Vo70

[RHough]

Originally Posted by Van Nostrum

So somebody else has already designed a system with a rotating forward foil which is used to steer the boat in tandem with the traditional rudders towards the stern of the vessel?

The benefit of having a foil forward is that the vessel will be a lot more controllable, the result of being more controllable is that the boats will not be placed under as much stress (the skippers will be able to relieve the stress before it builds up). All of these breakdowns can be attributed to an excess of stress in the hulls of these vessels. If remove the stress the breakdowns will not occur, simple right?

Posh.

The existing boats have methods to reduce stress. They just weren't used.

If some idiot tries 7G maneuvers in a plane that is designed for 3G he dies.

If some idiot rates a design for 7G and has no safety margin, they might be a murderer.

If the rigs and sails weren't capable of stressing the hull or steering system to failure there would be no problem. Expecting racers not to sail a boat as hard as they can or the design allows them to is folly.

The bulkhead failure after one of the rams failed on Movistar is a good case. Did the sailors fail because they didn't back off or did the design fail because it wasn't strong enough to continue after one of the rams failed?

The steering arm failure on is either poor design or poor judgement. Since when should an ocean racing boat have failures when it's being sailed in only 40 knots? Not racing in 40 knots is not an option, so it's a design failure.

One thing Mr. Van Norstrum is right about is that with a forward foil , at least on CBTF boat, the boat has much better control in broaching conditions. This according to CBTFco and many people who have sailed a CBTF boat in racing conditions. It is a proven characteristic of the type.
I just learned the ABN1 had a "massive broach" which caused her steering assembly damage; it may or may not have been prevented by using CBTF. Unfortunately, the Volvo rules prevent the use of CBTF with a fairly low cant angle of 40°.
------------------
All our second guessing and speculation is pointless now but it is becoming increasingly clear to me that something must be seriously wrong and I don't think it's with the sailors; the failures of so many boats-mono's and multies- structurally over the last few years is ominous in what it says about design and construction, in my opinion.
Maybe, before there is loss of life, there should be a 100% "stand down" and a major investigation by sailors, designers and builders to try to detemine if there is some common denominator to these seemingly different failures.

[mholguin]

Movistar failure derived from jumping out of a 5 meter wave... a bit extreme under the speed they were doing (20+ knots)

[Van Nostrum]

Originally Posted by mholguin

Movistar failure derived from jumping out of a 5 meter wave... a bit extreme under the speed they were doing (20+ knots)

If they jumped off a wave and broke it when sailing downwind then they had no chance if they tried to sail it upwind in rough conditions.

I believe they lightened the boat after they set the 24 hour record by removing important structural elements from inside the hull.

In hindsight, perhaps a rotating forward foil steering in tandem with the rudders at the stern of the boat wouldn't have helped prevent this breakage, however I am certain that ABN Amro and Sunergy and friends could have avoided their breakages if they had the additional control that a rotating forward foil would have allowed.

[koen]

Does anybody know why the australian boat has two sort of fences on the hull close to the rudders?


http://www.teamsunergy.com/images/la...11-2005_62.jpg

[Van Nostrum]

Originally Posted by koen

Does anybody know why the australian boat has two sort of fences on the hull close to the rudders?


http://www.teamsunergy.com/images/la...11-2005_62.jpg

Taking a guess, though maybe they don't want the back of the boat to slide around when they turn the helm? have seen some open boats (I think they were mini 650's) with daggerboards at the back which they use for downwind sailing.

[koen]

Yes but minis are steered by autopilot while these VO70's are steered manually

[Van Nostrum]

Originally Posted by koen

Yes but minis are steered by autopilot while these VO70's are steered manually

perhaps they don't trust their driving?

[usa2]

"Movistar failure derived from jumping out of a 5 meter wave... a bit extreme under the speed they were doing (20+ knots) "
"If they jumped off a wave and broke it when sailing downwind then they had no chance if they tried to sail it upwind in rough conditions."

Actually they would be fine going upwind, as they would not be going 20 knots. They can probably only go about 12 knots upwind on a good day.(i.e., flat seas). Downwind if they launch themselves off a wave they will land flat and there will be enormous forces subjected from the blunt shock of landing. They have much more power off wind than on it, so they might suffer more damage offwind.

[RHough]

It seems so simple to me. If a boat is able to sail downwind at 20+ in 40+ true, you can bet that sailors will do just that. If a typical wave height in 40+ wind is x metres, then you design the boat so it can be dropped repeatedly from x metres without damage. That's the way its going to be used, that's the way it should be designed.

[SailDesign]

Originally Posted by RHough

Posh.

Don't you mean "Tosh!"?

Originally Posted by RHough

The existing boats have methods to reduce stress. They just weren't used

Do tell us what these methods are - I have not heard of any, and would love to incorporate stress-reducers into my next design.

usa2 - you're right - upwind is not such a problem.

Steve

[usa2]

"If a boat is able to sail downwind at 20+ in 40+ true, you can bet that sailors will do just that."

Well, in theory, the Volvo Open 70 can do the windspeed off the wind up till 42 knots. That doesnt mean you go out there and sail 42 knots in 42 knots of wind. The sailors are supposed to throttle back to prevent the boats from breaking. Just because your nice shiny new Open 70 can hit 42 knots and can sail over 500 nm a day doesnt mean the sailors should push her to the max in a storm or gale. You need to finish the race in order to win.

Seems to me the sailors would know or should know from the designer /engineers what the "limits" are and should assume the designer/engineers know what they are talking about. I'm 92.3% sure that the boats were sailed using that information.
I rather doubt they'd just as soon die at sea as finish the race....
It's inconceivable to me that a Volvo 70 should fail in the conditions and at the speeds that have been described especially considering what they are likely to encounter on the rest of the trip.

[RHough]

Originally Posted by SailDesign

Don't you mean "Tosh!"?

Do tell us what these methods are - I have not heard of any, and would love to incorporate stress-reducers into my next design.

usa2 - you're right - upwind is not such a problem.

Steve

The existing method on the 70's is exactly the same as every boat that you've ever designed. The nut behind the wheel.

If the boat is not controllable at or above a certain speed, throttle back or ease the sheets.

I've always found good seamanship to be a great stress reducer.

I'm surprised that you bit at that troll.

[RHough]

Originally Posted by usa2

"If a boat is able to sail downwind at 20+ in 40+ true, you can bet that sailors will do just that."

Well, in theory, the Volvo Open 70 can do the windspeed off the wind up till 42 knots. That doesnt mean you go out there and sail 42 knots in 42 knots of wind. The sailors are supposed to throttle back to prevent the boats from breaking. Just because your nice shiny new Open 70 can hit 42 knots and can sail over 500 nm a day doesnt mean the sailors should push her to the max in a storm or gale. You need to finish the race in order to win.

You make my point. Sailboat racers are like teenagers. Designers should know that.

If the boat will sail at the windspeed up to 42 knots, you can bet that the crews will do it.

F1 engine builders don't tell drivers "Now Mikey, if you run the engine past 20,000 RPM it will break. Don't do that." They put rev-limiters on the engine so Mikey can't over-rev it.

42 Knots is the top of force 8, bottom of force 9:

Force 8: 34-40 knots, Gale, Moderately high waves (5.5 m)
Force 9: 41-47 knots. Strong gale, High waves (7 m)

If the design point is 42 knots boat speed in 42 knots wind, the design should handle the expected 5.5-7 metre waves. You don't get 42 knots and flat water in the ocean.

The boat shouldn't break within it's design envelope.