16 ft UL Geobat

Discussion in 'The light stuff area' started by inventing_man, Sep 8, 2008.

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  1. Sep 21, 2008 #41

    inventing_man

    inventing_man

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    DANG!! I didn't know they could do that . From what I could see on Utube it looked semi .
    Anyway for this project at this rudimentary stage , basic is the key word , slow and stable .
     
    Last edited: Sep 21, 2008
  2. Sep 21, 2008 #42

    addaon

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    And don't forget that paragliders are technically ultralights, and the new crop of aerobatic paragliders is rated to 16g (ultimate, I assume). Negative g's are a no-no, though, when your wing isn't rigid.
     
  3. Sep 27, 2008 #43

    inventing_man

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    To be less expensive ( especially in these times :dis: )I've bought some 1/4 OD aluminum tube from the local hobby shop and will try to form a 20 inch dia complete air frame . This will give me a better understanding of the parts , how to form and assemble them . Scale is 1" = 1'
     
    Last edited: Sep 27, 2008
  4. Sep 28, 2008 #44

    mstull

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    I spent quite a spell looking into making an aerobatic U/L with a symmetric or semi-symmetric airfoil. It's not impossible, but quite challenging. In real life, and in the formulas in AC103-7, those airfoils aren't particularly stall resistant. So it takes even more wing area to pass the stall speed limit. That extra wing area adds weight and drag.

    Another issue is whether a symmetric or semi-symmetric airfoil would be in any way useful. At the speeds legal U/Ls fly, and especially with that added wing area, the roll rate is so slow, getting the plane inverted, and recovering back to upright, isn't particularly safe or practical. It works out better on a biplane. It's shorter wings roll faster, and you can add the extra wing area without adding too much weight. You'd also need an inverted fuel system, diaphragm carbs, and a heavy, multi-point, pilot restraint system.

    That N-22 airfoil looks fine... very similar to the U/L standard Gottingen 387.
     
  5. Sep 28, 2008 #45

    Dana

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    I wonder if the MX Super was truly 103 legal? (Doubtful) It handled pretty good without being a biplane, though.

    -Dana

    Hardware: the part of the computer that can be kicked. If you can only curse at it, it's software.
     
  6. Sep 29, 2008 #46

    inventing_man

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    On the Stewart System for covering, I got an Email back from them that said the system is foam safe and will stick covering to aluminum or wood like you wont believe . " with a fresh Citrus scent while you work " ... :roll:
    Just passing info along , But this sounds like the cats meow for garage building UL's to me.
    ****** EDIT*****
    Just found out Stewart Systems are having a covering class in Huntsville Arkansas , Just 60 miles from here, this Friday - Sunday 3 - 5. I can only make Friday cause I have to work:ermm: Hopefull will gleen some info and maybe a sample or 2 .
     
    Last edited: Sep 30, 2008
  7. Sep 30, 2008 #47

    bmcj

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    I remember seeing photos of similar planes that flew pre-1925. I think it was in "Jane's All the World's Aircraft".

    Regarding stall speed, I seem to remember reading articles and posts that indicated the FAA uses a formula with weight and wing area to determine stall speed for Light Sport (or maybe it was ultralight) certification, not demonstrated stall speed as you might suspect.
     
  8. Oct 2, 2008 #48

    JMillar

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    You have the choice (I believe). You can go with the formula, or if you fail the formula test you can [try to] demonstrate it.
     
  9. Oct 2, 2008 #49

    radfordc

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    If asked (no one ever has been that I'm aware of), the UL operator must prove that he is in compliance with Part 103. The operator may do so in whatever way is acceptable to the FAA. Using the charts in AC103-7 is one acceptable way.

    Charlie
     
  10. Oct 2, 2008 #50

    Dana

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    The formulas in AC103-7 can be used to show that an ultralight (not LSA) is in compliance with the Part 103 requirements. Usually it's conservative... an aircraft may meet the calculated requirements for stall and max speed (and thus be legal) while in fact being considerably faster. Some manufacturers actually list "Part 103 stall speed" and "actual stall speed".

    -Dana

    Smallpox has been largely destroyed - should the virus be given endanged species status?
     
  11. Oct 3, 2008 #51

    fleetstreet

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    I realize this is way off base regarding what you're proposing, but I wondered if any of the data about the Vought V-173 / XF5U-1 "Flying Flapjack" or "Flying Pancake" might be of interest to you.
     

