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  #331  
Old 05-20-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Jeff, while I agree with your premise (that a well-design boat from a lucky or talented designer does not have to change balance when heeled) I totally disagree with your ice cream cone analogy.

The analogy should be to a cheese wedge, a slice of cake, or something similar and NOT something with the symmetry of an ice cream cone. The effect of balance and rotation on a symmetrical body like an ice cream cone, will be totally unlike that on a "wedge" like a boat.

And when all else is daid and done, a well balanced hull, one that stays in balance in a wide range of conditions including heel, is still as much a gift from the gods as it is the work of any designer. Even Bob has said, onceuponatime, that he was pleasantly amazed at how well some boats balanced.
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Old 05-20-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

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This is a promotional video by Benetau: can't you see the difference?
Yeah...the chick was doing most of the driving. Love it.
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  #333  
Old 05-20-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

"as much a gift from the gods as it is the work of any designer."
I don't believe that for one second. Been at it far to long to go for that.
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  #334  
Old 05-20-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Quote:
Originally Posted by hellosailor View Post
Jeff, while I agree with your premise (that a well-design boat from a lucky or talented designer does not have to change balance when heeled) I totally disagree with your ice cream cone analogy.

The analogy should be to a cheese wedge, a slice of cake, or something similar and NOT something with the symmetry of an ice cream cone. The effect of balance and rotation on a symmetrical body like an ice cream cone, will be totally unlike that on a "wedge" like a boat.

And when all else is said and done, a well balanced hull, one that stays in balance in a wide range of conditions including heel, is still as much a gift from the g-ds as it is the work of any designer. Even Bob has said, once upon a time, that he was pleasantly amazed at how well some boats balanced.
I chose to use a cone for my explanation because a cone is very easy to visualize as it rotates and because the reason that a cone remains in trim, i.e. that the buoyancy distribution remains the same, is actually the very same reason that a well modeled beamy boat would remain in trim as it heels.

That said, neither rotating a wedge shaped slab or a cone would behave precisely the same as beamy boat being rotated, but the cone actually behaves closer and uses the same principles. The point that I was trying to make is that by tweaking the rocker, bilge radius, and curvature of the topside in plan and section, a skilled designer can keep the trim essentially the same by keeping the buoyancy the same.

I also respectfully disagree with your comment," a well balanced hull, one that stays in balance in a wide range of conditions including heel, is still as much a gift from the g-ds as it is the work of any designer." I would echo what Bob says above about an experienced designer being able to eyeball and get things close to right the very first time. I am not a professional by a long shot. If there are shortfalls in the drawings within this thread, they come from my limitations as an amateur, operator error, and the limitations of the 2D software that I am drawing with. The fact that they are not a whole lot worse is because Bob is doing his best to keep my out of trouble.

One of the things that I have learned in this process is how quickly Bob can simply look at drawing and spot items that are out of wack even a small amount. When I have calculated some of these items I have been amazed at the precision of his experienced eyeballing.

But back to your comment, the better yacht design houses who are working with these super wide boats, have done enough of these that they too are coming to each design with an eye for what approximately works from the very first draft.

But professional yacht designers also have the benefit of very sophisticated 3D programs which can quickly calculate changes in trim at any heel angle almost on the fly. This allows the designer to tweak the shape of the topsides and bottom to keep the boat in trim as she heels and check their work as they go.

When a designer pushes a design towards the outer limits of conventional design, they become increasingly depended on have great computational tools to check their work rather than relying on luck. But even here, it is the skill of the designer that understands how much of these calculated results really can be relied on.

To me it comes down to my Olin Stephen's quote above about towing tanks, which essentially was that it still requires a skilled designer to design the model that gets towed. For all of the modern tools to validate and take some of the luck out of the equation, the reality is that it still takes a skilled designer with a good eye, to know what to put in the computer.

Jeff
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  #335  
Old 05-20-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Quote:
Originally Posted by outbound View Post
Jeff- are there any disadvantages to the wide stern double rudder vessels. I thought that given the designs we ( wife/self) looked at it seemed usable space ( carrying and accommodations) was somewhat comprised aft of the companionway. Also I thought about the higher risk of picking up lobsterpot lines and seine nets. Also thought boat would be more sensitive to weight ( supplies, spare anchor, etc.) placed near the stern. Finally though broad reaching the part of the now aerated stern would be slapped by the wave train. Issues of rudder feel and reliability seem to have been solved by having direct linkage to wheels.
?Your thoughts. Note you designed a single rudder boat as your "ideal boat". ?Why.
This weekend I received a couple thoughtful and thought provoking messages from Paulo, and in some ways your question parallels some of the items he mentioned, but perhaps from the other side of the mirror. Both comments seem to be touching on the fact that 'my version' of the is not very extreme, and that this design easily could have been drawn 20 years ago and more to the point, that the design does not take full advantage of some of the more recent 'advances' in hull design and foils.

For example, Paulo makes a good case for dual rudders, and for greater stability than the MV boat has.

But there are reasons that I did not feel comfortable pushing the design in that direction. These apply to the way I use a boat and so are would not necessarily apply to anyone but me. Bob may correct me on some of this as well.

As Paulo rightly pointed out, I do a lot of single-handing (or single-handing with passengers, if you know what I mean). These days the European single-and short handing designs much beamer and have wildly more stability, and therefore sail area than the 'My Version' boat. I must admit that I had considered that type of boat very early in my noodling.

But I also see all boats as a trade off, and one of the most important characteristic that I was looking for was light air performance. Beamy boats tend to have a huge amount of wetted surface. If you do not have moveable ballast, there is little that can be done to address that wetted surface other than getting into a kind of Ďarms raceí where the boat gets longer for its weight, then carries a lot more sail area for its weight until it can perform in lighter winds.

