This tool supports learning, teaching and early design exploration using established empirical methods, documented equation checks and model-test comparisons. Further validation and matched accuracy comparisons are needed before qualification for real-world engineering use.
This tool supports learning, teaching and early design exploration using established empirical methods, documented equation checks and model-test comparisons. Further validation and matched accuracy comparisons are needed before qualification for real-world engineering use.
Inputs
Define the ship, resistance method and water condition. Calm-water estimates for conventional displacement ships.
1 Hull geometry
The example supplies a complete set of inputs for trying resistance and propeller matching. It represents no measured ship or propeller.
Choose the hull file and confirm its units, axes and loading waterline. Read and check the hull, then review the preview and extracted values below.
Bulb and transom definitions, stern type, appendages and propulsion need your review. Import supplies the geometry inputs; the empirical method retains the applicability and accuracy scope documented on Benchmarks & validation.
Choose a JSON file saved by this tool. A setup restores editable inputs; a simulation opens its saved results.
— inputs you can edit and upload before calculating.
— the same example with recorded results, ready to open and view.
These files use an authored example, not an experimental benchmark.
2. Setup and method
Source notes (optional)
The published example does not state which wetted area its correlation allowance uses, so both choices are offered; the choice affects the correlation resistance, not the hull friction.
3. Main particulars
Use the loaded condition. LCB is forward-positive from mid-waterline length, not mid-Lpp.
Convert an AP-based LCB coordinate
AP origin; x forward, y port, z up. Supply both the aft waterline x-coordinate and LCB x-coordinate in metres.
4. Hull details
Hull geometry has been applied. Enter bulb area and its centroid, immersed transom area and stern type. Use zero only when absence is confirmed. Add appendages separately and supply propeller inputs before enabling matching.
Choose estimates explicitly. Zero bulb or transom area means confirmed absence in this setup.
5. Appendages
Wetted area [m²] and resistance multiplier 1+k₂ for each appendage group. An empty list means none.
6. Water properties
Enter density and viscosity for the intended water condition. No hidden temperature or salinity conversion.
Propeller & interaction
Match resistance to a supplied open-water curve.
7. Propeller and interaction
Delivered power is at the propeller. Engine/brake power, gearbox losses, machinery limits and attainable ship speed are not calculated.
8. Interaction factors from a model test
Use a matched resistance/self-propulsion test and the model propeller's open-water curve below. These factors describe that model, its loading and its test condition; they are not full-scale factors.
Rc must already be corrected to the propulsion-test water temperature. Enter the actual applied towing force; it may differ from the calculated friction correction. The current propeller diameter and water density are used. Speed is m/s and shaft rate is revolutions/s.
Comparison with the model test
Use model dimensions and Smooth model diagnostic mode. The comparison holds measured Rc − applied tow force fixed, then substitutes measured interaction factors one at a time and in combinations. It uses the selected method, area basis and RPM limits. It leaves your prediction inputs unchanged.
9. Open-water curve
The example curve is artificial and represents no real propeller. Import your own verified curve to study a real propeller.
Strictly increasing J, nonnegative KT and positive KQ. Linear interpolation only; no extrapolation beyond the supplied curve or RPM limits.
Save setup
Save an editable .json file containing the ship particulars, water, method, speed range and propeller curve. Geometry source information is retained; the extracted values can be reopened without the original mesh.
Analysis & results
Resistance components, effective power and propeller operating points.
Compute runs the current inputs and the speed range below. Reset clears the results and keeps your inputs. Open saved results restores a results JSON for viewing; a setup JSON restores inputs.
Ready. Review the example inputs, then compute.
Speed range
1–201 positive, increasing speed points. Geometry is static; dynamic sinkage and trim are not solved.
Resistance by speed
Total resistance is the sum of viscous hull, appendage, wave, bulb, transom and correlation terms. Hull friction is already included in viscous hull resistance.
