Hi Wouter,

Thanks for your concern over the structural integrity, stiffness and drag of my boat, I can assure you that your concerns are unfounded. You describe yourself as a Naval and Mechanical Engineer, I am the latter myself. Indeed I have 15 years of postgraduate experience, 5 of which in structural analysis of automotive and aeronautical structures, and 3 years as a computational fluid dynamicist. The remainder as a designer. So I am no amateur myself.



You start by saying that thinner hulls are faster hulls. You will often hear that thinner sections or hulls produce less drag, that is partly true at 0 degrees angle of attack but not between 3 and 7 degrees where a catamaran operates, here it is better to have thicker sections. In fact for low drag catamaran hulls are too long and thin. If you don’t believe me compare the drag coefficients of two identical aerofoils of say 10% and 20% thickness ratio at 5 degrees angle of attack, you may be surprised by the results.



I agree that having double the number of bows and sterns is detrimental but I hope I have made up for this in my other measures.



I disagree with your implication that an aerofiol shape is not an efficient shape at the transition plane, I have never come across this argument before and would be interested to hear on what evidence you have based this statement. After all catamaran rudders use aerofoil sections and they are surface piercing.



I am well aware that hulls need something to limit the sideways movement (by creating lift), my hulls should generate enough lift on their own without the need for any additional keel, daggerboard or skeg. I stand by my statement but may prove myself wrong in the coming months.



Now for the easy bit, your assertion that my boat is not stiff enough and is too weak is based on you making some wrong assumptions. You have calculated the deflection of a simply supported aluminium beam of some assumed dimensions. Whereas in reality the boat does have a structural mechanism that works in the same way as a dolphin striker and the cross beams are carbon fibre.



The mast, hulls and beams are all carbon fibre that is how the weight is kept so low.



As for the crack about needing to wear a crash helmet when I sail it, you are not the first and will not be the last person to criticize my design, but I have also had plenty of positive feedback too. The design is already a finalist in the International Concept Boat 2002 competition which is judged by a panel of respected naval architects. Winners will be announced in Jan 2003.