cardboard and duct tape airplane

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by wadeedward, Feb 9, 2006.

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  1. Feb 9, 2006 #1

    wadeedward

    wadeedward

    wadeedward

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    Carboard and Duck Tape Airframes

    Hey All,

    I have, despite the obvious risk to life and limb, taken a bet that I can indeed build and fly a cardboard and duct tape airplane for 1/2 hour at 50 feet.

    Now, I haven't worked in the field in several decades (not since being run over by that drunken judge really). I can use all the help I can get.

    Naturally, I plan to stretch the rules somewhat by making my own cardboard. I plan to form a sharp conical main spar of corrugated cardboard with formers formed of bidirectional outlaid corrugated cardboard and a glued and taped stressed skin of packing tub type cardboard with bidirectional corrugation and water seal the lot with duck tape. I'll stress the lot with air pressure. I plan to make it as big as possible, like an old O-40odd series observation ship, and count on economy of scale to make it light enough.

    It should work, as Goodyear (?) had a rubber air pressure stressed wing airplane in the sixties that I worked on the concept and drawings for that air dropped inflateable rescue plane.

    By the way, it must make use of lawn mower engines, and I must pilot it and I weigh a substantial 255 lbs. (Wouldn't want to make things easy.)

    I have nothing in the way of ability to calculate the likelihood of failure and my funding is nearly nil. But I've always been lucky designing by the seat of the pants.

    The bet is that if I can do it, three fellows I know will go into business with me; I'm a crippled deadbeat dad, broke with brain injuries, thus I really need help with the licensing end of rebuilding my economic life (note if you will under those conditions in Maine -Maine treats the brain injured as "mentally ill" and one can't bill the mentally ill for child support as it cost the state more money to treat the medical conditions exacerbated by the threats intimidation and downright abuse than the child support will ever justify - imposition of child support is forbidden the court by statute - but neither the DHHS nor the judicial care - the local mobs penchant for shooting people in the head seems to trump all legal aspects of this pathetic existence).

    Don't worry about me though, I've got food, lodging (courtesy of the State Mental Hospital and CHCS's shelter plus care!) and I'm a Bell Ringer for the Salvation Army (they tell me I'm even famous) - so perhaps even God has heard of me and is on my side! (wish I could afford a hair cut and the occasional toilet paper roll though...but who knows, If I don't get squished flying a paper and tape airplane I might get to own another business or two, maybe even buy a few more hospital helicopters for foreign governments! After all, we can't rely on GWB to do all the winning of hearts and minds can we? - not that he's not doing a bang bang bang up job!)

    I have always counted on humor to get me out of tough scrapes, and I'd hope that a cardboard and duck tape airplane might be a worthy medium.

    If on the other hand, this project has already been done there is no use reinventing the wheel so please send me any details you might have of any former attempts.

    Thanks and God Bless,
    javascript:smilie('')
    Bananna Wade Edward Hinson
    AKA: Hue Ward (of)Whos

    PS:I thank the fellow in that other forum for redirecting my inquiry here; but, please forgive my bad spelling and grammer and don't get too mad that the other forum passed the buck on this one! I have a bad habbit of making the same bad bets - some of which I never quite get around to doing, others ... well but, if you've heard this all before please thank you for the past help, but the brain injuries do keep me from recalling everything when I desire it. So, bear with me.
     
  2. Feb 9, 2006 #2

    StRaNgEdAyS

    StRaNgEdAyS

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    Interesting task for cardboard, but then I guess with the right planning anything is possible. One question I do have is what do you intend to use for power? I've a feeling that you'll be hard pressed to put an engine on it, but then with enough laminations i guess you could make sufficiently strong mounting points. I'd hazard a guess that cardboard would be too heavy to allow Human power though.
     
