How to build a better Swift?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Keshka, Dec 27, 2011.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Oct 17, 2012 #41

    Aircar

    Aircar

    Aircar

    Banned

    Joined:
    Feb 20, 2010
    Messages:
    3,567
    Likes Received:
    367
    Location:
    Melbourne Australia
    Thanks for the link Jarno (even better would be the aborted first flight attempts showing the ground looping :) --which disclose the problem with wing clearence and the low inertias -to their credit the Akafliegers posted the problematic flights as well as the end result . They still had problems on aerotow with the downwash of the tug tending to de stabilize the aircraft (reducing the angle of attack of the centre part of the wing and hence 'removing' wash out from the glider --in Australia we 'low tow' and stay under the tug's slipstream unlike the high tow used in Europe and the US so this would be presumably worse . [As an aside - my first flight in Germany was in the werkgruppe std .Cirrus -- never flown a Std Cirrus before and only got a very rudimentary briefing so I just did the usual and stayed in low tow which was apparently an emergency signal and I got towed around at tree top height until I cottoned on and went to high tow -- I came back a couple of hours later and nobody even commented ... I was told that it would be too hard to even get to fly in Germany first off but after presenting myself and logbook to the control tower at Hahnweide they gave me a luftfahrtshein without any hassle at all and a vague indication of where the Stuttgart approach zone was to avoid --I expected a check ride in a two seater or something but got dumped in the std cirrus and told I could fly it "so lange du wilst" . Also had never done any slope soaring before let alone with thirty or more other aircraft on the same ridge (Teck) so learnt fast .]

    The problem with tailess gliders is not always just how they behave in the air but what happens on take off and even more so on outlanding -- landing in a tall crop for example could be more than just exciting . We just had a motorglider accident here --a picture in the paper shows the aircraft belly up which is uncharacteristic of sailplane accidents but the tractor engine and conventional gear explain why --looks like it might be a Pipistrel Sinus or Dimona (only slight injuries happily)

    Forward sweep might be a solution provided the aeroelastics can be solved --the mildly forward swept Genesis is as good as the other tailed gliders it seems (and is semi tailed if it is being exact ) -- several highly forward swept gliders have failed --the Akaflieg Darmstadt "QuoVadis" as one example and the difficulties the SB13 had with flutter suppression and handling with aft sweep give cause for even more concern. The tailoring of the SB 13 to avoid flutter and placement of the spar far forward at the tips can result in control reversal in the extreme --the 'aeroisoclonic' (constant angle - under bending) such as the Short Sherpa was meant to avoid the instability that can result if the wing is too compliant (the spar is further AFT at the tips to counter the twist due to bending ) All in all the structural interactions in a pure flying wing and the ground handling habits are a big concern and reason enough to stick with conventionality - or try something else..
     
  2. Oct 17, 2012 #42

    Aircar

    Aircar

    Aircar

    Banned

    Joined:
    Feb 20, 2010
    Messages:
    3,567
    Likes Received:
    367
    Location:
    Melbourne Australia
    Postscript - Apologies to Jarno (when I took another look at the SB13 link lo and behold the aborted first winch launch attempt [windenstart] and the first aerotow attempt [erstflug] came up -- the flight off snow seemed a bit unwise even if just from white out , Both attempts end in ground loops and the pitch up puts the wing tip closer to the ground plus exposes a lot of the wing to catching something like grass or snow --for some reason the frame is wider than on the link I firstgot and more of the ground loop is visible --it is hard to exactly pin down the initiator of the yaw motion but it clearly is only very little resisted once underway . The geometry imposed by the needs of stability is not conducive to good ground handling and this has been a common issue with aft swept flying wings --in the 1952 world contest a Horten wing was entered and it too suffered ground loop damage -- the Karlsruhe design could be an improvement if they have absorbed the lessons of the SB 13 (or the earlier FS26 also elevator controlled 'tailless' design that was declared to be unsatisfactory ("es steht im die ecke") -'it stays in the corner' as they said of it --there was no FS27 but the next in line ,the powerplane FS 28 ,was in many ways very advanced but also unsatisfactory for other reasons (and overweight) -- some recent revivals of very similar concepts and for example Jay (Kemp's) avatar embody closely related ideas (and HITC's twin boom design has some family traits in common . Model flying wings seem easy to get 'right' in a wide range of parameters unlike their full size brethren and some amateur designs seem to avoid the issues that plagued the university or professional projects (for example the old FLAC - Foot launched air cycle of the 1970s --maybe it came closest to 'an improved swift' even if it preceeded the Swift by a good few years )
     
