Very low aspect ratio planes?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Inverted Vantage, Oct 30, 2009.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Jan 13, 2014 #241

    rotax618

    rotax618

    rotax618

    Well-Known Member

    Joined:
    Nov 1, 2005
    Messages:
    735
    Likes Received:
    287
    Location:
    Evans Head Australia
    By all means you can use any of the ideas in my sketches, I post them to seed ideas and to encourage others to take them further. It was once said that to make a small fortune out of aviation you need to start off with a large fortune, Most patents and copyright in this day and age stymie development and progress.

    Cheers
     
  2. Jan 14, 2014 #242

    highspeed

    highspeed

    highspeed

    Well-Known Member

    Joined:
    Apr 10, 2011
    Messages:
    275
    Likes Received:
    13
    Location:
    Spring, TX
    What is the design methodology for this sort of configuration? Do you start with the planform?
     
  3. Jan 14, 2014 #243

    rotax618

    rotax618

    rotax618

    Well-Known Member

    Joined:
    Nov 1, 2005
    Messages:
    735
    Likes Received:
    287
    Location:
    Evans Head Australia
    I have built a number of different aircraft over the years, a primary glider, autogyros, volksplane, flying flea, drifters, boorabees, savannah. As you can see from the list I have a curiosity as to how to build and fly a simple aircraft.
    As far as the faceted flying wing is concerned I originally wanted to investigate the flight regime of the facetmobile, Barnaby Wainfan came up with this brilliant concept out of the blue, and after many experiments I believe that it is possible to build an safe efficient sports aircraft based around the inverse zimmerman planform or a straight edged approximation of that planform.
    Most attempts to build small low speed deltas use a rounded LE and either a straight sweep LE or a double delta with strakes. I have never been able to get decent aerodynamic performance from these planforms, they always seem to have a great deal more drag at high angles of attack and in the case of the double delta a nose high deep stall - mind you I'm only experimenting with model gliders but SAAB found the same with their double delta fighter.
    Jet fighters with strakes are in a totally different flight regime, the are designed to be slightly unstable to increase their manoeuvrability, a sports plane doesn't need any instability.
    I don't have access to any flash simulation software, but I doubt that they work at this end of the flight regime anyway. And there are no sharp leading edged airfoils in the database.
    Commercial manufacturers are not interested because they couldn't sell anything that looked different so it is up to the experimenters and homebuilders. This is where most of the recent advances in the light end of aviation has come from.
     
    danmoser likes this.
  4. Jan 14, 2014 #244

    danmoser

    danmoser

    danmoser

    Well-Known Member

    Joined:
    Feb 1, 2010
    Messages:
    631
    Likes Received:
    186
    Location:
    Sandy, Utah, USA

    Tom, you hit the nail on the head with these points!

    The new interest in low aspect ratio airplanes is not coming from the likes of Boeing, Embraer, Canadair, Piaggio, etc.. it is a grass roots effort among amateurs, experimentalists and out-of-the-box visionaries..

    Large government and/or corporate initiatives always seem to be based on the refusal to admit past mistakes .. the NASA Space Shuttle being the poster-child .. the worst in terms of massive amount of money wasted.

    The most important innovations are always born in garages, it seems ;)
     
    Last edited: Jan 15, 2014
  5. Jan 15, 2014 #245

    Aircar

    Aircar

    Aircar

    Banned

    Joined:
    Feb 20, 2010
    Messages:
    3,567
    Likes Received:
    367
    Location:
    Melbourne Australia
    Barnaby didn't actually 'come up with the Facetmobile out of the blue " -- or did if you want to stretch a pun.. The F117 Stealth fighter (which is not actually a fighter either having no air to air armament, was his inspiration --and that came out of the Top Secret "have blue" program --the flying bathtub as it was called --so you COULD say it "came out of the BLUE" in one way .

    Barnaby was working for ACA associates (Julian Wolkovitch) in Torrance Calif --sharing a building with a fitness club actually, -they did consulting work for all the major defence firms and probably had access to the Stealth work fairly early on (Barnaby called it his "Geodesic airplane" at that stage (1990) and was interested in anything tailless including the Zimmerman type --I showed them some pictures of my super low aspect ratio models and joined wings etc --I got a job offer from Julian on the spot (after an hour or two of grilling..) Sadly he died before I returned the next year --Barnaby went to work for Northrop of Stealth Bomber fame..