  3. Feb 10, 2006 #3

    pylon500

    pylon500

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    Now this is getting interseting! :roll:
    Re,
    StRaNgEdAyS comments, You may need to create a set of definitions here to cover you with the bet.
    'To build and fly an airplane made from cardboard and duct tape' implies the above materials are to be used for the 'load bearing' majority of the structure.
    So, while that by definition precludes the use of steel cables for load bearing, (ie:a wire braced biplane) you probably still have the ability to install some 'Hardpoints', like bits of plywood, to attach motors, seatbelts (better safe than sorry!), wheel axles and so on.
    Just as long as you can prove they are not forming part of the PRIMARY load path.
    I had thought of many places you would need hardpoints, but with a bit of planning many of these could also be cardboard like control pushrods (rolled up paper tubes), undercarriage legs (use a mono wheel with tip skids, even the wheel could be cardboard!!), control belcranks (make them REAL big to cut down point pivot loads).
    As for your 'Duct' tape, here in Australia if you say duct tape, we tend to think of a plastic coated adhesive tape that has a cotton cloth backing with a very 'gummy' adhesive, that is very similar to a product we refer to as '100 mph tape'.
    This is of far better quality having more threads per inch (but still of cotton) and a finer grade of adhesive that is less likely to creep.
    BUT, while 100 mph tape is good, it is not as strong as fibreglass reinforced PACKING tape, which would be more in keeping with the 'built from boxes' concept, as well as being about a quarter of the price!:D
    This stuff has some serious tenslie strength so multiple layes of it would make good lower spar caps, as for compressive loads I would look at 'bundles' of cardboard tubes (minimum x3) tightly cross spiral (ie; both directions) wrapped to form top spar caps or more likely multiple top skin 'stringers' for the wing.
    OK, the wing....
    What do we need?:confused:
    A really DEEP wing to keep the top compressive loads down.
    We also need LOTS of wing area to keep us slow and do the 'concept of scale' thing.
    So far so good, these both help one another.
    What DONT we need.....:eek:
    Lots of bits and pieces to carry other bits and pieces and extra bits supposedly for stabilty and the like.
    So where am I going?
    Build a really big DELTA after all, this all probably started with a paper dart!! :gig:
    Maybe you need to look at building a double (or triple!) sized 'Facet Mobile".
    Who knows, Barnaby might even help out!?
    That's my nickels' worth.
    Arthur.
     
  4. Feb 11, 2006 #4

    velojym

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    A class group from my tech school participated in a glider contest in a nearby town. It's kinda like a small scale Junkyard Wars, and they are supposed to construct a glider from the junkpile provided.
    One year, they won with a foam and duct tape plane.
    The next year, our team bit the dirt with an chunk of corrugated cardboard and duct tape, which showed little planning and way too much weight. *sigh* When I get some time I'm gonna get together with my niece and try to do a bit better.
    It's good to step back once in a while, go simple 'n stuff.
     
  5. Feb 11, 2006 #5

    orion

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    Although not exactly cardboard as most of us klnow it, a full scale paper airplane has already been done by Molt Taylor and Jerry Holcomb. The technique, called TPG (Taylor Paper Glass) used Kraft paper, sandwiched between thin layers of glass. The paper stock was used for virtually the entire airplane, with the exception of a few wood pieces for siffening and in one or two areas, as the primary load carrying member (the paper would have been too heavy).

    A simplified version might be possible but should not be taken lightly (sorry about the pun) as the paper has a very low modulus and so, unlike more conventional airplane materials, would have to be designed for panel buckling more so than anything else.

    The task should be possible but will most likely have a very limited life and will be structurally very marginal.

    I like the delta idea but it will require quite a bit more power due to the characteristics of that particular configuration.
     
  6. Feb 13, 2006 #6

    wadeedward

    wadeedward

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    Thanks all,

    Actually, there was a stipulation in the bet that multiple small lawn mower engines be utilized as power plants. Yes I know, power to weight ratios are not ideal. But there was an airplane that flew with bungee assisted takeoff way back when with a three cylinder Franklin of quite a low rating and that carried two people; so I figure it all should even out. Again, I know that Briggs and Stratton do not make an approved engine, but at 500 feet above sea level there shouldn't be that much difference in operation - it should work. And with multiple engines the safety factor should be adequate. I've opperated these engines both here and in Monson on the hill and that is over 500 feet higher than here I would hazard a guess.

    As for the layout, I was going with a conventional monoplane with no landing gear similar to what I helped design in rubber and polyester for the US armed forces at the end of the Viet Nam war. (There were built two types one enclosed and one open cockpit the former a two seater and the later single). I would use the paper in place of the polyester and the duct tape in place of the rubber, sort of.

    As this design used air pressure to "stress" the airframe, buckling is not the problem, and it plays well off the strengths of paper, which we all know lie mainly in the tensile area. As for engine mounts I was thinking sandwiching the compressed cardboard between the engine and a portion of the lawnmower base.

    Finance is a problem, as I am a deadbeat dad; thus until I "get over" being a brain injured cripple or risk another heart attack and go to the court (I'm scared of court officials - one of them ran me over in a borrowed car and without insurance or conscience and some of the others seem to have covered up for him so this is a real issue with me) I cannot possess any money and I've only been gifted one working lawn mower engine and I'm pretty sure 3.5 horses just wont do it no matter how many bungee cords I use to sling her up with. I like the idea of making a documentary of the project (the last forum suggested this) and maybe I'll finance the project that way.

