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Thread: Raptor Composite Aircraft

  1. #466
    Registered User rv6ejguy's Avatar
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    Re: Raptor Composite Aircraft

    Quote Originally Posted by Toobuilder View Post


    I firmly believe "crow hops" are killers. The ground is what hurts you- get away from it as fast as possible. Remember the last flying car "high speed taxi" video? 'nuf said.
    I disagree. In this case, with the elevator design and quite unknown flight characteristics and proper C of G location, I'd be doing the crow hops so as not to get into a severe pitch up scenario which is irrecoverable and below the altitude where the Ballistic Chute will save you. No way I'd launch this towards the blue with much haste. I can think of 2 guys who'd be alive today if they'd done hops instead of full blown takeoffs. C of G and elevator authority issues in both cases.
    Ross Farnham
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    "The world is changed by your example, not by your opinion" Paulo Coelho
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  3. #467
    Registered User Toobuilder's Avatar
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    Re: Raptor Composite Aircraft

    "...if the mass is about right..."

    And that is my concern - it's NOT even close to right. I'm assuming that if they are this far off on such a small airplane, then EVERY component is overweight, driving the MMOI into the realm of "unrepresentative". Perhaps it's all in the engine, but I doubt it.

    Concerning the risk/reward issue - I agree that a skilled program team can often make a good decision, but the cynic in me doesn't think this particular program has the tools to pull that off. And I'm really questioning ALL aspects of this design now - structure, dynamics, control authority, etc. This is in addition to the epic mass properties fail.

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  5. #468
    Registered User Toobuilder's Avatar
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    Re: Raptor Composite Aircraft

    Quote Originally Posted by rv6ejguy View Post
    I disagree. In this case, with the elevator design and quite unknown flight characteristics and proper C of G location, I'd be doing the crow hops so as not to get into a severe pitch up scenario which is irrecoverable and below the altitude where the Ballistic Chute will save you. No way I'd launch this towards the blue with much haste. I can think of 2 guys who'd be alive today if they'd done hops instead of full blown takeoffs. C of G and elevator authority issues in both cases.
    With that much uncertainty, they should not even be doing taxi testing. Unless someone is doing TLAR on a radical new aero concept, then almost every configuration under the sun has data attached to it. Today, one can be quite certain the machine is going to be at least "controllable" if the designer did their homework.

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    Registered User rv6ejguy's Avatar
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    Re: Raptor Composite Aircraft

    Quote Originally Posted by Toobuilder View Post
    With that much uncertainty, they should not even be doing taxi testing. Unless someone is doing TLAR on a radical new aero concept, then almost every configuration under the sun has data attached to it. Today, one can be quite certain the machine is going to be at least "controllable" if the designer did their homework.
    Peter didn't do his homework here so you could be right. I hope he gets some good eyes on it all before attempting flight and I'd be very surprised if Peter didn't attempt to fly it given his stakes and time spent on the project.
    Ross Farnham
    Racetech Inc.
    16 years and 428.6 hours on Subaru Turbo powered RV6A
    "The world is changed by your example, not by your opinion" Paulo Coelho
    http://www.sdsefi.com/aircraft.html




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  8. #470
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    Re: Raptor Composite Aircraft

    Quote Originally Posted by Toobuilder View Post
    With that much uncertainty, they should not even be doing taxi testing. Unless someone is doing TLAR on a radical new aero concept, then almost every configuration under the sun has data attached to it. Today, one can be quite certain the machine is going to be at least "controllable" if the designer did their homework.
    I guess my point about flight tests was about gross static stability and control characteristics, trim behavior, flight control dynamics under air loads, etc. Dynamic stability and fine measurement of axis rates would be "off" with this prototype, but I'd rather see them test this elevator configuration now, for example, than pour a ton of money into a more-refined second prototype and only then discover that the pitch axis has control problems. If they're keeping this control system and outer mold-line, they're going to have to test it sometime, so they can either take the risk now or take it later after spending even more money. They also ought to get some idea if their drag predictions are "in the ballpark" from this prototype, since the outer moldline seems unlikely to change markedly on the next iteration, regardless of the interior structural redesign. In essence, the thing becomes akin to a full-scale wind-tunnel model, with the mold-line and controls being accurate to their design, but the interior made of solid wood, as far as the air is concerned.

    Dunno. As I said, you've got more experience at this, but unless they're starting the redesign process with an absolutely clean sheet of paper, I still think there's value in flight-testing this overweight machine. Extremely cautiously, I'll grant.
    "If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them." - Henry David Thoreau

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    Discussion Thread for the Project: Discussion: Conceptual Design of an "Inexpensive" Single-Seat Motorglider

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    Registered User Toobuilder's Avatar
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    Re: Raptor Composite Aircraft

    I'd like to see them test this elevator system now as well - but NOT as the primary flight control of a prototype vehicle.

    Subscale auxiliary surface on a known airplane surrogate, wind tunnel, or hell - bolt it to a truck and run it down the freeway!

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    Re: Raptor Composite Aircraft

    Quote Originally Posted by Toobuilder View Post
    ... bolt it to a truck and run it down the freeway!
    Ah, the well-tried Rutan method!

