01How engagements are structured
The anatomy of a design contract
Almost every naval architecture contract is phased: each phase ends in named deliverables, a payment milestone, and an owner gate where you decide whether to continue. Small studios may fold phases together; large practices split them further. The shape below is the industry norm for a custom power multihull.
Pay against deliverables, not hours — except for genuinely open-ended research (seakeeping exploration, TLP trade studies), where hourly with a capped estimate is appropriate.
P0 ≈5%P1 15–20%P2 20–25%P3 20–25%P4 20–25%P5–6 day-rate
Change orders: anything outside the written scope — an extra layout option, a re-run of the seakeeping study, a second GA revision round — should be priced and approved before work starts. This is where first-time owner relationships most often sour.
P0
Feasibility & requirements
Locks your goals page to physics and regulation: displacement and power budgets, seakeeping targets for the vertical-float ride, stability criteria, and the pivotal vessel-vs-structure regulatory question (it decides the rules your TLP option lives under).
DELIVERABLES Feasibility report · weight/power budget · regulatory pathway memo
P1
Concept design
General arrangement, hull form direction, aesthetics, preliminary hydrostatics, first weight estimate with margin, solar array area vs. windage trade.
DELIVERABLES Concept report · GA plan · preliminary hydrostatics
P2
Preliminary design
Faired lines, intact stability, seakeeping screening of the slender floats, preliminary scantlings, refined weight & CG, and the model-test / CFD plan. Gate G2: Sandy Hill Bay model-test and simulation review happens here.
DELIVERABLES Lines plan · stability book (prelim) · scantling basis · weight report rev.2
P3
Contract design
The complete drawing set and build specification shipyards price against. Freeze scope here — builder bids are only comparable if they bid the same design.
DELIVERABLES Structural GA · systems schematics · build spec · bid package
P4
Construction engineering & cutting files
Plate development and DXF nesting files for the aluminum, weld sequence planning, detailed systems, electrical load analysis, solar integration, FEA where required.
DELIVERABLES DXF/nesting files · weld schedule · detailed systems drawings
P5
Construction support
Site visits, builder RFI responses, change-order review, weight tracking, inspection coordination. Usually billed separately — see Section 05.
P6
Commissioning & trials
Inclining experiment (verifies the real weight & CG against the 37,000 lb estimate), sea trials protocol, punch list close-out, as-built documentation.
DELIVERABLES Inclining report · sea trials agenda · as-built set
02What contracts look like
Five ways to pay a naval architect
There is no universal standard-form contract in naval architecture the way there is in building construction — most firms use their own agreement, so everything is negotiable. Have a maritime attorney review the final draft ($2k–$5k; cheap insurance on a seven-figure project). The five fee models in play:
| Model | How it works | Best for | Watch for |
|---|---|---|---|
| Lump sum, by phase | Fixed price per phase with named deliverables; most common for a full custom design. | Your core design work — scope is definable. | Scope creep; make the deliverables register part of the contract. |
| Hourly / time & materials | Billed against timesheets, usually with an estimate or cap per task. | Open-ended research: seakeeping of vertical floats, TLP trade studies, stabilizer evaluation. | No cap = no budget. Always set monthly ceilings. |
| % of construction cost | Typically 3–8% for design alone, up to 10% including full supervision. | Designers who stay through the build; common on larger yachts. | Fee rises if the build cost rises — even through no fault of design. |
| Monthly retainer | Reserved hours each month, $4k–$20k/mo typical. | Ongoing owner-side technical advice across years. | Unused hours rarely roll over; right-size it. |
| Hybrid (recommended) | Fixed fee for defined phases + hourly schedule for extras and changes. | A novel seastead: defined hull work, uncertain research items. | The hourly rate card must be in the contract from day one. |
A COMMON PAYMENT CURVE ON A LUMP-SUM DEAL →
15% signing→20% concept→25% preliminary→25% contract design→10–15% at cutting-file release
Also ask who exactly is covered by the fee. Structural FEA, marine electrical engineering, mooring/TLP analysis, and interior design are frequently sub-consulted and billed on top. Get the split in writing before signing.
