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Thread: Flitter

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    Registered User bradyaero's Avatar
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    Flitter

    So I got tired of staring at the two sides of the flitter, putting off building a four foot hotwire, so I got out my carving knife (Chainsaw) and went at it. It's nice to see both sides together, I still have to do some fitting but in general, they fit, and it was a nice christmas present to myself, it was litterally snowing foam in my garage. Next I'll fit the halves together better and put the whole thing on a rotisserie so that I can get cleaning up the mess! Progress feels good no matter how small! If you have any suggestions, let em fly! Happy New Year, Greg

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    'The Piper Cub is the safest airplane in the world;it can just barely kill you.'
    - Attributed to Max Stanley ( Northrop test pilot) -

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    Registered User Rockiedog2's Avatar
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    Re: Flitter

    wow. tell us about it.

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    Re: Flitter

    Quote Originally Posted by bradyaero View Post
    So I got tired of staring at the two sides of the flitter, putting off building a four foot hotwire, so I got out my carving knife (Chainsaw) and went at it. It's nice to see both sides together, I still have to do some fitting but in general, they fit, and it was a nice christmas present to myself, it was litterally snowing foam in my garage. Next I'll fit the halves together better and put the whole thing on a rotisserie so that I can get cleaning up the mess! Progress feels good no matter how small! If you have any suggestions, let em fly! Happy New Year, Greg

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    So, like, what is it? Airplane fuselage? Race car? Are you building it moldless or is this a plug or something else? You are not allowed to just throw this out there without more in the way of description of type and mission and construction... Grin.

    Billski

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    Registered User Tiger Tim's Avatar
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    Re: Flitter

    Got nosy and google-y and came across this:

    Looks pretty sharp, and the CNC cut plug is a nice touch http://www.homebuiltairplanes.com/fo...ad.php?t=13953

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    Registered User bradyaero's Avatar
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    Re: Flitter

    I came up with the concept back in about 2000. I played around with flight sim models, and then found an aerodynamic engineer and then a cad guy to do the heavy lifting. After several iterations the plane took shape as you see it.

    I resurrected the wing from the ME163, its really quite a special wing you know. Had to go really fast and then become a glider, the only reason it was condemned to the dustbin of history was because of mach compression tuck... But for a GA aircraft flying under 600 mph it'll do just fine!

    The cad pic that Tim found doesn't show the leading edge slots but they are there to help airflow keep the elevons working near stall. It's a two person tandem, cog sits on the passengers' belly button, the wing is a re-developed eppler with aerodynamic twist and taper, I took measurements off a real ME163. The verticals are there for stability, I didn't want winglets, they are not necessary, a single fin had no place to go, so it grew two verticals, which actually drop a bit below the wing. Not being made of money (anyomore), I do what I can on it when I find some cents and some time. I'd love to get someone else involved, but haven't gone down that road yet. So there you have it, a potential GA flying wing.

    Happy New year, Greg

    --Conclusions--

    "The flitter has been shown to be a viable aircraft concept. Performance in terms of range, cruise, speed and rate of climb should be good for the relatively low installed horsepower. Aerodynamically, the aircraft is stable and has a cg range of seven inches. In terms of flying qualities, the aircraft is generally level 1 (mil-f-8785c) with some modes level 2. Loads fall within the range expected of an aerobatic aircraft, are well within the capability of either composite or metal structure. "
    'The Piper Cub is the safest airplane in the world;it can just barely kill you.'
    - Attributed to Max Stanley ( Northrop test pilot) -

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    Registered User bradyaero's Avatar
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    Re: Flitter

    Hi Bill,

    >>Are you building it moldless or is this a plug or something else? You are not allowed to just throw this out there without more in the way of description of type and mission and construction..

    At this point I am building it moldless, probably s-glass / epoxy. An interesting thing about the design is that the wing center spars really carry most of the loads, the fuselage doesn't really do a whole lot. First set of wings will probably be wood. , (the real ME 163 was wood). The wing is pretty thick (almost a foot at the root) so I am going to have to work hard to come up with a light strong structure. Powerplant can be many things, from a rotax to a lycoming. I am happy to report it is not a canard!

