Are we making any real design improvements??

Discussion in 'Sailboats' started by Wardi, May 3, 2004.

  1. Jeff H
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    Jeff H Junior Member

    I too just got around to reading the whole article and I also find it to be quite disingenuous and intellectually dishonest. Mr. Hughes seems to have a very sellective memory. Lets start with his prime criteria, waterline length to speed. Mr. Hughes is choosing to use the static waterline lengths for comparason. These older boats, designed to the RORC and CCA rules had incredibly short waterlines as a way to beat the rules. If I recall correctly, Margaret Ringtoul was a 46 footer sailing on a 32 '-6" static waterline length. Boats of this erea were designed to have extremely short static waterline lengths but to sail on much longer waterlines when heeled. If you were to compare speed to length of these boats using the sailing waterline lengths or the LOA's, or to compare speed to displacement for that matter, his whole contention would seem silly.

    He choses to compare the upwind times of modern boats with the reaching times of the older vessels, choosing to ignore that when beating, a boat sails roughly 1.4 times the distance through the water of a boat going up wind. Comparing speeds based on distance through the water vs rhumb line distances and comparing reaching to reaching, alone would change his ratios to the point of invalidating his claims of no progress.

    I raced on these older boats back in the 1960's. There was nothing easy or comfortable about sailing these old girls. They were sailed at heel angles that would be totally unacceptable today. They pitched and rolled through huge angles compared to modern IMS based designs, with roll and pitch rates that were not all that much slower than modern designs. When pushed hard they were miserably wet in any kind of heavy going, with their lee rails burried and solid water rolling across their foredecks and into their cockpits.

    When pressed these older boats developed the kinds of huge weather helms that were hell on shoulder joints and steering gear. There is a myth that these short waterline boats like the 'Margaret Ringtoul' had better tracking than modern boats. That's just plan bunk. The race boats of 50 years ago did not track any better than modern designs. With their full ends, comparatvely short keels, and thier attached rudders, the race boats of the 50's and 60's developed very small longitudinal directional moments of intertia. Modern boats with their the longer waterlines, finer entries and the increased moment between their separated keels and rudders actually seem to track better. Beyond that, the best directional stability in a sailing yacht is achieved with dynamic balance of rig and sailplan and there these old boats really did very poorly when it came to dynamic balance.

    Mr. Hughes cites 'Spray' as an example of why a multi-mast rig is better than a sloop, but if you do actually read 'Alone around the World' Slocum describes a boat that was grossly imbalanced under her original sloop rig, and so he was forced to cut down the rig pretty dramatically and then add the mizzen as a balancing sail. Yes, he made 'Spray' easier to sail by making her a yawl but I would categorize this rig change as solely overcoming what I would call a 'design flaw' in the original rig proportions, rather than a demonstration of the inherent advantages of a multi-mast rig. Right out of the box, modern racing sloops come with better balanced rigs, and with modern rigs whose balance can be quickly and easily fine tuned on the fly.

    Anyone who has ever raced a gaff schooner, would tell you that there is nothing easy about racing one of these old birds. Twist is controlled by playing both the peak and throat halyards on both sails gaff, and that was a constant battle going upwind. Those were not 'good old days' for anyone with a decent memory.

    I don't what boats Mr. Hughes raced on back in the 60's, but we sat on the rail back then just as we do today, only it was less comfortable (the high toe rails digging into your thighs and the solid water hosing you with each wave) and a whole lot less effective.

    Anyone who has ever raced in a mixed fleet of boats that contains modern and older race craft, will tell you if compared by LOA, or sailing LWL, or displacement, modern IMS based craft are much faster under all points of sail. With their lighter loadings, balanced helms, smaller heel angles, and smaller roll and pitch angles, they are easier to handle and less tiring on the crew. I race on both modern and tradition boats. While there is a different set of challenges and aesthetics to old boats, performance wise, and ease of handling, these newer IMS derived designs really beat the older designs hands down.

