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View Poll Results: The minimum length of l sailing yacht I feel like setting off in the roaring forties
a 35 footer 15 40.54%
a 40 footer 7 18.92%
a 45 footer 6 16.22%
a 50 footer 6 16.22%
a 55 footer 0 0%
a 60 footer 0 0%
a 65 footer 3 8.11%
Voters: 37. You may not vote on this poll

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Old 23-07-2009, 02:47   #16
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Been down there in a 32 ft two up, interesting but i was prepared to go round the Horn in it, ran out of money, went to the Caribbean to look for work, met a woman..............
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Old 23-07-2009, 09:01   #17
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The number of Vertues (25') and similar which have made the Horn is surprising. I've sailed my 25' Cape Dory above 51° north while coastal cruising, and would have had no compunction to continuing to Alaska in her other than much preferring warm water sailing.

Once the wave height is beyond your hull length there is little difference; I'd even say that if it's beyond half your hull length except I haven't had much experience in heavy weather on bigger boats. Ping pong balls make it to shore just fine.

My personal opinion is a boat should be designed to be managed the conditions expected. If you plan to sail above 50
° you want an inside steering station with a 360° view so a watch may be maintained without being outside in potentially terrible weather. Jester had this in a 26' boat, but it was an important element of the design. My boat doesn't, and I don't think it's appropriate for sailing that region. Could be done? yes. Should be? no.
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Old 30-07-2009, 12:58   #18
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Well, my point was that the contemplated trip does not implicate the Roaring Forties at all. It begins in Ushuaia which is nearly 55 degrees south and then proceeds 1000 miles further south through open ocean.
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Old 30-07-2009, 23:28   #19
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I have some smart remarks I hope (this is with the help of my books, I'm not a nautical architect!):

Instead of just looking at the length, other features are more important:

- Steering control. We're talking surfing down big waves. If you have a spade rudder, that's good. A skeg-rudder will be hell (AP won't cope) and a flap at the back of the keel means you will have limited to no control. Less control means you have to slow the boat way down to regain that control. That's why old farts in their traditional boats tow drogues (nothing against them, really!) while the whitbread racers scream past.

- Hull balance. When you heel, the shape of the hull part that is under water changes. The problem is that for many boats it becomes asymmetric with the rounding-up as a result. We are talking a knock-down or broach here, or worse. Old designs are often well balanced which is why they are still praised by many today.

- Length to beam ratio. You want a narrow boat for maximum directional stability. Many designs are beamy or very beamy because of some stupid racing class rules. Narrow is better and a 4:1 minimum length-to beam ratio is a good target. This means 10' beam for a 40' boat, 12.5' for 50' and 16' for a 64' boat (hey, that's Jedi!! ;-)

- Keel. Doesn't matter much; if the boat is beamy with unbalanced lines you will be in trouble regardless of keel type and if the boat is narrow with balanced lines it will steer good with fin or full keel. Traditional/classic yachts steer good because of their narrow hulls and balanced lines, not because of their full keel.

- Limit of positive stability (LPS, in degrees of heeling and still coming back up). It's not just cats that are very stable upside down. What is good: high freeboard, cabin structure, narrow beam and low center of gravity. Now comes an interesting part: big boats get away with a lower LPS. This is the biggest advantage of a big boat. The minimum values according to Dashew are:
25'-30' boats: 135-140 degrees
30'-35' boats: 132-137 degrees
35'-40' boats: 130-135 degrees
every extra 5 feet length can reduce LPS by 2 degrees until the minimum of 125 degrees is reached.
If the average designed cruising boat doesn't meet these criteria, it's not suited, period.

- Polar moment. The weight away from the center of the boat. This counters the heeling acceleration during wave impact on the beam or rolling. Hoisting a weight up the mast actually helps and was done in the old days. This is why dismasted boats are terribly unstable and carbon fiber masts are not always good.