    That particular innovation was born of an obscure Russian document translator who read and translated a document heavy with maths that essentially said that the radar return of any sized object could be eliminated --something held to be impossible . Whoever received the translation understood and checked the concept and the maths and that led to the Stealth aircraft "black' projects --after confirming the technology worked the first thing was the cancellation of the Rockwell B 1B -multi billion dollar production (It had been obsoleted in one stroke) The Russians apparently overlooked their own research or didn't believe it.

    None of this involved garages or backyards . The roots of the program that monitored 'enemy' technical publications started with Franklin D Roosevelt who was made aware that German nuclear physics publications (annals der Wissenschaft etc) could be purchased in neutral countries like Switzerland and Sweden --and then smuggled to the USA --the German research was being eagerly pored over by the Manhattan project scientists trying to develop an atomic bomb to drop on Germany ! (ref "the Farm Hall transcripts - Project Epsilon" and "The Secret War of Franklin D Roosevelt" ) --one informant even showed FDR in his own office how to put a phone call through to any of those countries which was being done by spies ..... the roots of the technology we now use are planted in strange ground.
     
    Norman and bmcj like this.
  6. Jan 15, 2014 #246

    rotax618

    rotax618

    rotax618

    Well-Known Member

    Joined:
    Nov 1, 2005
    Messages:
    735
    Likes Received:
    287
    Location:
    Evans Head Australia
    G'day, Apart from some faceted panels the facetmobile bears little resemblance to the F117 especially with regards to the aerodynamics. I think Barnaby addressed the fact that he was involved in the F117 project AFTER he had commenced experiments towards the evolution of the facetmobile. In any case no one else had come up with the idea, and most importantly no one else had the courage and conviction to try that planform and lifting body layout, I would say that "came out of the blue". The facetmoble was only a crude prototype to demonstrate what is possible using this layout, it was built on a limited budget and with time constraints - using models for proof of concept, not by a billion dollar aerospace company but by man with the help of his wife and a few friends.
     
  7. Jan 15, 2014 #247

    Aircar

    Aircar

    Aircar

    Banned

    Joined:
    Feb 20, 2010
    Messages:
    3,567
    Likes Received:
    367
    Location:
    Melbourne Australia
    I give up -- the Mona Lisa is a portrait but is unlike most other portraits only in matters of detail --if somebody had done a portrait of the BACK of someone's head and EVERY other portrait was NOT of the back but MR X then ALSO did another portrait of the back of somebody else's head and claimed that his inspiration was totally original but just happened to be like his next door neighbours (headback' portrait in that 'single' respect you might (or it seems, might not..) be inclined to think that there was a connection --and ONE had to be first.

    What in God's name does it matter how much he suffered for his art or used cigarette butts to paint it with or whatever other irrelevant detail ? the design CONCEPT has an actual origin and there can be only one origin .

    Surely FACET- mobile describes the salient feature (??) --the Facetmobile doesn't have a perky little V tail or jet intakes etc etc but, unlike ANY other aircraft till that time does have---wait for it,- FACETS (please don't drag the FACET 'opal' into this semantic tussle --it's already too disappointing :dis:

    Barnaby is not starving in a garret by the way (or ever did)and has worked for a multi billion dollar aerospace company for the last few decades --his wife is a rocket scientist (and wears a clinging T shirt with "and Yes I am a rocket scientist" printed on it --her figure is quite classical shall we say ... The point about the Facetmobile shape was that it was simple to make, not requiring molds or tooling and bereft of any aerodynamic smoothness or sinuous shape --you could knock up the basic shape in a few days (as a former claymodeller in the automotive industry this is the 'foam buck' stage where only a prismatic approximation of the eventual body with smoothly flowing curves is in existence --the real skill and work comes in getting compound curves right.

    I am going to withdraw from giving advice or any sort of input to these sort of threads from now on --it is just not worth the trouble and time and for the sort of 'reaction' of this kind -- and the vague sense of responsibility to forestall disaster or at least waste .

