Carbon fibre tube trusses

Discussion in 'Tube and Fabric' started by AdrianS, Nov 14, 2019.

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  1. Dec 4, 2019 #21

    bmcj

    bmcj

    bmcj

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    Wow! Those are some wildly articulated control surfaces. Has this plane flown yet? I’d love to see what that extreme surface movement does for it (to it?).


    By the way, this is the thread I was looking for when I posted this about a carbon fiber tube Corsair (sorta) look-a-like:

     
  2. Dec 4, 2019 #22

    BJC

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    Leo died as the result of a motorcycle accident in 1997, and development ended. It never has flown. It was conceived to be light, have lots of HP, and lots of control power, especially at low airspeed (think tumbles, micro loops, rolls at zero airspeed). Sean Tucker’s rudder deflects +/-60 degrees and 4 of the 8 ailerons are in the prop blast.


    BJC
     
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  3. Dec 5, 2019 #23

    litespeed

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    The idea of a tube carbon fuse has merit esp if all designed in 3d cad first. That would allow the printing to be simpler after optimising the truss. Printed gusset moulds certainly have advantages.

    The square tube would be the easiest to do and would also suit been clad in composite or carbon sheets. What about using the truss as a structural combination with the skin? Maybe even a scheme where it is a sandwich with tubes inside, foam in between open spaces and a skin on inside. That could be very strong and not excessive in weight. For the cockpit add a layer of kevlar on inside and back of firewall to stop accident ingress of nasty objects including the splinter effect of carbon.

    Naturally that is for a closed fuselage and not really a affordaplane style.

    Mike Patey has gone carbon skins to gain some rigidity but they are just bolt on thin skins, so may not be what he seeks in the end stiffness wise.

    Sorry for the tangent but just thinking of ways to use it in different cases of structures.

    If the addition of a few thousand in carbon tubes makes the best aircraft, I am for it. The cost of tube alloy in Oz is extortion.I love metal but will change for the best solution.

    I know we all want fast to build, easy and cheap. sometimes its good to just get two of those.

    I like the Corsair but not the price.
     
  4. Dec 5, 2019 #24

    litespeed

    litespeed

    litespeed

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    As a aside the gussets can be done without a printer.

    Will suit some gussets better than others.

    I say this as some designs might need lots of varied molds for all the gussets. That is a lot of print time. I don't mind too much - my son has two printers. And print time is free time in labor.

    Printed gusset molds could even be done in pull apart fashion to allow them to be used to align and hold the truss and gusset when gluing. Could give a impressive looking joint and just pull off after drying. Using them twice to ensure a perfect alignment sounds like a good design point to provide builder confidence and consistent quality.

    For outside joins you could have all the gussets flat- so just use simple flat plate carbon/carbon angle with the internal gusset doing all the shapes. The outer ones could just be as simple as alloy sheet bent. This would drop print time and give a nice outside for skinning/covering. Again square tubes, are easiest.

    This then brings up the ability to either make the molds available to others on loan/rent/beers or make kit sets of the gussets for fast build. Ideally all the molds are ganged together so are made on one large layup, much faster, easier and cheaper. Then all needed gussets and other small bits can be made in a day, bagged and let set with a diy oven possible for cure.


    Which then leads to the logical path of such molds......
    If we have it all cnc designed anyway, why not use a high density XPS foam- which is very cheap and cnc carve out the molds in one big thick sheet or series of smaller sheets.

    The machine could be a very simple DIY 3d router, cheap and a lot faster by days in machine time. A light sand and a lovely cheap mold set. Spray on PVA after your favourite sauce and sweet to use. It could even have a thin plastic sheet/film vacuumed on top. If we have a vacuum setup why not?

    This would make molds that are very quick, light but strong enough and cheap in materials. A small 4' by 4' sized 3d (even smaller could do) router is plenty and would allow much faster prototyping.
    Can be changed to do wire cutting as well for wing profiles or ribs etc.

    I like the printer idea, but think for overall speed and cost the router is better esp for folks that have not bought a printer or router yet. Having both would be even better, for the bits a printer is best at. Adapting a printer head and feeder to do much bigger stuff on the router 3d/4d machine has been done. Then best of both worlds in a small space.

    Just my ramblings on the idea, the beers cold, I need a distraction. Sydney is flanked by fire in the north and the sky is red. High winds and the fires just keep making their own weather. All the smoke has made the sunlight a red glow. Yesterday I drove north 200kms, it was like Mars had parked itself next door and we now orbit much closer to the hell.

    Makes sailing the ocean a real good idea.
     
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  5. Dec 5, 2019 #25

    Victor Bravo

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    That's pretty clever, excellent idea.
     
  6. Dec 6, 2019 #26

    litespeed

    litespeed

    litespeed

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    Thanks VB,

    Occasionally the brain cells hit each other in my black box brain.
     
  7. Dec 6, 2019 #27

    AdrianS

    AdrianS

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    How about square tube, flat gussets, and foam wedges that fit between tube and gusset, and help locate the tube?

    3d needs a bit more thought, but you could glue the tubes together with the foam spacers, then drape cloth over the joint.
     
  8. Dec 6, 2019 #28

    Geraldc

    Geraldc

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    I have been pricing square carbon tube and it is over twice the price of 4130 tube.

    For a flat panel you could make an outside carbon or glass skin on a layer of something it won't stick to.

    On top of that a mesh made of strips of pvc foam in whatever pattern suits. Then cover with another layer of cloth

    draped into gaps in foam then vacuum bag.This way the tubes are formed and gaps between filled all in one operation.


    upload_2019-12-7_8-28-21.png
     
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  9. Dec 6, 2019 #29

    BoKu

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    You're almost there! Say you use a piece of waxed 1/8" masonite for your molding surface. Say you curve it slightly by supporting it on arched cradles. Now you can make a fuselage side (or maybe even a wing skin), and you don't need those troublesome bulkheads and stringers. Also, since you have created a continuous web, if you use at least one ply of +/-45 cloth, you no longer need diagonal stiffeners.

    As an additional measure, if you put down some 0.05" or so thick strips of tooling wax or aluminum or whatever is handy along the edges of the panel, when you demold the panel you have a joggle where you can put shear tapes that join it to the next panel over.

    Wow, these carbon fiber tube trusses are fun when you leave out the "tube" and "truss" parts! :)
     
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  10. Dec 6, 2019 #30

    cheapracer

    cheapracer

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    I actually can't quite remember the exact process I was trying to achieve here.

    Think I was trying to make an inner skin mold maybe. Laser cut the steel to shape, 3 lengths of 1" square tube riveted on, and 1" foam cut into strips for the braces.

    Like that basketball that kept getting bigger and bigger, it will hit me eventually ...

    layup 2.jpg

    layup.jpg




    Hmm, my 'Lens" layout was my best, but I had a good reason not to follow up on it, and now I have resolved that reason while working on my current plane ... oh well, next plane!
     
    Last edited: Dec 6, 2019
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