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Hull Flexing
But the boat is not solid steel is it?
Cheers MC Peter Wiley wrote: Actually quite a few sailboats *are* much more rigid than you seem to know. You're taking your experience on plastic boats and assuming it is generally applicable. The flex in a steel or ferrocement hull is certainly there (everything flexes to some degree), but it's a fraction of what is common in lightweight toy racing boats which are built to minimal standards of seaworthiness and do, indeed, flex. In fact, the toy boats often break when coming off a fairly moderate wave, as recent Sydney-Hobart races have shown so well. The remark about water being much less compressible than the boat is pure & utter bull****. Even frozen water is a lot more compressible than steel. Also has lower shear strength, tensile strength etc. As to measurement of a boat to 0.005", I can easily believe that this is possible. It's not even all that difficult. Whether there's any point and whether the measurement is repeatable are different issues. Peter Wiley In article , The_navigatorİ wrote: That boats are built differently has nothing to do with it. Sail boats are not rigid nor even near it. To be as rigid as you suggest would probably mean they would not float. If you had ever been in a real boat beating to windward your would know they are *not* rigid. Put your hand on the forstay and look at it unloading when she buries her bow and look at it going tight on the crest (that's revealed by the luff bending). It's loading up/unloading because the boat is flexing. If you ever get the chance (assuming that any boat owner could put up with your big mouth and BS) have a good hard look at the hull of a boat pounding hard to windward and look and feel hull panels flexing. The boat needs has to flex to reduce impact loadings because water is much less compressable than the boat. Once again you reveal your lack of experience with big boats by suggesting otherwise. This typifies your inability to grasp even simple ideas. As for measurent of a boat to 5 thou, look at the coefficent of expansion of say GRP or even Al (which expands muchg less) and then tell me how much a boat moves during a typical day/night temperature cycle. Now you want to tell me it's easy to measure a 5 thou deflection over a 40' boat? Even if the boat builder had access to interferometric equipment (which I'm sure they did not use -as there would be no point in such an accurate measurement) it would still be hard. If you think it's so easy how come you need a 'crew'. Lets face it this is yet more Doug Kig (I'm a ****ing hero) BS. Have'nt you ever wonder why you don't make more money -after all, you are such an expert... My point is that Ella is not a large racing boat and yet still has more than 1 ton rig tension. Cheers MC DSK wrote: The navigatorİ wrote: I'd say It's BS because boats are simply not that rigid Oh yeah, and all boats are built to the same structural standard, aren't they. and it's hard to measure to an accuracy of 4 thou on big objects. Now that is total BS. It costs, but if you're willing to pay, I'll bring a crew and and gear, and show you how to measure movement in any axis on objects of any size & orientation down to 5 ten thousands +/- 1 It's part of what I do for a living, thanks very much. The NIST has occasionally asked me for advice on this type of thing. .... Even Ella has a backstay tension of 2,500 lbs when beating. Gee, and there's no difference between "2500#" and 15,000# is there? Why do I bother answering your posts? DSK |
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