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Safe Towing: Calculating a towline’s catenary and sag

Introduction Towlines connect a tug to the vessel being towed and are defined by multiple characteristics like Weight, Diameter, and Stiffness. The tension in the towline during the towing operation is not static but keeps varying with the distance between the tug and...

Designing the lashings of deck cargo using IMO CSS

Introduction More than 70% of the earth is covered by water, which makes shipping historically the easiest and cheapest way of connecting manufactures and customers across the globe and can be reasonably considered to be the artery of the global economy. An enormous...

Using MS Excel to evaluate the Stability of existing Barges

Barges are the simplest, and yet most widely used of marine vehicles. They are used for a variety of purposes ranging from carrying cargo in bulk or liquid, to even carrying passengers for short inland cruises. Barges are mostly towed by another barge called a tug,...

The importance of ULS (Ultimate Longitudinal Strength) and how to assess it for a damaged hull

by Alessandro La Ferlita, Naval Architect Ultimate hull girder strength represents the maximum capacity, of the hull girder beyond the structure fails. In fact, if the vertical bending moment applied overcomes a certain maximum value, the ship can collapse (Figure 1)...

How to calculate the strength of Midship Section of a Ship

The mid-ship section of a ship is a defining structural drawing of the vessel. It represents the most critical structural parameter of the vessel – its global strength. To assess how much of the bending moment (hog and sag) the vessel can tolerate, it is important to...

How to use empirical formulas to estimate the resistance of a Ship

How to use empirical formulas to estimate the resistance of a Ship Resistance estimation holds immense importance in the design stage of a vessel. Based on the results of the resistance estimation of a vessel, the selection of the right propulsion system is done....

Designing the berth mooring of your vessel with this simple yet effective method

A vessel at berth experiences much lower forces compared to a vessel in the open sea due to the milder environment, but it still requires a mooring configuration suited to the forces it experiences, and also suitable for the type of berthing configuration adopted. The...

Bulbous Bows – History and Design

by Bijit Sarkar, Naval Architect Introduction The eternal search of a naval architect – a perfect bow. Sadly, it never exists. Different bow forms are good for different types, sizes of vessels and seaways. What does a naval architect want out of the bow he designs?...

Understanding how buoys affect the catenary of a mooring line

What is a mooring line? Mooring lines generally comprise ropes, wires, chains or combination of wire and chain used to keep ships, offshore platforms and other floating vessels in position. It connects the structure either to the seabed using an anchor or the quay...

Calculating forces on a ship’s deck cargo – a simplified approach

A cylindrical deck cargo (Source: Wikimedia) Introduction A ship’s deck is used to transport many different types of cargo – from containers to large structures like cranes or heavy modules of an offshore production plant. During transport, the ship suffers from...


Excellent and Reliable

Costas Carabelas

Dear TheNavalArch,

CCTO is an almost 40 years Naval Architects company operating in the world wide Shipping industry as technical consultants with a significant variety of projects in our portfolio.

Six years ago we ascertain existence of your first products and we immediately decided to make use of them. The experience gained over the years is,

  • The software  you are developing are of an extended application  in our activities and every day questions we have to deal with. Let’s call this as ”LARGE SCALE “ application products”.
  • The Rules & Theory your products are based on are most reliable and of vast acceptance by the entities our projects are reviewed. Let’s call it as “RELIABLE & SAFE”.
  • The support we had from your side in each and every case we had a question was “EXCELLENT”.
  • Last but not least Your pricing policy is more than “FRIENDLY”

Please use our comments as an incentive for more products development in same spirit as above, assisting our activities.

Costas Carabelas
C.C.T.O. (Costas Carabelas Technical Office), Greece

Fine job..

robert p bob hill president 88029

You do a fine job of explaining the methodology and inputs to your spreadsheets which allows our people to make effective use of them immediately. We will certainly continue in the future, to purchase your products

Robert P. Hill, President
Ocean Tug and Barge

Time savers…

Jim A m

Just a note on the TheNavalArch’s programs, I have several and find them very well done, especially helpful is the very detailed analysis presented with each program (and the very reasonable price). The programs are real time savers and pay for themselves after a single use. The detailed outputs are well organized and ready to be included directly into engineering reports as is, with no modifications or editing required. I also find the articles on various topics sent out from time to time to be very informative and useful also. 

James Andel
P.E., Civil Engineer

Practical, straightforward…

Theo Haak TheNavalArch

I have been using the TheNavalArch’s spreadsheets already for many years in the maritime salvage industry with great pleasure.

They are practical, straight forward, understandable, written in a plain language and in line with the actual regulations of classification bodies.

Theo Haak, Owner
Haak Consultancy Salvage

Professional work…

tony laubreaux

Just wanted to thank you for your assistance with the two technical analyses we conducted recently.

I was pleased with the work provided, which was very professional. In addition, your response to enquiries and requests for further analyses was always prompt, which was very much appreciated.

I look forward to working with you in the future.

Tony Laubreaux
Laubreaux Marine SARL

Better than the software I am used to…

jose zorrilla

Your spreadsheet is great, even better that the software I am used to.

I am using it in order to design fenders for a new Harbour in Montevideo.

Jose Zorrilla
Civil Engineer,ACI,NACE

Great to have a double check…

Kris Decke

So far I have downloaded Lug and Cargo forces spreadsheets and use them daily and find them very useful.

I get similar results with my own spreadsheets so it’s great to have a double check as its very easy to make a mistake in a spread sheet

Kris Decke, Design Engineer

Reliable engineering apps…

IMG 20181026 WA0020

TheNavalArch’s products have been handy for us in getting reliable Engineering Calculations for critical Marine Operations like Mooring, Loadout and Towing which we carry out on a regular basis.

The Technical Support is prompt and helpful in clarifying doubts and queries. Technical Consultancy provided for Critical Loadout operations involving Ballasting and Stability Calculations have helped us deliver our projects timely.

Capt Kulwant Singh, Managing Director
EkOne Safety and Marine Management Pte Ltd, Singapore

Helpful in operations…

Thank you for the outstanding help we received during our project.

Your products have also been helpful to us in our operations.

Highnet Marine Technology(HMT, Korea)

Useful for quick checks

Bil Stewart TheNavalArch

I am generally pleased with each of the calculators.  I primarily use them for quick checks on intermediate stages of generally more complicated calculations

Bil Stewart, Founder & CEO
Stewart Technology Associates

Reliable engineering calculations


Over the years working as a Naval Architect I have reached out to TheNavalArch on many occasions on various projects for reliable engineering calculations.  TheNavalArch calculators are very reasonable priced and do a great job of explaining the inputs and methodology used.  As most companies and engineers have their own database of calculators, I have relied on the TheNavalArch for both new design of calculations as well as QA of existing engineering calculations.  The technical support from TheNavalArch is very prompt and helpful with any technical issues that have occurred.  The calculators are certainly a time saver with the peace of mind of correct outputs.  Keep up the good work and will continue to look to TheNavalArch in the future as a supportive resource to my engineering designs and projects.

Sean Cole, Naval Architect
Marine Services International Ltd

Hi There!

Welcome To


We endeavor to become the richest hub for quality online resources for the Marine and Oil & Gas industries. We currently house an array of marine calculators which are handy and easy to use in design and operations. You may also wish to checkout our technical Articles which are in-depth and written by some recognized industry experts. Do try our 'Engineering On-demand (EOD)' service which helps you get the best engineering analyses and design done by our panel of experts: quality work - on time, on demand.

We're based out of Singapore, and on the constant lookout for collaborators who are willing to share knowledge and content with the industry. To share your ideas and feedback, feel free to write to us.