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Thread: Looking for anyones input for a design

  1. #1

    Rolls Eyes Looking for anyones input for a design

    Greetings!

    Not sure how to start my post, or where i should start it but itís my first time so here we go.
    Iíd like to mention first, that I am not an aeronautical engineer nor claim to be one.
    This is a personal project Iíve been working on for a while now, in secret and would like anyone's input, be it the good, the bad or the ugly.

    so now for a story.....of how this design came to be

    Since age 8 during my first flight in a piper warrior, I was bit by the freedom of flight, since then I had always wanted to build a plane, but never really knew how much work it took to design, or to even build one alone.
    So in 2015 age 25 I had the idea to get in contact with an aerospace engineering firm, I wanted to get a quote for a design that I had in my head, they quoted me around $100K

    So after dyeing a little bit inside, I figured if itís that much money, I can do it myself. (boy I had no idea what I was getting my self in to.)
    so I purchased Solid works and got to work teaching myself how to use CAD.
    A year later i put my project on hold and signed up for College, I then went straight in to the Aviation Science program where I acquired my PPL.

    After getting my PPL I resumed my project and dove deeper in to aircraft building and engineering.
    I started buying every book I could find on aerospace engineering, from aircraft structures to aerodynamics.
    but I still wanted to know more, so i started asking around and was usually told, just to buy a kit and modify said kit, then to design my own aircraft.
    plus it was less of a head ache.

    So putting my project aside I went out and acquired the plans for the Cassutt Racer, thinking I would do that to get a better understanding of how a plane went together, though Cassuttís are a cool plane, it still wasnít my design, it was Tom Cassuttís design.

    So I went back to sleepless nights and more Solid works.
    I used the plans for the Cassutt, to teach myself, (with plenty of help from the many books i had acquired in a 7 year span) how to dissect the Cassutt with understanding, while learning/teaching myself Solid works.

    So after many (iterations, engine type changes, Failures of having to start all over again, all the sleepless nights after work, weekends glued to a screen over a crazy idea and the times being I was told it wasnít worth my time or the head ache....

    Iím now to a point where I would like to show it to who ever would like to see my design as a pathfinder but please Keep in mind that there are things missing in the photos on purpose, and that this project is still in its infant stages, there is still a lot that needs to be done.
    Also, if anyone would like to give me some constructive criticism or pointers, Iím always willing to listen, and learn.
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  2. #2
    Eric Page's Avatar
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    That's a remarkable story, and it's a very interesting design. I'm amazed that you've done this as a self-taught designer.

    It looks like it would have fantastic visibility. What's the mission for it? If it's intended as a high performance fun flyer, are you familiar with the SubSonex?

    The mid-mounted wing behind the pilot evokes gliders, but -- and I'm assuming symmetry not shown -- you appear to have a pair of small turbine engines at mid-fuselage. I hope you're well-off, because turbines ain't cheap. Sonex sells the PBS TJ100 for $74,000 each.

    Turbines are thirsty; two of them apocalyptically so. Mentally scaling from the size of a human in the seat, this appears to be a pretty small aircraft. Will you have enough fuel capacity to achieve the desired range/endurance while remaining under a reasonable weight limit?

    Just by eye-balling, it appears to have quite a bit more vertical stabilizer than it needs, and the lower one may either prevent takeoff rotation or be forcibly detached from the tail on takeoff.

    The aircraft appears to have symmetrical airfoils fore and aft. Is this primarily an aerobatic design?

    Is there any luggage space? There doesn't have to be, of course, but if you plan to fly it any distance you'll want space for at least a small bag with toiletries and a change of clothes.

    Retractable landing gear is heavy and complex. If it's necessary for the performance goals, go for it, but well-faired fixed gear can have surprisingly little drag. Watch a YouTube video titled, "Why It Goes So Fast." In it, Mike Arnold explains the simple aerodynamic tricks in his AR-5 aircraft, which achieved 213mph on 65hp.

    Very cool project -- keep up the good work!
    Eric Page
    Building Kitfox Series 5
    Member: EAA Lifetime, AOPA, ALPA
    ATP: MEL | Comm: SEL, Glider | ATCS: CTO
    Map of Landings

  3. #3
    Eric, Thank you Sir for the kind words!
    I actually posted this to soon, I was in the middle of proof reading when i accidentally fat fingered the post button.
    So some images were missing that i never uploaded
    also it would probably help if I shared some sizing and my close but not final small list of specs.

    Close Approximations, not final numbers.
    Aircraft length: 24'
    Wing span: 23.5'
    Aircraft weight: 1700lb
    Aspect Ratio: 2.3716
    Wing loading: 7.855
    Airfoil Root: NACA 23015
    Airfoil Tip: NACA 23012
    Airfoil Tail: NACA 0012
    Engines: X2 PBS TJ100, 584lbf at max power. (292 per engine)
    Power to weight ratio: 0.34 at max power.
    Fuel capacity: 55gal
    Fuel consumption: 2.2752 lb/lbf/hr at max power.

    The changes that I'm currently working on, you had actually touched on, the lower tail section, most definitely to large.
    The tail came off a previous design that got scrapped, along with the wing. they are close to the same as what i need for this design, the wing will have to stretch a little bit to get the mains to not hit the side of the intakes.
    The lower section of tail will be about half the size shown, and the wings will be a bit longer.
    The aircraft sits about 5.5' from the ground to the sill of the canopy, I designed the cockpit around my size being 6'4"tall and 250lb... I find that i don't fit well in most small planes. "I was quite surprised when i fit in a cassutt for the first time."

    The Mission I'm shooting for is more of a personal jet, Point A to Point B with fun in between,
    also With the capability of reaching 20,000ft, to save on fuel consumption.
    It would also be fully aerobatic, I still have room in the nose for a back pack size bag,and also behind the head rest.
    along with a spot for an O2 tank for any flying over 12,500ft.



    I have actually talked with the Sonex team, back when i first started designing this plane 7 years ago, they were very nice and helpful when it came to the materials i had questions about.
    In the beginning i had actually thought about fiber glass build up, like the AR-5 aircraft, and had stumbled on Mike Arnold's AR-5 video. some really good info in that.
    Since then i have gone to aluminum build up, i also had a frame design in 4130 steel tube. it was to clunky and over weight that way.

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  4. #4
    Dana's Avatar
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    Looks like a fair amount of forward side area, so you may well need that large tail... but on top; as Eric said what you have now will interfere with rotation and flaring for landing. Getting rid of the lower fin might also let you reduce the main gear length.

  5. #5
    I figure that ill just post my progress as i go.
    I removed the old section of lower tail, then created a new upper section, though I will still have to create the structure for the new tail,
    this wont be hard now that i have something to go off of.
    I changed the transparency of the new tail section but left the old tail for reference of the size difference.
    I started working on the lower tail cone just a little bit, it will probably change once i get some more figured out back there.
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    I also went ahead and built up some of the section behind the cockpit, for reference the O2 tank is about 15" long, and the plate that its sitting on is 37.5" deep
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