Power by speed
Propeller RPM by speed
Selected-speed results
Results table
When several operating roots exist, all are listed below the selected speed. Power/RPM curves show only unique solutions.
Downloads and run record
The PDF presents the engineering results, inputs and references; its attachments retain the full results JSON and software notices. Results JSON reopens the complete saved calculation. CSV contains the result tables. If inputs change, JSON and CSV still describe the previous completed run.
Run record
Benchmarks & validation
Prediction comparisons, numerical checks and validation priorities.
The implementation is checked against the equations and worked examples of its published methods, and its predictions are compared with KCS and JBC model tests. The resistance comparisons cover the stated model-test conditions; at the reported KCS and JBC design points, the errors exceed measurement uncertainty. Wake and torque discrepancies identify the next improvements; independent full-scale powering validation and matched comparisons with established tools remain to be completed.
Expand a section to inspect its evidence and limits. Numerical agreement and reconstruction of a measured test do not establish independent prediction accuracy.
Cases, tolerances and outcomes
JBC: resistance and propulsion
KCS: resistance and source comparisons
Propeller curves and model-test comparisons
Numerical verification
Validation priorities
The equations have numerical checks, and model-resistance comparisons cover KCS and two distinct JBC experiments. These studies define the conditions already assessed and the next qualification steps: matched accuracy comparisons with established software and independent full-scale powering validation.
STL/OBJ import reduces manual input work. Its geometry checks use analytic boxes, an asymmetric prism and a three-level Wigley refinement study. They verify geometry calculations, not resistance accuracy.
The next step is to establish accuracy for a defined use and operating range before qualifying the tool for vessel-performance decisions. The targets of 5% mean and 10% maximum error are screening goals of this project, not ITTC acceptance criteria.
| Work item | Next evidence needed |
|---|---|
| Resolve the KCS comparison | The equation and input sensitivity review is complete. Resolve the remaining geometry/test pairing and obtain matched form-factor and uncertainty evidence. Independently review the KCS assessment before accepting its accuracy. |
| Extend the JBC assessment | The 2015 point and the separate 2023 eight-speed comparison are complete as conditional studies. Resolve bare-hull and appendage area, stern classification and the trimmed ballast geometry. Obtain measurement uncertainty for the new dataset. |
| Validate propulsion separately | The consistent smooth-model treatment reduces power error, but empirical wake and torque errors remain. Three same-hull factor-transfer holdouts are conditional on measured resistance. Add independent hulls and wider conditions before generalising. |
| Establish full-scale performance | Verify a documented model-to-ship procedure if added, and compare with suitable full-scale speed–power evidence. Treat correlation and service margins explicitly. |
How the ITTC guidance applies
The resistance, open-water and propulsion test procedures guide the evidence and test-condition records. Their uncertainty guidance helps distinguish measurement scatter from model error. The ITTC 1978 performance-prediction procedure describes a separate model-to-ship route; this calculator implements the model-test thrust-identity reduction in section 2.3, but not the full model-to-ship extrapolation.
ITTC 7.5-03-01-01 addresses CFD. Its distinction between verification, validation and uncertainty is useful here, but CFD mesh-convergence requirements are not directly applicable to these empirical equations. Relevant numerical checks include curve interpolation, root completeness and force-balance residuals.
References
- NMRI Tokyo 2015: JBC case 1.1a — towing conditions, coefficient area and V&V workbook.
- NMRI 2023 JBC numerical workbook and Kuroda, Fukasawa & Hamada (2023), pp.63–72 — separate appended-hull resistance and MP705 self-propulsion tests.
- JBC case 1.5a and original geometry and particulars — separate self-propulsion record and CAD.
- Hirata (2015), JBC test data in NMRI — slides 5 and 8, particulars and measured form factor.
- Holtrop & Mennen (1982), An approximate power prediction method, pp. 166–170 — resistance and interaction equations.
- Holtrop (1984), A statistical re-analysis of resistance and propulsion data, pp. 272–276 — revised correlations.
