Vo70

[guit]

Here's a link to the company that proudly supplied the CK-hydraulics to:
*Team Ericsson
*PotC
*Movistar

http://www.marine-and-hydraulics.com/volvo070-ocean-race-news.html

It is our opinion, that with the systems now fitted to the two Volvo Boats, we will have a chance to demonstrate the high quality of the Rexroth and Hydraudyne components used in the control of the boat.

For the complete (positive) story, please visit the web-site yourself.

This might also be an explanation why Brasil1 has had no (little) problems with their ck-system

 

[Vega]

"we will have a chance to demonstrate the high quality of the Rexroth and Hydraudyne components used in the control of the boat"

 

[RHough]

I'm naive perhaps but why not include a shock absorber in the keel canting system?

Boats have always used hydrodynamic forces and flex of the structure to limit peak loadings. As hulls and rigs get stiffer the loads become localized and local failures are sure to follow.

How long would an off-road vechile last if you replaced the shock absorbers with solid struts? How much heavier would the structures have to be to prevent failures?

I would think that high shock loads from the keel and ballast would tend to upset the sails and reduce power. If the shock loading was limited the flow around sails and hull would would be smoother, and components less likely to fail.

It would be just like a crew on a trapeze, when the boat hits a wave the bodies of the crew flex and the hull and sail are not upset as much.

I would think that there would be no loss in speed, possible weight reduction in structure, and increased reliability. A fixed keel boat has to rely on stiffness of structure, the canting keel boat could be both lighter and smoother since loads would be controlled.

What am I missing?

 

[usa2]

The shock absorber would cause a loss in speed, because as it absorbed the impact, the keel would fall off toward the centerline, and the boat would heel over more during this, and then you would need to pump the keel back up again. Hell, if they built the supporting structures strong enough and had the proper hydraulics in there, you wouldnt need a "shock absorber". Fixed keels dont have shock absorbers.

 

[RHough]

The shock absorber would cause a loss in speed, because as it absorbed the impact, the keel would fall off toward the centerline, and the boat would heel over more during this, and then you would need to pump the keel back up again. Hell, if they built the supporting structures strong enough and had the proper hydraulics in there, you wouldnt need a "shock absorber". Fixed keels dont have shock absorbers.

I wasn't thinking about a suspension system that would allow the keel to move during normal sailing loads. The system would only allow a bit of movement when loads went beyond the normal envelope. The keel would be held against the limit stop by the ram as it is now, the spring and shock absorber system would be preloaded against the stop with the design load. It would only flex if that load was exceeded. It would not require the ballast to be moved again, the energy would be transferred to the spring and the spring would return the keel to its trim position.

An accumulator like those used in pressure water systems to reduce pump hammer would do the trick. The spring portion would be a gas compartment under pressure, the size of the orifice between the ram and the accumulator would control flow rate. Below the set deflection point nothing moves, when the load goes high, the keel forces fluid in to the accumulator and as the load peak passes the fluid returns to the ram.

 

[RHough]

Seven boats.

Two didn't finish leg 1, one had keel problems but finished.

Leg two isn't over yet and, one boat is out (keel system failure), 1 spent days in port for repairs (hull/deck/cockpit failure), one has a mast coming apart ( can't hoist main above 3rd reef), one of the boats that didn't finish leg 1 had to stop for repairs but continued (keel system), the other boat that didn't finish leg 1 is in port again to see if she can be repaired (hull/keel failures).

I don't think this reflects well on the state of yacht design. Of seven starters only two have not had major problems, and the race isn't even half over. One of the problem was collision related, all the others are just sailing.

When did designers forget how to build seaworthy boats?

Pretty sad to see one team and their trial horse sailing to new records while the other boats come apart.

Anyone want to buy a Farr?

 

[usa2]

"When did designers forget how to build seaworthy boats?"

When they found a rule they thought they could get around. (Actually i guess it was just Farr who did.)

They need to have a maximum weight for the bulb, as many others have said.
They also need to have minimum specs for the keel supporting structure that is capable of withstanding shock loads of up to 15 times expected.
The rams should be over spec'd the same amount.
Im just throwing a number off the top of my head, because 6 times safety factor wasnt enough and 10 times is common but has never been used like this before, so if 15 times is too much, oh well. They need at least one overbuilt part on those boats.

 

[sheila728]

Hello! I was wondering if anyone can help me? I'm looking for information on a cruise ship called The World? I believe it has condos in it? It is presently docked in Galveston Tx. Can anyone direct me to a site where i might find what i need? Thank you Sheila728

 

[usa2]

http://www.residensea.com/index.html

 

[RHough]

"When did designers forget how to build seaworthy boats?"

When they found a rule they thought they could get around. (Actually i guess it was just Farr who did.)

