Lashing safety in OOG shipments is determined by the methods, places, and position of a load. Practical experience repeatedly teaches us that even properly tensioned chains or wires may fail in trying to withstand the action of the sea or road, when the load is not carried on the balance or supported evenly.
Numerous teams are of the opinion that more or tougher lashings can offset a poor placement. It is a hazardous fallacy. In OOG shipments, lack of proper positioning of the loads results in uneven force paths that cannot be corrected by all the additions made to the sends at all. The product is excessive restraints on the one hand, slack on the other, and increasing laxity or even breakage in transit.
In the process of drawing up the lashing plan, the assessment and positioning of the load should be conducted in a manner that gives the highest weight possible and forces that are as distributed as possible. This step off, and the securing system begins on a disadvantage which it may never overcome.
Why Load Positioning Matters More Than Lashing Quantity
Positioning of the loads is the key chance that defines the forces on the load and restraints of transportation matters. Regardless of the number of lashings to put on them, and the strength of the lashings, they are determined to be effective by the direction and magnitude of forces which they are necessary to overcome.
With a load located in the center and intact, roll, pitch, heave, braking or acceleration forces are more evenly distributed throughout the securing system. However, make any slight change in position and you will add asymmetry to this: a side will experience disproportionate tension whilst the other will experience less load or slack. To add a few extra lashings to this situation will tend to spread the trouble instead of ending it – the imbalance will still persist, and fatigue or slipping will speed up.
Practically, we have had instances where crews would increase the number of chains because they thought this would create margin whereas the cargo would be moved by either not fixing the root cause of the problem which was improper initial positioning. Positioning determines the level with which the whole securing system is set.
Center of Gravity and Its Impact on Lashing Forces
The location of the center of gravity (CoG) is often not at the geometric centre of an over sized item particularly in the case of complex machinery, turbines or even a fabricated structure. An offset or a high CoG has a drastic effect of moving the forces through the load to the lashings.
At a position where the CoG is directly over the support base and is parallel to the container middleline, both the vertical and lateral forces are in equilibrium. The tension is predictable evenly in lashings. but an offset CoG forms a lever arm: when the vessel is rolled or the truck cornered the load strives to go around the point of offset and puts spiking tension on the lashings on the pull side and offloads on the opposite side. When this is repeated in a cycle, it produces fatigue, extension, or expulsion.
In severe instances, something unpredictable or poorly computed CoG has led to cumulative collapse – one lashing overloaded and snaps, creating weight to others until the entire machine breaks down.
| CoG Condition | Load Behavior | Lashing Risk |
| Centered | Balanced force | Stable restraint |
| Offset | Uneven force | Overloaded lashings |
| Unknown | Unpredictable | High failure risk |
Load Footprint, Contact Points, and Stability
The size and shape of the base of a load in contact with the deck of the flat rack or trailer makes the footprint of the load a direct determinant of base stability and the role of friction in restraining the load.
Flat footprints are wider and provide the maximum contact area and also friction and evenly distributes weight, eliminating point-loading stresses in the deck and aiding resistance to longitudinal or transverse forces. Small footprints produce more weight concentration, effective friction reduction and increase the likelihood of sliding or tipping, particularly when surfaces on the deck are wet or oily.
Point contacts on uneven footprints (typical on skids or protruding feet) cause stress piles that may deform timber dunnage or deck plating (as well as produce rocking motion that loosens lashings with time ).
| Footprint Type | Contact Quality | Resulting Stability |
| Wide and flat | High friction | Stable |
| Narrow | Low friction | Prone to sliding |
| Uneven | Point contact | Stress concentration |
How Poor Positioning Amplifies Transport Forces
The performance of the load during the dynamic forces at sea or road transport, acceleration, braking, roll, pitch and vibration, know how to directly act on the positions of the load. These inputs are predicted and absorbed in a well-positioned load which distributes them.
But ill positioning converts the medium forces into the harsh ones. An offset CoG increases rotational moments; the contact point is small and contact point unevenness permits the micro-movement which causes lashings to wear out early. This increase in degradation is caused by long journeys or bad roads: chains scratch, turnbuckles live, and timber sinews or crushes.
In our own practice shipments in which positioning has been hurried, with a view to meeting deadlines, invariably present the first indications of securing failure, namely, slack lashings and shifted loads being produced after only a few days.
Common Positioning Mistakes in OOG Shipments
Even hardened companies fall into these mistakes on schedule pressure or incomplete cargo statistics.
| Mistake | Incorrect Assumption | Consequence |
| Off-center placement | Lashings will balance load | Uneven tension |
| No blocking | Lashings alone suffice | Sliding |
| Ignoring footprint | Weight equals stability | Tipping risk |
Asymmetrical positioning is almost certain to be the most common one, as when teams are supposed to lash everything back into the center, physics tries in the opposite direction: asymmetry breeds.
Integrating Load Positioning With Securing Design
The choice of positioning should never be put behind intensive lashing design. It is not efficient and unsafe to attempt to design restraints around an ill-positioned load, you are going against the physics instead of using it.
When positioning and securing are both considered simultaneously, the behavior of the load can be modeled by the restraint logic: lashings are angled to oppose the anticipated directions of forces, blocking resolves the important contact points, and the extensive stability is enhanced. The root cause of this combined method is that it is based on adequate measurements of the site and 3D planning which minimizes instability and possible damage.
In engineered OOG cargo securing solutions that incorporate these principles from the start, see our dedicated overview.
Practical Positioning Guidelines to Improve Lashing Safety
These are field proven rules that should be followed when loading to install the securing system to success.
| Positioning Factor | Recommended Practice |
| Center of gravity | Align with container centerline |
| Footprint | Maximize contact area |
| Blocking | Use to stabilize base |
| Alignment | Match securing directions |
Always confirm CoG position using supplier data or onsite calculation and then final positioning. Get as much as possible of footprint by adding dunnage or shimming where necessary, and exercise early installment of blocking or bracing in place of base – never depend on lashings to put right what should not have been set wrong.
Conclusion — Lashing Safety Starts With Load Positioning
Lashing safety is defined in OOG shipments before even the first tie on the chain is resolved. Proper load placement by correct loads positioning provides balanced load forces, minimizes installation of stress, and stability of transport. When teams are keen in their placement and make it part of the larger team planning, they will not have to deal with the imbalanced forces and cumulative losses that everlasting most of the actions. The foundation can only be as good as the restraints.