Older content for Aeroexperiments website


This website is under construction! This page provides access to older content that has been "retired" from the main site map. Some of the material from 2003 and earlier still contains some interesting details of in-flight experiments that have not yet been integrated into the main content of the website. For the most part though the reader will be better served by focusing on the content listed on the main site map. Almost all of the content listed under "recently retired material" has now received a better treatment elsewhere on the Aeroexperiments website.

This page was last updated August 2007

Recently retired material:

Analyzing the "long-tailed slip" effect, with notes on how "airflow curvature" affects a swept- or delta-winged aircraft -- this article is overly complex and speculative, see the newer article "Tail moment-arm, airflow curvature, and spiral stability" for some related material.

Series on the aerodynamic coupling between yaw and roll in aircraft with sweep, dihedral, or anhedral

(NOTE August 2006: all the content in this section has now received a fresher treatment in the "Aerophysics Exploration Pages". Many items that are not yet covered in the main text pages of the AEP section are covered briefly on the page entitled "Pool of images for the Aerophysics Exploration Pages." This older material is still accurate to the best of my knowledge except for one point: I now feel that the suggestion that increasing wingtip washout (as opposed to increasing sail billow) will tend to create an anhedral geometry was unwarranted.)

1) How billow increases the net geometric anhedral of a swept wing, and other related topics--note: this is a rather long article; 2 through 7 are essentially self-sufficient, overlapping, subsets of the longer article, and are intended to present the subject matter in much more manageable pieces!

2) What's a rudder for?. (See also these two sections (#3, #4) in article 17b5

3) The real purpose of dihedral and anhedral: creating an aerodynamic coupling between yaw and roll

4)How sweep creates an aerodynamic coupling between yaw and roll

5) Competing effects of sweep and anhedral at various angles-of-attack

6) How billow increases the net geometric anhedral of a swept wing--abbreviated version

7) The effect of VG on anhedral: why the net geometric anhedral decreases as a VG is applied

Material from spring 2003:

This material was prepared for an earlier version of this website. Some of this content is still rather rough-cut but it will provide the reader with some idea of the questions I've been interested in. This material was created after I carried out a series of experiments with rudders and wing-tip drogue chutes to look at coupling between yaw and roll on flex-wing hang gliders, but before I had the opportunity to repeat these experiments on a glider with a VG, so this material does not address the relationship between the VG setting and the anhedral effect. Despite this, the content should be entirely valid, since the later experiments with the Airborne Blade confirmed (and added to) the earlier findings.

Experiments page --this page describes some of the questions I've been interested in and some of the methods I've used to address these questions, including flying flex-wing hang gliders with rudders and wing-tip drogue chutes to create yaw inputs to study the aerodynamic coupling between yaw and roll. The experimental results, and the underlying theory, are addressed only briefly here at this time.

Theory page --this page addresses dihedral, anhedral, sweep, yaw stability or "weathervane effect", coupling between yaw and roll, roll stability, slipping flight, skidding flight, coordinated flight, "centrifugal" force, the relationship between a sideways airflow component and a sideways aerodynamic force component, yaw strings, slip-skid balls and bubbles, balance of forces, common myths about turning flight, why you can't "feel" gravity, and more.


Older material:

Turning flight and sideslip in hang gliders --this is a very large and comprehensive article on the topic of turning flight and slips and skids, especially in hang gliders. It was last updated in July 2000. It covers all my early experiments on the relationship between pitch inputs and slips and skids in hang gliders and sailplanes and airplanes. This older article also contains a lot of theory; in particular the subject of "airflow curvature" is explored in detail. It does not include the results of my recent experiments with rudders and wingtip drag chutes on flex-wing hang gliders to explore the coupling between yaw and roll. I now it realize that the sections that deal specifically with coupling between yaw and roll in flex-wing hang gliders need to be revised to reflect the "negative coupling between yaw and roll" that is created by the large amount of effective aerodynamic anhedral that exists in most flex-wing hang gliders. (The article assumes that the dihedral-like effect from the swept wing will dominate over the anhedral geometry and create a "positive coupling between yaw and roll". This is valid for rigid-wing hang gliders but not for modern flex-wing hang gliders.) The basic idea--that our pitch "coordination" inputs actually serve to prevent the glider from diving, not to prevent the glider from sideslipping--is still sound, as is the treatment of "airflow curvature", and much more.

More detailed notes on specific areas of this article that are have been made obsolete by more recent experiments, are given at the end of the "Theory" page listed above.





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