Ground effect: height/chord ratio (ram / chord-dominated regime) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/ground-effect-height-chord-ratio/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
Catalog version: 2026-10-20

Sizes: see table below
- 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.

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)

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Progress in Aerospace Sciences (K.V. Rozhdestvensky, 2006): Wing-in-ground effect vehicles (review) — web — Publisher's page; dimensions are facts — https://www.hassanhameed.com/wp-content/uploads/2016/01/wingingroundeffectvehicles-130120003005-phpapp01.pdf
- Frontiers in Aerospace Engineering (2022): Review of ground-effect experiments on rectangular, reverse-delta and delta wings — web — Publisher's page; dimensions are facts — https://www.frontiersin.org/journals/aerospace-engineering/articles/10.3389/fpace.2022.975158/pdf
- NASA Langley (Fink & Lastinger): Aerodynamic Characteristics of Low-Aspect-Ratio Wings in Close Proximity to the Ground, NASA TN D-926 (1961) — web — Publisher's page; dimensions are facts — https://ntrs.nasa.gov/api/citations/19980231058/downloads/19980231058.pdf

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/ground-effect-height-chord-ratio/index.json
API: https://xemstudio.com/api/geometry?object=ground-effect-height-chord-ratio