Matty's Marvelous Modular Monstrosity

Discussion in 'Composites' started by Foundationer, Jun 28, 2019.

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  1. Jul 11, 2019 #41

    Foundationer

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    That sounds about perfect. Thing is how do I calculate whether the controls are going to bind? That seems like it's a hard thing to accurately predict so I'm building everything how I think it should be built, with calculation for spars and torsion and anti-drag etc. and then testing the controls work as part of the load test.

    There's a few interesting presentations on the Royal Aeronautical Society website - it had never occurred to me even to check it out even though it's just down the road.
     
  2. Jul 11, 2019 #42

    pictsidhe

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    Hand laid carbon doesn't come close to Marske graphlite in compression as straightness is very important. In tension, less difference. maybe BoKu will chime in?
     
  3. Jul 12, 2019 at 6:06 PM #43

    Foundationer

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    I'm going on holiday! Here's the latest 3 view. I've made the tailplane and a good amount of the wing already, I know the dimensions of those (I've decided the design of things is fixed when I can actually measure it with a tape measure) and the distances between them but the actual design of the fuselage has been 'in flux'. It now looks basically exactly the same as it did three years ago. Edited for ease of manufacture (slab sides). 3 view.jpg
     
  4. Jul 13, 2019 at 10:11 PM #44

    Foundationer

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    I'm having a problem: my carbon is wrinkling! I lay it down nicely on the part (elevator) bag it, wrinkles! First time I thought I must have screwed something up. Second time i'm pretty sure I didn't. How do I stop this happening?
     

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  5. Jul 13, 2019 at 10:13 PM #45

    pictsidhe

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    What is your bag material?
     
  6. Jul 13, 2019 at 11:31 PM #46

    Foundationer

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  7. Jul 14, 2019 at 11:48 PM #47

    Lendo

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    To All,
    Jim Marske figures are the maximum tested in a Laboratory and should be derated for everyday use. In his original manual he quoted 350,000 psi Tensile Strength and 280,000 psi Compression strength, I believe he has adjusted those figures since that print period, to what I'm not sure.
    Generally accepted figures (by designers) are 250,000 psi Tensile and 200,000 psi Compression.
    There are only two quality Carbon Rod Manufacturers (to my knowledge), I haven't got my notes in front of me, but one is in Europe and one supplies Jim Marske.
    Please be warned -the difference between proven quality supplies and say those from China are CONSIDERABLE.

    OK here we are, Europe Supplier is DPP Netherlands, and I believe Diversifield Manufacturers in the USA but won't supply direct to the public, but supplies in bulk to Jim Marske
    Hope that helps.
    George
     
  8. Jul 15, 2019 at 7:32 AM #48

    Victor Bravo

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    Love the Libelle sailplane influence in the forward fuselage... or is that borrowed from the Woodstock?
     
  9. Jul 15, 2019 at 9:43 AM #49

    Foundationer

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    I like the Woodstock! I also like the idea of making a buck out of MDF and a little bit of foam in the 'corners'.

    I have an order in with DPP - they're apparently making it beginning of August so will report back on it then!
     
  10. Jul 15, 2019 at 9:55 AM #50

    Foundationer

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    The 'anthropomorphic fit test article'. Also the 'does making a buck like this work?' article.
     

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  11. Jul 16, 2019 at 1:56 AM #51

    pictsidhe

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    Owing to my chosen method of construction, control binding is something I had to think about. I will be hinging the control surfaces to that their bending does not change with deflection. That should free them from self centreing or binding. It does make the hinges more complex, though.
     
  12. Jul 16, 2019 at 2:18 AM #52

    Victor Bravo

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    Like!
    Like!
    Like!
     
  13. Jul 16, 2019 at 12:37 PM #53

    Foundationer

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    I took that buck, wrapped tinfoil round it, slathered it in left over roofing fiberglass and resin and then cut up some foam to put in to make the internal seat/strengthening/bulkhead shapes. It was all a bit of fun.

    The big mistake was that my wife thought this was part of something I actually intended to fly in. Rather than something thrown together to see how well I fit. She was quite concerned!
     

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  14. Jul 16, 2019 at 12:41 PM #54

    BJC

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    What did you conclude? Looks tight.


    BJC
     
  15. Jul 16, 2019 at 1:01 PM #55

    Foundationer

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    It's really, really comfy! Could literally sit in it for hours! But yes, definitely a tight fit which is why I wanted to check & I actually decided I can make it smaller...
     
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  16. Jul 16, 2019 at 3:48 PM #56

    pictsidhe

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    Is that EPS or XPS? I never managed to find a cheap source of XPS in the UK. I'm in the USA now, where it is easy.
     
  17. Jul 16, 2019 at 4:03 PM #57

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    The white stuff making up the seat shape is some poystyrene insulation (eps? ) From when I replaced a bit of roof, the blue stuff is Dow floormate (xps?) Cut into sheets and glassed. Nice way way to make shapes and work out how to make it comfy. The actual flight version will be carbon/Kevlar/carbon with PVC foam inserts and uni carbon & kevlar 'rails' to give it some crash worthiness.
     
  18. Jul 16, 2019 at 5:31 PM #58

    pictsidhe

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    Dow 'Styrofoam' is XPS. If it isn't Dow, it isn't Styrofoam, but it may still be XPS. EPS crumbles into balls, XPS is far stronger. Once you've seen the two together, you know the difference.
     
  19. Jul 16, 2019 at 6:06 PM #59

    Hot Wings

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    Just buy a good sized insurance policy with her as a beneficiary. :D:eek:

    That is what my wife keeps threatening to do......but I'm probably not insurable. :p

    It does look snug, but comfortable. I presume it's a center stick rather than a side stick?
     
  20. Jul 16, 2019 at 8:55 PM #60

    Foundationer

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    Yup. XPS for the blue (which is also going into structural parts & moulds) and the white crumbly stuff is good for roughing stuff out but eventually going in the bin.

    Yup - centre stick with trim attached, flap lever and throttle(s) over to the left, and that's basically it for controls.

    There's not really supposed to be much room in this thing. You're supposed to wear it, as they say.
     

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