    If there are genuine 'emerging new technology ' issues that can benefit our activity I'll restrict myself to those . (that is the real subject matter this part of the forum is nominally supposed to address --besides which I won't have the time to waste shortly)
     
  8. Jan 15, 2014 #248

    Aircar

    Aircar

    Aircar

    Banned

    Joined:
    Feb 20, 2010
    Messages:
    3,567
    Likes Received:
    367
    Location:
    Melbourne Australia
    Just for the sake of completeness --http://en.wikipedia.org/wiki/Lockheed_Have_Blue. gives a potted history of the origin of the facetted airplane and ties down the dates of that origin . Some of the other links associated with the Stealth or Have Blue go on to refer to the Boeing Bird of Prey -the latest manifestation of the low observable design trend --my former housemate and flying,etc buddy (Lee) in Ohio in the early seventies ended up working on this project but didn't tell me anything about until after it was de classified (and we met again at Oshkosh..)
     
  9. Jan 15, 2014 #249

    rotax618

    rotax618

    rotax618

    Well-Known Member

    Joined:
    Nov 1, 2005
    Messages:
    735
    Likes Received:
    287
    Location:
    Evans Head Australia
    I'm sorry you feel that way AIRCAR, you obviously have much to contribute, I don't know Mr Wainfan and my knowledge of the circumstances of his inspiration comes from articles in Kitplanes, Contact and his own website. The point I was making is that the Facetmobile revived interest in low aspect sportplanes, it is by no means the ideal example, the design is easy to improve and the facets aren't necessary for efficient flight, nevertheless it takes someone to seed the interest. The real design inspiration is the planform that sheds the vortex and the sharp leading edge that starts it.
    Please continue to contribute to the thread, you obviously have a wealth of knowledge that can help us all. Encouragement is one thing but you learn more from criticism that causes you to look at your ideas in a new light.

    Cheers
     
  10. Jan 15, 2014 #250

    danmoser

    danmoser

    danmoser

    Well-Known Member

    Joined:
    Feb 1, 2010
    Messages:
    631
    Likes Received:
    186
    Location:
    Sandy, Utah, USA
    Well, whether inspired by a military project or not, Mr. Wainfan apparently did not have the Facetmobile effort either directed or funded by his large aerospace corporate employer.
    By all accounts, he & his helpers designed & built it in his garage/hanger in their spare time.
    I do not believe his personal finances or family relationships are relevant or appropriate to discuss on this forum.
    Moderators, do you agree?

    Anyway, back to the planform issue:

    It seems that most of the low aspect ratio airplane designs we are discussing here have a slightly forward swept trailing edge, sometimes called a "diamond wing."
    .. a few have a straight trailing edge (pure delta).
    .. almost none have a sweptback trailing edge, which is usually termed an "arrow wing"

    It seems to me there are a few potential advantages with the seldom-used arrow wing planform:

    1. Use of center section flaps deflected downward .. would have less of a nose-down elevator effect.. in fact, on my high AR tailless wing, flaps down produces a nose-up elevator response.

    2. Slightly higher AR combined with the strong LE sweep necessary to preserve vortex lift.. somewhat improved cruise performance at moderate speed.

    3. Pilot seat moved more forward, perhaps improving visibility.

    Most of the old CL,max wind tunnel tests were with pure delta wings w/ straight TEs.
    It indicates you get the CL,max peaking at around 1.5 when LE sweep is 65-70 degrees, corresponding to an AR range of approx. 1.5-1.9
    I'm thinking that the CL,max is more dependent on the LE sweep than the AR.
    Vortex structure studies show that the center portions of the delta's straight TE are not seeing much in the way of suction at high AoA.
    Perhaps cut out that section of wing area to make it an arrow wing and install TE flaps... you might get the same or more vortex lift with slightly less wing area. .. hmmm?? :ponder:
     
    Last edited: Jan 15, 2014
    henryk likes this.
  11. Jan 15, 2014 #251

    rotax618

    rotax618

    rotax618

    Well-Known Member

    Joined:
    Nov 1, 2005
    Messages:
    735
    Likes Received:
    287
    Location:
    Evans Head Australia
    I haven't investigated sweeping the trailing edge forward, I have been mainly concerned with maximising the wing area for a given AR. I have noted that a centre underbelly flap has been used to increase drag/ lift? on flapjack types. To get the best visibility a pusher engine with a swept forward TE would be the answer, where you would place the elevator/ ailerons is the question, but it is worth investigating.
     