032026 planning figures · USD
What the hours cost in 2026
Rates vary by region — US, UK, Netherlands and Australia sit at the top; reputable practices in Southern/Eastern Europe run 20–35% less; offshore drafting (Poland, India, Philippines) can be 40–60% cheaper but only works under strong senior oversight. Scale below: $0–500/hr.
Office day rate
$900–1,800Per day, engineering work. Site-visit days run $1,200–2,400 plus travel & lodging.
Full design package — your project
$150k–450k80′ (~24 m) aluminum trimaran, concept through cutting files & systems. At 24.4 m LOA you sit just past ISO 12215/12217 scope, so expect rules-based or classification-referenced engineering rather than small-craft presets.
Feasibility study
$8k–25k2–4 weeks, fixed fee. The ideal paid test-drive of a firm before committing the full contract.
Specialist studies (each)
$10k–60kSeakeeping/CFD package · active-stabilizer integration · TLP/mooring analysis · electrical/solar engineering. Often sub-contracted by the prime NA.
Construction supervision
1–3% of buildOr day rates across an 18–30 month build. Separate from the design fee in nearly every contract.
Class / plan approval fees
$10k–60k+If you choose classification (ABS, DNV, Lloyd’s). Separate from design fees; paid to the society.
Planning guidance only. Obtain 2–3 formal quotations — nothing normalizes naval architecture pricing like competition. Figures reflect US-dollar planning ranges for 2026.
04If you build a hundred copies
Replication rights & royalties
Here’s the single most misunderstood part of the business: buying a design does not buy the design. Copyright normally stays with the naval architect; you receive an irrevocable license to build one unit. Every hull after that needs its own license — so if a fleet of seasteads is even a dream, price those rights now, while you still have leverage.
A
Per-unit build license
Standard for additional one-offs: typically 50–100% of the original design fee per extra hull (sometimes 25–50% if plans just need re-issuing with no adaptation).
B
Series buyout
One-time payment for series production rights. Planning heuristic: 3–10× the single-build fee, depending on how much production engineering is included. Usually the cheapest path at high volumes.
C
Per-unit royalty
Typically 1–3% of each unit’s construction price, sometimes tapering with volume. Low up-front cost, but it compounds — fast, at 100 units.
D
Hybrid + series engineering
Smaller buyout + smaller royalty + a priced series-engineering agreement (jigs, production drawings, build-support for Hulls 2–N). This is where most 100-unit conversations actually land.
Also settle: who owns improvements developed during series production, your right to modify the design for later units, and how the architect is credited. And yes — this all belongs in the first contract, as pre-priced options.
Negotiate before the ink driesRoyalty estimator
Planning heuristic · not a quoteBase design fee (1 hull)—
Series buyout range (3–8×)—
Royalty per unit—
Royalty across fleet—
05Do they help during manufacturing?
Yes — and you want them there
Construction support is a standard (separately billed) phase. On a first build it is money well spent: the designer answers builder questions in hours instead of weeks, protects design intent, and keeps weight under control while the metal is being cut. Typical budget: 1–3% of construction cost, or day rate + travel for agreed visits.
M1
Plate cutting & procurement
DXF/nesting release; verification of 5083-H116/H321 plate certifications; consumables and extrusion schedules.
M2
Hull assembly
Weld sequence and distortion control, dimensional checks, coordination of NDE (weld inspection) — often via a specialist welding inspector the designer recommends.
M3
Deck & superstructure join
Alignment, structural continuity, and the dissimilar-metals discipline: isolation of stainless hardware from aluminum, bonding and cathodic protection.
M4
Systems, solar & stabilizers
Electrical sign-offs, battery installation to ABYC/IEC practice, stabilizer hardware integration and vendor commissioning.
M5
Launch · inclining · weight survey
The moment of truth: measured weight & CG vs. the ~37,000 lb estimate. A good designer has been tracking this monthly since P2.
M6
Sea trials & handover
Trial protocol, punch-list close-out, as-built drawings, manuals, and defined warranty-period support.
