# How to build a better Swift?

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

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1. Dec 27, 2011

### Keshka

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Hi all,
Thank you for reading my post. I will start with a little about me. I have been flying one form or another aircraft for 35 years. Everything from a Huey to a hang glider plus tons of R/C planes. Yes I got the bug early as a boy. I am an engineer but NOT an mechanical or aerodynamic engineer. I have build a BD-5 and have the kit downstairs for a Long-EZ. I am a proficient machinist with a commercial CNC Mill and lath in my shop plus most every other tool you can think of and a few you can't (grin). There is even an industrial robot down there (he is still waiting for a job)

With all that said, what do I want? I want a Aeriane Swift'Light. Problem is there current price is close to $30,000 dollars and over a year wait. I would love to build an aircraft in this category. So just what is that category to me? Must haves: 1. Foot lauchable at most hang glider sites (rolling launch were applicable) 2. Attachable engine for self launch 3. Right stick control for easy flight and ground handling. 4. Prefer the no-engine weight less than 120 lbs. I may need to run with this and even that is a bit much 4. When the engine, fuel, controls and misc support for it are attached, under 155 lbs 5. Able to hold me at 225 lbs 5. Glide ratio > 20 to 1 minimum. 6. Removable wings. Set up and tear downin less that an hour. 30 min would be great 7. No unrecoverable flight modes (tumble, flat spin!) Nice things: 1. Glide ratio > 30 to 1 2. One person assembly 3. Towable 4. Able to fly at 60+ without having the glide ratio drop below 18 to one (most flying will be in the 20-30 mph range "fun") faster is to go "somewhere" Things I can accept: 1. Wings carried in box on top of car 2. Longer set up time than most hanggliders. 3. If it met all of the above goals, up to two years to build at 6+ hours per day (hope for much less) 4. P rice, no greater than$15,000 and that seems silly for a 100 lbs of plastic and glue, but comparatively, probably reasonable

Musings:
Looks like a flying wing is the best choice if done right. No tail to strike on the hang glider ramp after your run. No drag, weight, or control systems from tail surfaces.

Things I don't know how to do. Engineer a wing.
1. Do I need winglets? Are they worth the effort, what shape, size and airfoil should they be?
2. Swept or plank? (plank seems easier and more stable. Is it?)
3. How to choose an airfoil. Or worse yet, design one.
4. How to determine wing loading and then come up with a spar/rib/skin that will support me.

5. Does the wing need to have a full composite skin to meet my criteria? “D” cell, fabric trailing edge seems more complex.

Learning the "things I don't know", NO!, It is not worth going back to college and getting another degree. Is there another way? I also would need guidance on WHAT to study.Example: Horton. Yes, a great man and pioneer but most of his teachings are very obsolete today. Even what Ilan Kroo did with the Swift is getting stale. Where is the new/pertinent stuff? Don't want to be overwhelmed with junk I don't need to know.

I have been reading on here and may other places and it seems there is a lot of interest in this form of flying. I find many started and only a couple completed works.

I went to all these sites: (and many more)
http://www.sailplanehomebuilders.com/ nearly all the companies listed there for plans or kits are gone or the product weights 400+ lbs
http://m-sandlin.info/ Mike is great! I would like to improve the performance and get rid of the tail.
http://www.marskeaircraft.com/flyingwings.html Jim Marske has also done some great work but don't think I could get that Pioneer III on my shoulders and run. Where would the motor go? Can I have the wings?
http://www.lutz-drachenbau.de/index.html Sky project....not done....probably too spendy from Germany and flies too fast to run
http://www.carbondragon.us/ Won't be flying with my buddies. They would have to tow me up then drive to launch and maybe I meet them in the air
http://www.aeros.com.ua/structure/al/al12_en.php Beautiful, No prices, little info. No one has one.

So tell me, am I all wet and just dreaming? It sure seems the specific knowlege I need should already out there, how to find it?

Dan Clemens
Summerville, Oregon

Last edited: Dec 27, 2011
2. Dec 27, 2011

### Keshka

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How Aeriane did it....

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3. Dec 27, 2011

### henryk

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BKB-1A, modyfikacja BKB-1 wykonana przez Kasprzyka w USA - Brochocki Kasprzyk Bodke
Bibliografia - Brochocki Kasprzyk Bodke

subindex

=BKB1-A \KASPER wing\=the only TUCK-resistent tailless glider/hangglider!

