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Thread: Go Fly - Where to post

  1. #1

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    Go Fly - Where to post

    The UL strip is a strange place to post a Boeing Go Fly proposal (http://goflyprize.com/) but here it is as I see no other place for a true experimental aircraft design discussion.

    Since the HBA sight is down as noted in the Hangar Talk section I am posting the following here. The proposal does qualify as an ultralight with the 254 pound empty weight UL limitation.

    As Phase I of the Go Fly completion is nearing completion I would like to publish some ideas and observations for the entertainment of the many HBA critics. Go ahead and make your negative (or positive) comments. Check my math and fire your arrows. English to SI unit conversions are approximate.

    Taking the 8 foot max dimension into account I have assumed a powered lift vehicle for the apparent VTOL or near VTOL requirement to operate within the 30 foot diameter 12 foot high cylinder. Furthermore a 200 pound minimum useful load is specified. Generally an aircraft that can lift its own empty weight is considered a good design so I made the assumption that a 250 pound empty weight and 500 pound gross weight would be a reasonable starting point. I am proposing to enclose the lift fans in an 8 foot diameter circular duct for safety and noise constraint reasons. Configuration study CAD drawings are available.

    With these figures in mind I came up with the following specifications for standard day sea level operation.

    Go Fly Entry Proposal J-1
    Specifications:
    Empty weight 250 pounds
    Gross weight 500 pounds
    Duct Outside diameter 8 feet (2.4 meters)
    Duct area 50 sq. ft. (4.6 sq. meters )
    Duct loading 10 pounds per square foot (50 kg/sq. m)
    Duct inlet area 50 sq. ft. (4.7 sq. m)
    Duct exhaust area 33 sq. ft. (3 Sq. m)
    Hover downwash velocity 55 mph (25 m/sec.) -Assume uniform steady flow.
    Hover power loading required 7 pounds / hp (1.8 kg/Watt) -Asssume100 % hp to thrust efficiency.
    Hover power required 72 hp (54Kw) -Asssume100 % fan efficiency and zero duct loss.
    Proposed rated power 100 hp (75 Kw) minimum for std. day S. L. operation.
    Note: 150 to 200 hp (110 to 150 Kw) Max T.O. )(one minute) power desired for the proposed VTOL operation.

    I am considering a 1/32 scale model to illustrate the proposed design. Some motor details and other design features are being evaluated. Additional information and suggestions are available. However, as others have concluded the likelyhood of success is problematical and therefore I do not anticipate an official design submission on my behalf. If any readers with a greater risk tolerance wish to advance the cause I welcome additional discussions.
    Last edited by jedi; 04-04-2018 at 06:17 AM.

  2. #2
    rwanttaja's Avatar
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    You assume a 100% HP to Thrust efficiency, 100% fan efficiency, and 0% duct loss. What are more realistic values for these, and how does this affect your required horsepower?

    Ron Wanttaja

  3. #3

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    Quote Originally Posted by rwanttaja View Post
    You assume a 100% HP to Thrust efficiency, 100% fan efficiency, and 0% duct loss. What are more realistic values for these, and how does this affect your required horsepower?

    Ron Wanttaja
    I thought others would like to fill in those details. Let me suggest 95%, 90%, and 80% as conservative numbers. All depends on how much expense and development effort goes into the project.

    We can nit pick efficiency numbers but if it can't be done power and weight wise with 100% efficiency there is no need to continue this proposal. That appears to be the general consensus at this point.

    I do do not see valid reasons to continue other than let's give it a good old college try. I've got other bigger fish to fry.

    Thanks for for your comments. Guess what I am really looking for are reasons to continue and possible support or encouragement. In other words, anyone out there that I can pass the ball to.

    Computer graphics skills or familiarity with large drone systems are desired experience.
    Last edited by jedi; 04-04-2018 at 12:57 PM.

  4. #4

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    2. Begin by looking at helicopter data. You will be able to find or calculate all the information you are asking for.
    3. Thrust to weight at liftoff needs to be at least 1.1 to 1.0
    4. Scaling is more difficult than it first appears. Orville and Wilbur tried to scale up their toy helicopter... they soon realized it would not work like that. In other words, small will work, larger may not.
    1. Don’t try to ignore Physics or Laws. Those will not change for you or any others.

    I really, really wish you well. I’m not trying to be Negative Nellie, but my degree makes me add reality to the equations.

  5. #5

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    10 pounds per square foot disc loading and 7 pounds per horsepower is about 60% efficiency (.6 Figure of Merit)
    But it requires a minimum of two rotors to cancel torque. And with just the two coaxial 8 foot rotors, cyclic is required for control.
    So the question is can you build this at under 250 pounds? What does a 72hp power module weigh? (motors, batteries, controller, gear reduction)
    Last edited by Bill Berson; 04-05-2018 at 11:21 PM.

  6. #6

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    We looked at this contest and came to the conclusion there were just to many breakthrough technologies required. The craft has to be a very small, light airframe, the noise restrictions are severe and the batteries are way too heavy. Using the example above and current battery weights. One hundred HP (75 kw) will cost 15 - 20 lbs per minute of operation and any VTOL will require even more. The stability and control requirements will require considerable development for such small, high power loading aircraft. A good exercise is to dynamically scale up an existing multi-rotor model to man-carrying size. I think you be amazed at the power required and the weight fraction of just he batteries.

    Vince Homer

  7. #7

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    Quote Originally Posted by Vince View Post
    We looked at this contest and came to the conclusion there were just to many breakthrough technologies required. The craft has to be a very small, light airframe, the noise restrictions are severe and the batteries are way too heavy. Using the example above and current battery weights. One hundred HP (75 kw) will cost 15 - 20 lbs per minute of operation and any VTOL will require even more. The stability and control requirements will require considerable development for such small, high power loading aircraft. A good exercise is to dynamically scale up an existing multi-rotor model to man-carrying size. I think you be amazed at the power required and the weight fraction of just he batteries.

    Vince Homer
    i agree Vince.

    B B, I like a dual quad copter configuration of 8 rotors with some overlap. If all electric 8 15KW motors should do the job. To much battery weight though.

    I think the concept would work well for a 50 pound useful load. I would like to see that built.

    250 pound empty weight. 300 pound gross weight. Numbers on that are reasonable.
    Last edited by jedi; 04-07-2018 at 09:59 PM.

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