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Discussion in 'Composites' started by cluttonfred, Dec 27, 2019.

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  1. Jan 2, 2020 #101

    Victor Bravo

    Victor Bravo

    Victor Bravo

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    You'd have to ask Autoreply for specific examples, but I believe he has posted one or more. Check the archives for posts by him on the topic of composites. Or ask one of the people on this forum that are in contact with him, and he might make an appearance on the forum to defend his position :)
     
  2. Jan 2, 2020 #102

    Staggermania

    Staggermania

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    You are correct, in that there is no logical reason.
    Logic has nothing to do with. Curves have broader appeal, which will broaden the market.
     
  3. Jan 2, 2020 #103

    Scheny

    Scheny

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    Marc, Airbus has build a "3d printer" which lays pre-preg carbon for the A350 wing in any direction and thickness. Just Google it.

    And BMW has a construction facility for the i8, where robots build the chassis by first putting pre-preg in a mold, then cutting the edges into form. Cirrus and Diamond already have similar processes in place.
     
  4. Jan 2, 2020 #104

    Marc Zeitlin

    Marc Zeitlin

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    The fact that someone has built a machine to do a thing is not an indication that it's "cheap" or even "cost effective". I've seen the tape laying machines at Boeing (and other MFG's) and I know that there are prepreg positioning devices. I'm quite aware how to use Google, thanks. Is there any evidence that the per lb. price of these layups, or the per sq-ft price of these layups, is cheap enough to allow for "cheap" carbon parts to be fabricated that could replace metal ones? Do you have the faintest clue how much these devices cost, and what that would mean from an amortization standpoint over the cost of a hundred or even a few thousand part production run?

    Using a $147K base price car as an example of something that's "cheap" is laughable - fairly obviously, BMW does not know how to fabricate carbon parts "cheaply", else they'd be using it on their low priced cars, not only the absurdly expensive ones. BMW (and others) are doing this as a learning process, to try to determine HOW to make it cheaper, so that they can eventually use the techniques for lower priced cars. But that clearly isn't the case NOW, which was the claim.

    You have provided evidence for exactly what I stated, rather than the opposite, which was what I asked for. The claim was for cost/time efficiency - no examples have yet been shown for either.
     
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  5. Jan 2, 2020 #105

    Jay Kempf

    Jay Kempf

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    Have been up close and personal with tape laying machines. There is no chance any time in the near to maybe distant future that they will every apply to GA or kit building. We're talking cubic millions and a large crew on expensive software working after expensive mold building just to put the first tape in place. Boeing, Airbus, BMW, can afford them but no one else. I went to the training for the software. YIKES!
     
  6. Jan 2, 2020 #106

    Victor Bravo

    Victor Bravo

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    Telephone for Autoreply, please pick up the black carbon fiber courtesy phone...
     
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  7. Jan 2, 2020 #107

    Hephaestus

    Hephaestus

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    A mechanized "a" axis and a 6dof robot arm is only multi million dollars if you're Boeing/Airbus and need FAA approvals.

    For the rest of us there are possible options in order for learning and development...

    :popcorn: but please continue :beer:
     
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  8. Jan 2, 2020 #108

    ScaleBirdsScott

    ScaleBirdsScott

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    While "industrial strength" tape laying and robo arms are still highly expensive, so too are industrial strength 3D printers; and yet my brother for christmas gave me a model on his new $250 resin printer that I can't tell apart from the same model made on a $200,000 industrial printer.

    A lot of cool tech is going to get somewhat to magnitudes cheaper over time as more hobbyists essentially do the hard part for mostly free, and then the startups try to rush in and capitalize. The only tradeoff is capacity, time, reliability, etc. Seems no-one still is putting 30 foot hobby grade gantry mills in their barn to carve boat hulls even if the price of a 4x8 foot gantry router can be found at under $3,000 today. But in theory it would be possible. There are multi-axis robotic arms coming that are the price of a laptop. One of those could, in theory, build at least an RC model. Carve the foam, lay tapes, etc. And so it'll only be a matter of time before the bigger arms start to get more reasonably priced. And then you could have a robot arm build a wing, drilling holes and pulling rivets and so on, just like Cirrus does.

