Physics Question. Gliders / Wing dimension.

SixPapaCharlie

SixPapaCharlie

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Gliders have a very long wingspan it seems. I am guessing all of this wing makes them slower and floatier.

Suppose you snapped 1/2 of each wing off and relocated it above / below the remaining wing in a bi-plane configuration.

Would it still be slow and floaty.
Would the glide ration and speeds be identical to the monoplane glider having the same wing area?

I am guessing not because then this would be being done in an effort to conserve space on a lot of planes but IF NOT, I don't understand why. You'd have the same amount of wing to plane ratio.

Would it? Wouldn't it? why?
 
The aspect ratio of the wing matters.
 
I think you'd lose some efficiency because of drag on the support structure for the wings. But I'm not an aeronautical engineer so what do I know?
 
Biplane wings take up space and weight gliders dont have. You want lift with the least drag. The gliders out there are the best compromises going. They've tried everything and settled on that.
 
coloradobluesky said:
Biplane wings take up space and weight gliders dont have. You want lift with the least drag. The gliders out there are the best compromises going. They've tried everything and settled on that.
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If I cut the wing and half and relocate the outboard portion the wing takes up the same amount of space that weighs the same
 
Yes but you have to ATTACH it. There isnt the vertical room. Gliders vertical dimensions are very small.

There is a reason you dont see many biplane designs. They aren't very efficient for a number of reason. One wing on each side is all a plane needs. Two per side can be made to work, but not as well.
 
The higher the aspect ratio the lower the (induced) drag, all other things being equal - so shorter span and longer chord with the same area will have more drag. Intersection and interference drag on a biplane also increase drag for the same area.

Nauga,
and a few thousand drag counts
 
Induced drag is your enemy - the flow over the tip from bottom to top produces the wing tip vortex which increases drag and reduces lift. That's why a high aspect ratio is good - minimum tip per area of wing.

Saw the wings in half and put one over the other and now you have 4 wing tips generating induced drag instead of 2. Double bad. Then as mentioned previously, there are several other effects as well.
 
Yea! The new next weird that comes to mind thread.
 
Capt. Geoffrey Thorpe said:
Induced drag is your enemy - the flow over the tip from bottom to top produces the wing tip vortex which increases drag and reduces lift. That's why a high aspect ratio is good - minimum tip per area of wing.

Saw the wings in half and put one over the other and now you have 4 wing tips generating induced drag instead of 2. Double bad. Then as mentioned previously, there are several other effects as well.
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In addition, putting control surfaces half as far away means they have to have (roughly) twice the area to be as effective. Even more drag there. And heavier controls.
 
Sac Arrow said:
I found a publication, circa 1923, that suggests that the lower wing has an interference effect that reduces the efficiency of the upper wing.

https://ntrs.nasa.gov/search.jsp?R=19930091216
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Or vica versa. It's called "interplane interference." The designers of the time tried to mitigate that by staggering the wings. Most put the top wing ahead of the bottom wing. Beech was the exception with their Staggering D-17.
 
Not directly associated with your question @SixPapaCharlie, but a number of gliders DO have removable wingtip extensions... want to go faster... add water ballast both center and aft (move CG rearward)... and remove the wingtips... want to fly slower (thermals)... leave the water at home, and put the tips on...
 
This is meddling with "the magic of flight". I demand a stop to such thought. In case we lose the magic.
 
Bro in law used to fly gliders and I was impressed with just how flexible the platforms were with wings and ballast... depending on the mission or competition for that day they would mod as necessary. Having said that, I've always been told that aspect ratio is key for any kind of foil efficiency. Newer sailboats have crazy thin and deep keels for the same reason

Note the striking difference in designs from the 1960s to today. Incidentally, to @SixPapaCharlie point, there were some boats that had "bi plane" style twin keels and the story is that they don't perform well at all compared to their more traditional cousins

upload_2017-5-8_20-22-51.png
 
Note, in the photo above, the modern boat does have "bi plane" style rudders, but that's more just to make sure one stays in the water when the boat is tipping on its side during aggressive sailing
 
The truth is that the long wings don't make the glider slow and floaty. They make them efficient which is why they have such good glide ratios. Look at the average speeds over a course flown in some of the contests. A good glider (sailplane) can average better speed than some of our powered planes and use only the towplanes fuel for a tow, for the whole flight. Like the others noted cutting the wings in half and attaching them to the fuselage justs reduces the efficiency and makes the glider slower. With the same wing area as before it might require higher speeds to keep flying.

Frank
 
wing root attachments are very draggy....doubling that with two wing sets isn't optimal. The cross bracing is also additional biplane drag.

wing tip induced drag...or wing tip vortex....is doubled.

so....nothing going bi is working in favor of that configuration. literally. :D
 
I apologize for the thread drift in advance... but there is some legit cross over happening in the "new breed" of America's Cup boats (and incidentally Steve Fossett was a big sailor, not just aviator). It's amazing to me that such small pieces of carbon fiber are able to hold up so much force and weight... not just the weight of the boat, but the forces of the wind, sails, water, etc. I don't think foils have Va and water is far less forgiving. It really has made me confident in the tech used on Cirrus, 787, etc. Composites are incredible. Anyway... back to the topic at hand, pardon!