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  12. Oct 3, 2008 #52

    Norman

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    The hole in the middle makes it a whole different creature. I don't know of any real data on annular wings, other than an article in “The Aeroplane” February 1947 and a few web pages. However there has been some work done with joined wings that should apply to some extent because the only difference between a geobat type and a typical joined wing is the curved leading and trialling edges
     

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  13. Oct 4, 2008 #53

    inventing_man

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    Stewart Systems Is a Grate Product . I would highly advocate its use . Its easy to use, and it even color indicates areas where there is not a good bond . To correct the bad areas a simple pass with a hot iron does the trick. Not flammable . non toxic . Good people behind the products too !!
    Its also way tuff to pull the fabric off frame members once its set. The fabric tares before the glue lets go ...... BUT hit it with and 350 degree iron and it comes off easier.
     
  14. Oct 12, 2008 #54

    inventing_man

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    Just wondering about putting the air control surfaces inside the hoop ring. I know its not efficient and will produce drag, , But Would it have a detrimental , disastrous effect to control ?
    To explain better , If there was a 2 inch dia. tube 3 -4 inches behind , and running the length of the trailing edge of the elevator and aileron?
    The trailing edge of these surfaces is 3/4 inch dia.
     
  15. Jan 7, 2009 #55

    Femmpaws

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    I have used Stewart Systems Ekobond on a couple of little projects. It's nice to work with and you clean up with water! Sure beats Fasttack!

    Someone was thinking of using a Clark Y airfoil for the UL Geobat. My question is why? There are better airfoils out there I know Harry Riblett's GA 30-613.5 has better lift and less drag then a 12% Clark Y. I have his book with the airfoil's plots as well.

    Seeing how the big thing is getting a lot of lift in as small a wing area as you can then go to the GA 30-615 or the GA 30-616.5 with the deeper wing profile you can make deeper spars using lighter spar caps. The deeper wing profile will also help in spar placement.

    Another idea that crossed my mind was, what would happen if you changed from round to a more elliptical shape to give you more wind span. Again you would get more wing area as well. I have seen the flow patterns on a swepwing and it does some strange things that doesn't help with lift. I think you could end up with the same thing here.

    I was also wondering what would happen if you set it up as a tractor engine. That way you put the pilot on the CG. There looks to be a lot of aircraft weight behind the point of CG. You would also get more lift out of the wing in the prop blast, over it being in free air.

    Oh just so everyone knows I'm a newbe to the list and saw the Geobat some years ago on TV. I do think it's a great idea and would like to see it make it into a full size aircraft. It's kinda on the same idea as the Join Wing from about 25 years ago.

    Yes I am a member of the EAA and have been a member for some years.

    Blessings all
    Paws
     
  16. Apr 22, 2009 #56

    xj35s

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    Inventing _man, how are you? Did you give up on the geobat? I'm very interested in what you've found.
     
  17. Aug 21, 2009 #57

    inventing_man

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    I have not given up on the idea . I started building a Airchair Pig Page for construction experaince in UL fabrication until my better half was laid off.
    Were kinda in survival mode with our income . Hope to resume soon.
    The Oval -ized theory may have some merit to it . As this UL verson needs to fly slow , unlike the GA version, It could serve well.
    The PIG I planed on Motoring with a 4 stroke 23 HP w/ 62 inch prop With 194 sq ft of wing area. This will dictate what needs to happen with the Geobat.
     
  18. Nov 13, 2011 #58

    Dandmmondrik

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    Yes ben browsing your sight 16ft geobat can u contact me.
     
  19. Nov 23, 2011 #59

    inventing_man

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    I sent an email to ya . What site ? the Pig page I linked to ? If so
    It's not my creation . Mike Sandlin is the owner of that site .All those aricraft are his designs . I'll be working the evening shift all week so I may be slow in responding.

    Turkey sandwich on the go will be my Thanksgiving :dis:
     
  20. Jun 13, 2017 #60

    rtfm

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    Hi,
    I wish to revive this old thread, in the hopes that there are some on the forum who might be interested in discussing the Geobat.

    My interest in this design isn't strictly speaking with a view to building a Geobat - but in building a Geobat wing mounted on a "standard" airframe. If you've been following the "Motorcycle of the air" thread (from page 99 onwards) you will have seen a few concept drawings of an airframe with a solid disk parasol wing. My feeling is that a solid disk is not very aesthetically appealing. Besides (as initially drawn) the disk in those sketches is mounted on a universal joint situated at the disk centre. The problem with that is that a disk flies with the CG at the 25% chord. Placing the universal joint on or near the 25% chord would present issues with a solid disk, not the least of which is the excessive weight of the disk behind the pivot and the fact that the main spar would optimally need to pass through the centre of the disk.

    For these reasons, I think a Geobat wing would be eminently more suitable.

    Having said this, I would dearly love to build a 20ft GeoBat. I don't think the design is either difficult to build or impractical to fly. It is basically just a wing, and a very compact (and light) wing at that.

    So please, if anyone is fascinated by or interested in the Geobat - please chime in with either your experience, research or personal design ideas.

    Regards,
    Duncan
     

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