One of the many unique features of the LBV systems is the umbilical. To many the understanding of how important the umbilical characteristics are to the capability of the ROV is unknown. Drag from umbilical is the largest of any part of the ROV. Consider that the drag is the square of it's diameter. To compensate for larger diameter umbilicals the ROV typically gets larger. Small ROVs with larger diameter umbilical are difficult to operate in conditions where there is current or longer lengths of umbilical in the water. The often used term "Tail Wagging the Dog" is an example of a larger diameter umbilical used on a small ROV where there is not sufficient power to overcome the influences made by the umbilical.

From the conception of LBV there were three (3) very important factors:

1. Small diameter umbilical
2. Bollard thrust
3. Power to weight ratio

LBV benefits from one of the smallest diameter umbilicals of any ROV. When demonstrating a ROV be sure to operate with longer lengths of umbilical and in a current to see how they perform. At depth the power of the thrusters should be such that it can maintain position without the umbilical greatly affecting the operation.

Here is a chart outlining the effects of umbilical diameter on drag. An absolute calculation is difficult as the drag coefficient is related to the curve in the umbilical in the water. For example the worst case scenario is that the umbilical be vertical creating the highest drag coefficient of 1.2Cd. The following chart uses a more average drag coefficient of 0.6Cd.

7.6mm umbilical at 2 knots creates a drag of 17.01lbs
10mm umbilical at 2 knots creates a drag of 22.34lbs
10mm umbilical creates 24% more drag thus the ROV must have 24% more power to overcome the additional drag.