  3. Oct 17, 2012 #43

    ultralajt

    ultralajt

    ultralajt

    Well-Known Member

    Joined:
    May 10, 2009
    Messages:
    1,560
    Likes Received:
    747
    Location:
    Slovenia
    Forward sweep flying wing is not good for footlaunchable glider!

    Hang Glider pilots will understand why, and for others I will explain why.

    When you stand at starting place (ramp or slope) forward sweept wing has no "wind vane" proprties. If wind dont blow direct into the nose of the glider it will not be stable and will rather yaw to the side oposite to the wind direction. If this happens just at the moment when you start to run down the launch slope, it could lead to the uncontrolled turn back around into the slope.
    Ordinary hang glider layout dont show such behaviour. It lifts the wing on the side of side wind, but it can be corrected, and nose is not yawing away from starting line.

    Mitja
     
  4. Oct 17, 2012 #44

    henryk

    henryk

    henryk

    Well-Known Member

    Joined:
    Mar 8, 2010
    Messages:
    4,646
    Likes Received:
    440
    Location:
    krakow,poland
  5. Oct 17, 2012 #45

    paul w

    paul w

    paul w

    Member

    Joined:
    Nov 23, 2011
    Messages:
    10
    Likes Received:
    1
    Location:
    Faversham UK
    Rearward sweep doesn't mean you can't use pitch neutral flaps but yes, forward sweep would certainly help with wing tip clearance. I think a bigger challenge is getting a longer wheel base...edit-mind you I suppose that doesn't matter if you're foot launching!
     
  6. Oct 26, 2012 #46

    BBJCaptain

    BBJCaptain

    BBJCaptain

    New Member

    Joined:
    Feb 20, 2010
    Messages:
    4
    Likes Received:
    2
    Location:
    Las Vegas, NV
    Aircar,

    The nice thing about the Millennium is that I now have the ability to be picky about where I land. I always land on wheels so I just program in my choice of LZ's into my Flytec 6020 and thermal around until I have enough altitude to make the next LZ. With 12k under my but I have 30/35 miles of gas in the tank to find a safe LZ : )

    The Millennium has 145 sq' of sail and with a wing loading of only 2.4 lbs per sq' ( at my chubby weight ) that's not much. The wing does flex but with the camera mounted at about 2/3's span on the D-tube you may not see much flex. Also I don't tend to put much more that 2 g's on the wing as I am just putting around in the sky.

    The look of the aft pilot C/G is simply a product of a swept wing.

    The cables don't actually hold up the hammock, they are there as a means for setup and maybe to keep the flex out of the 3" aluminum hang tubes. The cage is attached to the 4130 steel keel by 4130 tubing that is bolted to the 3' aluminum hang tubes. With the glider on it's back the hang cage is lifted up and swivels forward and up to about a 50 degree angle, then the two cables are attached at the back of the 3" tubes with a 3.5" pit pin to hold the cage in place. When you flip the glider over to finish the setup, it keeps the hang cage from collapsing. They are 1/4" and very strong. If you look in this video ( watch it on 720p HD ) you can see that as I am moving around the cables are slack and have no load even in flight. The 4130 vertical tubing at the nose and about mid hang cage have all the load.

    Also the Millennium is a breeze to launch in any kind of wind about 18mph. If the wind is 5mph+ the wing flies it self as you walk and there is minimal weight on your shoulders. In this video it is blowing in at 22mph.

