Marblehead foil design presents an interesting challenge because the maximum permitted draft is extremely generous. In most monohull keelboat classes, maximum draft is well short of the crossover where additional righting moment gained becomes outweighed by hydrodynamic and structural considerations. For most classes, draft can therefore be regarded as fixed (always go to maximum). In […]
Picking up where the last A Cat post left off, we were contemplating the relative merits of foam core and Nomex style aramid paper honeycomb. Honeycomb is a very efficient structural solution because it concentrates material in effective load paths between the skins. Each cell is braced at the interface with other cells, and there […]
Katana has the same waterline beam as Octave. Canoe body maximum depth has increased by 2.4mm. Maximum cross section area is unchanged, staying at a value that has proven optimal. Moving some midsection area from the turn of the bilge to the bottom of the hull gives a midsection that returns to being as close […]
A sneak preview of our next RM design: Katana. Katana is an evolution of Octave, incorporating improvements in several key areas. The individual changes are small, but sufficiently numerous to cumulatively warrant a new designation. This decision has been made with existing customers in mind as it will give them a clear option when placing […]
As mentioned previously, the choice of tooling material and shape depends on the construction process of the parts to be moulded. To decide on construction method we look at the desired properties of the finished product. The hull can be thought of as a box girder that has to resist global bending loads and […]
Graphic visualisation of hull wave height around a candidate shape. These simulations are very intensive in terms of processing power, so must be used selectively to keep time frames realistic. Fortunately we are in good hands. More will be revealed soon.
Just a quick progress report for those of you who are regular followers. Design work is going well with some very interesting insights already in the bag. A promising hull concept has been identified and tests have started on a family of variants.The opportunity came up to run some more advanced simulations than we had […]
Having chosen a hull and foil geometry, the next task is to execute the carefully optimised shapes accurately and efficiently. Class rules mandate a minimum overall weight of 75Kg for the complete boat with no other restrictions on material and shape above the waterline. Keeping weight at rule minimum is very important for performance as […]
Hopefully those of you who had the patience to follow this series of posts now have a clearer understanding of the state of play in A Cat design. This will be the last instalment on geometry and dynamics. I will cover structures and detailing in the next post.We saw that the boats are powered by […]
When we looked at influences on hull shape we concluded that minimum wetted area is a priority. Minimum wetted area for a given prismatic coefficient is obtained by using semi-circular cross sections. Prismatic coefficient in turn is driven by resistance to bow down trimming moment and by operating speed. Both are essentially functions of the […]