  12. Jan 15, 2014 #252

    Aircar

    Aircar

    Aircar

    Banned

    Joined:
    Feb 20, 2010
    Messages:
    3,567
    Likes Received:
    367
    Location:
    Melbourne Australia
    I am not 'spitting the dummy' over this topic (or any other come to that ) I like to return to the HBS forum to space out other more mundane work on the web and try to inject a little of a wider perspective perhaps -- I know that I am not too easy going when it comes to matters of fact -- and not afraid to voice an opinion when it is matters of opinion so please take that into account.

    Maybe I am one of those incurable optimists when it comes to the unconventional (see the Sorri Gudmundsonn thread if needing clarification ) and have had my fingers burnt and learned some hard lessons over the years --I see HBA as a place to collate the summed wisdom of many minds and to filter and refine the horde of speculations and wild ideas that sometimes do need to come down to Earth somewhat but not to be chained to it by the pessimistic counsel of those who only admit the 'tried and true ' -- there is a real need to break away from the same old design path that has never created a substantial market or operational use (compared to cars or refrigerators etc etc that have a real impact on daily life and society ) I would like nothing better than to inspire or conspire to get the wave of breakthrough flying machines that are possible to become a reality (even better to build one of them myself).. Enthusiasm has to be tempered with some level of hard nosed critical thought as well.

    there are good reasons why Barnaby's Facetmobile hasn't 'taken off' and why models of it -or almost anything else with a given power to weight ratio will fly (apparently) really well (everyone has seen the literal toilet seat fly very nicely in RC form ..) It is relevant that his wife is a fully qualified aerospace engineer --the inference is sort of that a 'dirt poor sod buster and his haggard wife struggled with dogged determination against all odds to do the impossible 'etc --images of the long faced farmer and his wife with pitchforks in the Classic American painting scene come to mind.

    Los Angeles is not like that and not the Wainfans - it is THE hotbed of experimental aircraft activity and every advantage to a developer including hordes of qualified engineers and materials etc etc at hand and a free regulatory environment. Just to balance the implied view.

    If you google 'faceted aircraft' it turns up on the first line of photos the Facetmobile and the F117 juxtaposed next to each other (a tautology I know) and other views of the F 117 and Have Blue showing the VERY highly swept trailing edge -- this is characteristic of the first stealth aircraft (and only a few others eg Barnes Wallace's variable sweep design Green Goblin and swallow (the 'swallow tail' being thus and going into the vernacular )

    The effect of high sweep on trim is the basis for the SWIFT --as Dan would know -Swept Wing with Inboard (far forward therefore) Flap tp TRIM so not surprising to hear your results and welcome --but the effectiveness of a flap is a f=direct function (sine possibly) of sweep angle and penalizes really high flap hinge line sweep , Nothing comes without a price --the tendency to shovel air spanwise also encourages tip stall and dutch roll so there are limits. So much for brevity...
     
    Holden likes this.
  13. Jan 15, 2014 #253

    Holden

    Holden

    Holden

    Banned

    Joined:
    Jan 19, 2003
    Messages:
    1,319
    Likes Received:
    140
    Location:
    USA
    Aircar and others.

    I feel your pain.... Very low aspect ratio is to make it useful.

    One reason the Facetmobil has not taken off in volume is because it is not competitively useful and does not add to the owner's status. It achieved the parity with high aspect ratio due to the low weight, and could be made cheaply as stated in an article posted here on HBA. But why no excitement and volume?

    People fly the current crop of airplanes to achieve some sort of group adherence or social status. In most cases an airliner with a rental car can beat a typical GA airplane in cost and time. There are a lot of airplanes that a person can fly to enjoy simple flying. A C-172 will do. It can carry some friends and it has some notion of wealth to those that think pilots are rich.

    What can I do with a Facetmobil? Haul a lot of stuffed animals? Carry foam in volume? Have a sense of flying in my living room? Who cares about the facets if I cannot use it daily. I don't. The fat section does not lend itself to folding to make it roadable, so why bother? Such a planform cannot be made narrow enough to drive on a road and therefore needs to fold.

