Keeping Cool

DSCF0053

The last weeks have been hectic for Craig and Team-21. With the World Championship only a few weeks away, the real race is to get as much water time as possible to make the final adjustments, and for Craig to find all of the little quirks of his new craft. In Britain there is a serious shortage of suitable stretches of water for testing hydroplanes and for racing. The situation has been made more difficult this year because the very wet recent weather has also reduced light and, with it, the length of time each day when a hydroplane can operate safely.

DSCF0054

The ’21’ has proved to be exceptionally fast and very robust. Few modifications have had to be made and it is now exactly on the correct weight for craft and driver. The engine has presented some challenges and Craig has had to return to the pits on several occasions for the tuners to strip and check the engine.

The difficulty has been a combination of the Class requirements that the engine be a standard engine, and the high performance of the craft. This has resulted in the engine cooling water intake being out of the water too long, leading to overheating problems.

When this occurred during the British National Championship Stage 2, at the end of May, Craig had turned in the fastest lap during practice and then had to return for engine checks when he felt the engine ‘nip’. A ‘nip’ is usually the precursor of an engine seizing up. It can be a result of fine grit getting inside the cylinders, but it is often an indicator of serious overheating.

His engine tuners had to strip down the engine and polish the cylinder bores. They decided not to fit the spare pistons because, on careful examination, the existing pistons only needed a thorough clean before reassembling the engine. Doing this in the open during a downpour was a challenge but the result was so good that Craig dominated the heats with a clear win for the day.

Further intensive testing and adjustments seem to have solved the problems. The trick is to mount the engine low enough that the cooling water intake is immersed often enough to keep the engine within its temperature tolerances at high speed, but to keep the propeller high enough to maintain the optimum thrust line at lower speeds and particularly at the critical cold start at the beginning of a race.

The OSY 400 Class rules are very strict and traditional. In particular, they prohibit the use of any parts, other than steering, that are able to move during a race. If the rules were to permit moving parts, much greater performance would be possible by introducing variable geometry for the engine and for ram-air intakes in the hull, all under control of a computer. Other hydroplane classes do permit some variable engine geometry because the engine has to be trimmed to suit the speed range.

DSCF0139

In any sport, where technology is directly involved, it is always difficult to steer a course between fairness and design improvements and maintain safety standards. The logical development of the hydroplane is the hovercraft and the design origins of the hovercraft were in attempts to create a layer of bubbles along a boat hull to reduce friction. The first hovercraft simply used a large fan to create a cushion of air under the craft and maintain it through the complete speed range. The next refinement was to add a rubber skirt to reduce the effort required to maintain the air cushion. A hydroplane builds up a cushion of air as it gains speed but loses the cushion when the speed drops and the craft banks into a turn. The air cushion also fails to keep the craft clear of the water at all times during a straight high speed leg of a circuit because there is little boundary control over the air cushion. One method of improving the performance of the air cushion would be to use variable geometry air scoops to inject additional volumes of air, particularly during lower speeds and during turns. To make this passive augmentation function reliably, the intakes would have to be constantly adjusted individually and only a computer would be able to do that fast enough.

Adrian Flanagan Sends Best Wishes

AGXNome1

Adrian Flanagan in Nome, Alaska, fitting a new cutless bearing to Barrabas. Early ice southward movement meant that Barrabas had to be winterized and left in Nome through the 2006/7 winter

Adrian Flanagan is preparing to fly out to Nome to get Barrabas back in the water and fully tested before the final stage of his record breaking vertical circumnavigation. As Craig attempts to win the OSY 400 World Championship, Adrian will be on standby for the final leg of his voyage from Russia, through the Arctic ice and back to the UK.

Adrian wishes Craig all the best in the World Championship.

ftnews.firetrench.com

agx.firetrench.com

bb.firetrench.com