# Inverted V-tail (anhedral V)

> What is an inverted V-tail and why use it?

- Category: Aircraft design › Tail configurations
- Kind: Standard part
- Basis: Design rules and figures from the cited sources; example geometry by Xem Studio
- Page: https://xemstudio.com/objects/inverted-v-tail/ · JSON: https://xemstudio.com/api/geometry?object=inverted-v-tail · Plain text: https://xemstudio.com/objects/inverted-v-tail/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

- An inverted V-tail points its two surfaces downward. Its rudder input produces proverse rather than adverse roll/yaw coupling: Stackhouse notes 'an inverted V-tail results in a proverse yaw', the reverse of the upright V whose yaw input rolls the aircraft the wrong way (Kitplanes V-Tails).
- Stackhouse adds that it has 'so many other drawbacks' that an upright V is usually preferred; the downward panels also bring the surfaces nearer the ground.
- Size it like an upright V: effective areas are 2S cos^2(a) and 2S sin^2(a) (McCombs). McCombs also notes negative ('cathedral') V-tail angles can help duration models because of a restoring effect.
- 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 |
|---|---|---|
| Effective horizontal / vertical area | 2S cos^2(a) / 2S sin^2(a) | McCombs 1994 |
| Reference build | same as V-tail example, panels angled downward (32.3 deg) | computed |

## Where the files are

- Charles River Radio Controllers (D. Stackhouse): [V-Tail Adverse Yaw (1999)](https://charlesriverrc.org/articles/design-and-construction/aircraft-design/tail-design-and-structure/vtail-adverse-yaw/) — web — Publisher's page; dimensions are facts
- Kitplanes (B. Wainfan): [Design Process: V-Tails (2022)](https://www.kitplanes.com/design-process-v-tails/) — web — Publisher's page; dimensions are facts
- Model Aviation (AMA), W.F. McCombs: [Wing and Tail Dihedral for Models (Dec 1994)](https://library.modelaviation.com/article/wing-and-tail-dihedral-models) — web — Publisher's page; dimensions are facts

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

Index: https://xemstudio.com/files/hardware/inverted-v-tail/index.json · license: https://xemstudio.com/files/hardware/inverted-v-tail/LICENSE.md

- inverted-v-tail-tail: [STEP](https://xemstudio.com/files/hardware/inverted-v-tail/inverted-v-tail-tail.step) · [STL](https://xemstudio.com/files/hardware/inverted-v-tail/inverted-v-tail-tail.stl) — inverted v layout: horizontal span 250 × chord 112, vertical 0 × 0 mm on a 500 mm boom, NACA 0009 surfaces

## Questions

**Why is an inverted V-tail less common?**

It gives proverse yaw but brings 'many other drawbacks' so upright Vs are usually preferred (Stackhouse, CRRC).

## Fits with

- [Tail volume coefficient (horizontal and vertical tail sizing)](https://xemstudio.com/objects/tail-volume-coefficient/)
- [Tail moment arm (tail lever arm ratios)](https://xemstudio.com/objects/tail-moment-arm/)
- [Conventional tail (low-mounted stabiliser and single fin)](https://xemstudio.com/objects/conventional-tail/)
- [T-tail (stabiliser on top of the fin)](https://xemstudio.com/objects/t-tail/)
- [Cruciform tail (stabiliser part-way up the fin)](https://xemstudio.com/objects/cruciform-tail/)
- [V-tail (butterfly tail with ruddervators)](https://xemstudio.com/objects/v-tail/)