# Wing endplates / side dams

> What do endplates on a car wing do?

- Category: Car design › Car aero
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/wing-endplates/ · JSON: https://xemstudio.com/api/geometry?object=wing-endplates · Plain text: https://xemstudio.com/objects/wing-endplates/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

- Endplates limit air spilling around the wing tips from the high-pressure side to the low-pressure side, which raises downforce and efficiency (HPA).
- UIUC tests found a larger endplate raised CL by about 0.096 at constant angle and cut drag 13.7% at constant CL (Jasinski & Selig).
- HPA's ballpark for home-built plates is to extend twice as far below the wing as above it. RC classes cap side-dam size in their rules, e.g. 40 x 20 mm on 1/10 touring cars (AARCMCC) and 80 x 80 mm on 1/10 off-road buggies (EFRA).
- Used on: Champ Car endplate (UIUC test).
- The file is a reference example built by Xem Studio from the numbers above (1/10 touring-car limits: 190 mm width, 40 mm chord, 20 mm side dam.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

## Sizes

| parameter | value or range | source |
|---|---|---|
| Endplate proportion (rule of thumb) | 2x as far below as above, e.g. 100 mm above, 200 mm below | HPA rear wing |
| Larger endplate effect | +0.0958 CL at constant alpha; -13.7% CD at constant CL | Jasinski & Selig (UIUC) |
| 1/10 touring car side dam | max 40 mm wide x 20 mm high | AARCMCC |
| 1/10 track car endplates | 25 mm above body x 100 mm deep | AARCMCC |
| 1/10 off-road side dam | must fit an 80 x 80 mm rectangle | EFRA |
| 1/12 pan car side dam | max 72 mm high | EFRA |

## Where the files are

- High Performance Academy: [Aerodynamic performance devices for club level cars: rear wing theory](https://www.hpacademy.com/courses/aerodynamics-fundamentals/aerodynamic-performance-devices-for-club-level-cars-rear-wing-theory) — web — Publisher's page; dimensions are facts
- University of Illinois / SAE: [Experimental Study of Open-Wheel Race-Car Front Wings (Jasinski & Selig, SAE 1998)](https://m-selig.web.engr.illinois.edu/pubs/JasinskiSelig-1998-MSEC-SAE-Trans-V107-S6.pdf) — web — Publisher's page; dimensions are facts
- AARCMCC: [Section 3: Electric On Road, Technical Rules (Oct 2006)](https://www.rctech.net/forum/attachments/australian-racing/180184d1162811203-aarcmcc-online-tech-road-oct-06.pdf) — web — Publisher's page; dimensions are facts
- EFRA: [EFRA Handbook 2010, Appendix 3: Electric Cars](https://www.efra.ws/wp-content/uploads/2010/03/Handb10App3.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/wing-endplates/index.json · license: https://xemstudio.com/files/hardware/wing-endplates/LICENSE.md

- wing-endplates-rear-wing: [STEP](https://xemstudio.com/files/hardware/wing-endplates/wing-endplates-rear-wing.step) · [STL](https://xemstudio.com/files/hardware/wing-endplates/wing-endplates-rear-wing.stl) — single rear wing: span 190 × chord 40 mm at 6°, endplates 20 mm, inverted NACA 4412 section (mounts from below)

## Questions

**Do endplates add drag?**

In the UIUC test a larger endplate actually reduced drag at constant lift by 13.7% (Jasinski & Selig).

## Fits with

- [Single-element rear wing (race car)](https://xemstudio.com/objects/rear-wing-single-element/)
- [Dual-element (two-element) rear wing](https://xemstudio.com/objects/rear-wing-dual-element/)
- [Swan-neck rear wing mount](https://xemstudio.com/objects/swan-neck-wing-mount/)
- [Gurney flap / wickerbill](https://xemstudio.com/objects/gurney-flap-wickerbill/)
- [Front splitter](https://xemstudio.com/objects/front-splitter/)
- [Splitter tunnels (front diffuser)](https://xemstudio.com/objects/splitter-tunnels-front-diffuser/)