    Greg
    'The Piper Cub is the safest airplane in the world;it can just barely kill you.'
    - Attributed to Max Stanley ( Northrop test pilot) -

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    Registered User Autodidact's Avatar
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    Re: Flitter

    That's very nice! And interesting, too. Really cool looking airplane and I'd like to know how it flies.
    As many takes as it takes.

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    Re: Flitter

    Quote Originally Posted by bradyaero View Post
    Hi Bill,

    >>Are you building it moldless or is this a plug or something else? You are not allowed to just throw this out there without more in the way of description of type and mission and construction..

    At this point I am building it moldless, probably s-glass / epoxy. An interesting thing about the design is that the wing center spars really carry most of the loads, the fuselage doesn't really do a whole lot. First set of wings will probably be wood. , (the real ME 163 was wood). The wing is pretty thick (almost a foot at the root) so I am going to have to work hard to come up with a light strong structure. Powerplant can be many things, from a rotax to a lycoming. I am happy to report it is not a canard!

    Greg
    How do you plan to do that, glass the foam, then carve out all the foam on the inside?
    Kennis vermenigvuldig je door het te delen.
    (You multiply knowledge by dividing it)

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    Registered User bradyaero's Avatar
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    Re: Flitter

    Hi auto,

    The first layer of glass is already on. My plan is to carve out the foam and then add my bulkheads and stringers. I think this is the quickest way to a prototype.

    Greg
    'The Piper Cub is the safest airplane in the world;it can just barely kill you.'
    - Attributed to Max Stanley ( Northrop test pilot) -

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    Re: Flitter

    On construction methods and mood less composites .....

    Is there a way to infuse resin in two or three steps?

    I was thinking about hot-wire or CNC cutting foam blocks into the basic loft lines, then further cutting it into smaller components (e.g. wing leading edge). Ribs or spars or bulkheads could be glassed before the blocks are glued back together.

    For example: The wing leading edge (D spar) would be wrapped in composite (e.g. Carbon fibre) and infusing resin.
    The second (infusion) step involves gluing the wing centre box to the leading edge, wrapping a second layer of composite fabric and infusing resin.
    Repeat the process until it looks like a wing.
    Is multi-step infusion possible with current technology?

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    Moderator autoreply's Avatar
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    Re: Flitter

    Quote Originally Posted by Riggerrob View Post
    On construction methods and mood less composites .....

    Is there a way to infuse resin in two or three steps?

    I was thinking about hot-wire or CNC cutting foam blocks into the basic loft lines, then further cutting it into smaller components (e.g. wing leading edge). Ribs or spars or bulkheads could be glassed before the blocks are glued back together.

    For example: The wing leading edge (D spar) would be wrapped in composite (e.g. Carbon fibre) and infusing resin.
    The second (infusion) step involves gluing the wing centre box to the leading edge, wrapping a second layer of composite fabric and infusing resin.
    Repeat the process until it looks like a wing.
    Is multi-step infusion possible with current technology?
    Yes.

    I doubt it's desirable though. Infusing foam is going to be heavy and most foams (XPS) will absorb enough resin to make your plane really heavy. Worse, foam has very low stiffness so it will compress under vacuum. With a skin and the mold on the outside, that's a non-issue. With a massive foam core wing, it'll deform a lot.

    It gets worse. One of the dirty little secrets of engineering is tolerance stacking. The moment you start adding up parts, dimensions of multiple parts or shapes of multiple parts, it is hell to get them all perfectly aligned, especially for a wing section. Worse, if you have varying stiffness in the structure (like a shear web and ahead of that just foam core), it is very easy to deform the "soft" part during joining. That's why virtually every molded composite wing has a top and bottom half; the stiff spar is far away from the joint and the LE is very stiff in bending up/down and fwd/aft, but pretty flexible in conforming to exactly the right airfoil shape if you use a mold.


