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Old 20-05-2008, 16:36   #16
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Originally Posted by Weyalan View Post
There is no doubt that hull shape is, to a lesser or greater extent, driven by rating rules and the need for speed at the point end of yacht racing. The current propensity for plumb bows (maximum w/l length for o/a length) and wide, flat, rear ends (for planing) and hard chines often seems to offend a conservative yachting public's sensibilities. Nevertheless, the benefits of the yachting arms race do trickle down to us, and since we aren't at the leading edge of yacht racing, we all amke the best of what we have. Whether our beloved boats's hull shape is optimal or even close to it is largely irrelevent because it is, in general, bought & paid for and we are out there having fun.

I agree largely with this post. Estrella is 36' and has all those overhangs and bowsprit etc. I wish she didnt. I am re-engineering my sprit so I can accomodate the anchor I wanted (last design was a failure) I prefer speed having been engineless and impatient in the sea of cortez and I wish my boat was a better performer. She has a wide beam so lots of interior volume. She would have much more if her bow was plumb. My anchor would stow beautifully on the stem with a simple roller (my anchor is going to end up on the tip of the sprit) and I wouldnt have the sprit in a buddy's garage right now waiting for me to strip, epoxy and paint it after I cut the cross beams off and change how the platform mounts to it.

If I had my druthers I would go again in a modern design boat. Estrella is very pretty but she isnt a performer. I knew that when we left to go cruising and told myself what everybody else does "I'm in no hurry and would rather be comfortable in heavy weather" I have encountered very little heavy weather (and I wouldnt say it was a cake walk) and a lot of calms during which I wanted a boat I could tack in 3 knots of wind ;-)

Anyway just my .02.
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Old 20-05-2008, 19:41   #17
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Having sailed newer plumb bow boats and now a classic 35' LOD and 26' LWL boat, I can say that I prefer the older design. Especially in heavy weather. She's more kindly in the slop and will run down newer boats with longer WL's. Case in point was us running to ground a Bavaria 36 MkII this last weekend. I'm sure he wasn't expecting an old horse like Oh Joy to run him to ground. I know I wasn't.
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Old 21-05-2008, 17:48   #18
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The shape of bows and sterns, overhangs and plum, are a sign of the times, and as the boats become faster, sails become more exocit, and shapes change, we've now passed hull speeds like a runner doing a 4 minute mille.
At one time, My FIRST 42 was "state-of-the-art" and probably the fastest boat on the water. The Admirals Cup shows this to be true, but The IOR designes of the 80s are not what they are today.
Origionally, the pointed stern and wide beams were to increse water line and to put back, what once you spread apart.
In the 70s and 80s, this was the norm, to get as much out of a full displacement boat you could.. And then designers found that by altering hull shape, you can exceed hull speed by changing the shape of the hull.
When hull speed is exceeded, turbulance takes place off the trailing edge of the boat so the shape at the stearn in no longer a factor. Cut it off flat, as who cares what happens to the water once it leaves the back of the boat.
Not olny were boat designes but also the trailing edge of the keels and rudders.
Ihe keels and rudders were shaped with a flat rear edge and the trailing area of the keel (last 2/3s) are flat laying to the trailing edge. This eliminated drag of the wetted surface and with a flat rear, the turblance was dropped off the back.
Over the next few years we'll probably see new changes to race designes and it will all trickle down to the boat we sail.
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Old 21-05-2008, 18:07   #19
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No doubt we'll see more trickle down. And no doubt the flatter underbodies and wider sections aft provide greater form stability and speed potential (to which I have already referred). They nevertheless also lead to increased weatherhelm, an increase in inverse stability and a less comfortable motion in heavy conditions, particularly to windward. It is decidedly not a 'win/win' situation.

For most sailors, however, the advantages of the 'modern' hull form outweigh the deficits. For offshore sailing with a full load of cruising gear/stores....