    I too want to return to the Mr. Hughes mention of the LFH quote (to paraphrase) 'When rating rules produce unwholesome yachts the rule is wrong." I don't disagree with that statement. I would say that boats like the 'Margaret Ringtoul', with their rule beating extremely short waterline length, deep canoe bodies and low ballast ratios, and dependence on huge headsails in order to beat the rule, would be a prime example of the case of a rule that produced an unwholesome design typeform. The IMS derived designs are less rule driven and seem to produce boats with better motions, more speed, and more seaworthiness. In that regard, I would say that LFH would approve of our current crop of race boats.

    Respectfully,
    Jeff
     
  2. tspeer
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    tspeer Senior Member

    Ahem... Aren't you ignoring the elephant in the room?

    There have been enormous strides in sailing comfort, speed, and efficiency in, say the last 40 years. Whether you look at passage-making speeds or race line honours, the winners are...

    MULTIHULLS

    The only way you can say there hasn't been progress is to exclude the category of boats in which the progress has been made. When you do that, it's not surprising the results are disappointing.

    Compare the Margaret Rintoul with a modern cruising catamaran. For example, take the Gunboat 62, designed for Peter Johnstone by Morelli & Melvin. She can easily do 16 kt to windward in about the same wind speed, a S/L of 2.0, and reach maximum speeds in the high 20's - say S/L of 3 or better. Average speeds I'm guessing are are probably around 10 - 12 kt, for a S/L of 1.25 - 1.5, and equal to the speeds of the 98 footers and double the Margret Rintoul.

    Take a look at this video (http://www.gunboat.info/video/safari.html) of a Gunboat 62 smoking a Reichel-Pugh 80 (doing 18.5 kt - S/L=2) and then say there's been no progress in sailing yacht design! Also notice the difference in heel angle. Not shown is the difference in interior appointments between the two boats. The catamaran is also unsinkable.

    Here's another data point: Francis Joyon, around the world in 72 days 22 hours and 54 minutes single-handed. First non-stop single-handed circumnavigation, 1969, Robin Knox-Johnston, 312 days. That's a 427% improvement in average speed in 35 years.

    I count advances in comfort, performance, safety. Cost, too, depending what you hold equal for comparison.
     
  3. SuperPiper
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    SuperPiper Men With Little Boats . .

    A monohull is TYPICALLY limited to a S/L of 1.34 (+/-). Two monohulls racing side by side are each sailing at S/L = 1.34. But if the 2 hulls are attached they can sail at S/L = 2.0?

    Explain that one to a stupid guy.

    Is it the NARROW HULL rule?
    Is it the fantastic reduction in weight?
    Is it the increased sail-carrying capacity?

    If the answers are YES, then what is the expected S/L for a light, narrow (DISPLACEMENT) hull with unlimited sail?
     
  4. redcoopers
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    redcoopers Member

    An S/L ratio of 1.34 is not set in stone. To understand why most 'typical' monohulls do not exceed this speed in normal conditions, we need to know what causes the resistance in the first place.

    If we divide all of the drag on the hull into two categories: viscous and residuary, two things can be shown. First, the viscous resistance is proportional to velocity^2 - it will always increase as speed increases. Residuary resistance, or wavemaking resistance, is a much more difficult monster. In fact, we are required to perform tank tests, CFD calculations, or other methods to find what the wave resistance will be.

    Now, the wavemaking resistance is not a smooth curve such as simply ~V^2. Instead, it has many "humps and hollows". Most monohulls experience a large hump right after S/L=1.34. Simply, it's difficult to get the required power to exceed the drag.

    The humps and hollws also explain why racing sleds are built so light today. These boats have enough sail-area that in certain winds, they produce enough power to get over this hump, and then start planing. Now, catermarans are different beasts than monohulls. When sailing upright, wake from one hull may interefere with the wake from another, causing cancellation and actually decreasing the wave-making resistance.

