DIVER-POWERED SUBMARINES present many of the same difficulties as any submarine. They are flooded inside and operate at ambient pressure, but the pilot still needs an air-supply, and can get through that supply at an alarming rate when pedalling at full speed.
These subs need control surfaces to turn, climb and dive, and a control system to operate them.
The sub must be able to manoeuvre, but not so quickly as to make it unstable and unable to hold a course.
With a limited operating depth, there is no need for adjustable ballast tanks, but diver-powered subs still need to be kept close to neutral buoyancy and trimmed to stay horizontal and the right way up, using weights and foam.
Buoyancy is also affected by the pilot’s exhaled air, which has to be vented away from the hull.
Navigation is limited by what the pilot can see. This is considerably less than a diver can see, because the pilot cannot simply tip upright or twist to expand the view.
I arrive at the first European International Submarine Race on the first of three race days. Some of the subs have already passed their safety tests, and Talon 1, from Florida Atlantic University, has snagged a buoy and damaged a fin on a practice run.
As the other teams submerge their boats to show that the pilot can exit in less than 30 seconds, and that releasing a dead man’s handle will allow a marker buoy to float to the surface, Talon 1 is ashore undergoing repairs.
The race venue is QinetiQ’s Ocean Basin in Gosport. This giant freshwater tank, 120m long, 60m wide and 5m deep, is usually used to test models of ships for the Royal Navy.
Under the direction of race organiser Dr William Megill of Bath University, QinetiQ’s dive team have laid out a course that runs up the right side of the tank, through a sweeping turn, then back along the left side through a series of slalom gates. The course is 175m long.
Straight 100m sprint races have been held biennially in the USA for more than 20 years, but the European race is not only longer but introduces navigational and manoeuvring challenges.
The first sub to complete the course is Omer 8 from École de Technologie Supérieure in Quebec. It consistently starts at full speed, because the team are on a mission to set a record.
Talon 1 re-enters the water during the morning, making a successful “safety” run before stepping up the pace.
Throughout the first racing day these two look likely to be the only teams to reach the finish line.
The others variously get lost, breach, crash into the bottom or walls, snag buoys, accidentally release their marker buoys, lose their hatches and break their drive systems.
After getting lost three runs running, Archimède V from École Polytechnique de Montréal finally makes a clear run towards the end of the afternoon, only for its gearbox to fail on the final run of the day.

DAY TWO BEGINS WITH the slalom part of the course being narrowed, and success for the British interest, Minerva from the University of Bath, though the team are taking it slowly to prevent their chain-drive breaking.
They achieve more slow completions, but also repeated chain problems when pilots attempt to pedal harder.
Omer 8 and Talon 1 maintain the proficiency they showed on the first day, completing most runs and taking turns in first place.
Talon 1 is slightly less consistent as the crew take turns to drive and experiment with different fin configurations, while Omer 8 with a dedicated pilot looks stronger all the time.
Having also suffered an early drive-system failure, Wolverine the Submarine from the University of Michigan is finally returned to the water in the afternoon and manages two clear runs with no faults, moving above Bath into third place.

THE THIRD AND FINAL DAY of racing sees the slalom narrowed further. Archimède V is back in the water with a repaired gearbox and steadily improving, as long as the team don’t get lost.
Minerva manages a number of successful runs and slight improvement in speed with its realigned drive chain, and gains a place on Wolverine, which suffers a number of aborted runs.
Having settled on a preferred fin configuration, Talon 1 continues with steady good runs, though the team continue to take turns to pilot.
Since the start, Maroon Harpoon has made plenty of runs, but all marred by a stability problem that causes rolling and breaching. The Texas A&M team have cut additional vents in the polycarbonate dome to encourage air to escape, but to little effect.
Omer 8 also makes an uncharacteristic mistake, crashing into the tank floor at high speed, snapping a fin and wrecking the ultra-fine propeller blades.
The Quebec team hastily recover it and set to work on poolside repairs, returning to racing later that morning to just keep their lead over Talon 1.
For the final afternoon race, each team gets one attempt at completing two laps of the course. A single lap has proved difficult for some submarines, however, and the way from the finish line back to the starting gate is not marked – none of the pilots is familiar with navigating this section.
Minerva completes the first lap and is looking good as it turns across the pool for a second, but turns too far and towards the central pillar. Seeing it ahead, the pilot turns the other way, again too far, and ends up behind the finish-line safety net.
Wolverine has completed several successful runs, but quickly aborts against the bottom of the pool.
Archimède has a good first lap, looks confused navigating back to the start but manages it and begins a second lap, only to lose the course by the timing gates.
Everyone has been wishing Maroon Harpoon luck. It’s the only sub yet to complete a lap. It has its best start yet, but then the stability problems reoccur and it veers off-course and breaches.
Omer 8 is ahead on points, so taking it easy and just finishing would secure an overall win. But the team also want a speed record, and as usual the sub takes off at a stunning pace, slowing marginally for the turn and the slalom.
Omer 8’s return to the start line is precise, and then it’s hard acceleration to the timing gates again, continuing through a second lap. Omer 8 is the first to complete the double lap, with only Talon 1 left to run.
It’s another fast start, though the sub’s greater size makes it hard to guess which is fastest. Completing the first lap, Talon 1 turns across the pool and cuts the corner between the start line and the first timing gate. This route is perfectly within the rules, so although Talon 1 isn’t running at maximum speed through the timing section, vital seconds have been shaved off the corner.
Talon 1 continues to complete a second lap ahead of Omer 8’s time to win the afternoon’s extended race.
Teams recover their boats while times are checked, judges add up the points and the winners are decided.
The overall result is close. Omer 8 beat Talon 1 to first place by 83.3 points to 82.7, with Minerva third with 68.1 points. Just as important to the Quebec team, they set a new speed record on their second and final lap, hitting 7.03 knots between the timing gates.
Talon 1 also achieved a personal best of 6.9 knots and Archimède V 4.94 knots.