- The skid factor. Imagine a big breaking crest on top of a huge wave. These are the conditions we're talking about down there. Now imagine your boat beam to that monster. Before the breaking crest hits you, you are already heeling too much in the throat of the wave and the breaking crest is there to finish it and roll you will.... or not? This is where the skid factor comes in. During the second of the impact of the breaking crest, will the boat stay put or will it skid down the face, absorbing the impact. There are several factors at work: first, the need for a high freeboard as this will provide the surface area to slide down on. Second the keel: a big surface area on the keel is a negative as it will help flip the boat. Third the decks: a beamy boat will immerse the deck at that beamy part much sooner, digging into the water and acting like a break. So again, what is good: narrow boat, high freeboard, small keel, shallow keel.

Cockpit: deep, secure, companionway in the center of the boat and not all the way down to cockpit floor (think where the water will be during excessive heeling like during a knock-down), handholds, secure footing (blocks you can stand on when heeled), volume not so much that it severely affects trim when flooded and big drains (remove any grills). Also, when the cockpit seats are opening with lockers underneat, where do those lockers drain? Into the interior? How secure are these seats and how are they gasketed? Loosing a seat can mean loosing the boat. All these requirements are amplified for smaller boats because movement gets more violent and cockpit flooding more frequent.

Stowage: same as low center of gravity. Those fuel jugs, scuba tanks etc. on deck: don't go where the seas are high. Also, everything must be secured.

Now I want to comment on some earlier posts in this thread. I read about 40' racers doing so well so 40' is enough. This is nonsense of course, they are racers and can't be compared to cruisers; they would not be safe for a cruising couple. Reality is that bigger is safer when all the criteria above are met equally. A beamy 50 footer with unbalanced lines is not as good as a narrow 40 footer with balanced lines. So, a boat designed for blue water cruising can be shorter than a boat designed for the Moorings in the conditions we're talking about. But when all else is equal, bigger is better indeed.

Last but not least: the crew. The racers down there have plenty crew, we cruisers do not have that luxury. This means that the boat's design must be oriented more to comfort, easy operation and safety than to performance. If at all possible, the auto-pilot or windvane must be able to steer the boat in these conditions, or we will not endure. This means that boat designs with roots in the racing rules are not good.

All the info in this post is from me, a Sundeer 64 fanatic, and Dashew, the designer of it and thus we come out well when looking at these criteria. But most, if not all, of the principles and factors mentioned are well known and accepted by all naval architects.

Other great blue water cruisers are the Koopmans yachts. They are somewhat more traditional and proven.

cheers,
Nick.
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Old 31-07-2009, 04:32   #20
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Multiple disagreements

I've been to sea in a 400' with a spade, balanced rudder that steered like a pig, especially so at higher speeds. And I've danced in stormy weather in a 25 footer with the dreaded full-keel/scimitar rudder that felt perfectly under control surfing *up* as well as down. Steering design is individual, and the best characteristics can be arranged in many different forms to gain proper control under the expected conditions. A good blue-water mono-hulled boat should be able to maintain good steering control up to about 130% the predicted hull speed; race boats and catamarans and other semi-planing hulls would need steering designs for their predictable maximum speeds.

While I generally agree that a narrow hull design is better, and that bigger is better, this has to be tempered by systems complexity and the obvious fact the forces involved increase geometrically with size. I would point out the 4:1 ratio is incorrect - it becomes progressively higher with length, and is a proxy for waterline beam when measuring capsize resistance. I don't generally consider length when looking at LPS; every boat should come up from a knock-down. My current boat's theoretical LPS is 160, but I can say she's come up from the spreader (and jib) in the water.

Skid-factor is a non-scientific myth. It is one collection of theories as to what may happen in certain extreme conditions, but it's no more true than several other theories which may also explain those conditions. It is a good basis for making design decisions, as long as you realize the basis for those decisions may be wrong. One of the argued elements of this theory is that greater beam is bad, but increased topsides is good, despite the fact that in the dynamic situation there is no distinction between the two surfaces (that is, extra beam will provide the same additional surface area as the additional topsides.) A second element of contention is shallow vs deep keel, since modeling would suggest that area and not depth is at issue. Further, the theory does not explain forward rolls, which by its tenets should be impossible yet happen with enough regularity to disprove it as a complete panacea.

