Winching Worksheet

Note: Vehicle winching and recovery is an inherently dangerous activity. Pangaea Expeditions strongly recommends that you seek professional instruction for proper vehicle recovery techniques.

At first glance, winching seems like a simple procedure. Hook a line up to an anchor point, press a switch on the remote control, and watch your stuck vehicle almost magically free itself. However, there is a nuance, if not an art form to vehicle winching. With the wrong set up, an easy extraction can burn up your winch, turning it into a useless anchor. With the wrong rigging, a shackle or winch line could break, sending a dangerous projectile hurling towards a vehicle, or worse, a person. But with the proper knowledge and training it is possible to make these recovery operations simple and safe. With the right training, you can even achieve the seemingly impossible, like moving a vehicle backwards using it’s own front mounted winch.

Of course, there are inherent risks when using vehicle winches, and we strongly recommend receiving detailed winching instruction from experienced, credible institutions such as Land Rover Experience, Overland Training or Bill Burke’s Four Wheeling America.

About your Winch

Of paramount importance in a vehicle recovery situation is ensuring that you have the proper winch for your vehicle’s application. At a minimum, you should have a
winch with a pulling capacity equal to or greater than 1.5
times your 4×4’s gross vehicle weight (GVW).
If you are unsure of the GVW of your vehicle, this is usually listed on the VIN sticker located on the inside of the drivers side door.

Winch capacity

One of the common misconceptions regarding winches is that the maximum rated winch capacity is available any time the winch is hooked up. Unfortunately, this is false. Maximum winch capacity is in fact determined by the number of layers of cable wrapped on the winch drum. The best way to think of this is like the gears on a bicycle- the fewer the wraps, the smaller the “gear”, the greater the pulling power.

Below is the rated winch capacity for typical 8,000lb winch.

# of layers Pulling capacity % of capacity
1st (Drum) 8,000 lbs 100%
2 6,800 lbs 85%
3 5,760 lbs 72%
4 4,960 lbs 62%
5 4,240 lbs 53%

As you can see based upon this chart, the number of layers of cable or winch rope on the drum greatly affects the winch capacity. With the top layer losing almost half the pulling power.

The first and most important step in a vehicle recovery is a stuck assessment. This involves simply taking your time and observing the situation. Figure out what is preventing the vehicle from moving forward.

Is it a traction issue or is something like a tree stump or boulder caught up on the frame?

What does the trail look like ahead? if you get unstuck, and there is another worse obstacle around the bend, then perhaps the best solution is to recover the vehicle backwards and pursue an alternate route.

What anchor points are there to use for vehicle recovery?

Once you’ve take the variables into account, then you make a plan for recovering the vehicle.

In order to make a recovery plan, you need to figure out the resistance values of the “stuck”. This will help in making an appropriate recovery plan.

Approximate Resistance Values

It is important to remember that these values are “approximate”.

Surface Resistance

Surface Type Resistance
Hard Surface 4% of vehicle weight
Grass 15% of vehicle weight
Gravel 20% of vehicle weight
Dry Sand 25% of vehicle weight
Clay Mud 50% of vehicle weight

 

 

The exact makeup of mud, type of sand etc all affect the actual resistance. When calculating out resistance values, its always better to err on the side of caution.

 

 

Depth Resistance

Simply put, the deeper the vehicle is stuck, the greater the amount of pull necessary to extract it.

Depth Resistance
Axle 100% of vehicle weight
Top of tires 200% of vehicle weight
Hood 300% of vehicle weight

 

Inclination Resistance

Another variable which increases the load on recovery is the angle of slope of the recovery. The steeper the angle, the greater the resistance.

To calculate, add 10% of total vehicle weight for every 5º of inclination up to 50º. After 50º, simply add the total vehicle weight.

 

Pulley Block Resistance

Running the winch line through a pulley block actually creates an inefficiency in the recovery rigging. Each pulley block in the rigging effectively increases the load on the winch by 8%.

Calculation Example

So what do all of these numbers mean?

When making a stuck assessment, you take in to account as many of the variables as possible and set up your rigging accordingly.

In a hypothetical situation, we have a Land Rover Discovery bogged down in 6″ of mud on an 20º uphill climb.

The Discovery has a weight of 6,000 lbs.

The surface resistance of mud is 50%:
6,000 x 50% = 3,000 lbs
A 20º inclination creates additional resistance of 40%: 6,000 x 40% = 2,400 lbs
The total resistance = 5,400 lbs

In this simple recovery situation, a single line pull with an 8,000lb winch should do the trick, provided we pull the winch line out to at least the 3rd layer of winch line.

If the vehicle was stuck axle deep, the resistance increases significantly:

[surface] 6,000(.50) + [depth] 6,000(1) + [inclination] 6,000(.40) = 11,400 lbs

In this situation, the winch line would at have to be paid out to the second layer and a double line pull with a pulley block back to the vehicle would be required to have enough pulling power to recover the vehicle.

As you can see the force required to extract a stuck vehicle can be quite significant. With the additional weight from equipment and gear found on typical expedition vehicles, those requirements can increase dramatically.

For your convenience, we’ve added a handy PDF download of the these resistance values.

Click here for the PDF winching worksheet

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