[wingspan33]

Tom,

As an example of one hang glider's root cord, I just went out and measured the camber of what we call the "nose" batten. This particular batten is just over 4' long and has a camber of 7" at around the 25% (from the LE) point.

Now, the nose to tail dimension of the sail (at the root) is longer than this batten by at least 2 - 3 feet. Also, the leading edge structure increases the camber height since it sits slightly below and just behind the nose batten. That would make the effective camber at the root cord of this particular glider to be 8" - 9".

Next, you ask about the lower surface camber. Well most double surface gliders have lower battens that are absolutely straight. This would appear to mean the wing has no camber in the lower surface. However, under in-flight loads the lower battens do deform to some degree creating some lower surface camber.

Personally, I have never tried to measure the difference from static (on the ground) zero camber to (minor) actual in flight lower surface camber (kind of hard to do). Also, almost every double surface hang glider only has 3 - 5 lower surface battens (as opposed to 6-10 upper surface battens) on either side of the wing. That means that the lower (outer) surface of the sail (more often without battens) will have a significantly greater amount of camber than the sail/wing closer to the root.

Now, as has been implied and stated directly above, What I have just given you is ONE example from one make and model of glider. There are literally dozens of other makes and models of hang glider, not to mention different sizes of most of those models. There will be minor (or more major) differences between these different designs.

However, with the typical modern swept wing hang glider (as derived from the early Rogallo design) will have upper sail battens that contain more or less camber and lower battens that have little or no (static) camber. It will also have a basic "A" frame structure where the slanting vertical parts of the "A" are the leading edge tubes and the horizontal cross piece is called the cross tube, cross spar, or even cross bar. It acts to place the sail under span-wise tension and is hinged at the mid point to allow the wing to be broken down for transport.

If the structure that you are planing on using deviates much from a general swept wing (Rogallo based) hang glider, then you are venturing into less well know territory. Your structure needs to be capable of creating and maintaining a functioning airfoil under a wide range of conditions.

It's also important to know that hang gliders are "plastic" and dynamically change their shape in a fairly complex manner while maneuvered by way of pilot weight shift. Hang gliders are what I would call the closest thing man has come to creating the out stretched wings of a large soaring bird.

BTW - I have contemplated creating flying wings that depart quite a bit from the typical frame design of the swept wing hang glider. So I can appreciate your interest.

[wingspan33]

Tom,

In going over more of the beginning of this thread it seemed (by page 2) that no one could give you the weight of a somewhat typical double surface hang glider's sail. Well, I happen to have such a sail sitting out in the garage. I went out and stepped, with it, onto my handy (fairly accurate) bathroom scale. This sail is in the 160 sq ft range as to area. It's weight was ~ 22 lbs. That includes the leading edge mylar sheet inserts, so you know.

A modern/current sail (even on a smaller wing) may weight 5 lbs more. That could be true since this sail is from the 1980s and manufacturers have tended to go with a slight bit heaver fabrics as time has gone on.

Considering this information, I would say that a hang glider's sail weight is roughly 1/3rd of it's total weight. I hope I'm not repeating what someone else has already posted.

[Bill Cummings]

Tom,
I watched a video over at the OZ report that was taken with a camera inside the double surface near the keel and looking in the direction of the wing tip.
The pilot flew slow and made a note of the speed then flew fast. The wing camber did change throughout the speed range. I will attempt to find that video and post a link here but I won’t be holding my breath while searching for it.
Any help from other net surfers would be appreciated.

[Bill Cummings]

Tom,
After searching the OZ report , “Scare and Cloud Hopper” each posted a link in response to my request for help which yielded a second video that I had missed.
Here is a Youtube link to:
WHAT DO SPROGS DO?
http://www.youtube.com/watch?v=olZlnPMLqHE#t=30

The other video is from Davis Straub’s Videos (Vimeo)
About Dustin’s Study.
http://vimeo.com/3635942
----also at:---
The OZ Report
http://ozreport.com/forum/viewtopic.php?t=39261
Both videos show the camber changing slightly with speed.
The sprogs of course look like they don’t do anything but in normal flight they are not supposed to.
After a stall and a past vertical dive the cable limiting the sprog movement would go tight which would bring the nose up to prevent a tumble. Internal Sprogs take the place and do the function of luff lines. Sprogs reduce parasitic drag by eliminating luff lines out in the air flow.