Brad
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Old 21-05-2008, 19:27   #20
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Brad,
Im wondering now, and maybe you have the info on this. I have a pinched stern, as most IORs of the 80s were designed. sails to weather and a-beam like it was on tracks, and so balanced at the helm, she'll lay over at 15 to 20 degrees and still stear with finger tip control.
But, in following seas, its a hand full. So bad at times, that I'll turn off just to keep the boat in control. The following seas will lift the stearn and push the back out from where it belongs. Is this situation differ between the older IOR stern and the newer wide body?
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Old 21-05-2008, 20:31   #21
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WOW! This thread has really turned out great. A lot of really good info here. Stand by for my next installment 'she sure is fat for a 30'
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Old 22-05-2008, 16:01   #22
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Randy, there could be a number of causes, although I suspect that the narrow transom isn't one of them. Firstly, a longer keel would help tracking in those conditions (although you can't change that). Secondly, it could be that your rudder is less than adequate to maintain course in those conditions.

You could (and should) move the center of effort forward - always reef your main before reefing down the foretriangle. If you are significantly overpowered in following winds and seas it is often easy to underestimate the true wind speed because the apparent wind will be lower over the deck. Next time try going to a double reef in the main and a working jib. If that doesn't do the trick, drop the main and try sailing downwind with just the jib alone. That should at least give you some additional information about the balance of your boat.

If conditions are truly atrocious, you may want to go with a drogue. On the other hand, if what you are talking about is less than fairly extreme conditions, you should still understand that in certain conditions (large following seas being one of them), most boats are a happier if they are not dead downwind. If you take the seas slightly off the windward stern quarter and keep the center of effort forward, she should be able to handle most conditions.

Brad
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Old 22-05-2008, 16:13   #23
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Brad
There's no problem with the keel or the rudder as I draw just over 9.6 and the rudder is down 6 feet. I've learned to handle the boat just fine and have logged more than a few thousand miles of open ocean on her.
I wasnt complaining if thats what you thought.
The question was, wether or not the design of the boat, being a narrow stern would have a different effect from the wide bodies being produced today in a following sea.
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Old 22-05-2008, 16:29   #24
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Quote:
Originally Posted by Randyonr3 View Post
Brad,
Im wondering now, and maybe you have the info on this. I have a pinched stern, as most IORs of the 80s were designed. sails to weather and a-beam like it was on tracks, and so balanced at the helm, she'll lay over at 15 to 20 degrees and still stear with finger tip control.
But, in following seas, its a hand full. So bad at times, that I'll turn off just to keep the boat in control. The following seas will lift the stearn and push the back out from where it belongs. Is this situation differ between the older IOR stern and the newer wide body?
IOR designs are, as a general rule, renowned for being a handful downwind. The earlier designs (1970's) were probably worse than the later designs. It is a recurring criticism of the IOR rule that the specific and detailed measurement criteria were available to all, allowing designers to exploit loopholes in the system to produce boats that rated extremely well, but unfortunately, that super-good rating was generally achieved, to some extent, at the expense of sensible design, stability & seaworthiness, but as long as the improvement in rating was greater than the decrease in performace, these "rule beating" designs would win races.

It is my understanding that some IOR boats have been re-faired in the aft quarter to get rid of the characteristic IOR pinched stern, with significant improvenemt in downwing handling. Nevertheless, this is a major exercise, and for most of us, the cost would outweigh the benefits.

It is interesting, for me at least, having an IOR boat of early 80's design, to be racing in a mixed fleet against much newer (brand new in some cases) designs of both IRC and IMS boats. The old IOR boats are actually still very competitive hard on the wind, and reasonable with cracked sheets too, but as soon as the breeze gets aft of the beam, the newer designs leave us for dead. Still, seeing 2 old 70's vintage IOR boats (Love & War and Bacardi) finishing 1st and 2nd (IRC) in the 2006 Sydney-Hobart (beating boats like Wild Oates XI, Ichi Ban, etc) gives us old IOR owners hope (it was a beat pretty much the whole race, in 15-20 knots - ideal conditions for these old "leadmines")... but I digress
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Old 22-05-2008, 17:59   #25
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Every boat is a studied balance of contrary conditions, and will eventually find its place on a series of scales. Various racing rules set the style for "what's sexy" for a larger number of boats built than those that raced, so for a while something like the IOR look sold boats to people who were really not racers. There is some merit in the resulting developements of, say, the CCA rule, and esthetics are almost exclusively in the eye of the beholder.

