Fun, exhilarating, electrifying!
Learning to dive for most people is something exhilarating and out of this world. The first breath of compressed air underwater, staring at our submerged world at close quarters is something many people do not forget. Something that comes close to this experience can only be diving with a Diver Propulsion Vehicle (DPV). You will have so much fun when you execute a fly pass over the reef. A flyby on the wreck, ability to carve turns and high-speed movements underwater. You move slowly over the contours of the bottom, watching out for hidden gems among the rocks. This experience redefines diver skills and performance.
Diver propulsion vehicles (DPVs), we call them scooters come in all shapes and sizes. A torpedo shaped design with a propeller mounted at the rear is a common design. You operate them when you squeeze a trigger to induce power to the motor. The motor will turn the propeller, which will send the scooter forward. Some scooters, like the Scubajet do not have a propeller; they operate with a water jet system. Scubajet scooters weigh as little as 4.5kg, easy to carry and are manageable by small divers. Alternative configurations might include back, or a tank mounted model which leave the diver hands free. Ride-on models and foot-mounted models are on the market too.
Power and Battery Efficiency;
The battery and its ability to store chemical energy are a critical part of the scooter, regardless of the configuration and model. The battery stores chemical energy efficiently, then it converts the stored chemical energy into electrical energy. This electrical energy is efficiently converted into mechanical motion. Through the mechanical motion the propeller will turn and cause a propulsive forward force. In the case of the Scubajet, it will suck water in and efficiently and forcefully push out the water like the mechanics of a jet-ski.
The run time of a scooter is important, which is a measure of the batteries capabilities. It is also the decider on the distance you travel with the scooter and the speed. Over time the efficiency of the battery will degrade, a higher value battery is a long term value.
Improved efficiency, higher performance and robust designs lead to higher costs. Scooters vary in price with an entry level around €400, some with price tags of thousands. The more efficient and powerful they are, the higher the price tag.
This factor is, unsurprisingly the one that limits the DPVs performance. Scientists and engineers alike are motivated to improve battery performance. The more chemical energy batteries can store, the higher the performance of the scooter. This technology of battery performance is within a given weight and volume. Other examples of battery technology being used today are laptops, cell phones, cars and even aircraft.
Scientists and technology experts warn about high energy-density storage. This dangerous factor brought about the unintended consequence that a Boeing 787 Dreamliner caught fire when the lithium-ion batteries shorted out. Lithium-ion batteries offer advantages with a high power-to-weight ratio. They charge more quickly and offer more desirable cycling characteristics. Some manufacturers of DVPs use lithium-ion batteries, others still use sealed lead-acid batteries. The lead-acid batteries bring with them some risks. Hydrogen gas is produced as a by-product during the charging process. As it accumulates, it might reach concentration levels that will explode.
To combat this problem, scientists improved the technology and added a catalytic element to the battery. They combine the atmospheric oxygen with the hydrogen before the concentrations reach dangerous levels. Divers who use lead-acid batteries must adhere to the safety rules of how to charge and maintain the batteries. Explosions occur and can be quite significant in size.
What to look for in a DPV?
First and foremost is the performance. Divers should consider performance versus the requirements of the scooter. The construction quality of the scooter is important as well as the depth ratings. At depth, seals and bearings suffer the most, so significant attention is required in this area. These factors vary in different models, and they are paramount to reliability of the scooter. Most DPVs have multi-speed settings. This allows for conservative battery power and increases the utility of the scooter.
Most DPV’s are heavy. They weigh between 20 and 40 pounds which is a lot for a small diver. The Scubajet weighs only 4.5 kg and is ideal for all recreational diving. The higher the performance the heavier the scooter becomes, because the battery size will increase.
We should take the buoyancy of the scooter into consideration too. They are often negatively buoyant. Battery-power meters and depth alarms are ideal for divers to help maintain their safety. Accessories such as lights can be useful if diving in dark environments.
DPV Course and correct training;
Correct training is key to safe scooter dives. It is not a question of the three Ps (point, pull and party). Learn how to use a scooter in the correct manner, take a course and practice in shallow water first. Learn the basic maintenance about the batteries, how to charge them and the safe operations procedures.
With a scooter we have increased risk factors on a dive, one being a rapid descent. This situation can cause a barotrauma to the ears as it becomes impossible to equalise our air-spaces. Rapid ascents and out of control ascents might and will increase the risk of decompression illness.
Buddy contact is not always easy, so dive the plan. Air and depth should be monitored and a plan in place in case of buddy separation.
If you loose or become separated from your DPV, this can lead to a seriously over or under buoyant situations. Sometimes divers arrive at unintended depths and find themselves in difficulty. When we use the DPV, we cover the distance much quicker. If some mechanical failure occurs to the scooter, we need to remember that unaided we have a long way back to safety in some circumstances – this applies much so to underwater, overhead environments!
Diver Propulsion Vehicles are super fun and redefine our underwater performance. The underwater world is vast, with a scooter it adds heightened risks to this beautiful environment. Take the PADI Diver Propulsion Vehicle Course with us and learn the correct knowledge and training for a risk free and super enjoyable ride.
Dive and ride safe everone this season1