Canting keel forces

couchsurfer

Super Anarchist
18,322
133
NA westcoast
...so if boats are tradeing up their rams so they can -drive it HARD-,,,whut'll break next?? <_< .......are boats also beefing up the frames :huh:

 

moody frog

Super Anarchist
4,294
112
Brittany
For the information of the canting-keelers bunch.

Some hints from an interview by CourseAuLarge of Hervé Devaux ( the ABN 1 engineering boss) just off the plane from Melbourne.

"The V.O.R rule has not always been interpreted in the right way which was prioritising safety.

Any exemple !

In the hydraulics field, I know that some boats use very high pressure rams.

[b]What for ? [/b]

Given that the force developped by a ram, is piston area x pressure, if you increase pressure, you can reduce the ram size and that of the whole system (including the oil quantity) saving weight in the process.

And

We have rams breakage !

.............

The general talk is about the use of titanium ?

................

It is difficult to know the exact configuration of the rams use. Some mix S/S, titanium, sometimes carbon, in proportions unknown to me. On ABN 1 the ram cylinders are made of titanium and it works. Our rams is "multimetal" (S/S-alum-titanium). On PoC a custom titanium part broke. Strange enough, the use of custom titanium parts in that place was prohibited by the rule...! Still PoC mainly suffered from a problem with the ram carbon shelf. It separated from the hull panel leading to a water leak.

Are they huge constraints in this area ?.

On VOR 70s the rams are only 300 to 400 mm above the keel axis, while the bulb is very heavy. The effort on rams is way over what can be seen on Open 60s : up to 165T on ABN1

.........

 
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couchsurfer

Super Anarchist
18,322
133
NA westcoast
For the information of the canting-keelers bunch.
Some hints from an interview by CourseAuLarge of Hervé Devaux ( the ABN 1 engineering boss) just off the plane from Melbourne.

"The V.O.R rule has not always been interpreted in the right way which was prioritising safety.

Any exemple !

In the hydraulics field, I know that some boats use very high pressure rams.

[b]What for ? [/b]

Given that the force developped by a ram, is piston area x pressure, if you increase pressure, you can reduce the ram size and that of the whole system (including the oil quantity) saving weight in the process.

And

We have rams breakage !

.............

The general talk is about the use of titanium ?

................

It is difficult to know the exact configuration of the rams use. Some mix S/S, titanium, sometimes carbon, in proportions unknown to me. On ABN 1 the ram cylinders are made of titanium and it works. Our rams is "multimetal" (S/S-alum-titanium). On PoC a custom titanium part broke. Strange enough, the use of custom titanium parts in that place was prohibited by the rule...! Still PoC mainly suffered from a problem with the ram carbon shelf. It separated from the hull panel leading to a water leak.

Are they huge constraints in this area ?.

On VOR 70s the rams are only 300 to 400 mm above the keel axis, while the bulb is very heavy. The effort on rams is way over what can be seen on Open 60s : up to 165T on ABN1

.........
.....any link to the interview??

 
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wraith

Super Anarchist
2,195
0
For the information of the canting-keelers bunch.
Some hints from an interview by CourseAuLarge of Hervé Devaux ( the ABN 1 engineering boss) just off the plane from Melbourne.

"The V.O.R rule has not always been interpreted in the right way which was prioritising safety.

Any exemple !

In the hydraulics field, I know that some boats use very high pressure rams.

[b]What for ? [/b]

Given that the force developped by a ram, is piston area x pressure, if you increase pressure, you can reduce the ram size and that of the whole system (including the oil quantity) saving weight in the process.

And

We have rams breakage !

.............

The general talk is about the use of titanium ?

................

It is difficult to know the exact configuration of the rams use. Some mix S/S, titanium, sometimes carbon, in proportions unknown to me. On ABN 1 the ram cylinders are made of titanium and it works. Our rams is "multimetal" (S/S-alum-titanium). On PoC a custom titanium part broke. Strange enough, the use of custom titanium parts in that place was prohibited by the rule...! Still PoC mainly suffered from a problem with the ram carbon shelf. It separated from the hull panel leading to a water leak.

Are they huge constraints in this area ?.

On VOR 70s the rams are only 300 to 400 mm above the keel axis, while the bulb is very heavy. The effort on rams is way over what can be seen on Open 60s : up to 165T on ABN1

.........
une pièce custom en titane s’est rompue.
The rule says all titanium parts must be standard, off the shelf items, so either this remark is wrong, or (shock, horror) somebody has bent the rules (as well as the titanium).

 

Chimp

Super Anarchist
1,161
0
The rule says all titanium parts must be standard, off the shelf items, so either this remark is wrong, or (shock, horror) somebody has bent the rules (as well as the titanium).
You can't expect the engineer from ABN to know everything about the systems in their competitors boats. I suspect some misinformation getting out somewhere. As I understand it the chief measurer made all the teams jump through a lot of hoops before any titanium parts were considered to be production and allowed.

