Issues and Solutions for kit- and plans-based sailplanes and motorgliders

Discussion in 'Soaring' started by TerryM76, Sep 3, 2019.

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  1. Sep 12, 2019 #221

    BoKu

    BoKu

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    The profile transitions were smooth, imperceptible to the eye. Probably ruled lofts between planform breaks. We measured the inboard end just outboard of the fillet, the separation for the 15/18 extension, and the tip of the 15/8 extension. We might also have measured in the vicinity of the inboard planform break, I don't recall.

    Edit add: The washin/out transition was pretty subtle, but it was quite clear when the light was just right.

    Edit add: We only measured one wing. But with the CNC'd Streifeneder molds, they are likely very symmetrical.

    --Bob K.
     
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  2. Sep 12, 2019 #222

    BJC

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    You are stuck in a technology trap, BoKu. I skipped the obvious step of placing the form on paper or mylar and dragging a pencil around the inside of the captured shape. (Stated for others; I’m certain that you know.)


    BJC
     
  3. Sep 12, 2019 #223

    Topaz

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    Tailwheels?
     
  4. Sep 12, 2019 #224

    Jay Kempf

    Jay Kempf

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    Yup, plural as you surmise.
     
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  5. Sep 12, 2019 #225

    Victor Bravo

    Victor Bravo

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    Wow Jay that's got some serious potential. I'm assuming you have little tailwheels under the rudders?

    EDIT: never mind, I see that questionw as already answered.

    What turns the propeller?

    All I need now is for everyone else to get out of the way so I can climb in and fly it off into the sunset....
     
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  6. Jan 19, 2020 #226

    lr27

    lr27

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    Just read this entire thread, which was quite an effort. Hoping I can remember the things I meant to comment on.
    ---------
    RC gliders, if they are strong and slippery enough, can launch twice as high with a winch as with a high start. Maybe three times. Huge vertical zoom at the end.
    --------
    Seems like this thread has veered off towards the expensive end of things.
    -------
    If carbon fiber is so good, and so cost effective, why not use it to make the sailpane cheaper rather than higher performance? How light can you make a motorglider that matches the performance of a 1-26? Can you make it light enough to comply with part 103? If you could, that would save a fair amount of money and presumably keep the FAA out of your life.
    -----------
    I think moldiess composite construction, but with vacuum bagging, might be a good direction. If you use semi rigid plastic sheets when bagging, that might eliminate the need for a lot of sanding. Especially if you can accept turbulent flow over most of the airfoil. I know a number of people who have made wings for models this way.

    These days, it's not that big a deal to make an NC foam cutter. If you can control the speed correctly, the wire can melt the foam by radiant heat alone, leaving an accurate surface that might not even need to be sanded, People I know have made such cutters.

    To keep the weight down, the chord for such foam core wings should be short. With carbon fiber, those wings could be fairly long instead.

    Maybe it's possible to create cavities in the foam after bagging, to save weigh, and maybe bag something inside the cavities for strength and stiffness.

    I'd better post this before the computer eats it, while I try to remember what else I was going to write.
     
  7. Jan 19, 2020 #227

    lr27

    lr27

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    Oh yeah. Those NC foam cutters could make foam molds too. Line with polyethylene sheet, waxed aluminum, or whatever.
    -------------
    Kollman Wings' website lists a kit for Marske's Monarch. 20:1 and 135 fpm. $12,500 Possibly light enough for part 103. It also discusses options for adding power, though I think that might raise the stall speed just above part 103 legal. I wonder how much the performance could be improved by enclosing the pilot?
    ---------
    Plans for the Carbon Dragon, the Woodstock, and the Windrose are available on line. If the performance figures for the long winged versio of the Windrose are to be believed, it's almost good enough that no one can sneer at it. Search engines can find these faster than I can cut and paste the URL with my phone.

    Maybe the Windrose could benefit from the vacuum bagging I discussed previously. Years ago, I spoke with Matt Redsell, who complained to me about the huge number of hours he spent fairing that wing.

    ----------
    It occurs to me that the range of a self launcher might be made respectable by use of a gas powered sustainer engine with two electric motors on the wing for climb. This might be helpful on the Windrose. It doesn't look like there's room for much of a prop in the designed position.
    --------
    Seems like flying wings along the lines of Backstrom's planks might save a lot of weight and work. And also leave a place for a pusher prop. Backstrom thought, later, that wider chord where the elevons or elevator were would reduce kinks in the lift distribution. I wonder what the planks were like to fly?
     
  8. Jan 19, 2020 #228

    Hot Wings

    Hot Wings

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    Don't worry about loosing posts with the new software. It does a very good job of it too.
    Aircar would have loved this feature. Really miss his input.............

    Just one data point before I have to go to the family Sunday breakfast thing:rolleyes:

    On my AV-36 project using carbon rods to replace the spar caps would save around 12000grams. That is 26 pounds for the spar caps alone. But I'm stuck using wood because it is what the original used.

    As originally designed the AV with non folding wings can be built under the 254# part 103 weight. With composites I'm confidant that a similar structure can be built light enough to include at least a sustainer class of power.
    The original, and relatively dirty, AV-36 real world tested at 24/1.
     