    Sunset Cruise - YouTube

    Rolla
     
    Last edited: Oct 26, 2012
    flyinut likes this.
  7. Oct 31, 2012 #47

    holger

    holger

    holger

    Well-Known Member

    Joined:
    Jan 31, 2011
    Messages:
    45
    Likes Received:
    4
    Location:
    Portland, OR
    Here is a Bright Star Millennium for sale on barnstormers.com: BARNSTORMERS.COM. Pretty!

    Holger
     
  8. Jan 26, 2015 #48

    jcoyier

    jcoyier

    jcoyier

    New Member

    Joined:
    Jan 11, 2015
    Messages:
    3
    Likes Received:
    0
    Location:
    Dallas
    Dan,
    I've had a similar interest for much the same reasons. I gave up and decided to build a B-10. Since I'm in Dallas, OR, I'd be very interested to find out if you ever went ahead and started a build. My B-10 is being built at the EAA shop in Independence, OR.
    John
     
  9. Mar 26, 2015 #49

    fltjnky501

    fltjnky501

    fltjnky501

    New Member

    Joined:
    Mar 26, 2015
    Messages:
    1
    Likes Received:
    0
    Location:
    Medical Lake, Wa
  10. Oct 1, 2015 #50

    Michael Kang

    Michael Kang

    Michael Kang

    New Member

    Joined:
    Oct 1, 2015
    Messages:
    1
    Likes Received:
    0
    Location:
    Spring, TX, USA
    Dear Sir:

    I would like to have someone build me some front-spar/leading-edges similar to the impact D-tube shown. Who and where could I contact? Do you know the price and approx wt/ft of this kind of D-tube?
    Thanks a lot.

    Michael Kang
    pckkang@yahoo.com
    281-364-9908 (USA)

     
  11. Oct 8, 2015 #51

    jwmflying14

    jwmflying14

    jwmflying14

    Well-Known Member

    Joined:
    Oct 9, 2014
    Messages:
    87
    Likes Received:
    8
    Location:
    Tucson
    A little late to the discussion (Okay, really late), however I believe we are chasing the same goal. Mine is entirely a thought experiment as of now, where as you seem to have time and the required funds to actually begin the build.

    I too see the Swift as a great airframe, however potentially outdated. There are better wings/foot launch sailplanes out there (primarily the Archaeopteryx), however as you had mentioned, they limit flying areas. Whether it be a wing span limitation or tail boom clearance. In the mean time, it seems as if (one of) the only potential way(s) to make any significant improvements on the swift would be primarily in the reduction of trim drag, and the use of higher lift, higher efficiency foils (or of course higher aspect ratio, which we have both deemed would be a limiting factor in operating areas). Even the high end rigid wings are reducing trim drag (Atos and Impact) by destabilizing the wing (slightly) and adding a horizontal. This being said, with a well faired harness and or pod, both the Atos (specifically the VR+, which has an in-flight adjustable tail) and Impact are achieving similar L/D figures as the Swift (20-24). This is the point where I began to think about a tandem/box wing configuration. The idea being that you could use better airfoils (usually coupled with a higher pitching moment), you could reduce structural weight (in comparison to a high aspect design), and it would keep the tail/aft wing high off the ground on launch and landing (no more risk than your typical hang glider). In addition, the box wing would provide higher span efficiency when considering a wingspan constraint.

    Anyways, it might be worth checking out, simply due to our similar performance interests, and design constraints. [Reduce the limitations of launch and landing, increase performance (L/D between 25-30), increased flight performance at and above typical flex wing and (potentially) rigid wing speeds, and reduce minimum sink.]

    https://www.homebuiltairplanes.com/...22246-tandem-box-wing-foot-launch-glider.html

    Sincerely,
    Justin
     
  12. Jan 25, 2018 #52

    jerhyn

    jerhyn

    jerhyn

    New Member

    Joined:
    Jan 25, 2018
    Messages:
    2
    Likes Received:
    0
    Location:
    las vegas, nv
    Joined this thread way late. but thought I would ask if you found an aircraft that met your needs ?
    Around 1980 I bought n flew an american Aerolights Eagle. At the time about 4500.00 bucks.
    I will find and scan some pics when I can find them.
    Technicaly it "could " foot launch, and met the weight limits for 103. Here in vegas we had 20 or so flying at the dry lakes and Jean ridge
    so when I saw BBJCAPTAIN cruizing vid I instantly knew the terrain.
    Jerry

    Ps. I found a pic of my model "rainbow" Eagle on google, this one isn't mine, but same engine, sail colors.
    eagle.jpg
     
  13. Jan 26, 2018 #53

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,697
    Likes Received:
    1,764
    Location:
    North Carolina
    You'll have trouble coming up with much improvement on the laminar rooftop airfoil that the SWIFT uses.
     