- NMRI Tokyo 2015: KCS case 2.1 — model-resistance comparison.
- Kim, Tokyo 2015 KCS resistance and self-propulsion report — slide 6 gives design-speed experimental resistance uncertainty.
- SRI KCS local velocity report — Table 3 supplies the KP505 open-water curve; the experiment description identifies model geometry and operating conditions.
- Gothenburg 2000 workshop: KCS geometry and conditions — distinct bare-hull and open-water records.
- Original SRI pressure report — model identity and test-condition evidence.
- Maasch et al. (2018), Shivachev et al. (2017) and the related thesis — additional KCS evidence reviewed for consistent particulars and uncertainty; not admitted to the resistance comparison.
- ITTC 7.5-02-02-01, Rev.05 (2021) — resistance tests; 7.5-02-02-02, Rev.03 (2021) — uncertainty in resistance tests.
- ITTC 7.5-02-03-02.1, Rev.04 (2021) — open-water tests; 7.5-02-03-01.1, Rev.06 (2021) — propulsion tests.
- ITTC 7.5-02-03-01.4, Rev.05 (2021) — section 2.3 model-test reduction; section 2.4 model-to-ship prediction.
- Win et al. (2016), KVLCC2 with and without rudder — Tables 1 and 4, and the experimental thrust polynomial on p.4; component inversion check only.
- JoRes full-scale benchmark programme and Krasilnikov et al. (2023), author preprint — MV REGAL evidence and data-access limitations; published version DOI 10.3390/jmse11071342.
- Sun et al. (2019), author preprint — full-scale sister-ship trials reviewed for completeness; published version DOI 10.3390/jmse8010024. Not scored as an OpenNAOE validation case.
- ITTC 7.5-03-01-01, Rev.05 (2024) — CFD verification, validation and uncertainty; conceptual relevance as explained above.
The tool works offline. Reference links open external sources only when selected. Source measurements and geometry are not included in this HTML.
About
This tool supports learning, teaching and early design exploration using established empirical methods, documented equation checks and model-test comparisons. Further validation and matched accuracy comparisons are needed before qualification for real-world engineering use.
Use the tool to study empirical resistance and propulsion methods and explore how inputs affect the estimates. Review the method’s assumptions and the benchmark evidence before interpreting a result.
Methods and limits
The calculator uses Holtrop–Mennen (1982) or Holtrop (1984) to estimate calm-water resistance. Effective power follows from resistance and speed. A supplied open-water propeller curve, together with hull–propeller interaction factors, gives operating RPM, thrust, torque and delivered propeller power.
The intended scope is a conventional displacement monohull in calm, deep water with one fixed-pitch propeller operating ahead. Equation checks have passed. Predictive accuracy has been assessed only at the KCS and JBC test conditions shown on Benchmarks & validation. Qualification for another hull or operating condition requires its own evidence.
The example explores the calculation. The separate KCS and JBC studies on Benchmarks & validation do not validate those inputs or a setup you import.
Range of application: not assessed against a numeric range. Holtrop and Mennen (1982, p. 166) limit the method to hull forms resembling the average ship and give no numeric range of parameters. The tool refuses inputs outside the limits of the coded formulas, a bulb centroid higher than 0.6 TF (the limit Holtrop, 1984, recommends for the bulb term) and, by its own guards, an L/B of 2 or less and a Reynolds number below 500,000. Holtrop (1984, Introduction) reports that the power predictions of the 1982 method for high-speed craft above Fn = 0.5 were often wrong and extends the data sample to improve the method; results above Fn = 0.5 are marked for both editions.
