[ News
| Homes
| Life
| Entertainment
| History
| Science
| Community
| Shop ]
| Sport
| Culture
| Cars
| Money
| Broadband
| Learning
| Health
| Dating
| Games ]
[ Text Only: Homepage ]
[ Graphical: Channel4 Homepage ]
[ Graphical page ] [ Home | Challenges | About Scrapheap | Forum | Links ] [ Credits | Apply for Scrapheap 2005 ]
[ The challenge and teams | Result | Hogs' diary | Knights' diary | Science | Related links ]
General science
The designs
Pros and cons
Anyone who has seen Saving Private Ryan will have seen a landing craft in action. With their huge ramps and flat bottoms, they can get right up on to a shallow beach and deploy men and equipment quickly. They were critical to the Allies' success during D-Day and were adapted to carry tanks, trucks and supplies as well as troops.
It's an idea which had previously been used by Norman, Viking and Roman armies and was looked at by Napoleon who constructed thousands of flat-bottomed barges for his aborted invasion of Britain.
Modern military landing craft are based on fast water-jet technology, large outboards or hovercraft technology, which means they combine speed, manoeuvrability and amphibious technology, which allows them to drive up the beach after they hit the coast.
Science at work
Displacement, hull shape and buoyancy
The smaller the area in contact with the water, the faster the boat would be – but a larger keel is better for stability.
Hull shape was important as the beach was shelved – the original Higgins Boats (famous Second World War amphibious landing craft), had a flat bottom so they could be beached before deploying troops.
Counterbalancing and centre of gravity
Building a stable platform for a potentially top-heavy craft was critical for handling ability – and no one wanted to drop their car in the lake.
Newtonian physics
Sir Isaac's law of equal and opposite reaction came into play at the deployment stage. The Thirsty Knights drove off their landing craft up the beach – sadly the equal and opposite reaction is to force the landing craft back into the lake – stranding their expert Bill.
In the end, the teams needed to get as much speed out of the craft as possible – sadly for The Thirsty Knights, a propeller is more efficient than a paddle wheel.
The teams had to build landing crafts capable of carrying a vehicle on water to a number of landing points. Each craft had to be capable of embarking the vehicle and the team from a beach, navigating on water and delivering the vehicle to a beach without grounding itself.
The only catch was it had to be powered by the same vehicle it would have to carry and deliver to the beach. The system needed to be quick to deploy and connect as the event was to be against the clock with the fastest team going through to the final.
The Thirsty Knights
Team expert Bill Rutland wanted to use super-heavy pontoons as the basis of the build – creating a buoyant raft which the car could sit on. The raft would have embarkation ramps at the bow and stern. The huge pontoon looked very heavy and full of holes.
To provide drive, The Knights used a metal tube and bearings to create a rolling-road drive system with direct drive to side paddles.
Because the team knew they needed to get close to a shelving beach, they decide to put the weight at the rear of the raft and, for this reason they went for a VW Beetle as its engine is in the back.
A friction drive system operated between the tyres and the roller. The advantage of this system is the speed of deployment and simplicity of operation.
They had planned to use two separate rollers so steering could also be aided by splitting the handbrake cable on the rear wheel and using the brakes and differential to steer each side – rather like a tank. But having only one roller meant they had to use a rudder which could be mounted at either end of the craft.
The paddles fitted to the roller were worryingly small but Bill seemed convinced. Everyone else muttered about cavitation and inefficiency. The team had difficulty gearing down the engine enough and the paddles span at a furious rate, digging a hole in the lake, but providing precious little forward momentum.
On the plus side, Bill and The Knights seemed to have a great time creating one of the daftest ends to Scrapheap Challenge ever.
The Hairy Hogs
Expert Sim Oakley planned to build a floating raft/pontoon using oil barrels as buoyancy. If needed, he could add buoyancy by taking floats from donor vehicles, such as old pedaloes. A deployable ramp was added for the loading and unloading of the parasite vehicle.
For propulsion, Sim used a propeller scavenged from a maritime craft that was connected to the car by an ingenious spline method. As a donor vehicle, Sim used a cut-down 4x4.
The team decided on a framework which sat on top of two lines of barrels. Ramps at one end of the craft gave access to the beach.
Using a four-wheel-drive vehicle meant they got drive from the car directly to the propshaft. Once they drove on to the landing craft, they disconnected the drive to the front wheels and inserted the rear propshaft which had a spline into the propeller's shaft. They then put the 4x4 into gear and the propeller turned.
When they returned to the beach and had to drive to the finish line, they took the spline out of the propeller – reattached it to drive the rear wheels and burned off the ramps up the beach.
It was a brilliantly simple solution but required perfect driving to line up the spline with the propeller – fortunately, Conn, the Hogs' captain, was up to the job.
A propeller is a very efficient method of propulsion on water, which gave the Hogs the speed advantage, and they had less drag in the water as the landing craft was a catamaran design. All round, a great solution to the challenge.
The Thirsty Knights
Pros