In most things we agree, but the emphasis on size alone is, in my opinion, stupid and dangerous. I'm now approaching 51° again. In these waters I am almost always the smallest boat, and usually the only sailboat. But it's interesting to me that the local professional mariners, who stay here through the winter weather, are in boats only somewhat larger than mine, while it's the summer visitors who own the big shiny boats that dwarf me. Are those big boats safer? Probably, so long as their crew can manage them and their systems do not break down. But the local yard has a boat specifically kitted out to race out into the islands to repair anchor windlasses and replace lost anchors and rodes.
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Old 01-08-2009, 16:59   #21
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Amgine,

I think you mean a 40' with spade rudder because I can't think of any 400' that steers like a pig! But I agree with what you write about the rudder: I should have made it more clear that it is the combination of all the factors that makes the best boat for blue water cruising. If you take a narrow hull with good balanced lines and put a long keel with attached rudder under it, it will still steer much better in following seas than a spade rudder under a beamy, unbalanced hull. I should have left out the "old farts" remark.

But, having said that, everyone knows that a NACA foil shaped spade rudder is MUCH more efficient than an attached/skeg rudder. This means that for the same surface area, it will provide much more lift and steering power. If you are in the club of "old fashioned is always better" like some cruisers are, you can just ignore this, but naval architects will all support this position.

Jedi can do sustained planing with working sails while (broad) reaching and the hull & rudder are designed for up to 26 knots speed over water. As our keel is very shallow for the size of the boat (6' 2"), some of the needed lift was moved to the rudder. This means we need a very big and efficient rudder that will provide good steering control up to 26 knots. It's design ended up as one of the first with a fibreglass shaft (rudder and shaft are 1 part) to cope with the higher than normal forces, and a 6' rudder draft. It is a spade NACA foil shaped rudder and I don't think any skeg hung rudder could match the performance.

Skid factor: yes, I knew it would come up as being described a fairytale ;-) I know that there is not much of a scientific basis; the theory is purely from observation. More beam might well be a good thing for skidding, but is undesirable because of other factors like length-to-beam ratio and, in a lesser extent, for more balanced lines (is easier with narrow hulls). After reading your message, I think you agree that it is "a good basis for making design decisions" even though nobody really knows why it works. I agree that less keel/rudder surface area is as important as less draft but draft is a factor because it provides a longer arm (more torque) to roll the boat.

On size: I clearly wrote that bigger is only better when all the other criteria are equally met. That is very different than "emphasizing on size alone". I think we agree to the principles but can't find the exact right wording.

You are clearly taking a standpoint supporting smaller boats. But if you really think that bigger boats are harder to handle and have more complex systems, you should have a look at the Sundeer designs. Not all "big boats" are the same. A well performing 64' sloop would be harder to handle than our ketch, for example. Same for systems: many 45 footers have more complex systems than us and I would put the complexity of the systems aboard Jedi at the same level of every 45' blue water boat. May be the hydraulic vangs are not used as much on 45' boats, but that sums it up. Also, you really think a bigger windlass is less reliable than a small one? I can assure you it is the other way around! No one is gonna haul the anchor by hand on a 45' either unless there is no wind or waves, and we can do that in those conditions too! For a bigger boat, the important things to watch are: can you hoist/lower/reef the sails alone or not and do you have enough $$$ to buy it and pay the higher price for marina's, hauls and anti-fouling. I agree that many are not suited for cruising couples or simply too expensive (show off toys) or slow or both.

cheers,
Nick.
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Old 01-08-2009, 22:07   #22
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No, I really meant 400', but in fact it turns out the ship is actually 636' long, 192 m. And it's rudder is rather larger than Jedi, and I've steered both from the bridge and from sitting attop its rudder post. It steers about as well as you'd expect a brick would, if a brick could float.

The efficiency of a rudder design has nothing to do with whether it is effective. It only means the rudder can be smaller to develop a given force. It really and truly has nothing to say about whether a spade, skeg, or keel-hung rudder will be 'better', however you happen to be defining better.

