Original designs and Real Flight as a tool

[Katonka]

I am doing a thread here on the use of "Real Flight" as one of your tools if you are a R/C modeler who likes to have the fun of designing your own aircraft. This is a very interesting and rewarding part of modeling if you are a RC modeler.

Times have changed through the years. Did you know that just 10 years ago, there was no such thing as ARFs? If you wanted to fly RC, you bought a kit or had someone else build a kit for you. There are over 150 members in our club. There are only about 10 RC modelers left and the rest are just RC fliers. I don't have the time. I don't have the patience. I don't have the skills. Etc. I guess it is the way things are, but I feel sorry for those who don't get to enjoy this part of the hobby.

Having the interest in model airplanes for some 56 years now, I have scratch built and designed somewhere around 80 to 100 aircraft. From 1/2A 10" controliners to 21' gas RC. Having this hobby turned into a business some 32 years ago did limit my modeling to purely business related aircraft. But I retired at age 55 and I am now able to build what I want and some of the fun projects I had to set aside.

I did not come across the "Real Flight" simulator until a couple years ago. But it didn't take me long to realize the uses for this RF as a tool when designing aircraft. And having designed and built all the "run of the mill" model aircraft, I now want to do what I call "Stepping out There"

And this is where RF comes into the picture. What can RF do for a RC modeler?

1. You can set up the physics of any aircraft in RF to any settings you want in the edit.

2. You can change the set up of any aircraft .

3. You can change the size of any aircraft.

4. You can change the color scheme of any aircraft.

5. You can fly the aircraft from any field or water.

6. You can control the weather conditions for any day or night.

This is some serious stuff here if you are building model aircraft. You don't know how to do all this? Just ask the ones who do. I am even hoping other modelers and designers will post in this thread and give info on how. I will too if asked.

O K, so RF's Physics are not 100% perfect. And the more you are "Stepping out There" the more you will notice that. And the flying of the aircraft has it's differances too. Depth perception, peripheral view, distance, etc.

But that doesn't change things. It still gets close enough to give you some idea of what to expect and how what changes you make will effect the aircraft.

Now we have a great asset here on Knifeedge. That is the bunch of great designers who have the ability to create anything the minds eye can see. And I can tell you from working with these designers that they are all very nice people who are willing to work with you if you are making any sense. Yes they are very advanced people who are sometimes very busy with a full life, but I can assure you the they all will try to help if they can. Make contact with them. The worse that can happen is that they will not be able to do it.

There are a great deal of aircraft in RF and KE and you probalby can even find an aircraft that is very close to what you need. Make some changes to it in edit, change the color scheme to what you are thinking and there you have it.

And this ability to fly this aircraft in RF with the color scheme you are going to have on your model is a real help for when it is time to fly the model.

Now there is another bank you can draw off here in KE. That is the people on KE that are real knowledgable about aircraft design. And some of them even have computer programs that can do things for you. And most of them also like to work with you if you are making any sense.

Now you have to be real picky here. There are more pretenders here than actual people who are in the know. Some are just RF tinkers and know nothing about the real thing. But when talking to those, they will give themselves away. Words are free, have them show you what they have done.

One of these real types is Carl (aka "Haole"). You woluld not believe the fun we have talking to each other about designs and aircraft. He is basically a power glider modeler, but has studied aircraft all his life. Like Doug (aka "DHK79") they have the know.

So try some of this when you build your next R/C aircraft. And some of you who are just using ARFs, step out there and build something. It is a whole lot of fun and quite rewarding.

BTW: I too like to help others. And I do have just a little bit of experience in this sort of thing.

Here are a few more views of the "Katonka" and my first attempt to design a Canard Pattern Ship. If there is any interest, I will post the progress of "Tona Wico" in this thread.

 

[willsonman]

I've played with this but have not taken the time you and Doug have. Big round of applause for the both of you. I've talked to Carl as well about actually making one of his models (Jack Knife) but I would be interested in some plans of the "Tona Wico" if possible for when I get the chance to make something that makes people look twice at at the field.

 

[inky00]

Both are beautiful aircraft,i can see from the designs that you like sweeping curves.I have designed a few of my own aircraft over the years but they were all depron models of no more than 30".I also really enjoy the building process but the trouble is as i am "the builder"in my group of friends its me that ends up doing all the repair jobs.

 

[Katonka]

The "Tona Wico"

It seams this aircraft has caught the eye of some here in KE. I do not know if there is a single person here who knows what this aircraft is about or even how unique it is.

