Sail vs hang glider wing

[BobbyFunn]

Always thinking sails are the last technology to be updated in the wing world I wonder if hang gliders although less popular, get more innovation applied due to safety consideration. There are also many records being broken for time aloft and distance flown.

Its interesting to note the similarities and differences.

Over all the newer hang gliders have high aspect swept back wings. Cut the glider in half and we're left with what looks like a headsail.

One item to note is the difference between the where the draft is located. Its really hard to find a good picture of a hang glider cross section. I did find a couple assembly videos. Like sails hang gliders have full length battens. These battens dont need to reverse so they have a permanent shape.

I'm looking at these battens and see that the max draft is in the first 10%- 20% of chord length. Most sails i have seen go towards 40% of chord (from front to back).

Anyone have a jib or mainsail with similar designs?

The attached photos show some battens and a decent wing section.


One other thing...while looking this up it was noted that for the newer high aspect wings, telltales are placed about 25% of the way out from the "root". This correspondes to 25% up from the boom. This seems to he the best indicator for stalls. Is there experince to back that up in sailing?

PS. Hope you are enjoying your sailing season. Pretty tough to get motivated to float the 170 with this summer heat, spurious winds and random thunderstorm.

 

[capta]

It seems the wing sails have a very limited wind speed window, which would make them impractical for most sailing applications, beyond calm water racing, and racers already have them available to them.
Since most cruisers and casual sailors are more interested in comfort, safety and ease of handling, I can't see much need for sails that are more efficient at the expense of those things.

 

[NotCook]

Saw an article several years ago about ocean tankers and ram-air parachutes like wings to help pull them along, kinda like a kite surfer.

Found this:

 

[Gunni]

Airspeed and very limited angle of attack are much different on a hang glider. Sailboats and aircraft share foil technology not wings.

 

[BobbyFunn]

Airspeed and very limited angle of attack are much different on a hang glider. Sailboats and aircraft share foil technology not wings.

Not sure about that. The hang gliders videos show take off at running speed with an incoming breeze with similar landing speeds. They can go very fast, like 80mph when diving down as when to prepare for a landing. Landing a hang glider requires building up a risky looking amount of speed so that they can burn it off and stall. Not unlike a sandhill crane coming in irresponsibly fast and then throwing those wings forward.

My first thought with narrow speed range was to think of a sailing object that can go 80mph and running speed..I came up with an ice boat. The speed record for ice sailing has some guy using what looks like a windsurfing sail. That also has a max draft that is very close to the leading edge, like 20-25% or so. The windsurfing sail is much smaller, but if scaled out it looks really close to "hang glider".

As far are angle of attack goes that sounds reasonable. The hang glider going for a distance record would try pick and angle that maximizes the glide slope. This usually results in a narrow speed range and a specific angle of attack. Glider is probably not looking for max lift, just min drag with just enough lift? Is the windsurfer on glide slope?

Would a sailboat be working a "glide slope" or is it going for max lift without stalling all the time? In other words...Given a constant wind, the sailboat sail is perpetually "coming in for a landing"?

Does the "glide slope" wing differ from a "landing wing" and that explains the change in draft location?

I'm looking at these videos of stalling planes and the telltales do seem to suggest the area closest to the root stalls first. Hang glider wings often have twist like sails and this allows more of the wing to have flow versus the entire wing stalling at once. I'm thinking if a sail is stalling often, "landing wing", it has waayy to much loft. The outhaul should be tightened and more twist given so that small errors in angle of attack aren't as common.

Im rambling..

 

[Gene Neill]

All I know is, hang gliding is definitely on my bucket list.

 

[Will Gilmore]

Bobby's third picture doesn't look like a wing as much as it does a sail. The hard wing sail seems to be the shape for speed records. Keep in mind, when speed is the goal, apparent wind from any reaching tack begins to look like a close hauled reach. If a sailboat can begin to think about 80 knot speeds, all wind comes from the forward quarter. It's getting there that may require other sail shapes. Then there are the down wind tacks that hang gliders don't have to deal with, otherwise, they are just parachutes.
NotCook's video was really cool. Has anyone tried an ocean crossing with one of those?

- Will (Dragonfly)

 

[BobbyFunn]

They look cool, they work for kite surfers. While looking around for this subject i found a kite surfing enthusiast working on a tool to convert cross sections to textile.

His designs also have a draft close to the leading edge.

This looks very close in design to the battens in the hang glider. (Pictures in first post)

http://wardley.org/computers/perl/conference/camel_kitesurfing/index.html

The kite surfing video from sbove has that kite looking squirrly swing in all directions. Looks like a maintenace nightmare for ships on a tight schedule. Looks fun for cruisers in trade winds.

 

[Jackdaw]

Hang gliders have swept wings to allow the pilot to be situated under the center of balance. A straight wing hang glider would be totally unstable without a tail structure.

 

[BobbyFunn]

Hang gliders have swept wings to allow the pilot to be situated under the center of balance. A straight wing hang glider would be totally unstable without a tail structure.

