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Thread: 16 ft UL Geobat

  1. #1
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    16 ft UL Geobat

    I dont know if it can be done ? Basing it on a continuous 2 inch T6 ring . Bent to remain in tension . Elevators, ailerons inside ring (ring goes all the way around) Clark Y fabric 'n foam ribs ply doublers , Twin tail booms span and attach across the diameter of the ring. Box Spar at CG .

    Any input??? thoughts

    1/2 scale ring bent , redneck wind tunnel trailer mount testing with 1/4 scale servos.?
    Last edited by inventing_man; September 7th, 2008 at 07:24 PM.

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    Registered User mstull's Avatar
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    Re: 16 ft UL Geobat

    Iman,

    I looked up the R/C Geobat to see what you were talking about. It is a very creative, odd design, that compromises efficiency for aesthetic appeal. I'm sure if it was someone's goal in life, he could make that shape into a "real" plane that flies. But it is doubtful it could be made light enough to be a Part 103 legal U/L.

    It takes an awful lot of wing area to pass the legal stall speed limit... much more than your 16' circle. It would probably take more than 24'... and then end up well over the U/L weight limit. Suggest you make it as an Experimental Amateur Built, and fly it as a LSA. I'm sure it would be a HUGE hit at Oshkosh or Sun-n-Fun... if it didn't kill you. Good luck with your project.
    Attached Thumbnails Attached Thumbnails 16 ft UL Geobat-fomie-geobat-1.jpg  
    Mark E. Stull
    mstull@wtxs.net

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    Registered User rtfm's Avatar
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    Re: 16 ft UL Geobat

    Hi,
    This would be a REAL blast to build. Basically, the front half is the wing, and there isn't a lot of it. I have to agree with mstull on this one. One of the limiting factors in this design is that in order to get sufficient wing area, you have to have quite a big circle. Which means a large tail area also. With "standard" wings, these can be as long as required. Your design needs to encompass the wing tips into the circular shape. A lot of weight.

    You effectively have an aircraft with heavily swept wings. Will you be able to get the CG positioned correctly for stable flight? Putting the pilot on the wing leading edge (I imagine this would be the cockpit location?) is going to be a challenge, CG-wise, I'd think. But hey - I'd love to build one...

    My 2c

    Duncan
    Last edited by rtfm; September 7th, 2008 at 08:19 PM.

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    Re: 16 ft UL Geobat

    Hi Mstull & RTMF . One of the members of the geobat team said that 16 foot would be the right number for a single place UL . Oddly enough the CG culminates more to the center of the circle and slightly nose heavy
    In the wind tunnel , test showed a very aerodynamic form with very little drag . The stats are impressive .The tester said " it seems we have a new type aircraft" STOL capable and very stable . . However being a UL we want slow and stable..... I do anyway. That is the qualities I would hope to draw out of it for a UL . It will be mucho testing before I even " think" about building , much less flying it. However a 8 foot rc controllable mockup could provide a road map to a workable design and fairly inexpensive to accomplish.
    Sure is going to be fun messing with it this winter .
    Open to Ideas and indigestions
    Btw i got's one of those foamies , it'l hover with a little head wind. But most foamies do too, so its not a definitive characteristic...at least in foam
    Last edited by inventing_man; September 7th, 2008 at 09:20 PM.

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    Registered User rtfm's Avatar
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    Re: 16 ft UL Geobat

    Hi,
    Good on ya. I think this is such an eye-catching design. Designing and building a large-scale model might be a great winter project. I'm envious.

    Keep us posted. If the wind tunnel testing figures translate into actual flight figures, you might well have the envy of every airfield on your hands...

    Regards,
    Duncan

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    Registered User Mac790's Avatar
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    Re: 16 ft UL Geobat

    Check out this link for more info about similar concept.

    http://discaircraft.greyfalcon.us/ARTHUR%20SACK%20A.htm
    Attached Thumbnails Attached Thumbnails 16 ft UL Geobat-fe2.jpg  

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    Registered User mstull's Avatar
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    Re: 16 ft UL Geobat

    Iman,

    Whoever suggested 16' diameter for an U/L hasn't studied AC103-7, or lives in another country (not the USA) that has different stall speed laws. The Geobat looks real cool, but can't break laws of physics.
    Mark E. Stull
    mstull@wtxs.net

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    Registered User billyvray's Avatar
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    Re: 16 ft UL Geobat

    Sweet, my dad and I helped the inventor build his first Geobats! I'm telling you, the dang thing is awesome. It goes fast and stable and slows down to almost a hover.
    Granted, that is an RC plane, but it outperformed similar size power/weight models. He's now on to bigger things - we keep in touch here and there. neat guy.
    If I remember correctly, we sketched UL version a few years ago and figured up to 20 ft diameter would be about max. The whole thing acts kind of like a lifting body so the area is pretty good size.