  9. Jan 19, 2020 #229

    BBerson

    BBerson

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    That's sort of an absurd requirement. By definition a motorglider will be heavier and usually more drag than the identical pure glider. Even Schweizer couldn't build a practical 1-26 motorglider of equal performance.
    So get beyond the idea of matching performance. A motorglider has vastly more other uses and doesn't need to be in an impossible competition with pure gliders. That goal leads to Stemme.....

    I would be far more interested in a motorglider competition if it was limited to a small span and low performance.
     
  10. Jan 20, 2020 #230

    proppastie

    proppastie

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    Original Carbon Dragon weighted 147 lb....add an engine to that. Same with Sparrow Hawk ....even higher performance
     
  11. Jan 22, 2020 at 3:17 AM #231

    Bille Floyd

    Bille Floyd

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    Yep -- i can match the performance of a 1-26, "With" a motor
    and a carbon spared wing / podded glider, and 103 compliant
    but
    It will land in 1/2 the space of a 1-26, and only match those
    performance figures, at anything under 58-mph.


    I'm a HG pilot ; those numbers are just fine , for me !!

    People talk about 40:1, or it don't matter ;
    but if there isn't more new blood in the soaring side
    of aviation soon --------- then your performance gliders
    won't have any pilots to Fly them , in another 30 years .

    The Last HG Fly-In, i attended at CSS, in San Bernardino,
    there were about 150 Hg pilots there ; most all of them
    would wanna fly, what i just suggested.

    Bille
     
  12. Jan 22, 2020 at 5:27 AM #232

    Victor Bravo

    Victor Bravo

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    But a LOT of hang glider pilots are getting older and getting tired of blowing out their knees, or are having trouble carrying a glider on their back. So self-launching, or capability to launch from the LZ and thermal... I'm guessing is a really good thing to pursue. That's how Mike Sandlin started with the BUG of course.
     
  13. Jan 22, 2020 at 10:39 AM #233

    Bille Floyd

    Bille Floyd

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    Yea Knees, hips, feet, and ankles :
    lucky me , that a bit of WD-40 , is all i need for the SS ankles
    to work better !! LOL
    paullangphotography.com .jpg

    I'v known Mike Sandlin , and Floyd Feronious, for 40+ years ; both
    of them are top-notch guy's !!

    Bille
     
  14. Jan 22, 2020 at 10:43 AM #234

    lr27

    lr27

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    I think it would be a pretty poor engineer who couldn't improve on a 1-26 when using a far stiffer, stronger, and lighter material in places. Plus maybe using some of the new aeronautical knowledge gained in the last few years. Probably the improvement would allow the use of a motor without dipping below the performance of a 1-26. That's why I picked it as an example: it's performance is moderate, but good enough to have fun with. If you want arbitrarily degraded performance, just buy a Quicksilver or build a Goat. Personally, I don't think 23:1 is in snob territory. I'm pretty sure there are hang gliders that do that well, for people who have tough knees and ankles.
     
  15. Jan 22, 2020 at 10:56 AM #235

    lr27

    lr27

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    P.S. Nothing against the Goat if it does well enough, but I think a self launcher with 1-26 performance probably has a niche as well. Especially if you don't live near a slope with a good road to the top.
     
  16. Jan 22, 2020 at 10:57 AM #236

    Bille Floyd

    Bille Floyd

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    Most modern Hang gliders, will have an L/D, in the 15 to 18:1 range .
    That dang pilot, hanging below the wing, with the control frame out
    in the breeze ; it wreaks havoc, on the parasitic drag , (at speed).
    Place the pilot in a clean pod ; and my 20 year old Exxtacy rigid wing
    will be right there with the 1-26 , (anything below 58-mph) my VNE
    speed.
     
  17. Jan 22, 2020 at 3:22 PM #237

    proppastie

    proppastie

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    In theory yes....but it takes a good engineer to get the job done. If it was so easy there would be lots of what you are looking for.
     
  18. Jan 22, 2020 at 3:23 PM #238

    BBerson

    BBerson

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    Maybe so, but look around, very few amateur motorgliders. The ones that exist have degraded performance from pure gliders. (Moni, Monerai with pod, Zenos, Miller Sport, RF-3, etc)
    Even Van, worlds most successful kit designer has suspended his RV-11 motorglider design. It is very difficult to place an adequate engine and prop on a glider. Gliders by nature are heavy and are towed by powerful means. Adding an engine isn't simple.
     
    Last edited: Jan 22, 2020 at 4:33 PM
  19. Jan 22, 2020 at 3:34 PM #239

    Hot Wings

    Hot Wings

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    I believe you misspoke!? :D

    Adding one without degrading the performance expected from a glider, isn't simple.
     
  20. Jan 22, 2020 at 4:43 PM #240

    BBerson

    BBerson

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    My point is is that degraded gliding performance is hardly a liability, since the airplane performance adds so much more utility. So a balance between the desired glider performance and airplane performance must be calculated.
    If you choose to equal a glider performance then you are going more for a high end self-launching glider. If you balance with more airplane performance it can be smaller and more likely completed.
     

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