    It doesn't mean its smart to plan on any of this being possible, but I can see an argument that in another 10 years the local maker spaces will be quite well-equipped with stuff like a modestly capable 6dof robot arm with various attachment options including spindles, printer heads, grabbers, CF laying tools, welding, etc. It's all starting to move quickly.
     
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  9. Jan 2, 2020 #109

    Hephaestus

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    The key was downsizing those huge ones they use for airliner wings. 6dof arms exist (pick one of the 100 on thingiverse) after that it's a track so it can travel laterally with the rotation. Doesn't need a 30' reach to adjust lay angle. Just moderately past the centerline.

    None of its terribly complicated - lot easier than the calculations going into the composites :)
     
  10. Jan 2, 2020 #110

    BBerson

    BBerson

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    I recall his comments about- "carbon is cheap because you need half as much" .
    Don't recall any estimates of labor hours.

    I remember Burt Rutan built a prototype car with carbon fiber. It was considered too expensive.
     
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  11. Jan 3, 2020 #111

    cheapracer

    cheapracer

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    Indeed he did say that, and there is genuine foundation for the statement, but I did counter with a simple real world fact: Where's all the cheap CF aircraft then, or for that matter, cheap CF anything, cars, bicycles etc.

    The answer is simply, they don't exist.


    And I will continue to counter, that with low price it will defeat that position, and as no one has done it yet to prove it, all points are moot. Curves do have broader appeal, but $100,000 price tags certainly do not.

    Last night I realised that I could do all my fuse quite cheaply with flat CF panels, and wing spars made from steel. Keep costs down, and weight stable relative to the weight savings from the CF fuse.

    People may gasp initially at the thought, but it is quite a logical layout, and safe handling plane with the low weight where it should be, and cheap.
     
    Last edited: Jan 3, 2020
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  12. Jan 3, 2020 #112

    BBerson

    BBerson

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    True. The Grob 115 might be mostly carbon, I don't remember. I talked to the Grob USA manager and he said that carbon only reduced structural weight by 15%. The Grob aircraft are Type certicated aircraft.
     
  13. Jan 5, 2020 #113

    Lendo

    Lendo

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    Black Shape Prime is all Carbon, seen it in Friedrichshafen Air Show Germany , I think 15% overall sounds about right as there are things that can't/ won't be made of Carbon - however if you need that 15% to meet some regulation, it's better to use Carbon than cutting weights to 'the bleeding edge of safety' or building for much smaller people. A couple of designs spring to mind.
    George
     
  14. Jan 5, 2020 #114

    BBerson

    BBerson

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    I think he meant carbon is 15% lighter then Grobs typical fiberglass. Or about the same as aluminum.
     
  15. Jan 14, 2020 #115

    lr27

    lr27

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    As far as the tape laying machines go, the expensive ones are for airplanes with what, 200 foot wing spans? If we assume that the expense of the machine goes with the volume of the parts it can make, then a 35 foot wingspan plane would need a machine that costs half a percent of the big one. I guess that's still kind of expensive, but maybe not impossible.

    I think that, considered as an industry, this homebuilding thing is small. So it will take a while for us to adapt to cheap carbon fiber. Looking at a nearby composite supply outfit, it appears that carbon tow is less than 5 times as expensive, per pound, as e-glass tow. Yet it's several times as stiff. Maybe one person will come up with a breakthrough, the way the Vari Eze was a breakthrough in its time.
     
  16. Jan 15, 2020 #116

    Jay Kempf

    Jay Kempf

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    It just doesn't work that way. It is cheap to make the axis longer. You still have to have all the expensive bits like the gantry with all the tape delivery gear and the head. Just runs on a track on the floor. Gantry width can be varied but there is a minimum. Power requirements were ridiculous for that thing. Took a day just to load and calibrate it once it was just installed, not to mention loading and calibrating the tooling in place (mold). Then there is the whole CAD/CAM Side of the equation. Takes an army to make it all happen. The head has laser tacking and place roll cut and imagine the tape (6 tapes wide on the machine I messed with) going through the 5th and 6th axis head. It was all mounted on the gantry and that was like a mezzanine. So heavy it had to be very powerful.

