Design Costs

ErikG ---

I believe a mast was broken in the AC this past year. It is possible that this failure was an attempt to "save face." The crew had a choice of losing the race or of putting more stress on the mast than the engineering showed was prudent and perhaps winning. (but then I am not privy to the exact reasoning of the crew or to the engineering of the mast.)

As for carbon fiber being leading edge. It certainly has many properties that often make it the best choice, but it is not leading edge for 2 reasons:

1) the properties of carbon fiber are well known and

2) the engineering equations have been solvable in the numberic sense for decades.

Certainly, the first carbon fiber mast was leading edge. As were the first use of a mandel wound mast, the first use of woven sleeves for masts.

Certainly, the first use of twin hulls was leading edge ....

I regard leading edge as a new direction - hence "leading."

I think that Timm has captured an important part of your view of leading edge as: when you don't have the time or money to do what engineering or testing is necessary.

I think that is a valid definition of leading edge.

 

Stephen, In case you did't know, the 12 meter hull scantlings were done to a scantlings code eg Lloyds.

 

Guest, could you do us all a favour and just sign off on your msgs, it just makes it easier to read the threads and to feel that you are actually discussing with a person.

My idea of leading edge is when you venture into untested areas where there are no good data or available testing to verify your calcs.
IE going faster than anyone else OR doing it differently than anyone else OR doing it in the most hostile envirnment where you can never be certain what the conditions will be like, this is all leading edge to me.

As for offshore raceboats there is NO way other than to actually building the boat itself and measure ALL the stresses on that particular config to really KNOW whats going on and then only at the windspeeds and wave heights and patterns ancountered during testing. [not very practical imho]

Testing a hull in a towing tank is pretty far from real life in the southern ocean! Dropping from the top of a wave in 40 knots of wind and in braking seas, how would you set up proper calcs for it? And if you really could do that it would only be valid in a situation like that.
We all know that FEA and CFD have a long way to go until they are a perfect replacement for doing tank and real life testing. The doulble knuckle bow in the last AC failed in CFD but worked in real life and in the tank.

Quote:"What goes for bridges goes for airplanes and boats.
In high prestege racing boats being second is worth nothing so some people break the boat to save face."

And saying that a failing mast at the AC WAS to save face is not really relevant is it? Since you don't KNOW that was the reason (which I doubt), you have to have more "beef" than that, do you?

Have you ever raced with a bridge? Did you win?

Being able to solve for strength in a static situation is worth diddley if your ultimate stress is WRONG! When you can't be sure of what the ultimate stress might be you generally assume a safety factor, but how big, and how can you be sure that it's not to small?
Static calculations and real life is not the same now, is it?

As I'm no pro and still learning I do appreciate being corrected when I'm wrong, but I state my belief when I think I'm right!

Enough rambling now... Gott go buy some Cristmas dinner stuff...

Merry X-mas all!!!

 

Yacht Masts & fly rods

Interesting aside on the materials engineering aspects of Carbon Fibre (graphite) for both fly rods and yacht masts.

Basically both are tapered cylindrical tubes.

The manufacturing processes are also similar I belive in that the carbon fibre cloth scrims are pattern cut and wrapped around a mandrell and impregnated with resin - then baked/cured and "popped" off the mandrel.

I think engineers are able - using the known strain to failure ratios of the parent material (Carbon Fibres in the vicinity of 1%) to calculate potential loadings using the Euler wall buckling theorem.

Snapping masts - breaking fly rods- just a fact of life - engineers or not - when your on the water Shyte happens - fish do unexpected things as do boats and waves sometimes.

On anothr unrelated topic mentioned within this thread - Lloyds (of London) design specifications....you wouldn't get me building a boat to lloyds specs - to my mind they are under engineered for oursea conditions at lloyds specs. There have been the odd failure here of commercial vessels built to Lloyds specs when operated above their particular rating in certain sea states conditions...

Split chine seams was one that almost bought a fairly well known local luxury liveaboard 100ft + charter vessel undone not so long ago - I see she's now for sale and the owners comissioned another newer (bigger) vessel, so no names no packdrill. I just hope he has the smarts to specify something a little stronger than Lloyds specs this time round.

Cheers!