I am having a lot of fun watching the swap variants and seeing what some of the sim fliers are doing to it. In just two days, one has already turned it into a couple jets and thinks it looks like a design concept that Lockeed had back in the fifties. (I guess if you close your eyes and don't really pay any attention to it, you can see that). Another has decided to turn it into a Rutan private plane.

What you are looking at here is a total new design concept for a fully acrobatic pattern ship.

Now what does that mean?

It means I have thrown all the design concepts of a canard as we know them, from guys like Rutan, out the window. His designs are of private aircraft, ment to be extremely stable, have excellant stall characteristics. and look as ugly as hell. All of this is fine if that is what you want. But do not try to do any form of acrobatics with it. The design concepts as they are applying them just won't allow that.

I could have designed it that way. But that is not what I am doing here. I am designing a canard that I hope to be able to fly in 'Pattern" type of R/C flight. I am going to assume that most of you, or at least the ones here that fly R/C, know what I am talking about. It is not that silly 3-d stuff that some are doing with their silly ARFs. It is precision acrobatics.

So here are the basic design concepts of a canard that I have thrown out the window:

I have placed the motor, canard, and wing all on the same thrust line. If you look at Canards you will notice that the canard is either higher or lower than the wing in order to keep the wing out of the wash from the canard.

I have used fully symmetrical airfoils on the canard and the wing. You won't see that on other Canards.

I have set the motor, canard, and wing all at "0" incidance. If you look at canards you will see that the canard has positive incidance from the wing.

These changes are for a reason. It is to have a canard that will fly in the inverted position without going berzerko. A normal Canard, if you were to go inverted with it would dive so badly that you would be lucky to be able to give it enough down to get it level and when you do, it would still be porpoising.

The motor has been placed in the front of the aircraft. Canards have it in the rear becaue you don't want the wash of the prop producing lift on the canard that you want to stall before the wing. I want the canard to be able to stall. Especially for stall turns and other acrobatic manuvers. Also it will make the aircraft much easier to balance. Not that big of a problem with an eletric, but a real bitch if gas.

I want the CG as close to the wing as I can possible get it on a canard and still have a functioning canard. Look at the formulas for computing a CG on a canard. I threw those away.

Now put all this together and try to make it work.

First off this will require a balsa glider. (see attachment) It is a matter of experimenting with the distance between the canard and the wing, getting the canard the right size, and getting the CG in the right place. This photo is of the final glider. Many changes were made to it along the way.

I can tell you that this glider will astonish you. Many of my designer friends have seen it fly and they just shake their heads. They never believed I could pull this one off. It can be thrown normal or inverted and produce the same glide path. It can be thrown straigh up and produce a stall perfectly and glide away. It will glide all the way to the ground, slowing down and all, and maintain the same glide path.

I can tell you that I will be moving the CG even further back than shown after the first couple of flights.

Now the next step was to take all this and convince Doug to make a RF model of it. (I already had Carl's attention).

Now before you start fooling with it, place the 3-way switch in the middle position and just fly it. I ask you, is this not fun or what? And notice the excellant landing ability.

Why a canard "Pattern" ship? Because my theory is to overcome the inertia effect of a normal pattern ship. With the long fuselage on them and pushing the elevator up or down to change attitude you have to overcome a lot of inertia. (the want for an object to continue going in the direction it is going). My theory is that lifting the nose of the aircraft will decrease this effect. Especially with the motor on the front of the aircraft.

Am I correct? Yes I am. Turn off the elevator, adjust the canard so you have the same size loop, and you will see the differance. What you feel is sensetivity is actually a quicker responce. And I feel it will also be more precise control.

This is my second attempt at this goal. The first one was successful as a flying model aircraft, but I was not happy with it as a pattern aircraft.

I did however have a lot of fun with a F-4 that I converted to a canard and wrote a joke article about. It was published in two magazines, on the cover, and flown at many Fan Flys. If you want to see the article in the magazine about it, I guarantee you will get a real kick out of it. Just give me an e-mail address.

So there you have it.

 

[rcplanefubar]

been using RF myself to test my own designs. You can see one of them on rcgroups. I call it the Wasp PPR ( Park Pylon Racer) . I would post link but I'm on my phone at the moment. Winter has gotten in the way of testing the real one. It will be fun to see how well RF has gotten it right.

