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Projects I Am Currently Planning To Build A Glow Engine Fixed Wing Rc Plane. Need Help With Airfoil Shape

Discussion in 'Airplanes' started by CrazyMonkeyFlyer, Oct 29, 2018.

  1. CrazyMonkeyFlyer

    CrazyMonkeyFlyer New Member

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    I am currently planning to build a glow engine rc plane. I need help with the frame design. What airfoil shape(example: NACA 2412) would suit if i need good thrust as well as suggest me a glow engine supporting the thrust required for the frame as well. I need a payload of around 4kg or less. How do i design my airfoil according to that? And i am looking for good glow engines with more thrust. So suggest me some of those too. Thanks in advance. :)
     


  2. rdsok

    rdsok Well-Known Member

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    I'm really not trying to pick on you and certainly don't want to discourage you from getting into the hobby that is really fun and exciting but... It's better when you are just beginning to start with one of the "bajillion" ( a made up word meaning a whole lot of ) existing designs than to start from scratch and dive into engineering something you don't have any experience in designing. Aeronautical engineering is not something you just decide to do one day without first having some basic experience.
     
  3. CrazyMonkeyFlyer

    CrazyMonkeyFlyer New Member

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    Hello Mr. Rdsok. Well, then help me out with the existing design and an engine that would fit the frame. And i am from mechancial background which gives me an edge to learn things quiet necessarily. So, i am interested in learning things i don't know too. I would be glad if you could help me out both ways. Thanks :)
     
  4. rdsok

    rdsok Well-Known Member

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  5. Tony

    Tony Administrator Staff Member

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    Randy is an ARF guy through and through, almost as much as he is an AMD fanboy :poke: hahahahaha.

    Airfoil shapes are numbered in the hundreds of thousands. Picking one for a particular task is quite hard especially when we have no idea what the plane is going to be doing.

    For example, here are some questions that came to mind when thinking about this...

    1. Is this plane going to be carrying a payload?
    2. Is that payload always going to be in the exact same place on the plane?
    3. Is this plane going to fly "scale" meaning never going inverted?
    4. Does the plane need to fly fast or slow?
    Those are the 4 that jump out at me right from the start. I know you stated a 4kg payload, but what is the overall weight of the plane going to be? We will definitely need this answer to suggest an engine to use. And speaking of engine, that brings up a whole new aspect to planning this out. As you fly, you are going to burn fuel. With a payload AND fuel burning, you are going to constantly be shifting the center of gravity of the plane. Can you do this with electric? It would take one question mark out of the total equation if you can.

    And to me, this sounds a lot like you are working as a student in a school trying to design a plane to carry a payload as a class project. I have video of a class at the University of Oklahoma doing testing but ultimately crashing in the end. This just sounds like something like that.
     
  6. CrazyMonkeyFlyer

    CrazyMonkeyFlyer New Member

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    I am sorry for the delayed reply Tony. But one concern of mine is i would go far enough to learn aeromodelling as i am already in the field of xcopters. I would want to learn pretty much everything about glow engines and glow engine rc planes. Interest is everything. I can learn things very quickly and as i am from mechanical background i can get pretty much about glow engines. I am already refering books for airfoils and aerodynamics. But i think that a person with knowledge and experience can help me better with aspects that are not in books. I am going to answer your questions but can you help me out with helping me make one. I am ready to spend but i want to learn. As questioned, the answers for the questions are as follows.

    1. Just two cameras one a small fpv and other for the view of ground.
    2. yes
    3. yes . To learn first with a non acrobatic plane.
    4. Not too slow not too fast.

    And as you were talking about the fuel too, i would also like to learn how the CG of the plane changes according to the fuel discharge. These challenges are meant to be settled rather than sitting in the corner and thinking oh a lot of problems, i will not learn this. I have a person who is good at flying planes, so you need to worry about the plane crashing like the school project unless the plane is made like a school project :p I would appreciate your support for making a plane for sure sir. Thanks in Advance.
     
  7. Tony

    Tony Administrator Staff Member

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    The school project plane (collage level engineer students) was actually built very well. Very good lift on the wing but I think it had a flaw of being too short making it too "pitchy". Was a great project though.

    I can sit here and type out on a keyboard until my fingers are bleeding, but nothing is going to teach much unless you actually play around and build some planes. Don't let that come off as harsh, just stating a fact. I just don't want you to get wrapped up in the text without going out and experimenting.

    Lets start with the payload. Since it is cameras and they are always going to be in the same place, that is a good thing. that means your C0G will not be shifting from 'releasing' a load. So this is pretty much a non point now.

    Fuel, this is going to be huge depending on the size of the plane and the size of the tank. I know nitro, but I have tried to stay away from nitro planes for this reason. Yet I have a 68" Decathlon with a 4 stroke and a 63" F4U Corsair lmao. But I have never flown them. I purchased them because it was a deal too good to pass up. basically, if you have the tank in front of the C0G, when it is full, it will be nose heavy or balanced depending on how you set it up. As you go through the flight, fuel is burned and the nose starts to get lighter resulting in a tail heavy situation. Tail heavy is very bad and makes the plane very hard to control. 3D planes like the Edge 540, Extra 260/300 and so on like to be slightly tail heavy, it helps them flip around in the air as well as hover and harrier. But I digress, this is beyond our scope.

    In a perfect world, you will want the fuel tank exactly centered with the C0G. This way as you burn fuel, you are only making the aircraft lighter and not adjusting the CoG. So try to make it so the tank is right at CoG. I know your next question and that is "how do I know where to set the CoG?"... Yea, that is a hard one to answer as it is different with every plane. On most traditional planes with traditional wings, set the CoG at 1/3 wing chord from the front of the wings leading edge (that was a little redundant lmao). This is only a starting point and you WILL have to adjust later on.

    As for wing style, I would use a flat bottom airfoil shape. These produce an incredible amount of lift which is what you need with a plane like this. Flat bottom is easy to build as well since you can do it on a flat surface and make the wing perfectly flat and straight. No jig required unlike with a 3D plane with a symmetrical wing. As for size of the wing/plane, that is going to be up to you, your wallet, and what you plan on doing with it. I don't have one on here (yet), but you need to use a wing loading calculator to determine what size to make the wing.

    Also, put a few degrees of dihedral in the wing. This will help the plane fly much more stable. Only about 3º is needed. 1.5º won't have as much affect on the plane, but will still help without it looking like the plane was stored only on the wing tips lol.

    Try this. Click on the Store tab at the top of the forum and download the RCH Trainer. I suggest V3, but you can do any of them. This plane has a KFM airfoil design which was popular back in the day when I created these plans, but now is a dead design and I need to update it. Build the fuse and then build a traditional flat bottom airfoil wing. Get some cheap electronics and fly it. Put a payload on it and fly it, adjust the CoG and fly it. If you crash, the most you are out is $3.00 worth of foam board and maybe a $3.00 motor shaft and a prop. This way you can test without risking a balsa build that took hours if not days or weeks. Foamboard is fantastic for prototyping. Give it a shot.
     

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