# Ground effect: height/chord ratio (ram / chord-dominated regime)

> What height-to-chord ratio do WIG craft fly at?

- Category: Aircraft design › Ground-effect design
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/ground-effect-height-chord-ratio/ · JSON: https://xemstudio.com/api/geometry?object=ground-effect-height-chord-ratio · Plain text: https://xemstudio.com/objects/ground-effect-height-chord-ratio/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files Xem Studio Design License (free to use and sell from, not to redistribute as files: https://xemstudio.com/license/)
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

**Exact dimensions.** True size, with no printing tolerance added.

## Notes

- Rozhdestvensky defines extreme ground effect as clearances of 10% of the main wing chord or less, distinguishing chord-dominated ground effect (flow stagnation under the wing) from span-dominated (induced-drag reduction).
- Moore et al. split ram effect (h/c <= 10%) from normal ground effect, and a review concludes rectangular wings are most effective within 15% of chord (Frontiers 2022 review).
- An isolated AR 2-3 wing at about 20% chord clearance reaches L/D of roughly 35-45, but hull, pylons and tail cut that by about 65% to 12-16 for a whole craft (Rozhdestvensky, citing Kirillovykh).
- The file is a reference example built by Xem Studio from the numbers above. Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| Extreme ground effect | h <= 10% chord | Rozhdestvensky 2006 |
| Ram effect regime | h/c <= 10% | Frontiers 2022 (Moore et al.) |
| Most effective (rectangular wings) | within 15% chord | Frontiers 2022 |
| Isolated wing L/D, AR 2-3 at 20% c | 35-45 | Rozhdestvensky (Kirillovykh) |
| Whole-vehicle L/D after integration | 12-16 (losses: hull ~40%, pylons ~15%, tail ~5%) | Rozhdestvensky |
| Proposed GE-zone definition | height where lift is ~30% above free-flight value | Rozhdestvensky |
| Reference build | span 600, chord 300 | computed (AR 2) |

## Where the files are

- Progress in Aerospace Sciences (K.V. Rozhdestvensky, 2006): [Wing-in-ground effect vehicles (review)](https://www.hassanhameed.com/wp-content/uploads/2016/01/wingingroundeffectvehicles-130120003005-phpapp01.pdf) — web — Publisher's page; dimensions are facts
- Frontiers in Aerospace Engineering (2022): [Review of ground-effect experiments on rectangular, reverse-delta and delta wings](https://www.frontiersin.org/journals/aerospace-engineering/articles/10.3389/fpace.2022.975158/pdf) — web — Publisher's page; dimensions are facts
- NASA Langley (Fink & Lastinger): [Aerodynamic Characteristics of Low-Aspect-Ratio Wings in Close Proximity to the Ground, NASA TN D-926 (1961)](https://ntrs.nasa.gov/api/citations/19980231058/downloads/19980231058.pdf) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, Xem Studio Design License, Xem Studio)

Index: https://xemstudio.com/files/hardware/ground-effect-height-chord-ratio/index.json · license: https://xemstudio.com/files/hardware/ground-effect-height-chord-ratio/LICENSE.md

- ground-effect-height-chord-ratio-wing: [STEP](https://xemstudio.com/files/hardware/ground-effect-height-chord-ratio/ground-effect-height-chord-ratio-wing.step) · [STL](https://xemstudio.com/files/hardware/ground-effect-height-chord-ratio/ground-effect-height-chord-ratio-wing.stl) — endplated wing: span 600, chord 300 mm, anhedral 0°, endplates 30 mm (scale to your craft)

## Questions

**How high should a WIG model fly?**

Extreme ground effect is below 10% of chord; reviews put rectangular wings' sweet spot within 15% chord (Rozhdestvensky; Frontiers).

## Fits with

- [Ground effect: height/span ratio and induced-drag reduction](https://xemstudio.com/objects/ground-effect-height-span-ratio/)
- [Lippisch reverse-delta ground-effect craft](https://xemstudio.com/objects/lippisch-reverse-delta-wig/)
- [Ekranoplan layout (low wing + high tailplane out of ground effect)](https://xemstudio.com/objects/ekranoplan-wing-tail-layout/)
- [Tandem-wing ground-effect craft (Jorg type)](https://xemstudio.com/objects/tandem-wig-configuration/)
- [Power-augmented ram (PAR)](https://xemstudio.com/objects/power-augmented-ram-par/)
- [Endplates on ground-effect wings](https://xemstudio.com/objects/wig-endplates/)