    Either way it's definitely an outlaw venture; I'm quite sure the FAA would frown on me flying again, even if it weren't in a cardboard airplane. (Maybe I could put it all on a fishing boat and get 200 miles out and have a go? - but I don't quite know how I'd legally pay for the stuff to make the plane out of or the transport outside the national airspace - of course cardboard is free, but duct tape! - that is precious stuff!) I'm asking for advice - please send no money!

    Wade
     
  7. Feb 15, 2006 #7

    pylon500

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    You mention some Vietnam time inflatables?, were these the GoodYear machines?
    If so, I remember that they relied on external wire bracing as well as the internal pressurising.
    If you are allowed external bracing the whole project is much easier. :D
    As for motors, if you have to use lawnmower engines, I would tend towards using two strokes where possible.
    I know a lot of people hate them, but, you need POWER with as little weight as possible.
    'Tecumseh' use to make a range of small two stroke mowers with engines that may have been based on McCulloch models, that have a one piece cast alloy case and barrel with a steel liner.
    With bigger carbs and a non restrictive exhaust, you could get around 10 hp from a 144cc model.
    I had two of these on my very first attempt to build something!! :D Just wish I could find the photos?!
    As for 'Duct Tape', remember the fibreglass reinforced tape....
    Arthur.
     
  8. Feb 15, 2006 #8

    tankboot

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    cardboard?

    You guys are nuts, however I was bet 3 years ago I couldn't build a flyable airplane from strickly home depot materials. I did it and won the bet, and it's still flying at 147.3 VNE.

    Construction methodology is paramount.


    Card board is heavy and useless in my humble opinion, I prefer foam, however it can be done, if you honeycomb several parts including the spar, build it as if it were a sailplane and utilize all methods possible to save weight, like covering it with brown masking paper, which is a dirivitive of cardboard. Worse case scenerio, I would also use solar panels on the tops of the wings, and fuselage and an electric "lawnmower engine" to power my craft in a perfect, abundantly funded world, in keeping with the bet. I would lauch myself (with a parachute on my back) from the highest point in america, and try to keep it gliding for the .5 you required, as the solar powered prop helps you maintain, and rising heat to keep you aloft. Generally speaking, Cheating is not wrong, (despite societies thoughts) finding new ways to cheat and win, is adapting and overcoming obstacles in the shortest amount of time.

    Remember the Kobiashi-Maru? (I think I spelled that wrong)



    Plenty of cardboard my be obtained behind appliance stores, or simply by asking for it at you're local big screen TV store.
     
  9. Feb 15, 2006 #9

    wadeedward

    wadeedward

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    Again marvelous stuff, thanks everyone.

    I like the two stroke info; I might need that and it sounds very nice indeed; very good power to weight ratios on two stroke engines, and the faster operation might actually help with keeping engine mounts together. The question is is there enough reduction in the drive train to be useful driving a prop? Would a model airplane prop work? Some of those jobs do 10hp.?

    I like the idea about using height advantages except for one small thing: one changes altitude too much for adequate safety in terms of engine reliability. I have crashed too many times already! Wouldn't want the carb to need preheat or variable jetting; I like the idea of saying I didn't cheat! And I like the KISS principle in all things.

    Instead, as with the rubber airplane, I would gain speed advantage through a ground launch assist; either by bungee or as per the Wright Fliers through a dropping weight. A Low tech. version of a JETO pack!

    I know that the rubber plane concept would be possible in paper; reinforced paper is comparable enough to polyester in terms of tensile strength. I know that there are reinforced card-boards used in shipping crates used for furniture; I used to work with furniture. I don't think that it would be cheating to pick what type of cardboard I chose to employ.

    Although there were rigging wires on the rubber plane they were mostly to keep the engine pod pointed in the right direction and upright! There were no real flying wires per se'.

    No, the craft would have flown with no wires at all, but the internal pressures might have needed to be different to keep that engine from eating the airframe. The tail was kept trim with wires, but again, this was not really required for flight, though it did help with stability of the flight controls, but I don't need to fly quite as fast as the speed that plane was intended to be able to achieve in a dive. I'm not planning on being shot at. So don't tell the FAA if you see me blown across the 200 mile limit!

