Case Study Class 40

[STYacht.com]

At the risk of being flamed, I am starting a thread on my own design. Mainly, I wanted to see if the images could be posted with a bit more clarity. Here goes:

Fig 1 from Part 1

Fig 2 from Part 1

 

[STYacht.com]

Next pair:

Fig 3 from Part 2

Fig 4 from Part 2

 

[Foolish]

Is it or can it be made Cat 0 compliant?

Andy

 

[longy]

Is back of coachroof really assymetrical? Or is that just fault of illustration?

 

[upstatesailor]

Is back of coachroof really assymetrical? Or is that just fault of illustration?

Maybe it is for a dedicated winch and all the lines that run through clutches on the starboard side of the coachroof.

Sam

 

[longy]

Yes, there is a island for the winch, but the overhang of the coach roof above that is not duplicated on the port side

 

[Buckie Lugger]

The coachroof is assymetrical, as the utility winch sits to the right of the companionway. This is instead of putting it in a central pod, like (e.g.) the Rogers or Marin designs.

Foolish: It's relatively easy to upgrade a Class 40 to Cat 0 spec at the design stage. You just need to split up the water tanks a bit more, and add a watertight bulkhead. I'm sure that Doug could do that for you.

The trouble comes when you try to upgrade a standard Class 40 to Cat 0...

 

[Rail Meat]

Nice evolution, Doug! Looks like you have found some interesting, unconventional solutions to the utilty winch and cuddy situation. The chine is a bit different also than in previous views. Me like, until I have to face her on a race course.

 

[alizee]

this pictures shows that the cuddy is symmetrical

 

[moody frog]

this pictures shows that the cuddy is symmetrical

Sorry, I see the companionway and roof-top opening offset to port.

 

[alizee]

Yes, that's the case.

 

[_____]

Doug,

Would you care to explain the choice of the shape for the keel bulb. Is that partly to reduce the chance of picking up up debris/weeds/obstacles?

 

[STYacht.com]

Doug,
Would you care to explain the choice of the shape for the keel bulb. Is that partly to reduce the chance of picking up up debris/weeds/obstacles?

That is right. This boat has been developed to attract Benelux, German, British, and Scandanavian owners for Class 40 racing closer to home. For the promoter and myself, the main races are RBI and OSTAR. The L keel was therefore chosen to avoid having to back down hard to clear garbage bags, kelp (or sharks!)

For interested parties, SYDE has entered talks with Race2Win for construction. The builder Ron Montier seems prepared to give this thing a push by investing in moulds, but we need a couple more deposits.

 

[_____]

That is right. This boat has been developed to attract Benelux, German, British, and Scandanavian owners for Class 40 racing closer to home. For the promoter and myself, the main races are RBI and OSTAR. The L keel was therefore chosen to avoid having to back down hard to clear garbage bags, kelp (or sharks!)
For interested parties, SYDE has entered talks with Race2Win for construction. The builder Ron Montier seems prepared to give this thing a push by investing in moulds, but we need a couple more deposits.

OK. So I seem to have guessed that one right. Not a boatbuilder myself, just a sailor, but my next guess is that this must have a performance trade-off. Granted that even only one incident will easily make up for whatever the performance penalty of this configuration is, how much would it be (if at all).

 

[STYacht.com]

OK. So I seem to have guessed that one right. Not a boatbuilder myself, just a sailor, but my next guess is that this must have a performance trade-off. Granted that even only one incident will easily make up for whatever the performance penalty of this configuration is, how much would it be (if at all).

To my way of thinking, a T keel, that is with the fin near the mid chord of the bulb is more easily optimized for performance. If the yacht is going to spend a considerable amount of racing downwind, it is probably a better configuration anyway. So the choice to go with an L keel is a question of comprimise.

I keep meaning to link here to the press release....

 

[_____]

To my way of thinking, a T keel, that is with the fin near the mid chord of the bulb is more easily optimized for performance. If the yacht is going to spend a considerable amount of racing downwind, it is probably a better configuration anyway. So the choice to go with an L keel is a question of comprimise.

Always a compromise, obivously. I have no idea what configuration would be more easily optimised for performance, or even why some configurations would be easier to optimise than others. No L-foils on the current crop of AC boats, but plenty money spent on T keel and bulb configurations there I guess and none of them seem to look alike so perhaps that is not easy either.

I just ventured shortly into the realm of boatdesign.net and others and recoiled because this design stuff gets very tough and mathematical very soon. Looking at your company website that is an important part of your line of work, so have you done any computational work on this quantifying the difference or not. Surely you did not just like the look of it and thought this may work well enough compared to a T keel. Or is there already a ballpark figure for that.

 

[Speng]

That is right. This boat has been developed to attract Benelux, German, British, and Scandanavian owners for Class 40 racing closer to home. For the promoter and myself, the main races are RBI and OSTAR. The L keel was therefore chosen to avoid having to back down hard to clear garbage bags, kelp (or sharks!)
For interested parties, SYDE has entered talks with Race2Win for construction. The builder Ron Montier seems prepared to give this thing a push by investing in moulds, but we need a couple more deposits.

Aren't kelp cutters allowed by the rule?

I have a question... most of the designers have been making fairly powerful boats for reaching conditions like you might see in an RdR or AZAB maybe but do you think there is a place for a narrower hull form for races like the OSTAR which are more predominantly upwind?

 

[SCARECROW]

Always a compromise, obivously. I have no idea what configuration would be more easily optimised for performance, or even why some configurations would be easier to optimise than others. No L-foils on the current crop of AC boats, but plenty money spent on T keel and bulb configurations there I guess and none of them seem to look alike so perhaps that is not easy either.
I just ventured shortly into the realm of boatdesign.net and others and recoiled because this design stuff gets very tough and mathematical very soon. Looking at your company website that is an important part of your line of work, so have you done any computational work on this quantifying the difference or not. Surely you did not just like the look of it and thought this may work well enough compared to a T keel. Or is there already a ballpark figure for that.

Obviously there is quite a bit more to it than just looking at it. You have to remember that the bulb location and the keel fin location are driven by two separate things. The bulb location ends up where you want the weight from an LCG point of view and the fin's location is defined by the CE and rudder size and location. The biggest advantage of a T foil is that the mass of the keel is approximately balanced around the fin so there will be less Torque applied to the fin structure when heeled over and bouncing up wind which in turn allows for thinner keel fins.

Not sure if this helps or not but at least it will give people something to disagree with.

 

[Buckie Lugger]

The rules really favour wide boats.

The Class 950 allows a narrower boat to carry more water ballast to compensate, but the Class 40 didn't want to go with this. They felt that additional water ballast would eat up too much internal space, and make the boats less comfortable!

There are narrower designs out there. The Owen Clarke boat is a relatively slim (4.15 or 4.3 metres), as is Seb Schmidt's. There are a few others too, I think.