 

MrD

Anarchist
821
0
so cal
Codger said:
This is really a fascinating discussion of "remote" failure analysis. It leaves me wondering if we have more and better engineering talent here on SA than in the FYD offices. Carry on please.
If you'd like some more technical insight, we need to discuss the concept of work. Quoting Marks' Standard Handbook for Mechanical Engineers "Units of Work - When the force of 1 lb acts through the distance of 1 ft, 1 lb * ft of work is done." Work is equal to force times distance, and it is also equal to the change in kinetic energy of a falling object.

The initial force acting is that of gravity and is equal to mass times acceleration (from Isaac Newton, F =MA), which in this instance is the universal gravitational acceleration (G) times the mass of the boat, i.e. W = G * M * D. When the vertical drop is 2 meters (about 6 feet) we get the change in kinetic energy is approximately equal to G * M* 6. When the boat hits the water, the process is reversed and the vertical motion is retarded. This amount of work is equal and opposite to that done by gravity. Figuring the work done over a 1.5 foot distance, it becomes A * M * 1.5, where A = the deceleration. Setting G * M * 6 = A * M * 1.5, we can solve for A in terms of G. It is A = 4G.

So we conclude that a boat falling 2 meters and squatting 1.5 feet below LWL upon impact will experience a force of 4Gs.

QED

This should be quite easy to demonstrate, lift a boat by crane and then drop it into the water from a height of 2 meters. Measure the G forces with an accelerometer. Compare the measured G force to the design G force. Draw your conclusion on the margin of error in the design. The hypothesis to be tested is that VOR 70s were not designed to fly!

>> VOR 70s were not designed to fly

I think you hit it on the head.

Dropping the boat would test it in one dimension. Try driving the crane at 24 knots before you drop it, and have a wave machine generate a 10 foot wave for the boat to fly into while it falls. Oh, and get an oscillation going with the bulb/hull too while you're at it. Then for extra points you can do it while heeling the boat, effectively swinging the keel beyond the 40 degrees from gravity y axis.

One of the things that can get us into trouble in engineering are overlapping cyclic events that cause stress in directions and locations that we don't anticipate. The way this would apply here is having a boat fly off a wave at 20 knots, bow pitches down, bow hits back of next wave pitching up suddenly, and the bulb keeps going. Then while the resulting moment is cycling through it's range for that event, the boat hull lands and creates another event on a different axis. So now you have two significant event cycles occuring at the same time. You end up with a resultant dynamic moment on a axis that can play havoc with your system if you don't design for it.

The pictures show the rams statically mounted to the keel arms, and the rams are shearing off due to fatigue. This would suggest to me that there is some constant twisting or bending going on that wasn't expected. Compression failures look different. Putting steel rams back in works because the steel can handle it, but it may be covering up a weak area of the design. A good question that has been asked is, why isn't that fitting a universal joint, like the guy from Brunel that wrote the article on the front page a few weeks ago suggested?

What appears to me to be happening here is that existing canting systems that have been tested and used on other boats are being re-engineered to be optimized for racing (make it lighter). These boats are field testing the new designs, on the fly. The ABN AMRO boats have had their share of ram failures, its just that they did their field testing before the race started.

I don't believe that penalizing teams for doing on-the-fly field testing is a good thing. They are being penalized enough, and the teams that did it ahead of time are collecting their dividends. After this race, the designers are going to have enough field testing to know how to make them better next time around, and you should see more titanium and fewer problems. And more pre-race field testing.

 

MrD

Anarchist
821
0
so cal
The rule says all titanium parts must be standard, off the shelf items, so either this remark is wrong, or (shock, horror) somebody has bent the rules (as well as the titanium).
You can't expect the engineer from ABN to know everything about the systems in their competitors boats. I suspect some misinformation getting out somewhere. As I understand it the chief measurer made all the teams jump through a lot of hoops before any titanium parts were considered to be production and allowed.
I wonder what those 'hoops' were, and whether it was feasible for the teams to make it happen in a vacuum. i.e., did the company have to make a certain number of them, and have part numbers, certifications, etc.

 

moody frog

Super Anarchist
4,294
112
Brittany
For the information of the canting-keelers bunch.

 

Some hints from an interview by CourseAuLarge of Hervé Devaux ( the ABN 1 engineering boss) just off the plane from Melbourne.

 

 

Are they huge constraints in this area ?.

On VOR 70s the rams are only 300 to 400 mm above the keel axis, while the bulb is very heavy. The effort on rams is way over what can be seen on Open 60s : up to 165T on ABN1

.........
 

.....any link to the interview??
 

HERE

 

but you might have problem as one need to subscribe after 24 hrs of posting.

 

MxThomas

New member
40
0
"Secondary heat treatment methods which alter the properties of a steel alloyby way of reducing resistance to corrosion in sea water and/or increasing

fatigue in variations in sea water temperature around 10C are not permitted."

I know from my own keel that post manufacture heat treatment of the welded structure is critical to relieve stresses induced in the manufacturing processes - as is post machining heat treatment of the machined parts.

The wording is unclear - but appears to disallow processes that would increase the resistance to fatique
Wraith,

it seems to me you missread; if I read correctly then only heat treatments that could affect fatigue or corrossion adversly are banned. So the rule makes sense

 
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