=very easy to build\constant chord\.

http://www.homebuiltairplanes.com/forums/light-stuff-area/2943-witold-kasper.html

-moore...

iff you have many time=

Nickel,Wohlhart 600p.bibel...

http://wvuscholar.wvu.edu:8881//exl...zL2R0bC9kM18xL2FwYWNoZV9tZWRpYS8xMzc1MA==.pdf

http://upetd.up.ac.za/thesis/available/etd-09182008-132941/unrestricted/01chapters1-3.pdf

4. Dec 27, 2011

### bmcj

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Wet dreams about planes? ... Been there! :roll:

5. Dec 28, 2011

### flyoz

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What about a homebuilt Millenium ?
Only moulds for the D-tubes that could be built as a group so the costs shared
The rest of the structure is mainly aluminum tube and fabric and its very portable too
Remember it was developed after the swift by the same original developers so there must have been a reason
Swift a great aircraft but too expensive for most , requires a big box , and too complex for a home builder
I think the Millenium got it just right and it can be powered as well - its a pity they stopped making them
Another option is the Guggenmos Cage hanglider - Index english
Another option is the Impact Glider ( D tube shown below )
Cheers
Flyoz

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6. Dec 28, 2011

### henryk

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7. Dec 29, 2011

### Aircar

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You will have to get a lot of wing area and camber plus external bracing to keep your lift up and weight down --the best way to get area and camber is via a sail --easily wrapped up for trailering or even removeable in flight to get away from the limitations imposed by the need for ultra slow flight at take off and landing . Most of the 'insolubles' arise from trying to make the same wing perform at high and low Cls -- how you go about configuring your particular take on design is up to you but the fundamentals are easily calculated from half a dozen parameters --starting with your own weight and rapidly determining the size and other characteristics that would be feasible . In normal design practice you plot three variables on a carpet plot and see where possible solutions might exist (eg Cl and wing area vs stall speed at various weights -- you can trade some variables and others are constraints ) structurally you can go for a super thick wing (eg Volmer Jensen's hang glider ) or a thin wing with external bracing or some other mutually bracing configuration --biplane, joined wing ,sesquiplane etc but in any case the highest feasible span is the best to lower sink rates and raise L/D --and flying wings can suffer from low Cl when trimmed (most do but not unavoidable) and are harder to ensure control during foot launch in 'worst case' situations except for the Rogallo type . The various 'birdman' 'Flugtag' etc competitions give some clues about getting tolerant foot launch configurations by the 'don't do this' route. Successful hang gliders are the best source of inspiration and the Swift derivative you refer to is among the best rigid wing designs as far as I know but might be outclassed or even "stale" as you describe by now but do not discount the amount of expert design know how that went into it or is needed to make any significant advance . The 2cfl canard hang glider from 1975 by Farner is still an unbeaten example of structural and aerodynamic efficiency that might well be studied for clues to improve the breed in my view.

8. Dec 29, 2011

### flyoz

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Here are some details of the millenium glider
Flyoz

9. Jan 2, 2012

### Keshka

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Thank you all for replying. Took me awhile to read all the links and get back to here.
flyoz and henryk: I think the type of wing used on the Millinum and the impact would be the best type of contruction for my project, using a D tube leading edge with ribs and sail cloth for the remander of the wing. It would be nice if the wings "folded" but not one of my requirements. I can carry them side by side in a nice box on the roof of my auto and put the fusaloge inside. I wished Bright Star was still making the "caged" Millenium. My problem would almost be solved. I still need it to be a little larger to manage a larger gross weight. (balistic chute, me and engine).

aircar: please don't get me wrong, I am very impressed with what Ilan Kroo and his team accomplished. I also belive the Swift is among the best rigid wing designs as far as I know. I should have titled this thread "attainable for the average hang glider pilot" instead of "better". It would be very hard for me to try to make the molds and such to re-create the Swift.

My thought tend to follow what Bright Star did with the Millenium, give up some of that fantastic performance of the Swift in exchange for easier construction and lower cost. I read this thread:
https://www.homebuiltairplanes.com/...lity-swept-wing-no-washout-elevons-alone.html
and need to read it again to absorb more but it seemed there was no concensus on the best control for a flying wing (did I miss it?). So back to some of my design questions. If I resolve to use a "D" spar that solves some of the aircraft format questions so next are the remaining questions:

1. Do I need winglets? Are they worth the effort, what shape, size and airfoil should they be?
2. Swept or plank? (plank seems easier and more stable. Is it?)
3. How to choose an airfoil. Or worse yet, design one.
4. How to determine wing loading and then come up with a spar/rib/skin that will support me.