    35' will be hand layup for a long while yet. Big-ish companies that want to certify will use pre-preg on some factory shelf life freezer program. That is outside the reach of most small shops.
     
  17. Jan 15, 2020 #117

    gtae07

    gtae07

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    THANK YOU! As an aircraft systems engineer by profession, this part has always bugged me. The checklist the FAA uses to determine whether you meet the 51% rule is very heavily tilted towards structural items. I’m exaggerating only slightly when I say that “wiring”, “electrical power system” and “fuel system” count for less credit than assembling a Van’s elevator from a kit (and that’s assuming you “roll your own” for those systems).

    I kind of get it, from one perspective; a bare-bones minimalist airplane doesn’t need most of the systems stuff so most of the work that’s there is structural. And on a fabric-covered airplane there’s more regular maintenance to go along with that. But on quite a lot of the new E-AB fleet, the avionics (and now, the propulsion) is more complex and beyond bare-bones. Showing that you beat two dozen ribs out of raw stock or pounded 14,000 rivets is great for bragging rights and winning prizes at Oshkosh, but the bulk of the maintenance issues on homebuilts (or really, cars and such too) comes in the mechanical and electrical stuff. Plus, that’s where the real head-scratching can come into play, especially when kits give good structural instructions but then don’t usually say much more than “at this step, install systems”. But as far as the FAA is concerned, you can pretty much buy those pre-assembled and install them for minimal penalty and no real understanding of what you have.

    Look at the E-AB accident stats; structural failure is way down the list. Systems problems (poor installation, poor maintenance) make up the bulk of technical causes.

    (Now when you get to large aircraft you see a whole lot of structural work going on, but a significant chunk of it is cold-working things back into shape and blending on corrosion, pitting, small nicks, scratches, etc. Lots of man-hours but a lot of it is simple stuff.)


    I do expect the FAA to relax the 51% rule in a way; the rule as it stands today will remain, but there will be another option. I think it will be something more like a cross with E-LSA—you don’t qualify for Repairman certificate automatically and have to go take a class like for LSA, for example. Or you can buy a more complete kit and build it exactly to plans, and get a short flyoff, but still have to do the classes.
     
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  18. Jan 15, 2020 #118

    cheapracer

    cheapracer

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    Make them build 100% of their fuel system, and demonstrate 100 times turning their fuel on and off.

    And make them write on a blackboard 100 times: "No, I can't make this final turn, I'll go around again".
     
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  19. Jan 15, 2020 #119

    lr27

    lr27

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    Jay,
    I'm sure you're right about some of these things, but it sounds like you're assuming that everything has to be done just like the big corporations do it. For instance, you talk about a minimum gantry width, but if the equipment is scaled to the size of the job, that width should be proportional to the reduced scale we're talking about. When the height, length, and width are all much smaller, weight, power consumption, etc will be FAR less. Don't forget that the tape can be narrower, or maybe even just tow. Big aerospace designs are optimized to the nth degree, but that's not worth it here. I'll be surprised if crazed hobbyists don't make huge advances on small scale tape laying in the next few years.
     
  20. Jan 15, 2020 #120

    Jay Kempf

    Jay Kempf

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    lr27. Tape is stable enough to go through the rollers. Gantry width has to do with delivery of tapes and all of the support gear. No gear other than power is on the bed. The weight and size of all that stuff drives gantry design. I know the people that developed all this stuff. So far there is only one way to do it. Gantry isn't that wide maybe 20-24' and the machine I was working with was 110' Y axis. Crazed hobbiests could modify an expensive 6 axis gantry to lay one tape but cutting and laser tacking? Maybe hot staking. Without that stuff it just is a non start. It really isn't necessary for anyone other than Boeing Airbus
     

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