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Design a boat hull, from a few answers to a CAD file.

Hull runs in your browser. Answer a handful of plain questions — how long, how fast, how deep a V — and it generates a real hull you can open, pull apart and refine. Every number you see comes from an actual hydrostatic integration of your shape, not a lookup table. When you are happy with it, export a solid model, a wireframe, or a table of offsets to loft from.

Hull is in closed beta. This manual is public, so read the whole thing first — then apply for an invite at hull@drpira.se, telling us a little about what you would like to design. We reply with a link that creates your account.

Your first hull → Request an invite
design waterline transom bow
A hull in Hull is a grid: transverse stations down the length, and seven named longitudinal lines running through them — keel, quarter beam, chine, half topside, sheer, half deck, deck centreline. You edit the grid; everything else is computed from it.

What you can do

Start from a boat, not a blank page

A ten-step wizard turns plain answers into a complete hull, with a live preview and a verdict on whether it floats sensibly.

Move every point yourself

Drag control points in the section view, or type exact coordinates. Lock an axis, give the optimiser a band to work in, or mark a hard chine.

Real hydrostatics, not estimates

Displacement, GM, LCB, waterplane area, prismatic coefficient, trim — integrated from your actual sections every time you move a point.

Let the optimiser cut the drag

A gradient solver moves the points you leave free to minimise resistance at your design speed — while respecting every lock and bound you set.

Fair the surface paid plan

Thin-elastic-beam smoothing pulls the wobble out of a hand-edited line without breaking your pins, ranges or hard kinks.

Take it to the shop

STEP, IGES, DXF and OBJ for CAD, plus a table of offsets and a keel & stem schedule as CSV for building from numbers.

Your first hull in five minutes

The short version. The full walkthrough covers each step properly.

  1. Sign in and click New project

    You land on your projects library, and the wizard opens over it.

  2. Answer the questions

    Boat type, then a starting boat — Sport skiff, Deep-V, Flat utility or Day runabout — then length, beam, speed and how deep a V you want. The panel on the right redraws as you go and tells you in words whether the boat is stable, sits level and stays dry.

  3. Click Create project

    The design lab opens with your hull in it.

  4. Open the Hydrostatics tab and read four numbers

    Displacement against Target mass, Trim (at rest), GM, and Freeboard (mid). Those four tell you whether the boat floats where you meant it to. What they mean →

  5. Run Optimize, then Export

    Leave the target on Balanced and press Run optimizer. Read the log. Then pick a format in the Export tab and download it.

The manual

01

Your first hull

The whole path end to end, from signing up to a downloaded file.

 02

The new-project wizard

All ten steps, every slider and what it does to the boat.

 03

The design lab

Viewports, stations, dragging points, pins, ranges and kinks.

 04

Optimiser, fairing & sweeps

The three targets, the metrics menu, auto-fairing, Pareto and speed sweeps.

 05

Reading the numbers

The hydrostatics panel, group by group, in plain English.

 06

Export, versions & sharing

CAD formats, offsets, lofting schedules, published versions, workspaces.

 07

Glossary

Deadrise, GM, LCB, porpoising, rabbet — the words, defined.

Plans & limits

Every plan gets the full designer: the wizard, direct point editing, the optimiser, all the hydrostatics, and every export format. What the paid plans add is scale — bigger and faster boats, more projects and people — plus two tools.

FreeMidTop
Projects210Unlimited
People in a workspace15Unlimited
Longest boat5 mUncapped *Uncapped *
Highest design speed18 knUncapped *Uncapped *
Auto-fairing—YesYes
Speed sweep—YesYes

* No plan limit applies, but the wizard's own sliders stop at 12 m and 45 kn on a planing hull — the range the planing analysis is built for — and at 18 m and 20 kn on a displacement one, which is bounded by its own hull speed rather than by the analysis. The wizard reports that limit as you set the cruise speed.

Beta invites do not land on Free. While the beta is running an invite creates your workspace on Mid, so the Free column above is not what you will be looking at — read it as the shape of the plans rather than as your limits.
Upgrading is a conversation, not a checkout. There is no self-serve billing page yet. Hit a cap while creating a project and you get an Upgrade required notice naming the plan that would permit what you tried; get in touch and we will move the workspace over. Nothing you have already made is affected in the meantime.

Not available yet

Being straight about the edges, so you can tell whether Hull fits your project before you invest an evening in it.

ThingWhere it stands
Sailing hulls in development — a canoe body with a fin keel, and the heeled stability that goes with it, are not modelled. A displacement motor hull is available today.
Multihulls in development — catamarans and trimarans are not modelled.
Importing a hull There is no DXF or offsets import. Hulls start from the wizard and are edited in the app.
STEP and IGES export Needs a geometry kernel installed on the server. If it is missing you get a clear message rather than a broken file, and the CSV exports never depend on it.

Ready?

Start with the walkthrough — it takes about ten minutes to read and you will have a hull at the end of it.

Your first hull → Request an invite Sign in
Hull — hull design for small craft. Get started · Glossary · Sign in