Dan

10. Jan 2, 2012

### Aircar

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That trailing edge collapsing system on the millenium wing looks to be pretty good -- why not see if you can get drawings for it or enough info to duplicate one if they are out of business ? It reminds me a bit of John McMaster's "Altair" flying wing from the early 1970s which is featured in a recent (1997) power point presentation by him on Biomimetics in aviation that I stumbled on a few days ago --if you cannot locate it I think I sent myself a link to it but I do not know how to cut and paste on this forum and am having problems with just posting (repeated box about 'leaving this page' rather than posting ..) I think that some sort of tail is a good idea to allow more aspect ratio and less sweep for better performance and a less critical wing design but a pure wing is more easy to mount a pusher prop and motor --checking the many ultralight sailplane types now on offer in the "leisure aircraft' annual survey publication has to be an essential step.

11. Jan 2, 2012

### flyoz

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For winglets look to the Varieze/Longeze designs - lots of working examples there - even the swift had to eventually put rudders on the tips to help with turning
IMHO the Millenium rudder setup is a good balance
For a plank you have to reflex the control surfaces and that reduces the available lift when you try to land ( see lots of info from Topaz ) so bigger wing areas = equal more drag and other issues
For running launches tails are problematic - you are virtually in the air before any reasonable speed is built up so the surfaces have to be quite large to compensate and you dont need them that big when flying
If you dont want a tail - the other option is swept wings but they too have to have reflex surfaces ( elvons ) and are generally twisted
If you add up all the variables the Millenium got it just right - folding the wing has real benefits even though there is a weight penalty and more parts
I agree with Aircar - the best option is to build a Millenium clone - i am not sure how the original designers would view this but with enough interest they may allow someone to get access to the original data
Either way it would be a small project - maybe build say 10 or 20 tops - get a group of interested people together so you can share the costs and work load etc
Almost all the aluminum parts could be milled CAD/CAM and the sails could be made by a third party - only the D tubes need moulds
For your interest have a look at the Parker aircraft for an example of a simple D tube wing thats built as one piece .
http://www.parkerprojects.com/altitude.htm

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12. Jan 2, 2012

### Aircar

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Without going back through this thread to refresh my memory as to what was deemed to need to be 'better' about the swift --some comments about the relative merits of plank vs aft swept tailless aircraft are not neccesarily accurate -- the aft swept wing can use unstable airfoils and high lift devices (in the centre section ) and end up trimmed at high Cl overall.
(but must carry a download at the tips or at least a very much lower cl --the plank type must have stable airfoils --reflexed median line which means either a lot of 'negative flap' at the TE and/or perhaps a drooped leading edge and the max Cl of such suitable airfoils does not have to be especially low (for example the NACA 23 series are very low Cm but high lift 23012 is a very popular choice for this reason --the Haig Minibat used a 'hooked' leading edge airfoil like a 'droop snoot' and appeared to be stable at least (with a forward swept wing ) It is surprising that the general idea persists that a flying wing cannot use a fowler flap or trim out the moments when there were several examples of such an arrangement already demonstrated --the Armstrong Whitworth AW 52 is the best example perhaps and precedes the S.W.I.F.T. 'concept' by decades .

The lift deficit at the root of a swept wing (due to the spanwise flow effect ) actually destabilizes an aft swept tailless wing as well as costing low speed performance -- the increase in local chord at the centreline is an essential feature then that seems to be missing in the millenium wing but could presumably be remedied and would best be done by an elevator/flap -- it may be that there is some other factor to consider before plunging in to do such a mod and tuft testing a millenium wing would be as essential first test and 'fly' it on a captive rig such as off a car roof rack for 'before' and 'after' results.

13. Jan 3, 2012

### Keshka

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More and more I am warming up to the idea of the basic Millennium concept. Looking at the finish work done on wings like the Aeros Phantom, I think if that level of work were applied to the Millennium design I could end up with a wonderful flying experience. I can study the Long EZ plans I have for details on the winglets. Seems in the news letters and such there was some conceptual information as well as construction details. Having held a Swift winglet in my hand, all I can say is wow! An amazing combination of strength and little weight. I will have to try to contact some of the Bright Star folks and see if any info is available on the Millennium and if they have any ideas about improvements. From "ya'll's" experience and looking at the design of the Millennium, can you see anything that would improve flight characteristics (nose angle, fin size, airfoils, wing length)?

The Phantom wing

aircar: boy that 23012 is not what I expected at all! have to delve into the "mechanics" of it.

14. Jan 3, 2012

### Aircar

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Just right off, the fact that the root chord shown on the millenium REDUCES notably whereas I would think it should actually increase (it might be an entry or visibility thing as well but this looks 'improveable' --Norman is the man who would know better than most-if not all,-- on this sort of things with flying wings and the like...

23012 is a stand out airfoil but does have a "cliff edge' stall (leading edge separation I presume ) --I know Beech built a laminar wing for the bonanza in 1947 and the 23012 (or 015 ?) and settled on the 23012 .