Older is not better. To my eye, the bluff bows and 'sort of' sterncastles from smaller commercial vessels of the nineteenth century are just pug ugly, But the long overhangs, gentle shears and massive gaff rigged sails of the earliest pure yachts are things of timeless majesty. A Shields emerging from the early morning fog, moving silently at five knots with no more wake than a white swan in a garden pond is a thing of such beauty that you just thank the passing skipper for the vision. My minimally raked bows and scooped sterns with dirty steps, dragging gallons of water to fill in behind my overloaded transoms are not going to inspire thanks from passers-by, but they are MY bows and sterns, and if this boat had those wonderful overhangs and placid wakes, she would belong to someone with much more money, would cost twice as much to berth, and would mandate a higher standard of sailing apparel than I seem able to wear. So when someone say "look at that sloppy cat" he knows me!
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Old 24-05-2008, 13:39   #26
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Weyalan, thanks for the informative post on the older IOR designs. Was the problem downwind with the prismatic coefficient of the hulls (they typically had fairly significant beam amidships , but as you say, very pinched ends)? Certainly there are a large number of boats with narrow beam throughout that have very good control in following seas.

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Old 24-05-2008, 14:22   #27
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I wonder if going downwind these three factors come into play.
The wider flatter stern will be more likely to plane.
The greater volume aft will on a slightly off square or quartering wave will rise more tending to bury the bow, and the greater torque of both volume and being further aft will have a greater tendency to turn the boat more broadside which is difficult to counteract.
Thirdly the absence of a skeg will reduce any lateral resistance to this torque.
If so the increase in speed and volume would come at the expense of control.
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Old 24-05-2008, 14:37   #28
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This is getting into the area of pure racing hulls and not Cruising boats that this
Forum is all about. But yes the entire reason the latest trends in the design of boats like the 60's racing around the world are to be a largely scaled up version of a racing skiff. The plane on the surface. the only way a 60ft boat can do 20+kts. They are very wet in sizable seas. The tend to almost wave pierce. The sea's just go straight over the top most of the time. It makes for very wet and wild sailing. To stop them from becoming submarines completely is all in sail design and how the effort "lifts" the bow instead of pull down on the bow. But these designs are a mile away from cruising and even semi cruising/sunday racing designs.
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Old 24-05-2008, 15:55   #29
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I think the point is that most older cruisers were in fact designed as cruiser racers and as such influenced by the rating rules of the time.
There are straight cruisers such as the Tayana Westsail Baba etc and straight racers.
Perhaps the majority of cruisers now fall in between.
The issue is whether overhangs setting aside any advantage at the time under the rating rules have any advantage apart from looks. Some say no I suspect yes, but ultimately theory gives way to practical experience.
I gather the S&S designs of the 70s were both fast and sea kindly.
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Old 24-05-2008, 19:50   #30
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Heres an article I found interesting in while researching the plumb bows, and flat bottoms of modern designs. Gets into more than just shape... how to harness the design to get them to hop up on plane and perform in light airs.
Bray Yacht Design and Research Ltd. - Ultra Light Displacement Boat

Cool stuff, but not a boat I'd want to build... (May just have to borrow some of the ideas that make them perform in light air though... )


Another that piques my curiosity is the Olson 40 intended as a long distance cruiser! Olson Ultra Light Displacement Boat

Ultra light, modern style but at her water line she has a canoe stern... and an open transom? Just plain weird...

Anyhow... I like my long overhangs. Gorgeous to look at...

Zach
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