Each of these diver-propelled torpedoes has unique features:

Hull built from a cork and glass-fibre composite, so buoyancy, stability and trim is largely in-built. The pilot’s view is through a large two-part polycarbonate window. Twin-blade contra-rotating propellers reduce roll. To reduce the risk of getting stuck against the tank bottom, Minerva has no lower fins, so should it ground the pilot has
a chance to recover. Weak point is a chain-drive with a tendency to jump when pushed hard. The other subs have purely geared drives.

Looks similar to Minerva, with contra-rotating props and a similarly sized yellow hull. Big difference is a set of stepping pedals, designed for greater push in a smaller space. This failed under hard load, to be replaced by a cycle crank. The team even sawed the heels off a pair of cycling shoes to get the necessary clearance inside the hull. Aborted a few runs, tipped nose-down against the bottom of the tank.

A sharper and larger sub, so that any of the team can fit in it. Tiny ducted propeller geared up to turn at a much higher speed than the others’ props. Stress on the gearbox led to almost a day under repair, but once back in action Archimède V had a few successful runs between getting lost.

Powered by a single twin-bladed propeller with scimitar-shaped blades. The hull has a side-entry hatch; the other subs have entry from above. Side entry allows the pilot to be strapped tight against the roof and thus able to pedal harder. Hull is a kevlar-and-foam sandwich with a large streamlined dome at the front. These details may relate to the sub’s tendency to breach out of control, though it had been runner-up to Talon 1 and Omer 8 at the 2011 US race.

Winner of the 2011 US race, Talon 1 has a single twin-blade propeller driven by a geared crank and plenty of leg-room for a pilot up to 6ft 2in tall from its “Gertler” oval cross-section, which also provides good roll stability. Long flat windows along the sides assist with navigation. The only sub with a compass, the ball of which also provides a pitch and roll indication. Buoyancy is so finely trimmed that the vessel just about floats at the surface as the pilot slips in, and is horizontal and neutral under water. Other teams practise in pools and smaller test tanks, but the Florida club spent time off beaches.

The carbon-fibre hull is relatively tiny, and the small pilot’s head is jammed right up into the polycarbonate nose. Propulsion is a cycle crank geared to a twin-blade prop crafted from slivers
of extremely hard stainless steel, mounted on a computer-controlled variable-pitch hub that can be reprogrammed between runs to optimise performance. Pneumatic control system for the hatch
and dead man’s switch. It will automatically release both if the pilot’s air supply drops below 500psi.

Bath University engineering lecturer and race organiser Dr William Megill began planning for the European International Submarine Race for student teams six years ago. The next race will be in June 2014, www.subrace.eu.
Bath became involved when a student approached Megill to build a submarine as an engineering project. The team failed to make the 2005 international race in the USA, but competed in 2007, 2009 and 2011.
Megill advises that while designing and building a submarine is a student activity, a team needs the backing of a member of staff to use their school or university’s engineering facilities. His experience is that teams need two academic years to design and build a submarine, so would-be 2014 competitors would need to start planning now.
Some students are involved just for fun, while others take an aspect of the submarine design and engineering as course projects. Most teams also need to raise sponsorship for materials and travel.
Non-professional team-members who will be in the water need a basic diving qualification. Each team’s diving must also be supervised by at least a PADI Divemaster or BSAC Dive Leader. Professional team-members need to be HSE-qualified.
If you are not a student or can’t wait until 2014, the next race in the USA is scheduled for June 2013 and is open to all.

Liddiard’s top tips for submarine-racers
  • As with any engineering project, keeping it simple makes a diver-powered sub easier to build, more reliable and easier to fix if it breaks.
  • The subs with better visibility for the pilot had fewer aborted runs from getting lost, and fewer points deducted from missing markers.
  • Choice of diving mask has a big impact on visibility. Many current diving masks are optimised for looking down towards the chest, perhaps at the expense of looking ahead and up or to either side.
  • The teams all said that regulator performance was not a limiting factor, but I suspect that this could change as higher average speeds are maintained and race distances extended. It is not just a matter of the performance of the regulator, but also a clean gas flow between first and second stages.
  • Have a good stock of spares. Fins and propellers can be damaged by collisions with the pool bottom and sides and snagging buoys. Chains and gearboxes break from stress.
  • The quicker a sub is ready for another run, the more runs a team can make. Turnaround can involve getting the pilot in and out, rewinding the marker buoy, changing the air supply and refitting the hatch.
  • The teams with more experienced divers and more in-water practice with their subs turned round much faster. They also made fewer errors, such as accidentally releasing the marker buoy, failing to secure the hatch, getting lost on the course, getting stuck on the bottom or breaching.