Love the looks of the pattern plane

 

[dhk79]

Now the next step was to take all this and convince Doug to make a RF model of it. (I already had Carl's attention).

Somehow I don't remember it taking a great deal of effort on your part to get me to play, all you had to do was say the "magic" word.

Besides, it was fun.

Doug

 

[Katonka]

Somehow I don't remember it taking a great deal of effort on your part to get me to play, all you had to do was say the "magic" word.

Besides, it was fun.

Doug

Yes Doug, that is actually the truth. I was just telling a story.

 

[Maj. Numbskully]

Awesome!!
This is exactly what I was talking about in post # 22 of this thread a couple of weeks ago
https://forums.realflight.com/showthread.php?t=25103
When you do complete our Tona Wico build Please come back and let us know exactly how far off or how close RF's physics model predicted your wico's RW's flight physics
also I'm really interested to find out if or how severe a possible "catch-22" situation arised in the process , As discussed in the same thread

 

[Haole]

Nicely written, George and thanks for the acknowledgment re: the fun we have sharing ideas.

I do want to caution anyone who is taking RF as a first step in modeling physics for an experimental design that for whatever reason, the CG in any given model in RF seems to be too far aft when compared to reality. I think it may be the way the programmers determined the solution for a wing's center of pressure and the resulting balance point to counter that with stable flight, but yeah take it with a grain of salt and fly with a safe margin ahead of what RF has predicted.

If you go with the third physics model that I emailed you where there is zero static margin on the CG, thus making the model a balanced tandem wing aircraft with really neutral attitude, I think it would be wise to scooch that CG forward an inch or more on your maiden flights and keep the canard's throw very limited.

You gotta admit that it's fun to see how it deep stalls when neutralized like that though--it does some really entertaining prop-hangs and can be safely recovered into harrier, then forward low-alpha flight. I have had issues with the short-coupled rudder getting me in trouble at low speed and think a quick fix will be to give it more exponential.

Anyways, fun stuff all around, a nice concept that will be a beautiful model and of course props to Doug for bringing it to RF for us all to enjoy. Good times.

Carl

 

[Neo]

This was a great article to post. I am more of a Tweak It guy in real life, I have built every SPAD, and have bought 9 ARFs and modified them them to my needs. I have though designed one aircraft of my own with help from a fellow club member. It was fun, lengthy, and flew like crap, but it was still great to have something no one else could ever duplicate or own.

This article actually makes me want to build this aircraft in the Simulator.

Sounds like you greatly adore Modeling, and I greatly appreciate this article.

Thanks.

 

[Katonka]

The "Katonka"

Now here is a real fun original design aircraft.

I doubt if many of you know this, but I was the very first modeler to ever design a counter rotating unit and design an aircraft around it. This aircraft was featured in two editions of "Scale R/C Modeler" and on the cover of the first one. The editor of the magazine, when he heard about the aircraft, personally flew to my home to take the photos and do the articles. (If interested, give e-mail address and I will send them to you.)

This aircraft was used as a center piece for a fashon show in San Francisco. After this aircraft was retired from flight. I sold it to a wealthy restauranteur who placed it in his retaurant in Carmel CA. It then went to the aircraft museum in Disneyland.

So I decided to do it again.

I have always liked the "Bugatti" I decided I wanted to keep that concept in mind while designing this one. Howeveer I knew It was going to require many changes to the design.

Now there is one thing you don't want to do with a counter rotating unit. That is have it involved in a crash or even a nose over. This will bend shafts, damage gears and all sorts of things. So that means a tri-gear undercarriage to have that nose wheel protect your investment.

I reversed the tail feathers on the "Katonka" from the "Bugatti" being I wasn't going to have a tail wheel in the rudder.

The stall characteristics of extremely tapered wings like these is horrific. You must do everything you can to help them. I am using a airfoil that changes as it moves to the tip. It starts out semi-symmetrical at the root and goes to Clark Y to the tip and the tip is a "Horner". Plus a degree of washout. Carl aka "Haole" computer drew the ribs for me

So I have the design finished and now I go to my hero Doug aka "DHK79" and ask him if he will do it in RF for me. It is fundamentally simple and basic, but with the wing this far back and this close to the tail feathers I am interested in getting some feedback through RF on rates, stall, and landing ability.

When Doug finishes with it and we start on the physics, we find that it is actually quite easy to set up. The main things I notice in RF is that it seems to hop down the runway until up is applied and unless the landing is perfect it seems to bounce back into the air when touching down.

So I build the aircraft.