Applicability and assessment requirements
| Calculation | Current coverage | What is needed for extension |
|---|---|---|
| Resistance & effective power | Full-scale empirical estimate, including viscous hull, appendage, wave, bulb, transom and correlation terms. Explicit smooth-model diagnostic mode omits the ship correlation allowance. | Matched vessel particulars and resistance evidence across the intended speed and loading range, with uncertainty and use-specific tolerances. |
| Propeller operating point | Supplied J–KT–KQ curve; estimated or supplied w, t and ηR. A model-test input workflow derives these factors by thrust identity for the tested model; they are not full-scale factors. All admissible operating roots are retained within curve and RPM limits. | Measured open-water and self-propulsion comparisons. Curve scale effects and interaction assumptions need a documented treatment. |
| Hull input | Local STL/OBJ import with units and axes, mesh checks, an even-keel waterline, preview and nine extracted inputs. Saved setup JSON restores the complete input form. | Confirm baseline, midship section, moulded breadth, bulb, transom and stern type. Mesh resolution and geometric defects remain the user’s responsibility. |
| Full-scale powering | Delivered power at the propeller. No model-test extrapolation or engine limit is applied. | A separate model-to-ship procedure and full-scale comparison; machinery limits and losses for engine power or attainable speed. |
Outside the present model: planing craft, multihulls, shallow water, wind or waves, dynamic sinkage and trim, cavitation and noise, propeller design, fuel consumption, direct STEP/IGES reading, and trimmed-waterline mesh extraction.
Version & licence
- Interface
- Version
- Numerical engine
- Version
- Build identifier
- Code
- Free to use under the OpenNAOE Tool Licence; bundled dependencies retain their own licences.
OpenNAOE Tool Licence, version 1.0
OpenNAOE Tool Licence, version 1.0 Copyright (c) 2026 Mohammed Abdul Hannan. All rights reserved. 1. Use. You may use this tool free of charge, for any purpose, and make copies of it for your own use. A school, university or other organization may also install it on the computers it manages, for the people who use them. It is intended for learning, teaching and early design exploration, not for commercial engineering work: if you use it for other work, including consultancy, or rely on its results, you do so entirely at your own risk. 2. Your inputs and results. This licence claims no rights in the inputs you give the tool or in the results it produces for you, and places no conditions on how you use, publish or share them. 3. Restrictions. You may not modify the tool, use any part of its code in other software, or distribute the tool or any part of its code, modified or not. Preparing your own inputs, including by editing copies of the example and configuration files the tool provides, is use, not modification. Others can obtain the tool from opennaoe.org. 4. Other licences. Third-party components are under their own licences, and any part of the tool that a third-party licence requires to be licensed under it is under that licence; the tool's notices list them. Those licences, not this one, govern those parts, and nothing in this licence restricts what they permit. 5. No warranty; no liability. The tool is provided "as is", without warranty of any kind, express or implied, including any warranty of accuracy or of fitness for a particular purpose. Its scope and limits are stated in the tool. The author is not liable for any claim, damage or other liability arising from the tool, its use, its results or any decision made with them. These exclusions apply to the extent permitted by applicable law. 6. Name and logo. This licence gives no right to use the OpenNAOE name or logo.
Third-party and data licences
Bundled shared hydrostatics/stability engine and geometry support
Copyright (c) 2026 Mohammed Abdul Hannan
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External cited studies retain their own rights; source datasets are not licensed by this tool.
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PDF report layout
-----------------
The report layout code is by Mohammed Abdul Hannan, adapted from the OpenNAOE Hydrostatics & stability tool. The Adobe core-14 font metrics it uses are under APAFML; their complete notices follow below and are also kept with the metrics in the tool's code. The PDF standard fonts are not embedded; reports are tagged but are not claimed to conform to PDF/UA.
Adobe font-metric notices (APAFML)
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Copyright (c) 1985, 1987, 1989, 1990, 1997 Adobe Systems Incorporated. All Rights Reserved.Helvetica is a trademark of Linotype-Hell AG and/or its subsidiaries.
Copyright (c) 1985, 1987, 1989, 1990, 1997 Adobe Systems Incorporated. All rights reserved.