    I have already thought of using thin film photovoltaic but I'm happy the idea doesn't sound too kooky to work to others. In fact, I've already been talking about a business loan to the government for several years, with just that point in mind. The thin film solar voltaic based on a copper film was my idea (copper is in and of itself a solar electric material - it is simply less reactive than those "expensive" materials).

    Eventually, I hope to have enough partners to defeat the deadbeat dad "laws" that prevent my saving people's lives by making redundant airframes. You can see that as I've laid out my cardboard and duct tape project, it is to be "fold-able". Using different materials, like diamond fibers and Mylar the weight becomes an issue only when inflated. (today a redundant airframe pack can be built in a package under one tenth the 400-600 lb size of the old rubber / polyester job.) Thus the size of the airframe if sustained flight is needed can match the output of the solar film's capacity to produce power. I will get back to you when I have proved that the power generated by the cells is enough to keep a rescue plane / redundant airframe aloft indefinitely. At that time we will no doubt have no use for ejection seats with parachute packs on board, and our civilian craft will finally have total redundancy in their systems, right down to the airframes.


    Thanks, Wade:ban:
     
  10. Feb 16, 2006 #10

    pylon500

    pylon500

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    Just had a bit of a dig around, and there has been a few attempts at making inflatable aircraft. :eek:
    some one tried to make an inflatable man powered delta! :ban:

    I'm not sure that trying to build a paper 'inflatable' plane is really going to work in that the amount of pressure you will need to create the skin stiffness you are looking for would then require extra structure to avoid bursting (I think?)
    Also found a picture of one of those Tecumseh engines I've got.
    I was running two of them as pushers on a trike I built, the props are home made and the last ones I was using were 30"D x 11"p.
    Arthur.
     

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  11. Feb 16, 2006 #11

    pylon500

    pylon500

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    Here's an inflatable wing.....
    Arthur.
     

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  12. Feb 16, 2006 #12

    wadeedward

    wadeedward

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    A correction

    I remembered a thing or two about that rubber airplane.

    The important thing is yes it did have flying wires. I can't believe I forgot this, as it was one of the principle argument I had with the fellow I was working with. I wanted them, he said the angle was wrong and they wouldn't work anyway, and that they might snag stuff on takeoff. I argued that the wings would bend under pressure and then the wires would work, as the angles would inherently change. As one can see on the films of the airplane, it did just as predicted, and as my partner was the test pilot, he was a tad happy when those wings stopped bending.

    Thanks for the info on the engines and the pic of that inflatable plane.

    Someone mentioned Goodyear, I believe we asked Goodyear, but they wouldn't build it, so we started with BF Goodrich.

    Wade
     
  13. Feb 17, 2006 #13

    J.L. Frusha

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    What about using a carpet tube for combe spar and leading-edge, with an outboard rib and root rib, skinned on top with that rip-stop style paper vapor barrier... ala Princeton wing?
     
  14. Feb 18, 2006 #14

    Daniel Tyrkiel

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    Tankboot
    Would you mind elaborating on that?
    You got me interested there. What materials, did you get your own mechanical characteristics, or just what the producer supplies?
     
  15. Feb 18, 2006 #15

    J.L. Frusha

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    Essentially, the Princeton wing is a tight fabric that uses one combo spar and leading-edge with a root rib, wing-tip and a cable or rope to keep the trailing edge tight. The fabric is attatched, so that it wraps over the top of the spar, forming the upper part of the chord.

    Rotating the wing-tip acts as ailerons ala Wright Bros. and wing-warping.

    As the air flows across the wing, the fabric adjusts itself into the most efficient airfoil for that portion of the wing, independantly, across the entire span, adjusting for the airspeed and all.

    This was developed in the Vietnam War, as part of an idea to have flying ejection-seats. The seat used a drogue-chute to extend a telecoping boom fuselage and the wing spars were hinged and cabled to swing into flight position, as the boom extended and locked.

    A pretty simple "T" srtucture, with the seat canted back, above the frame and a conventional (tail-dragger) landing gear. It used a small turbo-jet, mounted underneath, for propulsion.

    Basically, we're looking at a MONSTER-Scale model, using alternative materials...

    Another pair of designs are the "Maersk Momarch" and the "Woodhopper."(Not the Weedhopper) Both are ultralights...

    Monarch is a large flying-wing with a large vertical-stab and rudder, with a pusher-prop behind the fuselage/pod, underneath.

    Woodhopper had a glider-style wing and tailboom with seat slung underneath.

    Both used single-engines, but could be twin... If you could reduce the requirement to one powerplant, you'd be better-off.