15. Jan 3, 2012

### Keshka

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16. Jan 3, 2012

### Keshka

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I have been trying to get educated in the construction of the 'D' spar, setting up an excel spread sheet and doing the math.
Oh I hate this! lol, but I am driven.

quote from Billski (wsimpso1)
I use Timoshenko and Gere for mechanics of beams and such, and either Tsai and Hahn or Jones for composites. Abbott and von Doenhoff is the bible for developing the aero loads into the wing.

Do I need to go buy these things? Are they valid for my project?

Dan

17. Jan 3, 2012

### Norman

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18. Jan 3, 2012

### Aircar

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Can't help but notice the similarity to the Mitchell wing (and the way back FLAC Foot Launched Air Cycle ) -- it seems inconceivable to be foot launching with 155lbs on your back though or anything remotely like it and the incompatability of both foot launch and motorizing for this sort of design

The Easy Riser allowed the pilot to stand up 'within' the aircraft which was also itself extremely light as an externally braced biplane --thus the thrust axis was relatively low with respect to the pilot --you cannot cut out the centre section of a monoplane cantilever wing so easily although the small D nose of the millenium would seem to permit the pilot to remain at about the right place for CG if standing -- the performance and stability would both be very dubious if you had a big cut out on the centreline . --at least with a canard or some other configurations you can avoid the pilot being in the same place as the main structure carry through or lift surface.

The archeopteryx and several other high performance foot launchable designs are probably better benchmarks (and with a high tail boom the danger of tailstrike is avoided --there are several short fuselage 'tailed' flying wings for want of a better term like the Marske Genesis and other more birdform aircraft (birds are 'tailed' flying wings in the same way )

To get any sort of interthermal performance in a foot launchable aircraft really requires an in flight change of shape (nowadays called 'morphing'-formerly variable geometry ) -- there seems to be an over emphasis on airfoils and airfoil simulation software in general as though there is some magic in airfoil selection or design --beyond a basic matching of the type of aircraft to the class of airfoil the most prospective area for improved design is still in what Orion terms configuring and the designer as configurator . It is probably true that any incremental improvements in passenger airliners are going to come from micro level gains in CFD analysis and yet more rigorous design optimization and this has led to to great attention to airfoil design programs that have filtered down to the amateur design community and seem to appeal to the computer 'geeks' if that is not an offensive term . There does seem to be a lack of integrating skill in overall design at the same time --the hugely CFD analyzed Terrafugia transition could be cited as one aircraft that incorporated basic flaws that resulted in it being fully tooled and constructed with highly sophisticated CAD but it only barely got off the ground and was 'retired' without even doing a single circuit .

It is a sort of "penny wise pound foolish" approach in my view --putting attention in the wrong areas and neglecting the foundations.

For a foot launchable aircraft the parameters for minimum speeds and weights are extremely tight (depending a lot on uncontrollable variables like pilot weight and fitness, terrain surface, slope,altitude,wind etc and mirror at a different level the constraints on other extremely short take off and landing aircraft (STOL and ESTOL ) -- flying wings do not feature strongly in such a class because of low trimmed Cls and controllability but at the lowest weight end there are some compensating factors (eg you could delete a fuselage entirely but if you want the sort of glide performance stated it won't be with a pilot in the open -- the 2FL foot launched hang sailplane of ca.1978 best fits the criteria and with carbon fibre and some imaginative upgrading it could be a better option if you are firm about performance targets or wanted much better high speed performance --and more suited to rolling take offs without any tumbling etc as specified.

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19. Jan 3, 2012

### henryk

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20. Jan 4, 2012

### Norman

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I don't know about that. Dr. Morris is a pretty smart guy and I'm sure he put that engineering education from Stanford to good use. I, on the other hand, am just an architecture school dropout with an interest in aviation history and model building that has led me to a rather odd collection of books. One of those books has a graph of the induced drag increment due to sweep. The drag increment is practically nothing a 10 degrees sweep and less than 5% at 15 degrees. The lift valley that's partial to blame for this induced drag increment can be corrected by several means, increased root chord being one, but the Mill may not have a problem because the sweep isn't that high and the taper of the wing may be more than enough to compensate without any additional area.
I'm not convinced that the 2D stall of the 230xx sections maters very much. It's not like they stop flying altogether. There is an abrupt loss of a small percentage of CL and a large change in Cm toward negative. This could actually be safer than a soft mush because the sudden bump gets the pilot's attention. Most weekend flyers aren't going to fly through super-cooled rain either so that weird ice dam Riblet harps about is kind of specious too.

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