  14. Jan 26, 2018 #54

    Battler Britton

    Battler Britton

    Battler Britton

    Well-Known Member

    Joined:
    Nov 14, 2015
    Messages:
    490
    Likes Received:
    319
    Location:
    Montpellier,LFNG (Candillargues)
    OK....very late too..:gig:

    about cloth wing extention...an other way to extend!

    two early french design, the blue one still exist in a museum!

    14189728500_263a93dc71_b.jpg 14455.jpg



    19d6b238adcafd3e8ea915aa8aedc030.jpg b0dcb23212d870429cb61d292816aeff.jpg
     
    cluttonfred and Topaz like this.
  15. Jan 26, 2018 #55

    Battler Britton

    Battler Britton

    Battler Britton

    Well-Known Member

    Joined:
    Nov 14, 2015
    Messages:
    490
    Likes Received:
    319
    Location:
    Montpellier,LFNG (Candillargues)
    4576Z.jpg


    and, my all time favorite, foldable in a minute, but I can;t find news about this old concept...:cry:


    piccardeureka2.jpg
     
    cluttonfred likes this.
  16. Jan 26, 2018 #56

    Topaz

    Topaz

    Topaz

    Super Moderator

    Joined:
    Jul 30, 2005
    Messages:
    13,623
    Likes Received:
    5,275
    Location:
    Orange County, California
    Interesting. Another I've never seen before, and the most-pronounced "reverse sesquiplane" I've seen. Looking at the shot with the flaps retracted, you sure hope the flaps don't ever get stuck. Between the tiny wing area and the Reynold's Number at which those wings must be operating at landing speeds, I'd imagine landing in an emergency with the flaps retracted would be... "exciting"! :speechles
     
    Battler Britton likes this.
  17. Jan 26, 2018 #57

    cluttonfred

    cluttonfred

    cluttonfred

    Well-Known Member

    Joined:
    Feb 13, 2010
    Messages:
    6,353
    Likes Received:
    2,224
    Location:
    World traveler
    Don't cry BB! I found these pics of what appear to be pages from an old sport and ultralight aviation directory.

    Piccard Eureka Page 1.jpg Piccard Eureka Page 2.jpg Piccard Eureka Page 3.jpg
     
    Marc W and Battler Britton like this.
  18. Jan 26, 2018 #58

    Battler Britton

    Battler Britton

    Battler Britton

    Well-Known Member

    Joined:
    Nov 14, 2015
    Messages:
    490
    Likes Received:
    319
    Location:
    Montpellier,LFNG (Candillargues)
    thank you VERY much, Matthew, it is more than I ever found!

    I love this kind of design, light , small...very small ! foldable enough for all we all need , an afordable cute aircraft for sunrise/sunset flight....


    hey...a new thread title..AWAN....All We All Need!
     
  19. Jan 26, 2018 #59

    Battler Britton

    Battler Britton

    Battler Britton

    Well-Known Member

    Joined:
    Nov 14, 2015
    Messages:
    490
    Likes Received:
    319
    Location:
    Montpellier,LFNG (Candillargues)
    two more, Topaz..

    you are right, I can't imagine a landing without flaps!!


    216b10.jpg


    afc1ca036c3666f3f2e7a984d18b34d9--jacques-variables.jpg
     
  20. Jan 26, 2018 #60

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,697
    Likes Received:
    1,764
    Location:
    North Carolina
    Ooooh, I like that. Enlarge it a bit and you have a folding 103.

    I wonder if the Piccard family has any white sheep?
     

Share This Page

arrow_white