    I think we're all agreed that the ideal situation here would be a clean-sheet redesign with Peter playing the role of the executive admin and marketing department, and some experienced and qualified aero-engineer doing the actual redesign. If they'd been open to that, unfortunately, it probably would've happened the first time around.
    "If you have built castles in the air, your work need not be lost; that is where they should be. Now put the foundations under them." - Henry David Thoreau

    Design Project: Conceptual Design of an "Inexpensive" Single-Seat Motorglider
    Discussion Thread for the Project: Discussion: Conceptual Design of an "Inexpensive" Single-Seat Motorglider

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    Re: Raptor Composite Aircraft

    Maybe it’s time for them to consider investing in a turbine. Phase 2 could have heated leading edges. I’m curious how much that multi-turbo diesel monster weighs. I do wish them well and would never rain on their parade.

  15. #474
    Registered User rv6ejguy's Avatar
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    Re: Raptor Composite Aircraft

    Quote Originally Posted by Mark Z View Post
    Maybe it’s time for them to consider investing in a turbine. Phase 2 could have heated leading edges. I’m curious how much that multi-turbo diesel monster weighs. I do wish them well and would never rain on their parade.
    If I recall, the firewall aft weight with prop was a bit over 850 pounds. The parade grounds are already soaked with this latest weight debacle...
    Last edited by rv6ejguy; March 6th, 2019 at 08:20 PM.
    Ross Farnham
    Racetech Inc.
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    "The world is changed by your example, not by your opinion" Paulo Coelho
    http://www.sdsefi.com/aircraft.html




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    Re: Raptor Composite Aircraft

    Quote Originally Posted by rv6ejguy View Post
    No, I was mainly thinking of young Devon (SP?) who has thousands of hours working on Raptor. He's learned a ton which will be useful on the next project he's involved with...
    Aha. A much smaller scope than I was thinking you were describing.

    Yes - for the kid, it's a great learning experience, and maybe even for Jeff - building things is always a learning experience. Devon would have gotten as much (or more) out of building a COZY MKIV (or the functional equivalent, if you like something else) from plans though, and it would have only cost the investors about $300K (rather than the millions they've spent on this one) and one or two years to pay three people to build a COZY MKIV (3K hours at $50/hr, plus materials, etc.) and he would end up with a flying aircraft. An expensive lesson for one kid, and no airplane kit to sell...

    Quote Originally Posted by rv6ejguy View Post
    I don't understand why so many newb designers enjoy eating crow.
    They don't enjoy it, because they are unable to see that that's what's going to happen, no matter what they're told or by whom. We're just stuck in the dark ages, with our old ways of thinking. The problem is that although the "out of the box" thinkers ARE the ones that make the breakthroughs, only about 0.01% of the "out of the box" thinkers do so. The other 99.99% of them fail. I'm conservative, so that's how I bet. I'll never hit it big, but I'll be right 99.99% of the time.

    Thanks for explaining to what you were referring.

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    Re: Raptor Composite Aircraft

    You don't have to build a complete aircraft to test out of the box ideas. The engineering simulation tools available today are like never before. Unfortunately you also need some sound experience and judgment to know what they can do and which ones to choose. When I saw what Peter was doing in what looked like Solidworks flow sim, it made me cringe and his SR22 comparison was just a joke!

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    Re: Raptor Composite Aircraft

    Any engineering / designing effort requires good judgement, gained through a formal education in the physical sciences and from relevant experience. No software package is an adequate substitute for knowledge and experience.


    BJC

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  22. #478
    Registered User rv6ejguy's Avatar
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    Re: Raptor Composite Aircraft

    Quote Originally Posted by Marc Zeitlin View Post
    They don't enjoy it, because they are unable to see that that's what's going to happen, no matter what they're told or by whom. We're just stuck in the dark ages, with our old ways of thinking. The problem is that although the "out of the box" thinkers ARE the ones that make the breakthroughs, only about 0.01% of the "out of the box" thinkers do so. The other 99.99% of them fail. I'm conservative, so that's how I bet. I'll never hit it big, but I'll be right 99.99% of the time.
    Agree, my remark was facetious. I wonder how they will take the backlash when they fail after calling the established players a bunch of dummies before he started their own wonder project.
    Last edited by rv6ejguy; March 7th, 2019 at 10:28 AM.
    Ross Farnham
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    "The world is changed by your example, not by your opinion" Paulo Coelho
    http://www.sdsefi.com/aircraft.html




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    Re: Raptor Composite Aircraft

    Quote Originally Posted by rv6ejguy View Post
    ... I wonder how these folks will take the backlash when they fail after calling the established players a bunch of dummies before they started their own wonder project.
    ”They didn’t give us the time / money / support needed to complete the development of our break-through design.”


    BJC

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    Re: Raptor Composite Aircraft

    Quote Originally Posted by rv6ejguy View Post
    Agree, my remark was facetious. I wonder how these folks will take the backlash when they fail after calling the established players a bunch of dummies before they started their own wonder project.
    Guys , I would truly appreciate,and it would be far more accurate, if you all would stop using the word "they". The decision making process that led to this outcome was conducted in a very singular atmosphere. Both myself and Mark ( a successful competent engineer with many noteworthy projects in his cache, Viperjet,MX2,my Orion (2200 lbs empty wt, 4-6 place, TSIO 550 Cont.,all molded const.,Click image for larger version. 

Name:	received_326836794594164.jpeg 
Views:	33 
Size:	24.7 KB 
ID:	78894 larger than Raptor and Velocity XL),my RA2, and many others) tried diligently to positively influence the outcome of this endeavor to no avail and with much frustration and futility. Nuff said !!!!!!!!!!!!! Sorry for the exclamation points Bob K.😂😂😱

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