Due to the speed Jedi can regularly achieve, it can get away with a smaller rudder, not require a bigger rudder. However, most likely the designer compromised and selected a rudder size based on its lower displacement speed ranges, for safety. As to whether a different design rudder could 'match it', that would depend on what you're measuring: developed turning forces could obviously be exceeded, simply by altering the balance point but at other costs, and the structural strength of a fined skeg rudder would be stronger but again at other costs. Clearly Jedi's designer felt this rudder was the best compromise for his design goals.

I really and truly believe that larger boats are better and safer, and would dearly like a 125' cutter. But I can not afford to maintain the systems necessary for a single-hander 40' boat in a blue-water ready manner. The reason I cannot do so is the size and complexity of those systems, due to the geometrically increasing forces involved. I cannot even contemplate the costs of maintaining a 65' boat, from the mooring requirements to the electronics.

In my experience, the failure rate of larger windlasses is higher than smaller windlasses, dramatically so. The reason is exactly what you would expect: boat owners install too small a windlass in an attempt save money because the unit they're purchasing is already outrageously expensive, but the one they actually need is probably twice as much as that. Financial considerations are an important element of seaworthiness.

(Contrary to what I just said, the most robust/reliable windlasses I personally know of are installed on smaller commercial craft, and are often an order of magnitude larger than the ones found on larger pleasure craft despite similar or smaller sized anchors.)

In my opinion, the Sundeer line of boats are great for people with lots of money and nothing better to spend it on. And I wish I were one of them. Maybe that's too much honesty for this thread though.
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Old 01-08-2009, 23:52   #23
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Mentioned in an earlier thread,google :"Sven Yrvind",micro sailboats,circumnavigations.Gives a whole new perspective of "small".
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Old 02-08-2009, 00:15   #24
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Ah, you're talking about warships and 125' cutters etc. I was in the sailboat under 70' category.

You wrote:
Quote:
It only means the rudder can be smaller to develop a given force
so you didn't read my post good enough as I wrote:
Quote:
This means that for the same surface area, it will provide much more lift and steering power.
Again, we mean the same thing but you read my writing differently than I mean. So I will elaborate so that other readers don't get too confused: If a spade rudder with a NACA foil shape has the same surface area than a skeg-hung or attached rudder, the spade rudder will be much more efficient and provide more lift. I know you agree to that ;-)

Quote:
Due to the speed Jedi can regularly achieve, it can get away with a smaller rudder, not require a bigger rudder
Unfortunately not, we have an enormous rudder. The reason is that the keel alone doesn't provide enough lift so the rudder needs to help, much like a centerboard. Also, we need good steering at slow speeds; only racers have rudders designed for their higher speed range.
In other words: with a deeper keel, we could have had a smaller rudder.

Every keel and rudder is a compromise, even on racers.

Back to the size: indeed, a 125' cutter is too big for a cruising couple alone. But you really should open your eyes to the fact that 60-65 foot yachts don't need more electronics, nor more advanced electronics. We have the same wind/depth instruments, radar, GPS, VHF, SSB as 40' boats equipped for cruising. Same cost. Same for electric installation, plumbing etc. It is only at 20 meters (that's more than 65 foot I calculate) when you need bigger nav-lights etc. Between 12 meters (39' and some inches) and 20 meters all is the same. This is the reason many designs are just under that 20 meter limit.

