Diver Propulsion Vehicle
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A Diver Propulsion Vehicle or a DPV is an item of diving equipment used by scuba divers to increase their range while underwater where their endurance is restricted due to limited availability of breathing gas and need to avoid decompression sickness.
Also known as an Underwater Propulsion Vehicle or UPV, a DPV generally consists of a battery-powered electric motor which drives a propeller. The machine should be designed to avoid some predictable operating problems. It should be neutrally buoyant in the water. The diver should not be able to accidentally start the motor. The propeller should be shielded so that it does not damage the diver, the diver's equipment or marine life.
DPVs are useful for long journeys at constant depth where navigation is easy. Some divers engaged in cave diving and technical diving use DPVs. The machine helps move the bulky equipment the divers carry. It also allows them to make better use of their short underwater time because they have greater decompression requirements due to deep diving.
For many recreational divers DPVs are not useful. Buoyancy control is vital for diver safety: the DPV has the potential to make buoyancy control difficult and cause barotrauma if the diver ascends or descents under power. Navigation in visibility of less than 5 metres using a DPV could be difficult. Also, many forms of smaller marine life are very well camouflaged or hide well and are only seen by divers who move very slowly and are very vigilant.
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[edit] Types of DPVs
[edit] Manta-boards
This is merely an unpowered piece of board (usually rectangular) with two long ropes attached. It is towed by a surface boat. A diver holds onto it and keeps it submerged by holding it at the correct angle like an upside-down aerofoil. It is named after the manta ray fish.
[edit] Diver-tugs, tow-behind, scooters
The most common sort of DPV is where a diver is towed behind it holding onto one of its two handles on its stern or bow. These types of scooters are efficient because the divers rides in the slip stream of the scooter as opposed to a "ride-on-top" which must be ridden and increases drag, which affects scooter battery burn time. Even more efficient are the tow-behind scooters where the diver could wear a harness and backplate or BC with a front crotch-strap D-ring where the scooter is clipped by means of a bolt snap and tow leash with proper length. This way the diver rides above the slip stream of the scooter while remaining horizontal thereby minimizing the energy used to move water (bollard pull).
[edit] Manned torpedoes and similar
These are roughly torpedo-shaped or fish-shaped vehicles that one or more divers (often two) ride. Sometimes they sit astride it. Sometimes it has hollows in its top and the divers sit inside them. One well-known type is the manned torpedo or "chariot" which commando frogmen used in World War II. Similar vehicles have been made for work divers or sport divers; as these do not have a warhead, their bow tends to be pointed for better streamlining. One example is the Dolphin which was made on the Isle of Wight (UK) in the 1970s.
[edit] Subskimmers
These are a sort of RIB (inflatable boat). It is equipped to inflate and deflate itself. When submerged it seals its motor and runs with battery-electric thrusters. Thus it transforms between a fast light surface boat and a submerged diver-rider. There are these makes:-
- Subskimmer. This project was started in the 1970s by Submarine Products Ltd. of Hexham in Northumberland in England and passed through various hands. Its thrusters are on a rotatable cross-arm. There are pictures and more information at that link. The name "Subskimmer" is correctly a tradename owned by Alphachamp.
- Infernus. Infernus is smaller than Subskimmer. Their website is unfortunately only in Swedish. They use the word "subskimmer" as a generic.
[edit] Miscellaneous
One of the first commercially available DPVs was the Aquazepp built by Josef Rupprecht in Munich. The Aquazepps remain especially popular with cave and technical divers who appreciate the robust build quality and flexibity in customisation of the machines.
There are DPV's where the diver holds on in some other way. One example is the Protei-5 Russian diver-rider where the diver is clamped on top of it; there is a similar Russian DPV called Proton.
There is also a DPV called Proteus made in New Zealand, strapped onto the diver's cylinder.
[edit] Wet-subs
As DPV's get bigger, they gradually merge into submarines. A wet-sub can be classed as a small submarine where the pilot's seat is naturally flooded and he must wear diving gear. Covert military operations use (SDV) swimmer delivery vehicles to deliver and retrieve operators into harbors and near-shore undetected.