06How long does it take?
From contract to water
6–12 moDesign, family-size aluminum yacht
18–36 moOne-off 80′ aluminum build
±15%Weight tolerance until prelim closes
4 gatesOwner decision points before cutting
For your concept — three slender vertical floats, active stabilization, solar-dominant power, TLP option — plan toward the upper half of the design range. Your model-test and simulation gates cost a few weeks and save months of metal mistakes.
Design months
M1M2M3M4M5M6M7M8M9M10M11M12
Feasibility
Concept
Preliminary
Model tests + sim
Contract design
Structure + systems
Cutting files
Construction support
Owner gates
◆ G1 concept freeze · G2 model-test & simulation review (Sandy Hill Bay + CFD) · G3 contract freeze → builder bids · G4 cutting release · launch & trials occur 18–30 months later
Weight discipline from day one
Your AI-assisted studies estimate ≈ 37,000 lb (16.8 t). Treat that as a target, not a fact: require a weight & CG report with margin at every gate, hold an 8–12% margin until preliminary design closes, and verify with an inclining experiment at launch. Solar arrays, battery banks and habitation outfit are where seastead weights quietly grow.
07Your design, specifically
The specialist stack this seastead needs
One firm can be the prime for all of this, but confirm each discipline is genuinely covered — several are distinct professions. Budget the specialists as separate line items.
SP-01 · Prime
Naval architect
Hull form, structure & scantlings, stability (multihull criteria), integration, weight control. Insist on proven aluminum multihulls and builder references.
Engage: at contract · typical: 60–75% of design feeSP-02 · Hydrodynamics
Seakeeping & CFD
Slender vertical floats live or die on seakeeping. Strip theory / potential flow (AQWA, WAMIT, Orca3D) plus CFD (OpenFOAM / STAR-CCM+), validated against your Sandy Hill Bay models. Froude scaling: at 1:8, speeds and times scale ×0.35 — measure with an IMU on the model and decay-test heave/pitch.
Engage: preliminary phase · typical: $15k–60kSP-03 · Motion control
Active stabilizers
Interceptors (Humphree-class), fins, gyros (Seakeeper-class) or T-foils — each interacts differently with slender floats. Control-law integration with the seakeeping model is the real work.
Engage: preliminary · integration eng. $10k–40k + hardwareSP-04 · Power
Solar & DC systems
Array area vs. windage trade (windage feeds back into mooring loads), MPPT architecture, battery safety to ABYC/IEC practice, shore/generator backup. Marine electrical engineer.
Engage: concept → contract · $10k–35kSP-05 · Offshore
Mooring / TLP consultant
Tendon tensions, setdown, fatigue and springing; API RP 2T / DNV offshore practice. Decide vessel vs. floating structure early — it drives stability criteria, survey and insurance.
Engage: feasibility/prelim · $20k–80kSP-06 · Living aboard
Interior & habitability
Full-time living in an aluminum hull in the tropics: insulation and condensation control, freshwater making, HVAC, tankage, and interior weight that must stay inside the weight budget.
Engage: concept phase · interior design typically 3–8% of interior costSP-07 · Compliance
Classification / flag
Optional for a private vessel, but it eases financing, insurance and marina acceptance — and matters more for a permanently inhabited seastead with a TLP option. ABS, DNV, Lloyd’s, or a flag-state survey route. Get the pathway in writing during feasibility.
Engage: feasibility · society fees $10k–60k+08Attach this to the contract
The deliverables register
A contract is only as good as its deliverables list. Tick items off as you negotiate them into scope — and make final payment conditional on the whole register.
0 / 21 on fileDesign & engineering
Build & compliance
09Read before signing
Twelve clauses that must be in there
01
Scope + deliverables register
The Section 08 list, attached as an exhibit. “Design services” alone is not a scope.
02
Milestone payments
Paid against deliverables; hold back 5–10% until cutting files are released. Avoid schedules front-loading more than ~30%.
03
Change-order procedure
Written pricing and approval before extra work starts, with the hourly rate table attached to the contract itself.