Quote:
In my experience, the failure rate of larger windlasses is higher than smaller windlasses, dramatically so. The reason is exactly what you would expect: boat owners install too small a windlass in an attempt save money because the unit they're purchasing is already outrageously expensive, but the one they actually need is probably twice as much as that. Financial considerations are an important element of seaworthiness.
Hmmm, your reasoning is flawed. A bigger boat doesn't have a windlass that is too small because the right size is more expensive. The size of the boat is not a factor for that: it is a cheap mass-produced product that is supposed to be chartered and tied to mooring balls that get a windlass that is too small. Every good cruising boat, regardless their size, has a windlass that is matched to the boat, with power to spare. In that scenario, a bigger windlass has less failures just because bigger things are easier to make strong than smaller things. Any serious 60 footer comes with a windlass, so it's not the owner trying to save money anyway. I think you are just trying very hard to disagree with me! ;-)

I am going to end this discussion about wording, warships and 125' cutters now because we are way off topic. I tried to give a decent list of things that are really important for a blue water cruiser because it was lacking in the thread. I think I did a decent job and that you agree with the list and don't have more items to add to it?

cheers,
Nick.
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Old 02-08-2009, 10:43   #25
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You may may be right about being off topic. I would not have volunteered to be on that ship should it be ordered to circle Antarctica below 50°, yet I'd happily take several boats under 40' there if someone else was paying the maintenance - because they are designed to do exactly that kind of cruising.

Which is, ultimately, my point. Size is not as relevant as design goals.

You and I will continue to disagree when you suggest your vessel is the right size and design for all things. It's may be the best all-rounder for blue water cruising if you can afford it, but that means it does not excel at any one point.
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Old 03-08-2009, 00:55   #26
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Amgine,

Size of the boat is a very important factor for behavior in bad weather, high seas, storms etc. At some point, smaller boats can be overpowered by the conditions where bigger boats can endure. For the smaller boat, the experience and seamanship of the crew becomes much more important because their skill and endurance will make a big difference.

So all that I say is that size is one factor among many others (but it is a factor even though you don't agree much with that in your last post but you did agree with that in all your earlier posts!) and it is the boat that has most or all of these factors well implemented in the design, that makes the best blue water sailboat. A boat that lacks on some points, needs a better crew to keep it safe, or the other way around: a boat that is well covered on these points allows you to get away with mistakes that other, less suited boats, won't. Please note that I am not saying here that you must have a 64' boat.

You are correct about Jedi: we don't excel at any one point: racers are faster, smaller boats cost less etc. but what is your point?

When you look at suitability as blue water cruiser, it basically meets all desirable features plus it's pretty fast while broad reaching. The reason for that is that it is designed for it, unlike most other production sailboats. There are other examples, also for smaller boats: Koopmans, Amel, Island Packet are only a few of them. Examples of boats that were not designed for it is much easier: Beneteau, Hunter, Catalina, Bavaria are the first I think of. This doesn't mean that they can't do blue water cruising, it only means that they were not specifically designed for it. (chartering, day sailing etc. were the design criteria). If you want to optimize these boats for blue water cruising, that can be done too, but it will cost money, closing the gap with the first list quickly.

Affordability is only partly influenced by the length of the boat because the hull is only 30% of the total construction costs of a boat. The Sundeer 64 has an interior of only 39', with water tight bulkheads separating it from the other 25'. This means that the cost for building the interior (which is 30-35% of total cost) is only the same as for a 39' boat. This also saves a lot of weight. That, together with other weight saving techniques, means that she is easily driven and instead of taking advantage of that for making it faster, it was used for making the rig simpler and smaller. We don't even have back stays and the main mast is only 59' up from the deck. And that makes the rig as easy to handle as much smaller boats with comparable mast size, plus it significantly lowers the cost of the rig. It also means that most 50' boats have much more living space (and cost more). All this is just to show that, for selecting a blue water cruiser, you can't just start with defining the length of the boat as the first search criteria. It's much better to start with price and age and builder.

Affordability is also a funny thing. We meet many cruisers that at some point tell us that they wished that they could afford a Sundeer. That is just after they told us about their house(s) and cars that they still own or even about the land they just bought and the house they are building on it. They don't realize that their budget is a multiple of ours but they choose to put their priorities differently. They assume we too have a house and cars and all that come with that. And some (not just a few btw) even have a boat that costs more!

cheers!
Nick.
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Old 03-08-2009, 10:41   #27
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Size is an element of seaworthiness, but does not by itself positively affect the ability to survive storms and - carried to extremes - does exactly the opposite. Size does directly influence loads, and thus the cost of equipment which can reasonably and safely manage those loads and thus the maintenance cost as well.

