The fin at the back of BLOODHOUND SSC is essential for the lateral stability of the Car. In simple terms, it keeps the Car pointing forwards. You can think of it as being like the feathers of an arrow, keeping the pointed end first!
The fin is made of aluminium. It has around 100 bespoke machined aluminium parts in it and over 1,000 aircraft-grade rivets attach the aluminium skin to the fin spars. It will be attached to the Car using bolts that fix it to a ‘shear plate’ which is over 2m long and 400mm wide, yet only 2mm thick in places.
Why is the fin that shape and size?
Since the BLOODHOUND Project started, one of the main things that has altered in the Car’s profile is the configuration of the fin, which has changed from a ‘T-tail’ to a cruciform tail. This is because this shape turned out to be less prone to flutter.
The fin has to be big enough to ensure that the Car is directionally stable throughout the Mach (supersonic) speed range. Changing the fin to a cruciform design resulted in a loss in fin efficiency, so the fin was enlarged and the strake added. It now measures 2 metres high.
The next stage was to finalise the internal packaging of the Car. That let the engineers calculate its centre of gravity accurately and then finalise the design of the fin so that the centre of pressure was in the right place behind it.
The fin was built in a one-off, purpose-built fixture (or ‘jig’) in order to make sure that it didn’t move while it was being constructed, allowing it to be accurate to within one-tenth of a millimetre.
When the Car is moved to do its test and final runs, the fin will be transported in its jig to make sure it doesn’t get distorted or damaged in transit.