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  1. #1
    Rcstudent247's Avatar
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    Advise for edf wing

    Any advise on my creation would be greatly appreciated. Here is the specs. I used a 70mm edf, that came with a 60amp esc. From detrum. It is rated at 3600 kv. I used 2 9 gram servos that came with the fan. For the battery I will try a 2200 mah 4s 25c from gens ace. I used foam board from dollar tree with paper still on and added some flite-skin. I made a kf2 like air foil. Cut to the shape of a prop delta I found online. I am just looking for any tips or advise on my setup before I launch. I have seen some other plans put into what looks like a cad program where it shows cg and wind simulation, on other builds that would really help. The edf reads 1000 grams of thrust on the box. I estimate my rig will be around 650 grams all up weight. The dimensions are 27 1/4" wing tip to wing tip. And 24 3/4" front to back. And the mixed elevens are 1.5" wide and 8" long. Again any advise will help a lot. I'm sure other similar projects have been talked about a lot. I have read so many already. But mine is my own twist on a few others.
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  2. #2
    Lnewqban's Avatar
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    Cool

    Welcome to RCU, Rcstudent247 !!!

    It seems that any picture taken in the North Pole shows up upside down where I live

    Yours is a delta that is missing some area in the back.
    You could calculate the centroid of each elementary shape and calculate the centroid of the whole plane.

    I would go the easy, but not less accurate, way of tracing the half-shape (from the center line of the fuselage including the nose until the wing-tip)) over a flat piece of cardboard.
    If you need to scale it down is OK, it works the same.
    Then, cut the projected shape so you end up with a flat area that is similar to the half-shape of the wings plus half-fuselage.

    Next, you will hand that shape from different points around its periphery and will draw a plumb line for each position.
    All the lines should appear crossing at a common point; that is the centroid of the area and that is what any online calculator will find for the area that you enter into it.

    A line that is parallel to the center line of the fuse and that is drawn over that point will represent the mean aerodynamic chord (MAC) of that half wing and half fuselage combined.
    The length of that line will be the chord of the wind (from leading edge to trail edge including the elevator, if the line runs over it).
    Divide that line in four equal portions and mark the location of the leading 25% of that chord.
    Finally, your CG should be located 10% of the MAC forward.

    This site explains it better than I can:

    http://adamone.rchomepage.com/index5.htm

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    Last edited by Lnewqban; 10-31-2013 at 07:33 AM.
    Lnewqban - "God will not look you over for medals, degrees or diplomas, but for scars. He has achieved success who has worked well, laughed often, and loved much." - Elbert Hubbard

  3. #3
    Rcstudent247's Avatar
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    Cool I think I'm close if not spot on for cg. Do you think the missing area of the delta will affect flight?

  4. #4
    Lnewqban's Avatar
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    Quote Originally Posted by Rcstudent247 View Post
    ........Do you think the missing area of the delta will affect flight?
    Not at all.

    Good maiden flight and clear skies !!!
    Lnewqban - "God will not look you over for medals, degrees or diplomas, but for scars. He has achieved success who has worked well, laughed often, and loved much." - Elbert Hubbard

  5. #5
    Moderator BMatthews's Avatar
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    Well, yes and no. The big cutaway means that you have something more of a swept flying wing than an actual delta wing. In effect you've created a flying wing that is sort of like the wings on the English Electric LIghtning jet fighter.

    What it WILL fly like is the original prop model. And with that much thrust it'll likely fly faster and better.

    A couple of cautions. First off you have LOTS of thrust since it's showing as much higher than 1:1 thrust to weight. But EDF's are known for not having good acceleration from slow speed. And your flying weight is a good one which will provide a medium sort of wing loading. But it's small and short coupled. Put all these things together and it says that you want to be sure that it gets a good hearty javelin like throw so that when it leaves your hands or the hands of your launch assistant that the model is moving along at a good speed and aligned nicely with the path. So no nasty side arm launches that send it off with a lot of yaw or other oddities.

    As you get used to the slow speed operation it may well turn out that these cautions were needless and you can power up and lightly push it out with a cool looking underhand push. But until you know that this is the case it's best to be sure it's got some decent airflow over the wing before release.
    Witty saying to be plagarized shortly.....

  6. #6
    Rcstudent247's Avatar
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    Thanks for all the info. Maybe a bungee launch would be best.

  7. #7
    Rcstudent247's Avatar
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ID:	1937619Ok it took a while to figure out all the geometry for this wing. But thanks to the links and info lnewqban posted I got it dialed in. My first design had cg to far to the rear. I moved the edf forward and came up with a different nose to get it centered. 10% of 25% of MAC... I'm sure there is a better way to write that formula... All in all I don't think I added more than 10-15 grams. So 700 grams weight and 1000 grams of thrust.... 4s... 70 mm edf.. I'm going to maiden tomorrow and will film. Hand toss I hope.
    Last edited by Rcstudent247; 11-08-2013 at 03:04 AM.

  8. #8
    Lnewqban's Avatar
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    Quote Originally Posted by Rcstudent247 View Post
    ............I'm going to maiden tomorrow and will film. Hand toss I hope.
    Best of lucks !!!
    Lnewqban - "God will not look you over for medals, degrees or diplomas, but for scars. He has achieved success who has worked well, laughed often, and loved much." - Elbert Hubbard

  9. #9
    Rcstudent247's Avatar
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    Back to the drawing board. I had a friend hand launch... He launched great I throttled perfect and it was lifting nice, I gave a small lift on the right stick and the throws were way to extreme and it pulled a tight loop into the dirt. Although its ruined the air foil worked well and the thing had crazy thrust. I will rebuild until its right. No video thank god. But enjoy the pic
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  10. #10
    Lnewqban's Avatar
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    Quote Originally Posted by Rcstudent247 View Post
    Back to the drawing board. I had a friend hand launch... He launched great I throttled perfect and it was lifting nice, I gave a small lift on the right stick and the throws were way to extreme and it pulled a tight loop into the dirt. Although its ruined the air foil worked well and the thing had crazy thrust...........
    Sad to watch that picture
    Lnewqban - "God will not look you over for medals, degrees or diplomas, but for scars. He has achieved success who has worked well, laughed often, and loved much." - Elbert Hubbard


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