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    Re: 16 ft UL Geobat

    16ft would be the smallest size that would give you 100sq ft of wing area.
    Once you move up to around 22ft of wing span then it could be a 2 man ultalight
    if you had the right size engine.

    Most ultralights single place are in the 100- 120 + sf wing area seems like from what I can tell .

    Hey billyvray can you draw out where the aileron servos are located on Jeffs bat?
    I sent your dad an e mail, but has not replied . Guess hes busy workin on the big'un.
    Last edited by inventing_man; September 8th, 2008 at 04:58 PM.

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    Registered User xj35s's Avatar
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    Re: 16 ft UL Geobat

    I'd like to add my two cents. I'm a frisbee guy. the one with the hollow center are awsome. They are very stable in winds. I think this is a great project. With todays materials and light weight foam I bet it'd work.

    As per CG, looking at the RC version picture above it seems engine placement would balance the thing. A long aluminum tube for the wing edge, all the way around. Two plywood tail booms and the fuse is done. now just the ribs and fabric.

    Way cool.

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    Registered User radfordc's Avatar
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    Re: 16 ft UL Geobat

    Quote Originally Posted by mstull View Post
    Iman,

    Whoever suggested 16' diameter for an U/L hasn't studied AC103-7, or lives in another country (not the USA) that has different stall speed laws. The Geobat looks real cool, but can't break laws of physics.
    One question I'm not sure of....does Part 103 stall speed refer to "power off" stall or can you use the engine to provide lift for a lower stall speed (I don't think AC103-7 addresses this?). If so, then you could actually get into a "hover" mode using the engine for additional lift.

    Charlie

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    Registered User radfordc's Avatar
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    Re: 16 ft UL Geobat

    Quote Originally Posted by mstull View Post
    I'm sure it would be a HUGE hit at Oshkosh or Sun-n-Fun... if it didn't kill you. Good luck with your project.
    There was a "ring wing" plane that used to show up in the UL area at Oshkosh back in the mid-90s. I never saw it fly, nor know if it ever flew. Looked scary to me.

    Charlie

  13. #13
    Moderator Dana's Avatar
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    Re: 16 ft UL Geobat

    You can do ridiculous things with R/C models, due to the ridiculous power to weight ratio and the low Reynolds numbers, that you'd never get away with in a full sized aircraft.

    It's interesting, but I really can't see any practical advantages to such a design.

    -Dana

    Giving money and power to government is like giving whiskey and car keys to teenage boys.

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    Registered User WileEZ's Avatar
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    Re: 16 ft UL Geobat

    Quote Originally Posted by Dana View Post
    It's interesting, but I really can't see any practical advantages to such a design. -Dana
    When does it have to be practical? Granted if one want to make money off the design, etc., some practicalities have to be considered.

    But if one want to do something different, I'll say "go for it!" A lot of interesting and great discoveries and inventions were because someone wanted to fool around with an horribly impractical concept. I'll trust that the builder will know the limitations and not kill him/her self or others in the process.

    Building a model is a good first step, and one can decide to go full size or not based on the model studies.

    Quote Originally Posted by Dana View Post
    You can do ridiculous things with R/C models, due to the ridiculous power to weight ratio and the low Reynolds numbers, that you'd never get away with in a full sized aircraft.
    Agreed, I would suggest using the smallest, even slightly underpowered engine to more or less mimic "real world conditions".

    One gotta start somewhere!

    Beside, it would be kinda cool to see something like this flying even if it's totally impractical.
    WileEZ
    "All of my ideas are suspect until proven otherwise!"


  15. #15
    Registered User mstull's Avatar
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    Re: 16 ft UL Geobat

    Yes, U/L regulations specify that the plane must still fly at 24 knots (28 mph) with the POWER OFF. So stall speed must be 27.999 mph or less.
    Mark E. Stull
    mstull@wtxs.net

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