    Thanks BradyAero!

    How do you plan to keep the skin stiff enough with the foam removed, temporary external supports?

    Your plan should work if the outside surface is good enough. If not, you have the start of a plug where you can make perfect skins in one go.

    Do you plan to make the wings removable? If not, a single big mold (if space allows) for both the top and bottom half would be the ultimate way to make it extremely light and simple to build.
    Kennis vermenigvuldig je door het te delen.
    (You multiply knowledge by dividing it)

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    Registered User Victor Bravo's Avatar
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    Re: Flitter

    Pretty sure I have a Graupner or Multiplex molded foam flying wing electric that looks just like this Flitter. Flew really fast and reasonably stable.
    "Everything in this book may be wrong."
    Richard Bach, Illusions


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    Registered User bradyaero's Avatar
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    Re: Flitter

    Quote Originally Posted by autoreply View Post
    Yes.


    Thanks BradyAero!

    How do you plan to keep the skin stiff enough with the foam removed, temporary external supports?

    Your plan should work if the outside surface is good enough. If not, you have the start of a plug where you can make perfect skins in one go.

    Do you plan to make the wings removable? If not, a single big mold (if space allows) for both the top and bottom half would be the ultimate way to make it extremely light and simple to build.

    Hi Dana,

    Sorry for the delay in answering, I was away vacationing in Cuba.

    My plan is to carve out large sections of foam, leaving temporary foam bulkheads in place for support. Then I will glass the two sections together, and then place the real bulkheads and remove the temporary foam ones.

    I have split the wing design at the outside of the verticals. It is possible to hinge the wings at this point, or just make the outboard wings removable for road transportation.

    I have never done this, but do you have any advice on using acetone to melt out foam? Am I asking for trouble?

    Thanks, Greg
    'The Piper Cub is the safest airplane in the world;it can just barely kill you.'
    - Attributed to Max Stanley ( Northrop test pilot) -

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    Registered User bradyaero's Avatar
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    Re: Flitter

    Quote Originally Posted by Victor Bravo View Post
    Pretty sure I have a Graupner or Multiplex molded foam flying wing electric that looks just like this Flitter. Flew really fast and reasonably stable.
    Hi Victor Bravo,

    I've flown several similar wing models like the Projeti and the Raptor, they are super stable, fast and fun to fly but they use a symmetrical airfoil and have nothing to do with my wing, which is sophisticated and designed to do the real job at full scale, and is the reason why the ME163 and its variants flew so incredibly well.

    Greg

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    'The Piper Cub is the safest airplane in the world;it can just barely kill you.'
    - Attributed to Max Stanley ( Northrop test pilot) -

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    Re: Flitter

    Quote Originally Posted by bradyaero View Post
    ... I have never done this, but do you have any advice on using acetone to melt out foam? Am I asking for trouble?
    I've done this. The best advice I can give you is to plan well in advance for the vast quantities of flammable, gloppy, smelly, snot-like gooo that will come pouring out of your parts. It's virtually impossible to clean up, hardens into styrene plastic (no bubbles) when the solvent evaporates out, and will remain as a scum all over the inside of your parts unless you get every drop out quickly. Have rolls of paper- or shop-towels on hand, a very large metal trash can, and a fire extinquisher. You'll want to work over the trash can, so the stuff drains directly into it. Like I said, virtually impossible to clean up otherwise. Make sure the can doesn't leak. It sounds like such a quick and easy thing and I'll grant that it might be "the only way" in some situations. But mostly it's a gigantic PITA, start to finish.

    IMHO, you're better off building a plastic "dust hood" bigger than the part, wear a good-quality dust mask, and then removing the bulk of the foam mechanically with a fork. Finish off the removal with perhaps a light flexible sanding disk on the end of something like a Dremel.
    Last edited by Topaz; February 8th, 2017 at 07:36 PM.
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