- ACV: Air Cushion Vehicle
- AGEC: Aerodynamic Ground Effect Craft, German term for WIG boat
- Air injection: Russian term for PAR
- CG: center of gravity
- CE: center of Effort of a wing
- Ekranoplan: Russian for WIG boat, ekran=screen plan=plane
- FA: Free air, (out of Ground Effect)
- GE: Ground Effect
- GEM: Ground Effect Machine, synonym for ACV
- Hydrofoil (boat): boat with submerged wings that lift the hull out of the water at full speed
- IMO: International Maritime Organization
- HSC: High Speed (marine) Craft
- PAR: Power Augmentation of a Ram-wing, i.e. blowing of air under the wing to augment the air cushion
- PAR-WIG: Power Augmentation of a Ram Wing In Ground-effect
- SE: Surface Effect, same as GE
- SES: Surface Effect Ship, also called sidewall-hovercraft, a catamaran with a static air cushion between its hulls
- WIG: Wing In Ground-effect
- Wingship: American term for WIG boat
- WISE(S): Wing In Surface Effect (Ship)
- Airfoil Polars: Several parameters, the lift, drag, and moment coefficients and their relationship to the angle of attack characterize the aerodynamic performance of an airfoil.
- Chord Line: The straight line joining the leading edge to the trailing edge.
- Mean Line: The line which is exactly equidistant from the upper and lower surfaces of the airfoil. (also referred to as Mean Camber line)
- Symmetric airfoil: means that the distance from the Chord line to the upper surface is the same as the distance to the lower surface at every point along the chord.
- Camber: The maximum distance between the Mean Line and the Chord Line. (expressed in units of percent Chord.)
- Stagnation Point: The point at which the airflow divides. The air reaching the wing above the stagnation point travels over the top of the wing. The air reaching the airfoil below the stagnation point travels under the wing. The stagnation point is not fixed. It changes with angle of attack.
- Dihedral: means pointing the wing tips up.
- Anhedral: (sometimes called negative dihedral) pointing the wing tips down.
- Cavitation: occurs when an object (foil or propeller) moves through the water at high speed, creating very low pressures, so that the water locally starts to boil
- Leading Edge Radius: (just like it sounds) the radius of the leading edge of a foil.
- Thickness Ratio: The thickness of the foil expressed as a percentage of cord length.
- Aspect Ratio: Ratio wing span divided by cord length
- Under Construction
- Cl – Coefficient of Drag
- Cd – Coefficient of Drag
- Re – Reynolds number
AIRFOIL DESIGN RULES OF THUMB
After studying the basic elements of lift, playing with computer simulations like TBDP, Profili and X-Foil for a few months, I started to learn a few things about airfoils. First, for airfoils, rules are hard to come by because the various resultants tors seem to be co dependant. modifying some factors changes what I thought was a rule about another factor., (lift, drag, Center of lift For example: increasing the thickness ratio seemed to increase lift. But… in some cases, the addition of camber to the foil, negates that nice easy simple rule. : (
The first great challenge I found was the limited nature of the lift equations. Cl and Cd are both affected by changes in Reynolds Number, and Reynolds number is affected by velocity. So the so called constants are not constant.
Now that being said I have found some very basic rules of thumb.
- Water is approximately 800 times more dense than air. Lift and Drag are both proportional to Density. Therefore water drag is very very very bad. and water lift is very very very good.
- Tip vortices are inversely related to Aspect Ratio.
- Tip vortices increase drag and reduce lift.
- Increased lift portion of Ground effect is related to Cord length
- My goal is to use Vortices to my advantage. I had two conflicting objectives. Minimize wing tip vortex and capture some of the energy stored in the vortex.
- Generate Vortices and to
Cl – Coefficient of Drag
Cd – Coefficient of Drag
On line References:
EAA Light Plane World magazine (August 1986). © 1986, Chris Heintz. http://www.zenithair.com/kit-data/ht.html
SE Technology; http://www.se-technology.com/wig/index.php
Ray Preston: Aerodynamics 1, http://220.127.116.11/aerodynamics1/
This software,Dr. Stefano Duranti.: Profili Graphical interface for X-Foil http://www.profili2.com/eng/default.htm