Pandora box

Discussion in 'Composites' started by stanislavz, Oct 15, 2019.

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  1. Oct 15, 2019 #1

    stanislavz

    stanislavz

    stanislavz

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    This thread is special case of this one : https://www.homebuiltairplanes.com/forums/threads/devfus-foam.32338/ and one special persone

    I was asked, to design and help build an fuselage of ul class high wing. Now, as a prototype do come fk-9

    [​IMG]

    Happy part - front will be combined - metal tube frame for structural / crash protection. Tail - only composite. So - all from door rear edge to tail - is composite. And yes - it is with some pros and cons.

    For pros - it is a perfect part to be made in a foil-on-foam mold, possible to mold in one piece.

    For cons - you have 4 point to connect it to tube frame. But tube frame itself is "main connector for all main/heavy parts".

    Pros - connector in composite aircraft is a hard thing to design and build

    Question - which kind of data is necessary for calculations ?
    Should it be done as stressed skin with some support walls later added ? Or all could be incorporated in a single step using precutted \_/ pieces of foam in one single process ?

    Like this : [​IMG]
    As i see it - biggest isuue here would be wall buckling under load.

    Inspiration/design philosophy - do it nice on both sides, and as fast as possible, by using clever/smart solutions.

    Should i add here some vision on possible wing building ?

    I can call it as a corrugated plastic construction, with non-load bearing foam formers.
     
    Last edited: Oct 15, 2019
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  2. Oct 15, 2019 #2

    Pops

    Pops

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    I like the looks.
     
  3. Oct 16, 2019 #3

    Riggerrob

    Riggerrob

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    look at some of the 1930s vintage airplanes that were built with steel tube centre fuselages, but sheet aluminum aft fuselages: Hawker Typhoon, North American Harvard, etc. They will provide hints on the sorts of stiffeners and reinforcements needed to distribute loads from the steel cage to the monocoque aft fuselage.
     
  4. Oct 16, 2019 #4

    Dana

    Dana

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    I like it too. A little like an older fastback Cessna but with other modern styling touches.

    Also look at the Aero Commander 100, which is also a steel tube cage with an aluminum tail... and a reputation for being very solid compared to the Cessna 172 everybody mistakes it for until they look at the rudder.
     
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  5. Oct 16, 2019 #5

    Pops

    Pops

    Pops

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    There was the Darter Commander and the Lark Commander. Darter 2 place with a Lyc-320 and the Lark is the 4 place with the Lyc -360. Friend of my used to own a Darter. I have helped on the conditional inspection on it and did some radio work on it.

    The factory for the first few ( can't remember the number) was close to my wife's family home in PA. I visited the factory in the fall of 1960.
    Steel tube fuselage to rear of wing and aluminum fuselage to the tail and aluminum tail surfaces.
    The factory was so small they stacked the tube fuselages outside against the building wall.
     
    Last edited: Oct 16, 2019
  6. Oct 16, 2019 #6

    narfi

    narfi

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    Ive only seen pictures of the kits, how much steel tube is in the fuselage of the Zenith 750s?
    [​IMG]
     
  7. Oct 16, 2019 #7

    BBerson

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    Post #1 looks like a Glastar. Same tube frame cabin and fiberglass aft fuselage.
     
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  8. Oct 16, 2019 #8

    Will Aldridge

    Will Aldridge

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    Also look at the Mooney Mite. Steel tube cockpit and engine mount and I think monocoque wood tail cone.
     
  9. Oct 16, 2019 #9

    stanislavz

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    Thank you all for suggestions. Yes, combined fuselage - tube front with monoquoe end is best example. Will dig into details onto suggested airframes. Biggest X for me is joining points - where place them (on four corners ? ) and should both parts work combined on torsional load or not ?

    Will open new thread on calculation. But not yet.

    Plus - any one know similar paper for fuselage ? https://researchspace.ukzn.ac.za/bi...Neall_Neville_2017.pdf?sequence=1&isAllowed=y
     
    Last edited: Oct 16, 2019
  10. Oct 16, 2019 #10

    BJC

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    BB already mentioned the GlaStar. The GlaStar and the Sportsman use a welded 4130 tube structure starting with the firewall, and ending with four points just behind the lift strut to fuselage connection. The composite shell has attachment points at the firewall and several other places forward of the lift strut. That arrangement has been reliable.

    Here is a 22 year old discussion, with a photo that shows 14 shell attach points.

    edit: https://glasair-owners.com/glastar-...neral-tips-for-glastar-fuselage-construction/

    BJC
     
    Last edited: Oct 16, 2019
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  11. Oct 16, 2019 #11

    stanislavz

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    Could find that thread ? I was not able to find it.
     
  12. Oct 16, 2019 #12

    BJC

    BJC

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    See post #7, above.

    Also see my latest post. I added the link.


    BJC
     
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  13. Oct 16, 2019 #13

    stanislavz

    stanislavz

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    Totally super information. Will have to buy an membership, most articles are for members only.
     
  14. Oct 16, 2019 #14

    stanislavz

    stanislavz

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    And of possible way of easy reainforcement. Lets say stringers placed each 20cm, formers each 80cm... Or 8 - 24 inch. Will it help on thin fiberglass shell ? How thin skin can you go on such a frame ?[​IMG]
     
  15. Oct 17, 2019 #15

    Patrickh99

    Patrickh99

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    For more ideas, look at how an engine mount attaches to an aluminum or composite fuselage.
     
  16. Oct 17, 2019 #16

    stanislavz

    stanislavz

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    Could anybody give an input on #14 post ?
     
  17. Oct 20, 2019 #17

    rv7charlie

    rv7charlie

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    If you're talking about fiberglass over a steel tube frame, you'll need a lot fewer formers than for a traditional fabric cover, simply because the skin will be at least somewhat self-supporting.
     
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  18. Oct 20, 2019 #18

    stanislavz

    stanislavz

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  19. Oct 25, 2019 #19

    stanislavz

    stanislavz

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    First results...

    [​IMG]

    And this with less slices between tail sections

    [​IMG]

    And no slices :
    [​IMG]

    And question : fk-9 with uniform tail vs any metal tail with one join

    This:
    [​IMG]

    Versus:

    [​IMG]

    Will it have any signification advantage on strut braced wing ? Or only negligible ?

    I had friend of mine, which have told me if two flat plates are joined on less than 7 degree angle - flow is laminar.
     
    Last edited: Oct 25, 2019

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