[Creeper]

Has anybody ever tried to make a Hang Glider with a greater emphasis on length. I keep thinking of those paper gliders we used to make as kids. Paper darts still have a large surface area but it's lengthwise rather than widthwise.

Once aloft it seems to me that such a streamlined fighter jet profile would be faster than the traditional glider which has now become standardised.

[sg]

Early hang gliders were much longer. They have evolved into shorter wider wing. A higher aspect ratio gives you more performance. If you were to make the glider longer with stubby wings like a paper airplane, your glide performance would go down.

High performance, looks like this:


Low performance looks like this:


As you can see, hang gliders look more like sailplanes every year, with increasing aspect ratios

[Creeper]

I can see that soaring would improve with a much wider wing but I've never seen a really long glider. Even those early models weren't that much different. It seems like designers went in the direction of copying the Albatross. Does it really matter whether the surface area is mainly across the width of the wing or longitudinal?

Seems to me that a longer backward wing would offer less air resistance and thereby increase speed and wing camber effect. Thus increasing lift.



Found these images in a Yahoo search for "paper plane"




A model scaled up large enough to carry a human being would be an interesting project. I think if it were taken into a slight dive it could probably pick up quite a bit of speed.

[sg]

Increasing your span and aspect ratio reduces induced drag. http://en.wikipedia.org/wiki/Induced_drag

The $150,000 dollar glass super ships (Sailplanes), look like the below for a reason.
They have the best glider ratio of any aircraft around. 50+/1 glide ratios. Amazing.

[FormerFF]

Aircraft have to deal with two types of drag. Induced drag is the drag created by the wings to produce lift, and parasite drag, which is the drag created by the rest of the aircraft moving through the air. Induced drag decreases as the aircraft's speed increases, while parasitic drag increases. So. for our low speed glider, induced drag is substantial.

When producting lift, wings create wingtip vortices, as the higher pressure air under the wing meets the lower pressure air on top. Increasing span mitigates the effects of these vortices. Have you ever seen an airliner with winglets? They act as a vortex fence and reduce the drag created by the vortex.

The only aircraft that use short span/wide chord wings are military fighters and some aerobatic aircraft, which need to be manueverable and strong. Airliners use long span wings because they are more efficient. Longest span of all (for the weight of the aircraft) are high performance sailplanes. Typically they have a span of 60 ft or so. A Boeing 717, which outweighs these by about 110,000 lbs has a span of 93 ft.

[Creeper]

I realise that swept wing and delta wing designs are usually reserved for high speed aircraft approaching the speed of sound. I just don't understand why it has been totally ignored in hang gliders.

Induced drag might diminish but Hang Gliders aren't powered like planes. The only lift available is from thermals. A sleeker shape could pick up speed from a shallow dive and speed increases lift. It is also harder to build a wider wing than a 'short but longer' one. I still think chord might have some advantages over span.

Greater chord rather than span in the aspect ratio would pose its own design problems but similarly wouldn't it also offer an alternative kind of flight and greater speed? Other than paper planes I've never seen this even tried.



Has it been tried? I've been surfing around looking but it seems to be an idea that hasn't been experimented with. Am I right? As it would be easier to build than a wide wing craft I might have a go at it.

[sg]

This stuff is well researched and any aerodynamics expert will tell you, even before you start, that you will end up with a glider that has a totally s*** glide ratio and sink rate

Then there are practical problems, like, how do you land such a beast? You can flare a hangglider for landing because its so wide and not long.

A glider that had a similar shape to the RC model above, would not be flare-able. The tail would touch and drag the ground well before you could get the nose high enough to bring it to a stop. You wouldnt be able to slow down enough and slam into the ground

You would have to land on wheels only, most likely. In any case, its already fairly predictible what you would end up with, and it wouldnt be good.

[rallyant]

I fly RC also and that includes a couple of EDF Jets. my F16 has a pretty good glide ratio but its also dam fast. very slipery, must land very fast, ortho with a bit of power it can come in slow. with hi delta,

but look at the F111 and the Tomcat. (swing wings) the wings are out for take off and all hi performance flying then swing in for hi speed.
wing loading is important

[FormerFF]

The span vs chord thing is not specific to hang gliders. More span is more efficient in all subsonic aircraft. Again, look at the airliners being built today, they're all high aspect ratio wings, and they fly fast.

You could build a wide chord hang glider, it would be much like the early Rogallo based gliders you saw in the 70's. So I would say it has been tried, and has been superceded by higher aspect ratio designs.

[FormerFF]

Say, what time of day is it in Australia?

[Creeper]

Just after 1pm.

[sg]

High performance hang gliders can do 70,80,90+ mph = 145kph How much faster you wanna go?

[rallyant]

a good 300kph 1 inch off the ground

[GTPilot]

along with the faster speeds of a delta wing comes faster stall speeds ... which means faster take-off and landing speeds.

besides that i don't think the faster speed of that wing shape would out-perform a wider wingspan in soaring.

[rallyant]

I want full 3D flight too.. upside down and backwards

whats the time in the USA while were at it?

[GTPilot]

9pm, west coast. i'm guessing east coast australia is 7 hours behind us .. but a day ahead of us. i visited melbourne once.. what an awsome country you have down there.

[rallyant]

yeah were almost at the start of the world. NZ and some of the islands start each day befor us.
glad you liked it here.
everyone has there tasts. i prefure some of the warmer places in Aus myself.
tho melbourne does have its attraction.

A lot of dam nice places in USA to from what i have seen.
i guess the big diferance is in the last 200 yrs we have only grown to 20 million as aposed to you guys with what is it now 240million?

[sg]

[rallyant]

ahh i like the idea of all kinds of flying but yeah. fast and low has always interested me a lot.

[Creeper]

According to http://www.paperplane.org

600kph is the speed at which delta wings become useful.

Thanks for your feedback guys. I've learned a lot I didn't know but confess I'm still curious about this lemon. I'm hooked on the idea of a hang glider that flies like a hawk now.

Paper airplanes definitely work. I think we can all agree on that. What I need to work out is how large it would need to be in order to carry say a 90kg man. How large would the delta wings need to be?



We've established a fast launch is necessary. My first thought is to drop it off a cliff but I don't think I'd get too many volunteers.

I guess a runway launch in the traditional style of a sailplane might be best. Towing it into the air using a ferrari or something. Either that or a boat tow.


Already I'm wondering about where this could go if it worked. What about a hang glider with wings that change shape? Wide for launching and soaring. Varying to chord for diving and picking up speed. Sounds like an engineering challenge but it wouldn't it be cool to have the best of both worlds.

So what should I build this giant paper airplane out of? Other than paper.

I'm thinking of calling it a 'Delta Wing Hang Glider'. No good? Paper Tiger then? Dart? Swift?