Sailors come from all kinds of economic situations, and a very large percentage of the cruising community have no shore assets, little or no income except when they pause to replenish the cruising kitty. For most of these sailors, like myself, the initial cost and the ongoing costs of a vessel like Jedi is simply not imaginable. If it were otherwise there would be thousands of Sundeers around the world, rather than the exciting motley I find in remote destinations such as here in Port McNeil. Of the foreign flagged vessels right now there are only two which are longer than 40' here above 50°, and one of those is a motorboat.

I would encourage any sailor interested in sailing in high latitudes to purchase the largest blue-water design they can reasonably maintain - I'm not against size as I've repeatedly said! But saying it's the best or only way to go is untrue, and a disservice.
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Old 03-08-2009, 13:03   #28
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Further to jedi's comments, I'd take a 40' Morgan Giles sloop I sailed on in the Channel (40x10x6) over a 65' IOR boat anyday if I were sailing there. Great boat- former RN sail trainer- went though a 10' chop like it was on rails.

Ours is similar: 48 x 12 x 8'. Long, skinny and deep. Those skinny, tippy International rule boats of yore or CCA rule boats have the advantage of a very high angle of vanishing stability. An AVS of 120 degrees or less (like way too many modern boats) scares the bejeezus out of me. (too many encounters with $#^%@# weather).
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Old 03-08-2009, 21:26   #29
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S&S: you are right, IOR boats are not good blue water cruisers, they are racers with lines that are not designed for optimal seaworthiness (nor for optimal speed as they have to comply with the rules).

Also, I am interested to learn which boats have an AVS/LPS of 120 degrees or less! Even big boats, 50' and up should have at least 125 degrees. I would not go to sea in any boat 120 or less!

And your boat meets the 4:1 length-to-beam ratio, good! The draft is a bit much though... we have enough trouble with our 6'2" already!

Amgine: length of the hull does not directly influence loads and cost of equipment. It is the weight & windage of the boat and surface area, height & weight of the sails+rig that are the factors. Thus, a 40 ton 50' sailboat will experience (much) higher loads than a 25 ton 64' sailboat.
However, for most standard production boats, there is a relation between length of the hull and all factors I listed above, so the comparison with length alone normally gives a rough indication.

Economic situations: I think it matters a lot in which area you look. Here in Panama, with all the yachts transiting the canal, a huge percentage of the live aboard cruisers still have houses, cars etc. In Miami on the other hand, we only met a handful like that and all the rest had just the boat. Many Hunter owners have a house!

Overall, in the Caribbean, I think that at least 25% still have a house.

There should be more Sundeers! They built 10 Sundeer 64's which were all sold in 1993 for $447k and launched in 1994. According to my insurace surveyor, the cost of building one today would be $1.2m (!!!), while the 2nd hand market is from $750k up. A 56' Sundeer will be well over $400k today but they are all younger. It is hard to buy a Sundeer 64, we had to wait 2 years before one came on the market and the broker (there's one broker who lists almost all Sundeers) send me regular emails asking if we want to sell. For me, this indicates that there are much more buyers in the market than available boats, but not many of them would pay the price of a new one as it would cost today. The market for blue water cruisers is very small compared to the total amount of sailboats sold anyway.

ciao!
Nick.
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Old 04-08-2009, 09:08   #30
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Quote:
Originally Posted by s/v Jedi View Post
I have some smart remarks I hope (this is with the help of my books, I'm not a nautical architect!):

Instead of just looking at the length, other features are more important:

- Steering control. We're talking surfing down big waves. If you have a spade rudder, that's good. A skeg-rudder will be hell (AP won't cope) and a flap at the back of the keel means you will have limited to no control. Less control means you have to slow the boat way down to regain that control. That's why old farts in their traditional boats tow drogues (nothing against them, really!) while the whitbread racers scream past.
Not sure about that, ours surfs fine (keel hung rudder)- the difference being that our rudder is rather large. I wouldn't damn them all, but I'll agree that a goodly number of older boats with "flap" rudders are underequipped. We hand steer in large following seas anyway so that might be it too.

Quote:
- Hull balance. When you heel, the shape of the hull part that is under water changes. The problem is that for many boats it becomes asymmetric with the rounding-up as a result. We are talking a knock-down or broach here, or worse. Old designs are often well balanced which is why they are still praised by many today.

- Length to beam ratio. You want a narrow boat for maximum directional stability. Many designs are beamy or very beamy because of some stupid racing class rules. Narrow is better and a 4:1 minimum length-to beam ratio is a good target. This means 10' beam for a 40' boat, 12.5' for 50' and 16' for a 64' boat (hey, that's Jedi!! ;-)
Balanced underbodies are underappreciated when it comes to directional control. A long centerplane makes a boat more forgiving as well.

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- Keel. Doesn't matter much; if the boat is beamy with unbalanced lines you will be in trouble regardless of keel type and if the boat is narrow with balanced lines it will steer good with fin or full keel. Traditional/classic yachts steer good because of their narrow hulls and balanced lines, not because of their full keel.
I'll buy most of your arguement, but in my experience a long longitudinal plane does help (the down side being that they don't turn as smartly as fin keeled boats) the real advantage of a long keel comes out when hove to- then you want a big longitudinal plane.

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- Limit of positive stability (LPS, in degrees of heeling and still coming back up). It's not just cats that are very stable upside down. What is good: high freeboard, cabin structure, narrow beam and low center of gravity. Now comes an interesting part: big boats get away with a lower LPS. This is the biggest advantage of a big boat. The minimum values according to Dashew are:
25'-30' boats: 135-140 degrees
30'-35' boats: 132-137 degrees
35'-40' boats: 130-135 degrees
every extra 5 feet length can reduce LPS by 2 degrees until the minimum of 125 degrees is reached.
If the average designed cruising boat doesn't meet these criteria, it's not suited, period.
There are tradeoffs. High freeboard presents a greater SA for a breaking wave to impact, and shows more windage. there was a good deal of testing in the UK that was reproted in Marchaj's book that's pretty compelling. What has to be remembered is that although it takes more force to roll a big boat in the first place, once you're rolled and within the AVS, it'll also take more force to right you. The IR boats were the best from this criterion AVS= 180 deg (but you sail on your ear) It's good to check with the builder/designer to find the AVS (there are quick and dirty calculations you can make but they're at best a guess)

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- Polar moment. The weight away from the center of the boat. This counters the heeling acceleration during wave impact on the beam or rolling. Hoisting a weight up the mast actually helps and was done in the old days. This is why dismasted boats are terribly unstable and carbon fiber masts are not always good.
In praise of the heavy aluminum stick- couldn't agree more. The trade off is that you can't carry as much sail for a given angle of heel ( but we're not racing)

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- The skid factor. Imagine a big breaking crest on top of a huge wave. These are the conditions we're talking about down there. Now imagine your boat beam to that monster. Before the breaking crest hits you, you are already heeling too much in the throat of the wave and the breaking crest is there to finish it and roll you will.... or not? This is where the skid factor comes in. During the second of the impact of the breaking crest, will the boat stay put or will it skid down the face, absorbing the impact. There are several factors at work: first, the need for a high freeboard as this will provide the surface area to slide down on. Second the keel: a big surface area on the keel is a negative as it will help flip the boat. Third the decks: a beamy boat will immerse the deck at that beamy part much sooner, digging into the water and acting like a break. So again, what is good: narrow boat, high freeboard, small keel, shallow keel.
I've never seen this in action, but per my previous comment a high polar moment (resistance to rolling)and low freeboard (less opportunity to put wave energy into the hull) seems more plausable. Also the harder chine of most new boats ( dependence on form stability) is a bad choice for severe weather.

Great post, everyone has to think these things through and make appropriate decisions based on their comfort level. I'd just add that small windows and appropriate storm covers are a necessity for boats encountering bad weather. Most production boats have too much glass.
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