No doubt. The old school versions were glorified paper airplanes. The pilot was balanced in the center area of the big triangle shape. Then, they figured out that the rear center of that triangle provides almost no lift, was heavy, and increased drag. They cut that out but left the delta shape like you say. Kinda like cutting holes in I-beams.

It was more advantageous to make wings longer versus simply making wing area longer. That wing design also is easier to keep level. The triangle wing was a disaster for airplanes until computers with ai were able maintain level flight.

 

[RussC]

Hang gliders have swept wings to allow the pilot to be situated under the center of balance. A straight wing hang glider would be totally unstable without a tail structure.

They've gotten much "straighter" over the years however. the newer ridged wing designs have also dropped the mini "tail structure" they originally used on the end of the keel.

 

[Cowpokee]

BobbyFunn, the type of hang glider you are comparing to a sailboat sail is known as a single surface glider. One significant differance in comparing the two is that sailboats are limited by hull speed whereas a hang glider is limited by air speed. If you look at the polar curve of a single surface hang glider, you will notice the sink rate increases dramatically as the air speed increases much over 30 mph. (typically from 200 fpm to well over 800 fpm) On a sailboat, this significantly increased drag leads to excessive heeling. To overcome this excessive drag on a hang glider, they've added sailcloth to the underside of the wing. This is known as a double surface glider. Another performance addition that was added to later designed hang gliders was variable geometry. You can pull a cord while in flight to "flatten" the wing. (similar to pulling on the outhaul and cummingham at the same time) This allows for greater air speed without as much drag. The trade off as you might expect with a flatter wing is that less lift is generated. Another significant downside on a hang glider with the VG full on is a reduction in the handling characteristics. The next step in development is what Russ C refered to as the rigid wing. This is designed more like a airplane wing than a sailboat sail. It even has flaps to increase lift at low speed.

BTW Beneteau has experimented with putting this design on a sailboat.

 

[LeeandRick]

Another significant downside on a hang glider with the VG full on is a reduction in the handling characteristics.

Cowpokee, How many times have you been on final and realize the VG is still full on? Or you didn't do proper lubrication on the cocoon zipper? ....
BoobyFunn, The reason hang gliders speed up on final is due to a possible wind gradient, where the wind at 50' is greater than ground level. It's not fun to stall at 20'.

 

[BobbyFunn]

All I know is, hang gliding is definitely on my bucket list.

For sure. It would he a deathwish with my absentmindedness and clumsiness.

Id be on 6pm local news. My rig would be wrapped around an oak tree in the new "Open Hills" subdivision. I would be on video squirming out of the bag like a new monarch butterfly.

First responders would do nothing, cause if you help a butterfly break out the coccon they wont develop properly.

 

[RussC]

Really drifting off-topic here, but I have to make this one comment.
Hang gliding is NOT a sport you can "try some day" or put on your "bucket list",... unless it happens to be the last item on that list. There are places all across the country that offer tandem flights for those who would like to experience that, but to fly solo requires extensive training by certified instructors. the days of the 60s plastic wrap, duct tape and bamboo gliders build in the back yard and tested on your local cliff are long gone. please check out USHPA for information on where to get instruction or a tandem flight near you. I flew for 18 years (91-2009 and have over 2000 hours of flight time. Some of the best experiences of my life. I'm still here and breathing without aid because I started out with competent instruction. some others didn't and aren't

be safe out there! over and out.

 

[Cowpokee]

Cowpokee, How many times have you been on final and realize the VG is still full on? Or you didn't do proper lubrication on the cocoon zipper? ....

One particular instance comes to mind... I was at a site that I hadn't frequented much where a film crew was set up in the Landing Field. Since I was getting low while ridge soaring, I pulled on full VG in order to make the field where the cameras were. I was so focused on having the proper altitude for the camera on the downwind, base, and final legs that I had neglected to release the VG. Ended up executing perfect flare timing for a nice one step landing.

 

[BobbyFunn]

One particular instance comes to mind... I was at a site that I hadn't frequented much where a film crew was set up in the Landing Field. Since I was getting low while ridge soaring, I pulled on full VG in order to make the field where the cameras were. I was so focused on having the proper altitude for the camera on the downwind, base, and final legs that I had neglected to release the VG. Ended up executing perfect flare timing for a nice one step landing.

Your just taunting us dreamers now. Dreamers who dont want broken legs so we watch go pro videos instead.

VG looked it up. Variable geometry. I saw saw dude on youtube gopro yanking the cord by the handle bar while in flight . I figured it was more like a vang.

On smaller boats i wonder if anyone is flaring the mainsail to stop the boat; i know thats a good way to go backwards. Then again boats gave so mych resistance with water that its not as useful.


Interesting all the variations of landing. The belly slide is adorable.

Loving the insight thank you. Gonna do some experiments with draft location.

I wonder if draft on sailboats is further back because sharper angles and convex shapez are more difficult to broadseam. Sharp curves are also difficult to reverse as in tacking. I had this problem with rc sails. The material needs to be really thin in rc sails in order to broadseam and expext tbe broadseam to reverse to an exact reverse shape.