More Stuff Done Wrong?

An ama bow broke off during the race.  70′ trimaran? Clearly the only time we get to see inside.  Most of us.  Picture below.

Its time again for speculative forensics.   One would assume that if they going to spend a couple of million on it, everything would be perfectly engineered.  I learned long ago that just because they are famous or expensive, it doesn’t mean it was done right.

And again, I can only go off of what I can see here.  If anyone knows any of it first hand, let me know.

First it sure looks like a carbon fiber keel and a carbon fiber band running down each side just above the stringer.  Rule of mixtures error if so.  If you use carbon for global loads, there better be enough of it to do the whole job. Regulars here already know that the stretch to failure of carbon is around 1%.  The other fabrics have much more stretch.  So the carbon would have to fail before the other kinds would begin to help much.

I would not have used a stringer.  They increase the panel aspect ratio, which is weaker.  The closer to 1:1 a panel can be, the better.

That core looks really thin to me.  It looks like 12mm but am sure it couldn’t be that thin.  I would have had no less than 25 mm and maybe even 40mm thick.  I forget what colors of core denote what density.  Maybe someone has it handy.

Finally, that hull skin fabric sure looks like e-glass, or more likely Kevlar.  Dude.  That has already been covered.

They could have called me.

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5 thoughts on “More Stuff Done Wrong?”

  1. Other things possibly done wrong. Four out of five new boats failed within a few days.

    http://sailinganarchy.com/wp-content/uploads/2015/10/post-106437-0-80951600-1446216726.jpg

    Apart from the design concept which I have insufficient information and knowledge to question, I’m surprised to see such a coarse weave and heavily crimped fabric, and no sign of uni in the caps of these longitudinals. Looks like the bargain basement roll of carbon I used to own—-.

    Or perhaps the design concept is sound but Neptune just doesn’t like some people ? Alex Thompson interview:
    http://sailinganarchy.com/page/2/

    Hate to say it Kurt, but “they” are never going to call you. People hate to have their errors pointed out or have somebody suggest a better or more efficient way to do something.

  2. Kevlar does have its place. For instance if the huge cow catcher front wings on Indy cars were required to built of kevlar instead of carbon they would have less tendency to shatter into a million pieces under impact, and Justin Wilson might be alive today.

  3. Look at the compression failure at the outside edge of the bulkhead. I see no cove, no gaps filled, minimum angle cloth. I’m no engineer, I don’t even play one on tv, but shouldn’t the connection between the bulkhead and the skin be the last place to fail, if ever? Wonder what the other piece looks like?

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