Looks a bit like a short Pilatus :-)
Nice job. D'you know if it's aerodynamic enough? :-)
The Paper Aircraft Released Into Space team is assembling for the imminent launch of our Vulture 1 aircraft into the blue yonder, and here for your viewing pleasure are some further constructional details of our advanced all-paper vehicle. Before getting stuck into the snaps, those of you who aren't up to speed on the Vulture …
So far PARIS is looking pretty good, but there are three points I think you need to revisit:
(1) There doesn't look nearly enough dihedral on that wing. I'd want around 10 degrees dihedral on each wing half. A nicely stable 14" electric free flight model I built, Thistle 14, has 13 degrees and my competition F1A gliders have 7.5 degrees.
(2) How big is the tail plane as a percentage of the total wing area?
It looks rather small. Thistle 14 has a 37% tail with a fuselage length about the same as yours - 1.85 wing chords measured between the LE of the tail and the TE of the wing, giving a tail volume factor [*] of 0.7. This compares with my F1A design which has a 16% tail on a 4.13 chord fuselage for a tail volume of 0.64, so if your tail volume is any less than 0.7, you should fit a bigger tailplane before any test gliding is done.
(3) You seem the have the wing and tail set at more or less the same angle.
Thistle is the same, but with a much different wing section. It flies OK with the balance point at 0.58 chords behind the wing LE, but you'd be better off with the balance point further forward at 0.35 - 0.4 chords and the tail angled TE up relative to the wing. With a sensible starting point you'll then need to adjust the tail setting for a safe glide by hand-launching it over some long, soft grass. But, with the tail and wing glued in place, how will you adjust the tail setting?
A good plan would be to make the tail angle adjustable while you're replacing it with a bigger one.
[*] tail volume TV = F/C * T/W
F is the distance between the wing TE and the tail LE,
C is the wing chord,
T is the tail area and W is the wing area.
You cannot put very sophisticated electronics on the plane, but at least you can put a decent antenna without adding too much weight.
If, and that's a big if, you had the proper equipment to transmit a strong enough signal from the ground, that could make a hell of a radio control glider.
I seem to remember an article many years ago, when - just - supersonic fighters were being tested. The bloody wings kept falling off, and the janitor!! (bogwasher, if you will) of the establishment overheard the conversation.
He suggested perforating the wings at the point of failure. "How so?" came the reply. "Because when you tear loo-paper, it never tears at the perforations..."
However, I think it's apocryphal.
I really didn't believe it, either.....
But, your examples are based around metal.
School-issue(d) "IZAL Medicated*" non-absorbent toilet paper was another story. (Anyone old enough to remember that - apart from me, 'natch?)
Grief, I think IIRC we were rationed to 2 sheets each. It DID NOTHING. After a decent school dinner, all the kids had turds on their heads after a futile effort to eliminate Klingons.
Wait a mo'....
Wasn't the PARIS project looking for a non-absorbent, light, fiercely indestructible form of a paper??? Oh, go on, folks, do me a favour and throw some of that stuff as high and as far as you can!
* For those who wish to remiss...
(Oh, the rest of the site's worth a looksee, too...)
In the bogs in a park where we used to go for picnics (the park, that is, not the bogs). Every sheet was marked "Government Issue', as if anyone was likely to steal it anyway. About as absorbent as aluminium foil, and considerably less comfortable to wipe with. Ah, nostalgia. The old times weren't all good, give me a roll of Andrex any day. You can keep the puppy, though.
"We slapped in some extra uprights (indicated) under each spar to absorb the downward force created by the wings in flight:"
Surely, during flight, the wings are actually lifting the plane up? Pre-release, and after landing, the wings will indeed exert a pressure downwards (from their weight) - but during flight the wings are pushing up against the fuselage, since they are the source of lift?
when the plane is flying there will be a force exerted upon the wings in an UPWARD direction.
The wings are attached to the fuselage and this UPWARD force would if unresisted rip the wings off in an UPWARD direction. Spars added under the wings will be under tension NOT compression (when in flight). However during lift the spars maybe under compression.
Of course the above completely ignores the reality of air pressure pockets and wind currents which will cause possible (high) positive and (low) negative loads on the wing surfaces during flight - or aleast I hope that is why you have attached spars? :-)
BTW I think the idea of going bigger (next time) and adding a small laser gyro and with some very basic electronics to tie the GPS into some servos to aim/land the plane at a destination.
Perhaps aim for a paper based shuttle - complete with heatshield :-)
Then the military will want some :-)
I think you are mistaken, unless we're talking at cross purposes...
During flight, the only uplift is coming from the wings. This therefore means that effectively the fuselage is hanging off the wings.