    When we tested the Sea-Era in the wind tunnel we confirmed that the flow stays attached over the FACETED and double STEPPED underside of the hull. Why did it remain attached...leading to low drag? We had two STEPS and both had attached flow that converged to the tail area of the delta for low drag. Why then use a facetted hull on the Sea-Era? The point is how to use this vortex effect in a design to achieve SOMETHING USEFUL.

    In the Sea-Era, the point was that air stayed attached but water did not, nor did the faceted (flat) bottom create a suction like a curved hull does. By using the facets we solved two serious water issues: 1) flip over and 2) suction. Both were proven by Paul's accidents, one of which was on video. We learned that hull design can be better with faceted surfaces. Great, but how does this make it useful in context of a design that makes it a daily use thing? It does not. It is only in the context of the total vision that this facet concept plays out.

    What problem does the Facetmobil solve? How to invert the ugly curve? Make is so ugly it is beautiful? Look, I can fly with the spoilers out... Might as well make it a lawn mower design and really impress your friends.

    The problem with this industry is not that people are not smart, clever, intelligent, skilled or super cool dudes. It is the vision. Whether it is an ICON A5, Terrafugia, Aeromobil, Facetmobil or the other 2200 roadables that failed. When the goal is to impress, usefulness takes a back seat. Nobody gives a rats rear about vortex this or that unless you are an aero junky.

    I want something useful. In 100 years no airplane has been made truly useful for the common man on a daily basis like a car is. NONE! That is the measure of the craft, not some drivel about planforms, vortexes, or drag this or that.

    Very low aspect ratio is to make it useful. That is the beginning and end of it.

    Holden
     
  14. Jan 15, 2014 #254

    Holden

    Holden

    Holden

    Banned

    Joined:
    Jan 19, 2003
    Messages:
    1,319
    Likes Received:
    140
    Location:
    USA
    I agree for the most part, but making another airplane is not the point. It MUST be useful. How does Low aspect ratio make it useful on a daily basis? When it is useful, people will buy and large corporations will put money into it. How does low aspect ratio make money? In what context? I have explained several times how it does, but zero response....

    Here it is again. The low aspect ratio is to allow it to LAND ON ROADS when lightly loaded, and with the addition of panels, it can be made a heavy hauler. It can carry the 4-6 people if the need arises, but when time is the key (daily use) and 1-2 people are in it (normal for most 4-6 place airplanes) then it can go narrow (lose the panel wings) and LAND ON THE ROAD. This concept of LANDING ON A ROAD is unique to LOW ASPECT RATIO airplanes. This ability to LAND ON THE ROAD make it USEFUL.

    So, why low aspect ratio? Answer....drum roll please.... TO LAND ON THE ROAD. Unless you are planning on landing on the road, why use low aspect ratio? It does not make folding easier, so the argument about less hangar space is not valid.

    Without the ability to LAND ON THE ROAD, an airplane is not useful...period.

    Holden

    PS, Did I mention the need to land on the road?
     
    Last edited: Jan 15, 2014
    delta likes this.
  15. Jan 15, 2014 #255

    danmoser

    danmoser

    danmoser

    Well-Known Member

    Joined:
    Feb 1, 2010
    Messages:
    631
    Likes Received:
    186
    Location:
    Sandy, Utah, USA
    I was not aware of flap effectiveness dependence on sweep angle.
    It sort of makes sense, but I can't seem to find a reference on it.
    .. can't find it in Horner's lift book or any my other aero books, and a quick web search comes up empty.
    Do you have a link or reference you can supply on this? Thanks.

    Is this the sweep angle of the hingeline, TE, LE or c/4 line? .. or a combination?
     
  16. Jan 15, 2014 #256

    bmcj

    bmcj

    bmcj

    Well-Known Member HBA Supporter

    Joined:
    Apr 10, 2007
    Messages:
    13,083
    Likes Received:
    5,011
    Location:
    Fresno, California
    Not true. I, myself, had built some faceted lifting bodies (flying models) as a kid, long before the advent of the F-117 or Facetmobile. There were others too, as some of my inspiration came from others who had done the same and were featured in various flying model airplane magazines.
     