O K, How many of you know how to figure and set the CG on a prop powered aircraft? I've only done this about a thousand times. I usually like my CG at about 25 to 28 % of M.A.C. on a scale aircraft and about 28 to 33 % on a acrobatic aircraft. I set it at 27 % on this one even figuring the fillets in M.A.C..

Well the "Katonka" is done and it is time for it's first flight. I head down the runway, it accelerates real fast, and it is time to rotate.

I apply up and it instantly jumps straight up, I apply down and it instantly jumps straight down, I instantly apply up again and it pancakes on the runway. All this in about two seconds and never getting more than five feet off the ground.

Well the fun part of all this is to listen all the modelers there and their diagnose and suggestions. Too much travel, tail heavy, bad design, etc. It is best to just listen and not say much.

O K, it acts like it is tail heavy, but how can that be when the cg is in the right place? Even if the rates were too high, just how crazy off would you have to be to get that much of a reaction? I've flown aircraft tail heavy and with too high of rates before.

It takes me a while. I do not know how many modelers would have ever figured it out.

Can it be that I have designed a prop powered aircraft that has a lifting body? That has to be it.

I recompute the center of lift like I would for a jet aircraft. It comes to a movement of the CG of over 1 5/8" on this size aircraft and comes out at about 9% of the wings M.A.C. (try putting the CG there on your next airplane and see how unhappy you will be.) But I am leary of this. It is just too drastic of a change and too far out of the park. So I place it in the middle and back to the field.

This time it leaves the ground. There is a funny thing that happens to you when you leave the ground with a severely tail heavy aircraft. You wish it hadn't. Now I am hanging on the best I can and it is only through luck and perserverance that on the third attempt I was able to nail the landing.

Back to the drawing board and I am going to place the CG where it called for it.

Third time at the field. Many modelers here. They all want to see George's folly try again.

But it is my turn. The jaws are dropping as this aircraft rotates and flies just like I wanted it to. The speed is just right, the loops are perfect, the rolls are too. The sound of it is something else and it is a beauty in the air. And these funny things it does on take off and landing in RF do not exist in the model. I now have a prop plane with the CG at 9% of the M.A.C.

This was about a year ago. I have built another one now. The new one is 7 pounds instead of 8 on the first, the mains were moved up to match the new CG, and I took some of the anhedrel out of the tail for aesthetiics reasons. It is even more nimble and responsive. The CR unit just keeps on ticking. It is a serious crowd pleaser when at a Air Show or just fun flying at the field.

Want to see it fly? This is it's fourth flight and not all that fancy and not all that great filmed, but you will get the idea.

http://www.youtube.com/watch?v=WwcnpBh0E2c

 

[Maj. Numbskully]

I have though designed one aircraft of my own with help from a fellow club member. It was fun, lengthy, and flew like crap,

Thanks.

LOL....that sounds familiar

 

[Katonka]

Excellant

Now for all you guys who are flying this aircraft in RF, I want you to know that Ghimmy47 has done a variant of this aircraft's EA that has really improved it's performance here in RF.

Especially the take off and landing part that I never was able to get right in the physics.

I suggest you try it. I have and I will be using it.

 

[willsonman]

I do wish there were some more accessible resources to instruct us on how to make plans from the 3d meshes we make. I've looked over at RCGroups and RCScaleBuilder and the majority of users there use solidworks or autocad. For how powerful Max is I am sure there has got to be a way to make some nice plans. Put it on a PDF and take it to kinkos. It may be my simple ignorance but I think that it would be a great addition. Free RF planes on the swaps... visit the forums to get a zip of the plans to actually make it.

 

[dhk79]

I've had the best luck in making actual plans by exporting the aircraft as a DXF file. Since RealFlight models are solid rather than framed objects, you still have to "build" the plans up in AutoCAD but you have a good 3D shell to work from. For the wings' rib sections I use a program called Profili2 to create ribs that transition from one cross-section to another.

Doug

 

[willsonman]

Yes, profili is a great program even for laying out washout I believe. Does exporting as a DXF give you any advantage other than using a different program? Do I basically have to cut out the fuse formers from the length of the fuse and lay out a CS template (front/back mapping?)

 

[dhk79]

DXF doesn't give you any advantage over any other format, it just is the most convenient to go between 3D Studio and AutoCAD. The limitation is really based mostly from the type of model being used by RealFlight - a low poly solid. DXF output shown in AutoCAD in the attached.