    If you could get away with filling the cardboard tubing with triple-expanding foam, the resulting pressure and foam core will add strength, while adding minimal weight.:pout:
     
    Last edited: Feb 18, 2006
  16. Feb 18, 2006 #16

    J.L. Frusha

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    Another idea, might be to run with the Maerske Monarch ultra-light design. Essentially, it's a flying wing, with a large vert.-stab & rudder, a pod slung beneath and a pusher-prop, behind the seat...

    Cardboard and light wood construction are very similar... Basically, we're talking about a MONSTER-Scale model airplane. The only significant factor is that we have to worry about pilot-safety. People have made some weird stuff, using strange components, for the sake of flying and model-flying.

    I like the Tecumseh and prop... A pair mounted to either side of the fuselage, like the old prop-job airliners, meets your 'multiple lawn-mower engine' requirement... If the weight is still too high, for the power, a third could be put behind the seat.

    However, IF you could beat that down to one powerplant, I think you would be better-off. it becomes an issue, when your power:weight ratio interferes with structure strength, to compensate for added weight and bracing to deal with stresses from static weight, vibration and the varying torque-moments and push/pull off prop-thrust.

    It's the old 'Power of Squares' problem... twice the size, quadruples the weight, requiring more structure(hence more weight), to achieve the same structural integrity... Bigger ain't necessarily better.:pout:
     
  17. Feb 21, 2006 #17

    wadeedward

    wadeedward

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    Actually, the larger a structure is the more strong it tends to be for a given thickness, and for practical reasons there is usually a minimum effective thickness and usually a maximum effective thickness as well with regard to one's chosen material, especially in a structure that must by nature bend. Thicker material choices tend to distort past their limit of elasticity and self weaken quicker, as they are themselves larger "levers" working against themselves.

    The Japanese Zero is a prime example of this thesis; when it's designer wanted to strengthen a particular part, he shaved it down to where it would bend without failure.

    I understand the typical thought on the theory of scale, as anthropologists understand it. But I am also aware of some of the reasons why a 747 is so darn efficient. An ant forty feet tall, scaled up perfectly will of course be a cripple the first time it tries to stand up; conversely a 747 radically scaled down would not be anywhere near as efficient a flying machine as the less efficient wake alone would "suck the life out of it"!

    One merely has to study hydrodynamics to understand the principle of the large hull and the principle does at speed work out pretty much in the same general direction for aircraft as boats.

    Drag, not weight is the thing with aircraft. Most people miss this when studying airframes. This is the reason why most WWI aircraft were made so "poorly". I think people concentrated too much on absolute weight, rather than the all important ultimate drag to power ratio. Drag actually goes down per unit of frontal area as scale increases; one of if not the most draggy shapes for it's scale is that of a thin cable!

    This is why I say I intend to make my aircraft as large as possible, given my resources: I know that unit weight per surface area must go down as unlike the ant the interior of an airframe is lighter than the airframe itself and therefore the bigger the lighter for a given lift capacity.

    Conversely, I know that without resorting to "tricks of the trade" my compressed air interior will begin to tell as the interior size increases. Compressed air acts more like an ant's interior than an airplane's interior!
    Obviously, a hollow sphere (or just about any shape) of a given thickness grows in interior volume faster than it grows in weight, but of course my plane will be at least partially compressed air and as anyone knows who's lifted the spare tire after lifting the flat compressed air weighs a tad more.

    Norton motorcycle frames evolved into the Commando type for just this reason: for a given weight of metal, the theory goes, within the practical realm the stiffness of a single large tube is greater as the size increases, even as the thickness decreases. Obviously, there is a practical limit to the extent one can "thin down" before nature will find a means of introducing a buckling force.

    I find for practical situations one is better off doing the math after one has proved the concept; the math is good only for preventing lawsuits in the real world. This is why the mosquito was built with private money...generalities in mechanical "trends" are usually sufficient to improve known structures. But a business plan cannot pass muster at the bank or in Parliament without lies. It's best to know your lies are a little true.

    We simply don't know enough to be able to predict real world events; but if one goes into court and says that he experimented until it worked then the law will interpret this as incompetence personified. The lawyers want to be baffled with bull so we as practical men give them theory in adnuaseum (sic), but we don't live by theory. We live as the Wright Brothers by reasoned experimentation. We learn that untested theory killed off some of the best early men of aviation.

    So, I intend to test my beast first. Then fly.