They need to have a maximum weight for the bulb, as many others have said.
They also need to have minimum specs for the keel supporting structure that is capable of withstanding shock loads of up to 15 times expected.
The rams should be over spec'd the same amount.
Im just throwing a number off the top of my head, because 6 times safety factor wasnt enough and 10 times is common but has never been used like this before, so if 15 times is too much, oh well. They need at least one overbuilt part on those boats.

I don't agree.

I think the rule is elegant. There already is a maximum weight. The designer has the choice of putting that weight into the hull or the ballast bulb. Every kilo saved in the hull is an extra kilo in the bulb.

It is a great rule! Get greedy and skimp on hull safety factors and your boats end up slower than if you had built them stronger in the first place. How much faster do you have to sail to make up for mid-leg repairs?

In the days of the Whitbread 60's, does anyone remember who designed the hulls that were delaminating? Was it all the boats or just one design house? I don't remember.

It looks like the ocean still rewards more conservative designs, even within the extreme framework of the VO70 rule.

Just because one designer can't seem to get it right, that's no reason to change the rule.

 

[Vega]

I think the rule is elegant. There already is a maximum weight. The designer has the choice of putting that weight into the hull or the ballast bulb. Every kilo saved in the hull is an extra kilo in the bulb.

This rule tends to give fragile boats. The designers scrap everything they can in the hull, hopping that the boat doesn't come apart, to put more weight on the bulb. Later the sailors will pay the bill.

I say that the bulb weight should be fixed and that you should have a minimum weight, not a maximum weight, one that allows the designer to make very strong boats, leaving away the temptation of gaining speed at safety cost.

 

[RHough]

This rule tends to give fragile boats. The designers scrap everything they can in the hull, hopping that the boat doesn't come apart, to put more weight on the bulb. Later the sailors will pay the bill.

I say that the bulb weight should be fixed and that you should have a minimum weight, not a maximum weight, one that allows the designer to make very strong boats, leaving away the temptation of gaining speed at safety cost.

I see exactly the same problems with a minimum weight rule. Designers will still try to put a high percentage of the weight into the bulb. There would be no effective limit to RM, the loads on everything will go higher. The good design houses will still build boats that don't break and sail well, other designs will have failures. The only thing that will have changed it the speed and and load at which the failures occur. The sailors would be exposed to failures at 35-45 knots rather than 25-30 knots.

Traditional designs got slow when driven upwind with too much sail, they were faster with lower rig loads. When you combine greater sail carrying power with brittle structures you get a boat that has a structural speed limit. The sailors must learn to keep the speeds within the envelope, just as a pilot must control the loads on an aircraft. Too many G's and something breaks, so the pilot has to control the loads. It is just another skill that the sailor needs to learn. A G meter and a black box might serve the sailors well. The designer uses a safety factor of some magnitude and the boat gets rated at perhaps 1/2 of the design limit. When the peak G loadings hit that point the sailor knows it is time to reduce the loads or risk failure. If a boat suffers a failure, the black box data could be used to better understand the loads involved.

I think the maximum weight rule is an excellent way to reduce loads and keep the boats safe for the crew. The potential speed of the boats is limited by the maximum weight.

 

[Vega]

I see exactly the same problems with a minimum weight rule. Designers will still try to put a high percentage of the weight into the bulb.

I have said:

"I say that the bulb weight should be fixed and that you should have a minimum weight"

If the weight in the bulb is fixed they will not try to put neither more nor less, because then they will be out of the rules

So, all the other (minimum weight) of the boat will go to the hull and mast. If this minimum weight is on the safe size, as it should be, they will have to be very poor designers to make an unsafe boat.

 

[RHough]

I have said:

So, all the other (minimum weight) of the boat will go to the hull and mast. If this minimum weight is on the safe size, as it should be, they will have to be very poor designers to make an unsafe boat.

If you fix the bulb weight and make the total minimum weight high enough to try to guarantee safe boats, the design challenge is reduced. The VO70 rule as it stands seems to show that it is possible to build safe boats to the rule and also that it is easy to create marginal boats.

The only way that new ideas and structures will get developed is if the design is challenging.

As maximum weight is reduced the boats must get slower. Efficient structures with very high strength to weight ratios will have to be designed to keep the power up and win races.

Moving and or variable ballast has given the designers a new challenge. The good designers and engineers with rise to the challenge, the designers that can't figure it out will do poorly ... as it should be.

Changing the rule so that mistakes cannot be made kills the design, it reduces the variables so traditional methods can be used. That would not be progress in my opinion.

 

[Vega]

Moving and or variable ballast has given the designers a new challenge. The good designers and engineers with rise to the challenge, the designers that can't figure it out will do poorly ... as it should be.

Yes...in Portuguese we have a popular saying : "quem se lixa é o mexilhão", that means - The ones that are f..... when things go wrong are always the less important - that in this case are the sailors. If the f...... guys, when things go wrong, were the designers, I would gladly agree with you