The boat has suffered delamination around the aft cross arm resulting in cancellation of her first face to face with the big tri’s.
Next opportunity: the transat.
Hydrofoil like speeds have been recorded by the boat so far: 28knots in 15knot wind…
Doug Lord
–High Technology Sailing/Racing
My dear friend lorsail!
Delamination seems to be a big problem of cats and tris. Of course, the manufacturing process is important. However, one starts to wonder if strength and fatigue calculations have been conducted? In monohulls the forces acting normally are strongly related to the displacement of the yacht. On some yachts, like the Volvo Ocean Race yachts, strain gauges have been used to measure the strains. Hence, calibration have been made to tests. In the case discussed above the forces acting probably are more difficult to predict.
Regards,
Booster
Funny this, I broke the aft beam on my cat this week too…
Luff 'em & leave 'em.
Hi lorsail and Lingley!
Without knowing the forces acting on the cat and tris its difficult to predict the stresses. However, a reasonable guideline regarding the region discussed must be to increase the radii in the intersections of the crossbeams and the hulls.
Regards,
Booster
Hi again!
Lets discuss methods to predict the forces insted of fighting! Let us apply Master of Blaster technology. Simply applying twice the displacement of the yacht to the rig, and calculate the responding forces seems to be no good under this post. This, assumption is based on a so-called step-function that simply says that the highest stresses you can get under long-duration dynamic loads is twice that under static load conditions. Hereby, the front of the load-history is the extreme case, a step. In reality all loads ha a slight ramp in the early stages. Even a nuclear blast has a ramp! Believe it or not, but the nuclear blast is treated as a long-duration dynamic load since its duration normally is longer than one-fourth of the fundamental period of normal structures. Typically, the strength and stiffness of the structure shows the strongest contribution to reacting the external load, while the wheight of the structure is of comparatively less importance. The other extreme case is impulse, where you theoretically have an infinitesimally short duration and a high load value. The load is integrated over time and result in an impulse. If the duration of the load is substantielly shorter than one-fourth of the fundamental period of normal structures this approximation is valid. Often this is the case using conventional weapons. Typically the wheight of the structure strongly react the load and must be a component of the analyses. The step-load approximation probably is valid in case of displacement monohulls. The impulse approximation seems unrealistic in case of non-monohulls as well as monohulls. Here, one probably have to do more detailed analyses, taking the entire load-history into account. The finite element method can be used to study such problems (a computer based method). Most yacht design offices use it. One example is the keel of Ben Lexcen’s Australia II, which Lloyds (or some similar certification registration) found to be OK according to such calculations. By intuition it was hard to figure out how the “upside-down” keel should be able to sustain the load at the hull interface!
Regards,
Booster
Booster: You never cease to amaze. Thank you for your insights, they are a constant joy.
By the way, my friend the Swedish Chef, says chicken is the national dish of Sweden (although he never seems to have success getting the birdie into the pot). Is this true?
Thanks Langbord!
Well, the standards of Swedish Chefs… By the way, compare Smorgasbord to Langbord. There is a some resemblance. In swedish “bord” means table (or on a boat its sides). “Smorgas” can be translated to a slice of bread with butter. Lang can be German and meaning long. By the way, the origin of “lord” is the old anglo-saxon word “lavard” meaning keeper of bread…
Regards,
Booster