Copyright (c) 1985, 1987, 1988, 1989, 1997 Adobe Systems Incorporated. All Rights Reserved.ITC Zapf Dingbats is a registered trademark of International Typeface Corporation.
Modified by OpenNAOE (2026): only the advance widths (WX) are kept, rearranged by scripts/pdf-fonts.mjs for the
WinAnsi encoding (Helvetica) and for the Unicode characters listed (Symbol, ZapfDingbats); the header values
Ascender, Descender, CapHeight and XHeight of Helvetica are kept. Nothing else is taken from the AFM files.
This file and the 14 PostScript(R) AFM files it accompanies may be used, copied, and distributed for any purpose and
without charge, with or without modification, provided that all copyright notices are retained; that the AFM files are
not distributed without this file; that all modifications to this file or any of the AFM files are prominently noted
in the modified file(s); and that this paragraph is not modified. Adobe Systems has no responsibility or obligation to
support the use of the AFM files.
PDF engineering glyph outlines: Inter Regular 4.000.
Copyright 2016-2023 The Inter Project Authors (https://github.com/rsms/inter).
Modified by OpenNAOE (2026): subset glyph outlines and widths, scaled to thousandths of an em; nabla from Delta and four mapped signs.
This Font Software is licensed under the SIL Open Font License, Version 1.1.
This license is copied below, and is also available with a FAQ at:
http://scripts.sil.org/OFL
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SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
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Modified Version refers to any derivative made by adding to,
deleting, or substituting in part or in whole any of the components
of the Original Version, by changing formats or by porting the Font
Software to a new environment.
Author refers to any designer, engineer, programmer, technical
writer or other person who contributed to the Font Software.
PERMISSION & CONDITIONS
Permission is hereby granted, free of charge, to any person
obtaining a copy of the Font Software, to use, study, copy, merge,
embed, modify, redistribute, and sell modified and unmodified copies
of the Font Software, subject to the following conditions:
1) Neither the Font Software nor any of its individual components,
in Original or Modified Versions, may be sold by itself.
2) Original or Modified Versions of the Font Software may be bundled,
redistributed and/or sold with any software, provided that each
copy contains the above copyright notice and this license. These
can be included either as stand-alone text files, human-readable
headers or in the appropriate machine-readable metadata fields
within text or binary files as long as those fields can be easily
viewed by the user.
3) No Modified Version of the Font Software may use the Reserved Font
Name(s) unless explicit written permission is granted by the
corresponding Copyright Holder. This restriction only applies to
the primary font name as presented to the users.
4) The name(s) of the Copyright Holder(s) or the Author(s) of the
Font Software shall not be used to promote, endorse or advertise
any Modified Version, except to acknowledge the contribution(s)
of the Copyright Holder(s) and the Author(s) or with their
explicit written permission.
5) The Font Software, modified or unmodified, in part or in whole,
must be distributed entirely under this license, and must not be
distributed under any other license. The requirement for fonts to
remain under this license does not apply to any document created
using the Font Software.
TERMINATION
This license becomes null and void if any of the above conditions
are not met.
DISCLAIMER
THE FONT SOFTWARE IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL
THE COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF THE USE OR INABILITY TO USE THE FONT
SOFTWARE OR FROM OTHER DEALINGS IN THE FONT SOFTWARE.
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Verify the download
Compare the HTML file’s SHA-256 with the checksum published alongside this version on opennaoe.org or its Zenodo record.
Calculate the checksum of the downloaded file, then compare all 64 characters with the value supplied with that same version. The commands use the name that opennaoe.org gives the file; replace it if your copy has another name.
Windows · PowerShellGet-FileHash .\opennaoe-resistance-propulsion-1.0.0.html -Algorithm SHA256macOS · Terminalshasum -a 256 opennaoe-resistance-propulsion-1.0.0.htmlLinux · Terminalsha256sum opennaoe-resistance-propulsion-1.0.0.html
A matching checksum confirms that the files are identical; it does not establish the accuracy of the calculations.