Wouter,
Do U think pre bend makes a boat stiffer and that therefore adds to performance?
No, prebend is nothing more then a trick to fine-tune the stress situation in the mainbeam. Platform stiffness is not affected by it in any measureable way, neither positively nor negatively.
Pretty much the prebending of the mainbeam allows a designer to transmit all the mast step load to the dolphinstriker assemble and have the mainbeam act only as compression strut under the mast step loads. This frees the mainbeam up to take care of the platform stiffness. In effect, by doing this one can more economically load the mainbeam up and possibly make it lighter. It does not however improve stiffness in any way or form. It is a way to make the mainbeam break or damage threshold sit at a higher level or reduce weight on the setup. Neither of which is of much concern on a F18 platform with their huge (heavy) beams.
it effects tow in-out of hulls, it effects canter on the hulls, it effects the twist in the hull, it effects mast hight..gee it effects quite a bit on a catamaran.
All of these things are not affected. Meaning in the sense of being only affected in a totally negligible way.
Do a home experiment. Tension a 8 feet long line between two chairs at home. Now pull the middle of the line 15 mm upward (3/5th of an inche). Do you see the chairs moving ?
No, because the chairs will have moved by 0.0001 mtr. or 1/300th inche. And this is what I mean by being unscientic. Yes, it is true to some effect on two in is taken place, but todays populace is apparently challenged in recognizing the shear negligiability of such an effect. Note here how increasing your (partly inward facing) sidestay tension will have a much bigger effect on the toe-in of your hulls and even that will still be negligiable.
Isn't it wise to ONLY rule on things that actually do matter ? That is my point in this discussion.
Do U think knocking anothers class that you are not involved in helps the sport?
Why do you think that I'm knocking "anothers class" ?
Can I not disagree with some detail and NOT disagree with the overall setup or even disrespect a related group of people.
If I say that 1+1 = 2 am I then disrespecting and insulting all the people who dropped out of their high schools ?
What a weird way of looking at things.
Do U think the F16 rules are perfect?
Who introduced the F16 class ? I certainly didn't.
Why are you guys not confronting me on the actually point of discussion ?
Why is this 15 mm prebend rule in the F18 class rules ?
The rest appears to be only tactics to change the subject.
The F18 rules obviously work..there are such a variety of different shapes/designs but basically they all get to the top mark at the same time. Maybe the 15mm prebend might slightly have something to do with this.
Exactly the same argument can be had with respect to say A-cats where they do not have such a rule.
The fact that a class may or may not be succesful may well not be related to an individual rule like this. It is silly to argue that the succes of the F18 class somehow was related to having this 15 mm prebend rule. That is unless you also want to claim the opposite at the same time that NOT having this prebend rule was the cause of the A-cat class succes.
There is a logical conflict here. And that I call unscientific. It borders on anecdotal.
There is a lot of professionals/experts in the F18 class that are not concerned that rule is in there becuase just maybe they think it is relevant.. or do U know better.
This assumes that some unspecified person in another class is always to be regarded as more wise then a mere mortal like myself. But is it never shown why. I case some are forgetting; my background is such that it doesn't "underdo" for 99 % of the all the catsailors out there. I don't likje writing it down, but I actually do have a formal education in this field, I've done extensive math work on these boats and done simulations. The results of these have ended up in actually commercially build beach catamarans. Additionally I have set up a catamaran class from scratch, including analysing and creating a set of class rules. Maybe the question you pose should be asked in reverse, why do you think that I wouldn't know better ?
But all this is just another "changing subject" thing. Lets get back to the point of this discussion.
Why is it beneficial for the F18 class to have the 15 mm prebend rule ?
Wouter