    Holden likes this.
  17. Jan 15, 2014 #257

    Holden

    Holden

    Holden

    Banned

    Joined:
    Jan 19, 2003
    Messages:
    1,319
    Likes Received:
    140
    Location:
    USA
    If the flaps follow the swept wing, then it directs (shovels) air outwards. If the flaps are in a cupping shape (outer edge forward), then they would be effective. The question is how to get the sweep back in the wing as you describe AND the forward cupping of the flap. A large belly split flap would work perhaps. But is there not a better way?

    Holden
     
  18. Jan 15, 2014 #258

    danmoser

    danmoser

    danmoser

    Well-Known Member

    Joined:
    Feb 1, 2010
    Messages:
    631
    Likes Received:
    186
    Location:
    Sandy, Utah, USA
    Actually, I thought there was quite a lot of response!
    We've thoroughly discussed the "transport efficiency" parameter (Wu/D; useful load per unit drag at some useful cruising airspeed) as being a more appropriate measure of aircraft operation economics than L/D.

    Low aspect ratio airplanes have the potential to make more money, in other words, attain a higher transport efficiency than conventional planes, if;
    1. Structures can be properly designed to take advantage of the potential for lower empty weight, and
    2. Aircraft operation time is predominately high speed cruise.

    As to your "it MUST be useful" sentiment, I disagree.
    One the great things about amateur aircraft builders is precisely the point you are making .. they often do things just for the fun of it .. not necessarily motivated to make something useful.
    The typical corporate approach is to create new products only if they are provably useful/profitable.. if you can't sell a new product idea to the "bean counters", the new product development effort does not get approved.
    Corporations are also a bit sluggish to adopt new ideas because of the inertia and legacy of old products .. the old "that's the way we've always done it" syndrome.

    However, many inventions that eventually turn out to be very useful were actually born purely out of the just-for-fun motivation.
    So I think it is very important to continue to encourage amateurs to keep on creating "wild & crazy" new things, even if their eventual usefulness cannot be proven.
    In its essence, that is what this forum is all about .. don't you agree? :ponder: :)
     
    Last edited: Jan 15, 2014
  19. Jan 15, 2014 #259

    Holden

    Holden

    Holden

    Banned

    Joined:
    Jan 19, 2003
    Messages:
    1,319
    Likes Received:
    140
    Location:
    USA
    Yes, I agree on the surface. Most people somewhere in the back of their heads want to become a Cessna and have the concept accepted and produced. There is this desire to "make a mark" in some. You may not have it, or that mark is only to come up with the idea, publish it. If it is purely for the fun of it, then it is a just fine in my book. Knock one self out... Makes more sense than a wing suit or a bungy jump.

    My goal, however, is to produce airplanes in volume so that the average guy can fly and I want to make a business out of it. This view is more aligned to the corporate view and for the drive to make it available to all.

    This forum to me is a good place to debate and get reactions to concepts. It gets the brain working and the ideas flowing. For, example, Aircar stressed the importance of having a roadable that can be large, medium and small and not just a one off two place. He also hates landing on the road. Without the debate, I may not have come to this realization of different sizes for my design until later, nor would I have realized just how important landing on a road is, which Aircar totally disagrees with. In both cases, agree or disagree, Aircar's input helped. So, with a little help from my friends, I see the light or darkness. I notice that I, as well as others, can get fixated on a concept and get "stuck" in the mud. This forum is like a wench to a 4 x 4 stuck in the mud. Sometimes we just keep spinning the wheels and get more stuck the harder we try. Then some guy comes along and pulls us out of the mud.

    Holden
     
    danmoser likes this.
  20. Jan 16, 2014 #260

    bmcj

    bmcj

    bmcj

    Well-Known Member HBA Supporter

    Joined:
    Apr 10, 2007
    Messages:
    13,083
    Likes Received:
    5,011
    Location:
    Fresno, California
    Ross (Aircar). Check your private messages... I sent you a bit of trivia that I felt probably didn't belong in the public post area.

    EDIT: nevermind... I just got your reply. Thanks
     

Share This Page



arrow_white