I can only imagine the bending forces on that little piece of carbon fiber. Mind you, these boats aren't small
upload_2017-5-8_20-39-33.png
 
Tantalum said:
I apologize for the thread drift in advance... but there is some legit cross over happening in the "new breed" of America's Cup boats (and incidentally Steve Fossett was a big sailor, not just aviator). It's amazing to me that such small pieces of carbon fiber are able to hold up so much force and weight... not just the weight of the boat, but the forces of the wind, sails, water, etc. I don't think foils have Va and water is far less forgiving. It really has made me confident in the tech used on Cirrus, 787, etc. Composites are incredible. Anyway... back to the topic at hand, pardon!

I can only imagine the bending forces on that little piece of carbon fiber. Mind you, these boats aren't small
View attachment 53387
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Don't get too confident!

 
Theoretically a wing of infinite span would have no wing tip and therefore no induced drag from a wing tip voritice. The closest practical thing to an infinite wingspan is a large span high aspect ratio wing. That's why a biplane with the same total additive span and wing area isn't the same thing.
 
@GRG55 love the narration. "Fresh" breeze followed by the boat turning into a "banana." I'm honestly surprised those boats don't break more often. I mean, they lose their masts pretty often but you rarely see the hull just failing like that. Crikey!
 
GRG55 said:
Theoretically a wing of infinite span
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Didn't Bleroit experiment with some "infinite" style wings? I suppose a circular wing like his still has some "tip" to it where it curves back, but I think it's an interesting thought exercise in trying to recycle that tip vortex
 
Tantalum said:
Bro in law used to fly gliders and I was impressed with just how flexible the platforms were with wings and ballast... depending on the mission or competition for that day they would mod as necessary. Having said that, I've always been told that aspect ratio is key for any kind of foil efficiency. Newer sailboats have crazy thin and deep keels for the same reason

Note the striking difference in designs from the 1960s to today. Incidentally, to @SixPapaCharlie point, there were some boats that had "bi plane" style twin keels and the story is that they don't perform well at all compared to their more traditional cousins

View attachment 53385
Click to expand...

Not the same thing at all.

The long thin keel on the racing boat is to create the longest moment arm with the lowest form drag (not induced drag as in a glider wing) in order to allow a smaller keel bulb that can still counter the ever increasing sail area on the enormous masts above those comparatively small racing hulls.

The reason for the "twin keels" is because the long thin keel in a racing boat is completely impractical on a recreational boat in tidal waters with shallow draft. Twin keels are still very popular on recreational sail boats in places like England where the latitude results in large tides and there are numerous tidal flats such as between Portsmouth & Port Solent and off Bristol. By contrast, off the Pacific Northwest coast of North America, where I learned to sail, the coastal area is composed mostly of steeply plunging slopes so a conventional single keel dominates the boat designs, but even there the practicalities of having to bring the boat into bays and marinas at low tide limits how deep the keel can be made, compared to a pure all out racing yacht.
 
Tantalum said:
@GRG55 love the narration. "Fresh" breeze followed by the boat turning into a "banana." I'm honestly surprised those boats don't break more often. I mean, they lose their masts pretty often but you rarely see the hull just failing like that. Crikey!
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When composites fail they usually fail spectacularly. Composites are brittle when they fail. No permanent deformation failures like aluminum.
 
Hadn't seen that sinking. That was impressive.

Have read a lot of maritime books and stuff, it's always been interesting to me (being a complete and total land-lubber with an ex-Navy dad, probably caused curiosity) and the stories of how fast heavily laden ships with little buoyancy reserve sink, is always amazing to me.

No personal interest in doing anything like it, but the stories and books by the solo sailors who go 'round the globe on sailing vessels and some of their close calls, are just hair raising.

Some of the most eerie stories are of the single crew sailing vessels who have to at some point get anywhere near major shipping lanes with the monster cargo haulers -- at night -- as they work to maneuver into various major ports. And their stories of nearly getting run down by massive vessels who simply never saw them in the dark, even with radar reflectors on masts and all the modern amenities to try to make themselves noticed. Snapped masts, decks awash, boat turned into a floating junkyard and they're pumping out water for all they're worth.

Or just the weather. Being rolled over and over. Or trapped in the doldrums without a puff of wind.

Amazing adventurers and planners, but I don't think it's for me.
 
GRG55 said:
When composites fail they usually fail spectacularly. Composites are brittle when they fail. No permanent deformation failures like aluminum.
Click to expand...
ya but those plastic planes have a chute.....:D
 
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