Tom, I hope this aids your design creativity because we all want something better and we would like to make you rich. (Soon)

[Rick Masters]

[Bill Cummings]

Rick,
That fellow in the Reliant Robin is quite the comedian. I laughed so hard that I nearly flooded my eyes.


But as I recall Tom said his three wheeled vehicle steered by means of the two rear wheels.
Might that make a difference?
Kind of like a forklift backing up. (No. scratch that. That was a bad example.)

[JoeF]

sit down hangglider, that will be powered by a PMDC electric motor with lithium batteries. Body weight will not shift from side to side the way hanggliders currently do. Although batteries will move fore and aft to help balance the hangglider. It will also have joystick controls,and should weigh between 70 and 80 pounds with a wing span of about 30 ft. I have no plans to fly more than a few feet off the runway to take full advantage of ground effect

Such a project might not be a hangglider. Though the battery mass movement involves a bit of weight-shift control for some pitch authority, that alone does not qualify a craft as "hangglider." It seems like the target of your project might be a powered primary glider, a kind of non-hangglider ultralight craft (a sort of powered aircraft).
Tom, here is a primary glider without a mounted engine:

Here is a drawing of another primary glider (non-hangglider):


Here is a launch point for primary gliders: http://en.wikipedia.org/wiki/Primary_glider

Chord of airfoils: http://en.wikipedia.org/wiki/Chord_%28aeronautics%29

Here is one aerodynamics-for-students document:
http://aerodynamics.aeromech.usyd.edu.au/

Most anything tossed out into the atmosphere of a planet results in a glider. A shoe tossed becomes a glider; give the shoe enough moments and altitude and a gliding dynamic will result. Each specific glider will have its resultant dynamic profile responding to any built-in control system; control something during the glide and the dynamics will probably be altered; the sum total of control effects will give a spectrum of resultants. It is easy to build a glider; it is easy to design a unique hang glider; it is not so easy to design a novel hang glider that has a dynamic spectrum under control that specifically meets a specific performance-and-safety description.

Let the combination of payload and wing be integrated to form "hang glider."
The tendons of Otto Lilienthal were hang lines for his hang glider. Absent the payload (most of his body) hanging and one gets a glider, say the shoe or one of Otto's wings.

Identify two subsets of "hang glider" by way of hang lines: tendons for one subset and hang lines for another subset. The sit-down pilot rigidly connected to a wing of a system might not qualify to be in one of those two subsets of hang gliders, but might qualify to be in the more-general glider category, perhaps a primary glider or perhaps a non-primary glider. The subset of hang gliders using hang lines to the payload-pilot are free-flying kite systems with a net path in the air that gives the notion of gliding. The Falcon 3 by Wills Wing is a kite system of the sort used to glide through airs; hang line count (the count of kite tethers) varies from 1 to 8 or or more.

So, Tom, it seems your project is a non-hang-glider project. The first blush feel I get from reading the posts of the topic is that you might want to motorize a primary glider to get control via aerodynamic surfaces and some pitch control by moving the batteries that will power your powered aircraft. Such realm is highly visited by powered glider enthusiasts. If one is aiming at "power-off gliding" using motor for launch and safety-in-range for landing, then motor gliding (using as a base a hang glider, primary glider, or non-primary glider, or sailplane) might be the realm to explore.

The following hang glider has a very high sink rate, very low wing area, high speed glide, very low L/D, and high safety when flown free in the air, but very low safety during the landing phase of a glide, if landed say at sea level on earth after a flight from higher than a couple of feet altitude AGL:

Some gliders are constrained by a cable; here is a foursome payload zip-lined constrained: