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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 ‘arms race’ 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 ‘My version’ I was concerned about abusing Bob’s 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 Bob’s 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 Outbound’s 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 ‘My 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 haven’t 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 can’t say that any one type is truly any worse than the other in that respect.

Jeff
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