    I might add: in the making of that rubber airplane we flew too fast. (There was a war on after all.) The plane was tested statically but not dynamically! When the airplane was aloft a rather frightening thing happened. The wings began to flop back and forth like a bird! Only the underside "compression" cable kept back the oscillations and prevented the collapse of the wing...it acted as a friction damper! Good thing it was intended as a single use airplane!

    In making that other airplane you sent the picture of we lacked sufficient air pressure! The darn thing would barely fly! A gust of wind would spoil the airfoil and down it would go!

    I've thought about it and have decided to build a full scale model and test it with a half galloping ghost type FM radio control. I'll tether the beast down to prevent it from "running away" and to make it somewhat legal. I'll use a computer as both some of the "human like" ballast and to act as a part of my radio system. I've got an extra computer, and I think visually it will look awesome. I'll use a child's toy to give the computer "orders" - one of those microphones one can hear on the radio. I think Ronco sells them...

    If anyone knows of a regulation I'd be breaking either with the FAA or the FCC please let me know! (I can't afford a fine!)

    Thanks,
    Wade

    PS: be aware, a little knowledge is a dangerous thing: if your going to try this at home be sure your tether is "good" and "secure" and that you have fire fighting equipment nearby and that you can pay the fines from the EPA for the nearly inevitable pollution. If you plan on digging a foxhole for protection from flying debris please be aware that burning fuel and oil will inevitably flow into it. So, wear your fire proof undies, etc.

    Better yet...don't try this at home! Forget I said I might!
     
  18. Feb 21, 2006 #18

    tankboot

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    Cardboard Airplane?

    Wade you are incorrect on several of you're thoughts and assumptions concerning aerodynamics, weight/drag & turbulence.

    The 747 (as you mentioned) was tunnel tested for many months at 1/20 the scale, as is EVERY airplane prior to construction and final engineering. If an airframe fails to perform EXACTLY as it should, it is re-engineered accordingly. Size has some small relative association, however it is nothing in comparison to you're incorrect ideas. air is air is air is air, regardless of it's size. Everything else AROUND it, may be effected differently, (there are thousands upon thousands of variables here which may change this) but the airframe itself makes no difference whether it's 3ft long or 3000 ft long, weight and shape being relative of course. There are multitudes of books on this subject you might read.


    D. Davis
     
  19. Feb 21, 2006 #19

    orion

    orion

    orion

    Well-Known Member

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    As you indicate Wade, a little knowlege can be a dangerous thing. And if you truly believes what you write, then I can only conclude that a little knowlege is just what you have. Some of the erroneous statements you make can be attributed to a possible mixup of terminology, but some are just plain off the mark.

    For example in the first paragraph, for a given gauge, contrary to your statement a larger structure is not stronger than a smaller one. The larger structure will have a larger cross sectional moment of inertia and as such for a given gauge it will be stiffer. For a given load, the stresses within the larger structure will be lower than in a smaller equivalent structure however, the actual strength is purely a function of the material and the structural configurational makeup. While this may sound a bit like nit picking, it is in actuality far from it -your reasoning may lead you down some pretty dangerous paths.

    This, coupled with your next bit of reasoning, could lead to almost guaranteed problems. It is true that the stresses within a structure do end up in the stiffest part of the assembly and yes, there are examples where removing a bit of structural material may actually be a fix for a potential component failure. However, these instances are very rare and should not be a part of a design process unless you really, really, really know what your doing. I remember only a few examples of this phenomenon that were demonstrated in a university class, and in the nearly thirty years that I've been a structual engineer I've run into this only once. Often this is only a consderation in structures that undergo large deflections or a high level of relative motion. If an airplane encounters this type of condition, it's time to hit the silk.

    Your discussion, reasoning and examples of parallels demonstrate only a very basic understanding of the principles involved in this process and as such, I strongly urge you to get responsible help in this endeavor. Yes, I think it just might be possible to design a cardboard based airplane for a one flight adventure but given your limits on material, the choices and makeup will have to be very carefully considered and analyzed.

    Math is not just useful for avoiding lawsuits, it more than anything else is for keeping yourself alive. "Proving" the structure before doing the math is the ultimate example of putting the cart in front of the horse and is a virtually guaranteed way to get yourself inducted into the "Darwin Awards" hall of fame.
     
  20. Feb 21, 2006 #20

    tankboot

    tankboot

    tankboot

    Active Member

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    cardboard

    "Here, Here young fellow" he say's (with a rustic English accent')

    Wel said Orion, and I agree with every statement.


    Duane

    Aerospace Engineer III

    Boeing Aerospace
     

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