Stepped hull — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/stepped-hull/  (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
- Steps break the planing bottom into several high-pressure leading edges, reducing wetted area and friction drag. Each step must be ventilated, or the step face stays wet and drag rises (BoatTest).
- Steps can add roughly 8-12% performance but are not worthwhile at low planing speeds, about 35 knots for a 30 ft boat. Poor designs can hook in turns (BoatTest).
- Twin steps tolerate CG variation better than a single step (BoatTest).
- Used on: White Iveco (Fabio Buzzi, 1984).
- The file is a reference example built by Xem Studio from the numbers above (Reference RC mono: 585 mm length and 20 deg transom deadrise (SV Design Stealthwake data); 181 mm is an unlabelled width in the same source's deadrise diagram.). Sizes the sources do not fix are illustrative; scale the example to your own vehicle.

parameter  value or range  source
Performance gain  roughly 8-12%  BoatTest
Worthwhile above (30 ft boat)  about 35 knots  BoatTest
Early hydro step  75 mm step, 2/3 aft  Wikipedia (Hydroplane)

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- BoatTest: Watch your step (stepped hulls) — web — Publisher's page; dimensions are facts — https://boattest.com/article/watch-your-step
- Wikipedia: Hydroplane (boat) — web — Publisher's page; dimensions are facts — https://en.wikipedia.org/wiki/Hydroplane_(boat)

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