“Wind’s up” calls tunnel engineer Paul Sims, noting a ribbon tell-tale as it begins to flutter and the Drag2Zero wind tunnel at the Mercedes Petronas F1 facility settles into a sustained but subdued roar, blasting air at some 12.5m/s at the carefully-poised form of Olympic pursuit silver medalist and multiple world champion Wendy Houvenaghel.
She is on her second visit of the year to the tunnel, where aerodynamicist Simon Smart, formerly of the Red Bull F1 team, is putting her through a series of tests aimed at reducing the drag she generates as she travels through the air.
It is worth doing because, she says, she hopes to save as much as one second per kilometre over a race distance of some 30km.
The race concerned is the Chrono Champenois in early September, a road time trial, which she plans to ride partly as preparation for the Olympics and partly to give her an alternative event in London 2012 should she not secure a place on the team pursuit squad, her primary objective.
Her machine is a Trek Speed Concept TT with Bontrager Aeolus 9.0 front wheel, Zipp rear disc and Rotor non-circular chainrings supplied by her local bike shop, Ricci Bike Chain in Redruth, Cornwall. It is clamped to the floor of the tunnel via the rear wheel hub, the front wheel being rotated by a drum under the floor to ensure realistic results.
Key to the operation is consistency. Using the same equipment set-up from test run to test run ensures that measured differences must be attributable to whatever is changed between them. There are no overshoes, for example; not because they can’t be worn throughout today’s session, but because they weren’t worn during the previous visit .
For this series of runs the changes being made are to handlebar height, choice of head fairing – Uvex or Giro – and, interestingly, to posture – or more particularly to the degree to which Houvenaghel’s back drops between her shoulders. Allowing her trunk to “sag” between them seems to save a few grammes, perhaps by reducing frontal area, perhaps by improving the shape she makes on the bike. The difficulty facing Smart is measuring the tiny variations in a drag figure that might total just 1.5kg for the cyclist and machine combined. A matter of a few grammes here and there may well be enough to secure the desired improvement, but measuring them reliably is not easy even with the sensitive instruments of the tunnel.
For Houvenaghel, there is another aspect to sitting in the tunnel. Should a tiny variation in posture be found to be beneficial, she needs to be able to ride in that position, which means learning how it feels and memorising it for use on the road.
After some three hours of on-off testing, during which she pedals against resistance to simulate the aero effects of body movement, she climbs off looking suitably tired. So are we; watching from the relative quiet of the cabin is almost more exhausting than being in the tunnel.