Therefore turn the wings are applying/extering an upwards force from the spars into the fuselage. If you want, you can show this quite easily with a pencil and a wedding ring (2 things I have to hand) at my desk - but anything long and thin (ooh-er) and then something to go around it will do.
To simulate pre/post flight - put the pencil through the ring, and either put it on the desk (landed), or hold the ring (suspended pre-launch by cable to fuselage). In both cases, the pencil will rest against the bottom of the ring, and your supports will do the job they are required to.
To simulate during flight, hold the pencil in the air - at which point it will push against the top of the ring (hanging from it), and the supports will only exert any force on the spars as a result of the glue... The majority of the pressure will be transferred straight to the top of the fuselage.
A couple of paper spars front<->back across the top of the fuselage (in contact with the wing struts) will give you a better contact area for the upwards force - but that may be unnecessary/overkill - the fuselage shouldn't be that heavy.
Who had to learn how real planes flew before the RAF would let us play with their aircraft, I can state definitively that he's right.
The wings create lift, but at the point of connection to the fuselage they exert a downward force because of the upthrust on the wings. You know, every action has an equal and opposite reaction, and all.
Anybody that disagrees simply appears to be understanding elementary aerodynamics, but not basic engineering or physics.
When its flying the wings are exerting an upward force on the longerons forming the top corners of the fuselage and a much larger downward force at the center of the fuselage where the spars join.
The upward force on the longerons will be equal to half the weight of the fuselage (the weight is carried by two longerons) plus a little more because, with the balance point at 30-33% of the wing chord, the tail will be generating a small down force to keep PARIS stable.
The force at the centre of the spars will be larger because the wing lift can be considered to be acting half-way out along the wing and you have two moments that have to be in balance if the the wing is not to fold up: the product of the lift produced by the wing times half the length of a wing half must be matched by the product of the upward force on the spar join at the fuselage center line times half the fuselage width. The wing length is at least 5 times the fuselage width so the force at the spar join is at least 10 times the weight of PARIS.
You need the main spar stubs inside the fuselage to be strong (glue in another straw either side of the top straw) and add four diagonal bracing straws from the centre of the main spar down to the bottoms of the nearest uprights in the fuselage sides. Simply adding a doubler straw to the rear spar should do the job for it.
Surely the point where the spar first meets the fuse acts as a pivot. Lift then pulls the wing up meaning that the 'free' end of the spar gets a corresponding downward force, but the pivot point and hence fuse experiences a net upward force. It's called 'flying'.
I'd have put some dihedral in the wings for stability - even if it has an active autopilot, it's not a stunt plane, it should be designed to be stable and easy to fly to minimise the control needed.
That tail looks very stubby - hope the cockpit is both light and short so the CoG ends up somewhere close to where it needs to be...
Is it getting any test flights? Even a hand throw down a flat field?
You *are* mistaken, I'm afraid.
On the ground, the plane sits on its belly, and the wings are supported by the structure underneath them. So stronger struts in the fuselage under the wings will hold the wings up. In the air though, the fuselage is dangling from the wings. So since the wing struts go through the fuselage, you need strength *above* the wing struts to keep the fuselage attached.
Think of David Blaine twatdangling in a box. On the ground, the box base rests on the ground, the sides (and David Blaine) stand on the base, and the roof is propped up by the sides. But mid-twatdangle, the box is hanging from a hook in the roof. The sides are then suspended from the roof, and the base (and hence David Blaine stood on the base) is suspended from the sides.
Or for the ultimate twatdangle, consider a paraglider or parachute. The pilot hangs off a bunch of strings attached to the chute above. The chute is not pushing down on the strings - the pilot is hanging off the strings which are pulling *down* on the wing above it. Pushing on strings tends not to be a profitable exercise.
Of course, if your paper straws are strong enough then this might not be a problem. But it does show up a worrying lack of familiarity with flight and basic mechanics, and suggests that no-one at El Reg remembers any of their O-level physics lessons about forces (apart from the bit in the lesson where you flicked a pellet at Jessie Smith in the row in front).
That the wings are structurally strong enough to support the limited weight of the fuselage.
However, any lift generated by the wings in flight will cause them to act as a lever, with the fulcrum being the point of entry into the fuselage. At this point, the force acting on this fulcrum is the weight of the fuselage pulling down, so you'd better be sure it is properly attached. On the other side of the fulcrum, where the wings enter the fuselage anda re attached on the inside, the force generated by the lift will cause a moment around that fulcrum, resulting in a downward force from the end of the wing inside the fuselage onto the supporting struts.
So in summary, there should be an upward, tension on the struts attached to the wing at the point where the wing enters the fuselage, and a downward compression on the struts attached to the end of the wing inside the fuselage. This would tend to fold the wings upward and inward without sufficient strength.
Of course, IANAE (I am not an engineer) but I do remember my A-level physics from all those years ago.
