A lot of Australia's shipbuilding and sustainment engineering doesn't happen at the primes. It happens in small consultancies and fabricators: naval architects and marine structural engineers working on refits, structural modifications, lifting and handling, transport engineering, and the wharf, dry dock and ship lift steelwork around them.
That work has two things in common. It gets checked hard, by the class surveyor, the prime's checking engineer or a marine warranty surveyor. And the engineers doing it usually work in spreadsheets or Mathcad. For firms building the next generation of Australian shipbuilding and sustainment work, there's now a better fit.
The calcs behind maritime structures
- Lifting design: padeyes, lifting lugs, spreader beams and rigging, with the dynamic amplification and skew load factors the lift calls for (DNV-ST-N001, for example).
- Sea fastening and grillage for load-out and transport, against the vessel motion accelerations the marine warranty surveyor will check.
- Plate and stiffener checks on modifications and new steelwork: plate panel buckling, stiffener section modulus and fillet weld capacity, to the class society's rules (DNV, Lloyd's Register or ABS) and AS 4100 side by side.
- Repeat structures: equipment seats, brackets and foundations that differ only in their inputs.
None of these is exotic. What makes them expensive is redoing them from scratch on each job, and then defending them to a reviewer who can't easily follow someone else's spreadsheet.
A calc platform built for the next generation of shipbuilding
Mathcad has been the standard for readable engineering maths for decades, and plenty of established firms run on it. CalcTree is built for the way growing firms work now: in the browser, shared across the team, scripted and AI-assisted.
- Cheaper to start. A free plan, and paid plans from US$14 to US$34 per user per month (pricing). Mathcad Prime starts from about US$859 per user per year (PTC store, checked October 2026).
- More capable on one page. Readable maths with real units, Python in the same page, and AI that drafts new calcs from the ones you've already verified.
- Built to connect. An API, an Excel add-in and an LLM skill, so checked calcs run inside the software and scripts you already use (more below).
- Reviewed and versioned. The checker signs off on the page, with full revision history, instead of a file emailed back and forth.
If you're weighing up every option, free ones included, see our honest guide to Mathcad alternatives.
What maritime calcs need
Calcs a surveyor can follow
Readable maths with units carried through, rule and clause references on the page, and the inputs in one place. The class surveyor or checking engineer reads the calc rather than reverse engineering it.
Sign-off that sits on the page
The checker reviews and signs off the page itself, with version history underneath. When the calc is revised after a design change, everyone can see what changed and who approved it.
Logic built once, reused every job
Build the padeye check or the equipment seat calc once, get it reviewed, and reuse it with new inputs on the next job. That's the same idea Australia's maritime sustainment planning keeps coming back to: repeatable designs with consistent assurance, rather than each consultant rebuilding the same check. We think standards belong in the workflow for exactly this reason.
Steel design that starts from Australian plate
We're building welded plate girder design logic to AS 4100 with engineers working on Australian maritime infrastructure, including an optimiser that trades web thickness against stiffener count using real fabrication rates. Local supply is plate, and the design logic should start there.
Works with the rest of your stack
Marine structural work runs across spreadsheets, scripts and, increasingly, AI assistants. CalcTree plugs into all three.
- API. Run a checked calc from your own code, scripts or pipelines, and get the result back with the working. See automating calcs with Python and the API.
- Excel add-in. Call a checked calc from a spreadsheet cell, so the logic lives in one reviewed place and the workbook just passes inputs. See the Excel add-in.
- LLM skill. Claude, ChatGPT, Gemini or Cursor can find, run and build CalcTree pages. The AI does the reasoning and CalcTree does the maths, with real units. See the CalcTree LLM skill. An MCP server is coming soon.
So a lift plan workbook can call the reviewed padeye check for every lift point, and the numbers in the lift report are the ones the checker signed off.
Moving over
The free plan includes Python, the API and the Excel add-in. Existing Mathcad files can be converted into CalcTree rather than retyped.
One honest limit: CalcTree runs in a desktop browser and needs a connection today. Offline use is coming, but it isn't here yet.
Start with one calc
Pick the check your team rebuilds most often, a padeye or lifting lug is usually a good first one, and build it properly once. Request a calc and we'll build it for you, or send us a Mathcad or SMath file and we'll convert it. Book a call with our team.
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