THE SHIPWEIGHT CONCEPT
by
Runar Aasen
Stein Bjørhovde
BAS engineering AS/ShipWeight

An introduction to the philosophy, background and technical solutions behind ShipWeight.

Download paper here: The ShipWeight Concept

SAWE Paper No. 3244
Category No. 13

WEIGHT CONTROL AT ULSTEIN SHIPYARD, NORWAY
by
Runar Aasen
Stein Bjørhovde
BAS engineering AS/ShipWeight

For Presentation at the 61st Annual Conference
Of Society of Allied Weight Engineers, Inc.
Virginia Beach, Virginia
20-22 May, 2002

Download paper here: Weight Control at Ulstein Shipyard, Norway

SAWE Paper No. 3504
Category Nos. 5 & 13

METHOD FOR FINDING MIN AND MAX VALUES OF ERROR RANGE
FOR CALCULATION OF MOMENT OF INERTIA
by
Runar Aasen, Technical Sales Manager
BAS Engineering
Bruce Hays, Principal Naval Architect
DRS Defense Solutions, LLC, Advanced Marine Technology Center

For Presentation at the 69th Annual Conference
Of Society of Allied Weight Engineers, Inc.
Virginia Beach, Virginia,
23‐26 May, 2010

ABSTRACT

Modern ship design practices require knowledge of a vessel’s mass Moment of Inertia (MOI) for various aspects of performance analysis. To find an accurate MOI value of an object, one needs to know the object’s actual shape and density to be able to calculate the MOI through integration. Determining the exact MOI for a complete vessel, comprised of thousands of items, is not practical. Instead, engineers simplify the parts of the vessel to point objects or to standard shapes like a box or a cylinder, and calculate an approximation of the MOI. The accuracy of this approximation is dependent on the number of parts the vessel is divided into and how well the shape, orientation and density of each of the simplified items resembles the real objects. The quantification of the inaccuracy involved is seldom addressed. This paper describes a method to find the absolute error range for this simplified MOI calculation by finding the extreme values the MOI approximation can generate, and quantifies the effect that an error in MOI can have on the results of various types of performance analysis.

Download paper here: Method for Finding Min and Max Values of Error Range for Calculation of Moment of Inertia

SAWE Paper No.
3505 Category Nos.
13 & 21

EARLY STAGE WEIGHT AND COG ESTIMATION USING PARAMETRIC
FORMULAS AND REGRESSION ON HISTORICAL DATA
by
Runar Aasen, Technical Sales Manager
Stein Bjørhovde, Head of Development
BAS Engineering AS/ShipWeight

For Presentation at the 69th Annual Conference
Of Society of Allied Weight Engineers, Inc.
Virginia Beach, Virginia,
23-26 May, 2010

ABSTRACT

Estimation of weight and center of gravity is an essential task in the design phase of a vessel, and the 
quality of this work will be crucial for the success of the project. It is important to have the best possible 
estimate for total lightship weight, but when it comes to construction and installation there will be a 
demand for detailed budgets. A certain detail level for the weight budget will also make it easier to find
the reasons for any deviations that may occur during the monitoring phase.
The use of parametric estimation based on several reference ships and regression lines has traditionally 
been characterized as too demanding, because of time demands as well as complexity. This article will 
describe some assumptions and methods that make it possible and preferable to use parametric 
estimation on a regular basis when designing and building a ship, either by the use of built‐in formulas 
and graphs found in spreadsheets, or by the use of database related weight control systems like 
ShipWeight. This article will discuss topics like breakdown structures, methods, selection of coefficients, 
selection of detail level, reporting and exporting of results, together with design changes and reestimation.

Download paper here: Early Stage Weight and CoG Estimation using Parametric Formulas and Regression on Historical Data

SAWE Paper No. 3562
Category No. 25

PARAMETRIC ESTIMATION OF ANCHOR HANDLING TOWING WINCHES
by
Stein Bjørhovde
Runar Aasen
BAS Engineering AS / ShipWeight

For Presentation at the 71st Annual Conference 
Of Society of Allied Weight Engineers, Inc.
Bad Gögging and Manching – Bavaria, Germany – 
05-10, May, 2012

ABSTRACT

Anchor Handling Tug vessels (AHT) are ships built to handle anchors for oil rigs, in addition to towing the
platforms into position and in some cases operate as Emergency Rescue and Recovery Vessel (ERRV).
Compared to ordinary offshore supply vessels, AHTs are characterized by large winches for towing and
anchor handling, open stern for landing of anchors and a large bollard pull.

The winch packages for anchor handling tug vessels are large and heavy constructions with weight that
varies from 150 to 900 tonnes and may represent as much as 15% of the lightship weight for the vessel. In
addition to significant weight, it also influences a lot on the vertical center of gravity (VCG) og thereby the
stability of the ship. Also the longitudinal center of gravity (LCG) is significantly influenced by the layout
and positioning of this equipment.