From the pictures, it appears to me that the two wings were attached to each other, and not anchored "in the middle". Therefore the only physical contact between the wings and the fuselage would be where they entered - with nothing attached to them in the middle. This therefore means that the leve/fulcrum will merely cause internal stress within the struts going through the wings at the middle of the fuselage, with no impact on the fuselage itself - since there's nowhere for it to be transferred to.
Looking more closely (last image on page 7) the support for the "downwards force" is at the entry point into the fuselage, and although the wings are attached to each other, picture 2 on page 8 suggests there is nothing in the middle...
However, picture 3 appears to show something from the middle of the wings to the fuselage (something to do with the release mechanism) which is, I believe where any downwards force would be exerted.
Either way, support for downwards force at the entrance to the fuselage isn't right - unless it's been too long since I did any physics... :)
I build these things for a living, and although I do not doubt that the wings will reduce the rate of decent somewhat ("fly"), I am sure that weight could easily have been reduced substantially, and performance increased. I will spare you the long and tedious analysis.
The additional strengthening of the fuselage will indeed undergo tension, so unless the but-end glue joints have been strengthened locally, the tubes will probably do little.
To all who discuss levers: The bending force created by the aerodynamic lift is simply carried over into the other wing (assuming continuous wing spar. All the fuselage sees is an upwards force, no bending force.
Anyway: Good luck on Saturday. Bring enough alcoholic beverages to either celebrate or forget .
...even if it has a very good glide ratio at groundlevel atmospheric pressure... there essentially is none at the starting point.
Which is rather worrying in another way. If the plane plummets to earth for the first part of the trip, the sheer speed will rip it apart when it enters the denser parts of the atmosphere - possibly letting the electronics freefall the rest of the way.
So, i'd attach a small parachute to the electronics and leave it inside the plane. If something goes horribly wrong - and it most likely will (this *is* the maiden flight of a prototype airplaine) - then there's a chance the parachute will come out and at least slow down the electronics and leave enough parts intact to get some pictures from the flash card.
My money is on this happening. At least, it would be if anybody I know would take it. They all consider anything other than the glider hitting the ground sans wings as a suckers bet.
I mean seriously. There is almost certain to be insufficient air for PARIS to glide when she's released at that height, so she'll stall and fall to a point where she can glide, likely reaching her terminal velocity doing so. I haven't bothered doing the calculations, but I suspect that's going to rip her wings off given it's supported by paper straws. Even if it doesn't, she's going to go in like a meteor as she doesn't have anything to pull her out of a dive apart from luck unless i've missed something in the design.
The only way I see this having a happy ending is if she goes down in a flat spin, and I don't think that's likely with the design.
More happily, the electronics package is unlikely to weigh enough to reach a terminal velocity capable of breaking the flash card, so we'll probably get the pics regardless. I'd like some pics of the condition the camera is in when it hits though.
...quite a low aspect-ratio wing. I would have expected something looking a bit more like a U2 in terms of aspect ratio. What's the wing loading? Will it actually fly in any meaningful sense at 100mb range air pressures? Or maybe you're hoping that it will just fall in a controlled manner and automatically start gliding straight-and-level when the air density is high enough for it to generate sufficient lift? An X-plane simulation would have been interesting, not that I know enough about X-plane to have done it myself.
On terminology - the rudder and elevators are the flappy bits of the tail surfaces, on aircraft that have them - as yours are fixed, they're more properly called the fin (or vertical stabiliser) and horizontal stabiliser.
Interesting project, I look forward to the results!
Appear to be misunderstanding the comment in the article about the downwards force.
As explained by several commentards already, the joint to the fusealge acts as a fulcrum, the net force will be up, but the internal parts of the struts will be pushed down (due to said fulcrum). The strengthening is in place to stop the wings dihedral increasing as they load up.
on whether the wing spars running through the fuselage are connected to each other and stiff. If they do not flex or kink, then the fuselage will be suspended from the wing when flying, but if they flex or are not connected together, then the inside ends of the spar will move in the opposite direction to the ends of the wings around the point where the wings enter the fuselage.
From what I can see, there is a join in the spars on the mid-line of the fuselage. This could potentially be a weak point, possibly allowing the spar to kink at the join. Adding bracing to prevent this happening looks like it is a very good idea. Would it not have been an idea to stagger the joins on the individual spars? Or have additional uncut straws to reinforce it so that the joins did not occur at the same point? Oh well, too late now!
I would worry about the weight distribution. I think it looks like it will be tail heavy. The design looks like the sort of thing you would use for a powered plane, which has significant weight at the front (the engine). Do you get the opportunity to see if it will glide before attaching it to the balloon?
The fuselage/wing interface fulcrum will surely present a downwards force on the ends of the wing spars inside the fuselage (and an upward force where they pass through the fuselage).
