Main sponson-arm: February development update
Considerable effort was devoted to the design of the main sponson-arm some time ago, including determining the optimal cross-sectional shape, windtunnel testing it on a tenth-scale model of the boat, and undertaking computational airflow analysis (CFD) in verification. Finite-element structural analysis (FEA) and related work was also done, but then we backed off to concentrate on other aspects of the boat's development. We've recently picked up on the sponson-arm work again, with a view to getting it built as soon as we possibly can, and to this end Mike Coulthard and Tony Maddison are busy resolving the remaining issues.
The main sponson-arm joins the three hulls together. It is a part-aluminium/part-steel structure, with bonding employed extensively in its construction. When completed it will be bolted to the main hull spaceframe, then the sponsons will be bolted onto each end. Three box-section BSI 6082-T6 aluminium spars make up the arm's primary load-bearing span. These will be encased in a symmetrical-section aerofoil ‘shell’ that contributes additional stiffness and strength. The precise shape of the aerofoil was decreed by Mike Green, our chief aerodynamicist.
Loyal, longstanding sponsor Radshape is going to help us build the sponson-arm, but we have quite a lot of work to finish off first. Prior to actually manufacturing the arm, various items of hardware need to be designed and built to treat the parts. Meticulous preparation is everything where bonding is concerned, so special facilities are needed. Radshape has vast experience with bonding, as does Tony Maddison, so the skills are already in place.
In the CAD image above it can be seen that there is a secondary sponson-arm sited behind the main arm. The secondary arm – which is actually two separate arms, port and starboard, so as to leave space clear inside the hull for the engine – will not be required for the initial trials on water, so there are no plans to manufacture it at the present time.
Updates on work on the main sponson-arm will be published here as progress continues.