Experience shows that it might be difficult to identify reliable weight and center of gravity (CoG) for this
special made equipment from fabricators and suppliers in an early design phase. Based on this we want to
study which parameters are relevant for estimating weight and CoG for anchor handling / towing winches,
and how these parameters can be combined in mathematical formulas that can be used in regression based
estimation.

The advantage of using regression is among others the quantification of uncertainty (standard deviation)
related to each specific estimation method and thereby the possibility to decide which methods that are the
most precise, and to evaluate whether parametric estimation can be used at all. An evaluation of the
uncertainty requirements will be performed as well.

Download paper here: Parametric estimation of anchor handling towing winches

UTILIZING CAD/CAM MODELS FOR ONGOING WEIGHT ESTIMATION AND CONTROL
by
Runar Aasen, BAS Engineering, Aalesund/Norway, runar@shipweight.com
Patrick Roberts, ShipConstructor USA, Inc., Alabama/USA, Patrick.Roberts@ShipConstructor.com
Nick Danese, Nick Danese Applied Research, Antibes/France, ndar@ndar.com
Lawrence Leibman, DRS Technologies, Inc., Maryland/USA, lleibman@drs.com

ABSTRACT
Controlling the weight of a vessel over the design and engineering lifecycle is critical but is an ongoing challenge for shipbuilders. Excellent tools exist for both weight estimation and control and design and engineering; however the area where these two meet is often filled with Microsoft Excel spreadsheets or databases developed in house by individual shipyards. These approaches leave much to be desired. This paper will explore the implementation and benefits gained by integrating existing design and engineering tools with existing weight control applications.

Download paper here: Utilizing CAD/CAM Models for Ongoing Weight Estimation and Control

SAWE Paper No. 3625
Category Nos. 17

METHODS FOR REPRESENTING CONDITIONS ON A WEIGHT DATABASE
by
Stein Bjørhovde
Runar Aasen
BAS Engineering AS/ShipWeight

For Presentation at the 73rd Annual Conference
Of Society of Allied Weight Engineers, Inc.
Long Beach, California,
17-21 May, 2014

ABSTRACT

This paper will look into several conditions that can appear in a weight control project and where all of them need calculation of weight and center of gravity as a variant of the standard lightweight calculation at point of completion. Requirements and wishes for a weight control system to handle these conditions will be discussed and addressed against methods and solutions.

Download paper here:  Methods for Representing Conditions on a Weight Database

SAWE Paper No. 3720
Category No. 21

A PRACTICAL AND PROACTIVE WAY OF MANAGING WEIGHT & CENTER OF GRAVITY UNCERTAINTY USING THE SUCCESSIVE PRINCIPLE
by
Runar Aasen
Stein Bjørhovde
BAS Engineering AS/ShipWeight

For Presentation at the 78th SAWE International Conference
on Mass Properties Engineering
Norfolk, Virginia
May 18-23, 2019

ABSTRACT

One of the challenges in mass properties is how to handle the uncertainty in an early stage estimate of
weight and center of gravity (CG) and its impact throughout the life of the project. Risk is sometimes 
defined as the product of consequence multiplied by uncertainty, and for many shipbuilding projects the
consequence of missing the mark on either the weight or CG can be dramatic. That makes reducing 
uncertainty essential to avoiding a high-risk project.

Dr. Steen Lichtenberg started as early as the 1970’s to develop a method for proactive management of 
uncertainty using the Successive Principle. The method is a practical way to manage opportunities and 
risk. The underlying philosophy states that realism in forecasts requires a qualitative phase as well as a 
quantitative phase. In the qualitative phase, an analysis group of people should be established, while the 
quantitative phase should establish a basic structure of main items, followed by a systematic detailing 
process and an action plan.

While the method typically handles uncertainties related to the economics of large projects, this paper 
will look at how the principles and processes involved can be applied to the weight and CG challenges 
during ship design and construction. A general introduction to the Successive Principle will be given, 
the basic applications will be presented, and discussions and examples of use cases will be 
included. The goal is to add another tool to the toolbox of the weight engineer to help ensure successful 
projects.

“If you start with certainty 
You will finish with doubt 
If you start with uncertainty 
You will finish with certainty”
Sir Francis Bacon, philosopher (1561-1626)

“Uncertainty has several names 
For the fool, it does not exist 
For the afraid, it means risk 
For the brave it means also opportunities” 
Freely from Victor Hugo, author (1802-1885)

Download paper here: A Practical and Proactive Way of Managing Weight and Center of Gravity Uncertainty using the Successive Principle