at the anatomy of an airplane, thats for sure)
But I was thinking that maybe asomewhat shaped foil cold help the rear end track/stabilize a bit better. But I guess that it could mess it up more if done wrong, than a flat profile.
I haven´t tried any different foils for thatpurpose in the Design-Foil.

It was interesting to look at the drawing you posted, I will look in to that a bit more.

Thank you for all the help, I greatlyappreciate it!

BMatthews

The only "bad" thing about flat plate tails is that they MAY have somewhat of a reduction in reaction to small angles around neutral.  But on a hot aerobatic model this can actually be a good thing since it makes the model less nervous to small control inputs but it can still snap it's heart out with full throws.

As for tracking and stability that comes from the ratio of tail to wing area and the length of the tail.  It doesn't come from adding thickness to the tail surfaces.

You know.... there's only one way to find out this for sure.  Build a model where you can change the stabilizer and make flat plate, diamon and fully airfoiled options and try each of them.

Nitrovein

Thank you for that input, that will help me allot. That idea of making the tail removable was truly a good idea!
The vertical tail (with rudder) will be harder to make that way (if I stay with the ideas that I have right now) but the horizontal tail could be done that way.

I will look in to the ratio between tail and wing some more, see if I can find some useful ideas.
I have tried several ideas in the simulator, mostly gone to the extreme to see thedifferences, but thatdoesn't give me an exact size to go with.

The more I find out, the more I´m starting to like this. Great hobby!

BMatthews

Check the sticky threads at the top of this aerodynamics forum and also in the Scratch Building and 3D CAD forum.  There's some useful links in them to basic planform sizing guides to design a more or less generic style of regular model.  Also download a lot of the free plans and study them for planform ratios and structural building ideas. 

Plagarism in model design is a time honored method of learning.  So you may as well follow in the footsteps of those of us that have also copied a lot from those that came before us, who copied a lot from those that came before them....

All of this is to say that if you see a planform that suits you but it just needs some shape changes that keep the same area and moment arms or that change the wing tips to something  you'd rather have and maybe a different airfoil... then these are all valid and the model will fly pretty much as well as the design that you were inspired by.

Nitrovein

I have looked at the sticky treads a bit, will look at it more. The tricky part is that before I have finished the fuselage I don´t have a weight estimated, so I shouldprobably start there. I might be way of with the wings I have planed.
It´s like they say, it´s no point ininvent the wheel again... So it´s best to learn from othersmistakes, before I start doing my own...

At least it feels like I´m getting somewhere now. I can understand why people build severalplanes, I have so many ideas that this thingwouldn't get of the ground!

Nitrovein

I thought I should revisit my old subject and hopefully get some more good input.
Work has been slow on the airplane, but I have done a little at a time.

I have decided to go with stabilator (did I get that wright..?), but wasn't sure about "one" thing.
How important is it to get it tight/close to the fuselage? Will there be a noticeable turbulence/disturbance if the gap is to large?

Any ideas would be greatly appreciated!

AA5BY

The only flying stab I've seen on a model was on a turbine model seen a year ago. The configuration allowed the plane to do a very high alpha landing flare like probably sixty degrees. Not having seen such previous, my initial reaction was that something amiss was happening. It was beautiful and it alone worth the days outing to watch the turbines.

Franco2fly

As in the picture I posted, the flying stab works fine.. and the gap between the body and the stab is not consequential.  What little airflow passes through the gap only meets the two steel rods.  Your biggest challenge is getting the hinge point correct and the amount of throw, but with the modern radios of today this should be fairly easy.


KKKKFL

Nitrovein

Good to know, I will try to get it as close as possible, but don´t wan´t the risk of binding.
Yes, I will have to take it slowly with the amount of throw. Dual-rate will be used!