04
Revision limits
e.g., two GA rounds and one layout option per phase. Beyond that, change orders apply — fair for both sides.
05
IP & build license
Architect keeps copyright; you get an irrevocable one-unit license plus pre-priced options for additional units and series rights.
06
File release terms
What you receive: PDFs always; DXF/nesting files as part of the build set; native CAD files are negotiable — say which, explicitly.
07
Standard of care & insurance
Services to professional standard (never a guarantee of fitness); liability cap; proof of professional indemnity cover, $1M+ recommended.
08
Schedule + response times
Phase dates and an RFI turnaround commitment (48 hours is a good target for build phase).
09
Termination & handover
Either party may terminate with notice; you receive all work product paid for to date, in usable form.
10
Confidentiality & publicity
Designers usually want portfolio photography — agree when and what. Protect anything you consider proprietary about the seastead concept.
11
Governing law & disputes
Jurisdiction, mediation-before-arbitration ladder. Cheap to agree now, brutal to fight later.
12
Warranty-period support
Defined support during the first 12 months after delivery — design queries are inevitable once you live aboard.
10Pattern recognition
Red flags & smart moves
✕ Red flags
✕No references from completed aluminum builds — monohull GRP experience doesn’t transfer cleanly.
✕Deliverables described vaguely (“full design package”) without a register.
✕Requests more than ~30% before any deliverable exists.
✕No weight-tracking process, or unwilling to report weight & CG at every gate.
✕No professional indemnity insurance, or refuses to show the certificate.
✕Scantlings offered as “experience-based” with no rule or calculation basis.
✕Won’t price replication / series rights up front — “we’ll work something out later” is how fleets get held hostage.
✕Unfamiliar with multihull stability criteria, or dismissive of your TLP/habitability questions.
✓ Smart moves
✓Commission a small paid feasibility study first — a two-week test drive of the relationship.
✓Get 2–3 competing quotations against the same deliverables register.
✓Interview the actual people doing the modeling and drafting, not just the principal.
✓Write the Sandy Hill Bay model-test and simulation gates into the schedule as decision points.
✓Spend $2k–5k on a maritime attorney’s contract review.
✓Visit a yard that has built one of their designs, and talk to that owner.
✓Require monthly weight & CG reports once construction starts.
✓Get the classification/flag pathway decision documented in feasibility — it echoes through everything, including the TLP option.
11Put these in front of every candidate
The interview sheet
Q01
Which aluminum multihulls have you delivered end-to-end? Can we speak with the builders and owners?Look for names, hull numbers, and willingness to make introductions.
Q02
Who specifically does the modeling, scantlings and drafting on our project?The portfolio belongs to the firm; the work belongs to individuals.
Q03
How would you analyze seakeeping for slender vertical floats — in-house or with partners? Which tools?Expect AQWA/WAMIT/Orca3D-class answers plus a CFD plan.
Q04
What is your weight-tracking process, and what margin do you hold at each phase?If the answer isn’t concrete, keep shopping.
Q05
Are plate development and DXF nesting files included in the lump sum?Some firms hold them back as leverage for the build phase.
Q06
What is included versus sub-contracted: structural FEA, electrical, mooring/TLP, stabilizer integration, interior?Get the list and the mark-up policy in writing.
Q07
What professional indemnity insurance do you carry, and what is the liability cap?Ask for the certificate, not the promise.
Q08
How do you price additional builds and series rights — and will you fix those prices in this first contract?The question that separates fleet-ready firms from one-off shops.
Q09
Will you support our scale-model testing program and help interpret results against simulations?Good firms welcome owner testing; great firms instrument it with you.
Q10
What classification or flag-state path do you recommend for a permanently inhabited seastead with a TLP option?Listen for the vessel-vs-structure distinction — it’s the pivot of the whole project.
Q11
What is your RFI turnaround during construction, and how are site visits priced?48-hour target; day rate + travel in the rate card.
Q12
Can we see a redacted sample contract and a complete deliverable set from a past project?A confident firm says yes quickly.