I considered going that route, but since this design was starting with a target displacement, I decided that it would get to be such a large boat that it would lose much of its charm for me. Instead I tried to produce a more moderate design, and tried to draft hull sections which balanced form stability with wetted surface so that the boat. That meant keeping the beam down to something reasonably narrow compared to the European short-handers. It meant giving up a lot of ultimate speed, for other subjective criteria.



And since the beam was moderate, And I could use a rudder with a generous depth and area, I came to a conclusion that dual rudders would not be necessary.

But beyond the specifics of the boat, are the limitations of this exercise. While I am very much indebted to Bob for looking over my shoulder and keeping me out of trouble, when I first started the lines for ĎMy versioní I was concerned about abusing Bobís time and good graces. As an amateur, it was easy for me to recognize that to develop a reasonable example of one of these newer extreme beam boats, it would require lot more experience and better software to develop than I had at my disposal. As a practical matter, I would have needed way more of Bobís time if I was going to try to develop a reasonable approximation of one of these more aggressive designs and I did not feel that I had a right to ask Bob for more time than he had signed up.

Which brings us back to Outboundís questions; as I interpret his questions (below) I think that these are all fair to ask:
Is there a higher risk of picking up lobsterpot lines and seine nets?
Would not these boats be more sensitive to weight ( supplies, spare anchor, etc.) placed near the stern?
Broad reaching would the part of the now aerated stern be more prone to being slapped by the wave train?

I think that the answers lie in the specifics of the design. It is possible to minimize the likelihood of catching a trap line, but few boats are designed with that issue in mind.

I would think that these newer boats should be very tolerant of loads near the stern, and have a lot of volume back there as well. For any given displacement these wide beam boats should have more overall surplus carrying capacity.

So for example, if we compare a 14,700 lb disp., wide beam boat to the ĎMy Version boat, it should have more carrying capacity and tolerance for changes in weight distribution. In all honesty, my sense is that the My Version design would be comparatively intolerant of weight placed near the bow. The actual chain rode storage would ideally occur through a pipe that lead the chain aft into a locker under the vee-berth (oh wait, we havenít drawn the interior plan.)

The slapped by a wave train issue is not one that I can answer with certainty. In terms of slapping by passing waves, the worst boats that I have sailed were boats with long overhangs when a wave came up under the counter. But I have experienced that feeling of waves colliding with the topsides and bottoms of a wide range of designs, and I canít say that any one type is truly any worse than the other in that respect.

Jeff
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  #336  
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Re: Bob Perry's take on Wolfenzee's dream boat

Thank you for the thoughtful answer. Always learn something when you post. My boat will be sailed 95+% of the time by one as it will be just my wife and I so we will take turns. Hate the engine and it's a sailboat so agree with your thinking but came to similar conclusions as you perhaps for different reasons. Mostly right brain not left and what the admiral would accept. If you pursue this would take a look at how boreal handled this issue. Seemed very clever. They designed a pipe dropping the rode in the dead middle of the boat. Doesn't seem to intrude on the interior and looks like it would run freely. A lot of places I've been are mud bottoms. Would think area would have to be airtight or have really good way to clean chain or you get a stinky boat even with just a little residua. Maybe have v berth air and watertight so would serve as collision bulkhead as well. Defer to your skills. Please don't feel pushed. I realize this is doodling and not your "day job". Tell me to stop anytime you want.
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  #337  
Old 05-20-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Quote:
Originally Posted by bobperry View Post
"as much a gift from the gods as it is the work of any designer."
I don't believe that for one second. Been at it far to long to go for that.
I have found that to be a fairly common attitude amongst extraordinarily talented people. It comes so easily and naturally to them that they don't recognize the uniqueness there. True it takes a lot of hard work to actualize an innate "God given" talent but without the talent all you have is a lot of wasted effort or, at best, mediocre results.

I could play the piano 12 hours a day for the rest of my life and I wouldn't be as good as Van Cliburn was when he was a child.
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  #338  
Old 05-20-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

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Originally Posted by bobperry View Post
Having a bit of a hard time following your argument there Wolf. Jeff and I NEVER idscussed "rating" and we never would. It just has zero application to this excersize. As for "planing"? Forget about it. A boat like this can never plane. It might surge a bit on a wave face with the right wind aft of the beam but it will never, ever plane. Even Jeff's latest iteration would never be a "planing" boat. Maybe a brief surge or surf but not planing.

As for what you have now? I'll stick to the facts:
I'd say you have nice old design, pretty sheerline as drawn, narrow and quite full forward with a lot of deadrise and slightly hollow garboards amidships increasing towards the transom. The point of max beam is quite far forward resulting in a very full bow. The full keel has a nice profile to it with plenty of "drag" angle. It's a nice, a very pleasant design.
The bow is not full at the waterline, there is a significant flare (?), look at the waterline measurements. The purpose of this flare it to keep the cockpit dry in heavy seas.
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  #339  
Old 05-21-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

Wolf:
You have a half angle of entry of 30 degrees at the DWL. That is very full by any criteria.
As I said, "resulting in a very full bow."
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  #340  
Old 05-21-2013
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Re: Bob Perry's take on Wolfenzee's dream boat

I am beginning to think, that wolf does not feel his boat needs to be improved per say..........

Others of us on the other hand......well anyway, way late here on the left coast, need to go to bremerton tomorrow,,,,,,clean up boat for the weekend, race wed night.........now if I would have won the powerball, we could let bob and jeff design me a boat the way I would like it......a bit shorter than icon, similar on some parts.....less on others........2 rigs in one........time for bed!

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