You can see that the spars from each wing have been bonded together this isthe weak point in the design; as the air density increases and the wings begin to resist the downward force of gravity the loading on this central joint may be sufficient to break the bond, resulting in the wings folding together and a rather faster return to Earth than we all want to see...
Lancaster bombers had a 'main spar' which ran through the fuselage as a single unit and into the wings for mounting and therefore creating a stronger joint for the wings to attach to the fuselage and the wings to support a higher loading.
Of course, unless we are expecting to undertake some aerobatics on the way down (increasing the wing loading) then picking PARIS up by the wings and giving her a bit of a shake should show if any strengthening under the central wing spar joints and/or *above* the wing/fuselage interface or attaching via a 'main spar' might be required.
Excellent job everyone, here's to clear skies and no wind!
Ok, let's simplify the whole mechanical system to demonstrate it.
Imagine you have two wings, no fuselage, and they're hanging from the ceiling with a bit of string tied around each wingtip (an adequate representation of the situation in flight). Now fix a thin, heavy rod in the middle, as a simplified version of a fuselage without any extra supports. Of course there's nothing holding the wings apart, so the wings "clap hands" and the whole thing folds up.
Now we want to add something to stop the wings clapping hands. Because we're using paper straws, this needs to be a strut (or struts) that's in compression. Where do we put it this strut? Answer: AT THE TOP, so that the wings are pushing against it. With the dihedral on the wings, this forms a short, wide inverted isosceles triangle, and the wings can't clap then hands without crushing that top strut. Assuming the struts need to be in compression, this is literally the only place you can put anything which will hold the wings apart. Anything below the wing is simply dangling - it doesn't matter how many extra struts you want to add, or where you put them.
Of course, this assumes all the struts are in compression. Because these are paper struts, so in tension they're just going to rip apart. Try pulling on a paper straw and see what happens - the coiled paper just uncoils and rips. If you add some more of them then you might improve a piss-poor design to just plain poor, but you'll get a lot more benefit from those struts by putting them where they're mechanically useful. Which will be ABOVE the wings.
1) I'm flying home from Portugal on Saturday. You've got all day, so try not to hit me, please?
2) I found I needed a main spar with seven 6mm straws in hex formation to provide enough strength for 60" wings to support a 300gm load with 100% safety overload. I hope yours is sufficient.
May Vne be higher than Vfreefall...
Physics schmisics. I don't care if the bloody thing tears itself into a million pieces on the way down. This is an epic amount of work, it looks bloody brilliant and the entire attempt drips "ballsy" and "awesome." It is a grand thing to have your favourite morning newspaper not take it self too seriously. Even more to have them involved in fully grown-up-like behaviour such as making paper aircraft.
Enjoy the flight and ignore any naysayers! Even if you miscalculated somewhere – it’s still an excellent way to spend one’s time. Where do we donate for towards Lewis' homemade aircraft carrier? The pressure is on the two of you to provide all of the EU's military capability now...
This (even if the plane spontaneously suffers an existance failure as the release mechanism catches fire, and turns the balloon int o a new hindenburg) has been a great source of enjoyment in a dull and humdrum world...
Cheers for the fun, and apologies if I've put a damper on it for anyone - certainly wasn't what I meant..
Also, as for flying, £5 says that it doesn't land immediately under where it is released, and therefore it will have flown :)
I hope the PARIS team have a ball. The PARIS series has been
a blast and the Forum always fascinating and informative.
Props to the creators of a project of inspired, rare and precious loonacy.
The plane certainly looks sturdy enough. Did I miss a mention of
Trim Tabs somewhere ? Can't wait for the tele-photo shots !
My concern about falling MKII release mechanisms was addressed
in the location piece, thanks Team. But ( 'sob' ),, IS there no way
Spanish badgers et al could be warned of the admittedly very slight risk ?
Anyway, Bless PARIS and all who* sail in her !
Oh, I found this neat calculator on the interwebs.
obligatory icon comment below
Boeing found with the Dreamliner that they had to strengthen the wing spars near the point of insertion.
I fear that you may need to do the same - by strengthening the box where the spars come together, the weakest point becomes the spar in the wing, near where it joins the fuselage.
You might need to double up the spars near the fuselage and terminate the additional, short spars at slightly different places, to make the bending mode of the wing less abrupt.
School-issue(d) "IZAL Medicated*" non-absorbent toilet paper was another story. (Anyone old enough to remember that - apart from me, 'natch?)
I remember it ... my Grandfather was a great fan of it!
A few months back while driving somewhere there was a wonderful 30min documentary on R4 about the history of Izal toilet paper and lots of interview with people who used to/still make it.
Think this explained how their marketing line was if you bought their disinfectant you got the paper for free ... posisbly the original BOGOF!
Biting the hand that feeds IT © 1998–2019