>>The Marstrom A Class hulls are famous for their strength.
This is not a correct conclusion from this test. As a matter of fact Booth made skilled use of how the design parameters behave when loading up a platform.
Let me run through the points
>>Is 2.5m wide, instead of 2.3m, : Does not seriously increase loads on the platform. the increases are accompanied by equal magnitude reductions.
>>The mainsail is 15sm instead of 13.94sm, ; Doesn't matter ; righting moment determines the laod on a platform not the sail area. Amount of sailarea only determines how much more you need to depower a rig at the same high wind conditions
>>The boat weighs 78kg instead of 73 kg, ; This is neglectable
>>And of course it has a 15sm gennaker. Spinnaker does not introduce higher loads on the sidestay than when sailing upwind. It does not load the hulls up more than a jib does on the same upwind course. I haven't done the calcs on mast compression yet. Mast foot and beam however are unimpressed by a spinnaker. The increase in load is simply to small when compared how much a beam is overdimensioned to get the optimal beam stiffness. Beam is never in risk of breaking only flexing to much.
>>The hulls didn't break. : The hulls are build to resist shock and point loads this make the hull alot stronger than necessary for the sailing loads. Only serious point of concern are the sidestay chainplates. These do experience increasd loads to 170% to 200 %
>>The mast didn't break. : It was a M20 mast ; it was designed for double trapeze spi use.
>>The daggers didn't break. : This is interesting, These see increased loads to again 170% - 200 %
>>The rudders didn't break. : Rudders are less critical than the daggerboards. so if the dagger hold ..
>>The hardware didn't break. : Yes well, that is because for small open boats there is pretty much one line of breakstrength used on all boats from 14 foot to 22 ft.
>>I think the issue of strength has been resolved.
Yet but the issue of flexing hasn't. For example It is not difficult to design a mast thatwon't break but it is difficult to design a mast that won't break and flexes in the right way and to the right amount to make a boat well behaved.
>>The boat was used for a couple of weeks max and it has not broken yet.
This is also interesting as indeed damage to beams and other stuff is nearly always the result of metal fatigue and low tension ruptures. These two do require above anything else "time". Still I trust Goran to design his products in such a way that both failing mechanism are unlikely to occure on his boats. Mostly these tow failing mechanisms are the result of lapses in design.
Wouter