    But, cancellation is a tricky area. Not quite yet are designers actively using this effect (however, there is a tool just being published which can help). Simply, catermerans can utilize a lot more sail power because of the increase in righting moment. This lets them get over the humps and hollows of the wavemaking curve a lot more easily.

    So
    1) Yes, cats are narrow - they don't need beam to increase righting moment. Wavemaking resistance can be shown to be loosly proportional to Beam^2.
    2) Yes, a fantastic weight reduction helps a cat to accelerate off a wave. Remember, however, that weight will not directly affect the steady speed of a boat. (F=ma, not F=mV).
    3) Yes, cats can carry a whole lot of sail-area. This is most responsible for letting them be able to exceed S/L=1.34.

    So, what is the excpected S/L for a light, narrow hull with unlimited sail? For most monohulls upwind, it's 1.34. It's all because of the available righting moment which the hull and the keel can produce. If you have a 30 foot boat with a deep lead keel 13 feet down, you'd probably be able to exceed this because you have a massive righting moment.

    If we're talking about downwind, however, you'd want to scrape the entire keel off of the boat to reduce the viscous drag. You don't need a righting moment when sailing downwind (well, practically, you do), so if you put on enough sailarea, a monohull could almost start to fly...

    Hope this helps,
    Jon
     
  5. tspeer
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    tspeer Senior Member

    Very few cats depend on wave cancellation - in fact the interference is generally adverse. But sailing multihulls also have such wide separation between the hulls that the interference effects are minimal.

    The real answer to their speed is the drag hump at hull speed is so much flatter for the narrow hulls than it is for the wide heavy displacement monohull that the same drive results in a much higher speed. Their drag increases monotonically with speed, albeit steeper in some areas and flatter in others, but overall the curve is much more shallow than for a monohull.

    So they're not exempt from the same influences that lock in the ballasted monohull, it's just that the consequences are far less severe.

    The issue of righting moment is the other reason for their speed. A multihull can shift its center of buoyancy all the way out to the leeward hull, making the separation between center of gravity and center of buoyancy almost half the total beam. A monohull can only move its ballast, say, half the keel depth to windward (30 deg heel) and the center of buoyancy maybe 1/3 the beam to leeward. That's a difference of maybe, a beam's width? So the sail-carrying capacity of the multihull is far higher.

    Then there's the lighter weight, which means less wetted area and less wave drag.

    So the end result is far higher sail area/displacment, far lower displacement/length, and much more easily driven hull shape. These all contribute to the speed.
     
  6. Wardi
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    Wardi Senior Member

    Fundamental improvements

    Measure of performance
    Billy Hughes has chosen to use Speed/Length ratio as a basic parameter for comparing performance. Many of the responses so far have also chosen to refer to this measure, but in fact it is not a good parameter to use at all. Boats of the same length can vary greatly in displacement and sail area. In practice there is around 25% difference in speed/length possible between heavy displacement and light displacement boats of the same length. This has been completely overlooked in the arguments put.

    So when Margaret Rintoul achieves S/L= 1.126, it would equally be expected that an open 60 should be able to manage at least S/L of 1.3 under the same conditions to be considered of equal performance. And yet the figures quoted show a S/L ratio of only 1.26. So it is not so clear on this basis that an open 60 is in fact a design improvement!
    Faster.... absolutely, faster for its length.... well yes, as would be expected, ...........but not necessarily faster when you consider its displacement, length and sail area! :)

    Configuration vs fundamental design improvements
    I am actually quite intrigued at the very mixed response to this discussion. ;)
    Perhaps most surprising to me is how difficult it seems for most people to separate fundamental improvements in performance from basic configuration changes. To be very clear I think I need to explain what I mean:

    a) Fundamental design improvements
    Let us assume we have two boats of the same displacement, waterline length and sail area and of similar configuration. Then any improvements to the rig, hull shape etc resulting in one being consistently faster than the other could be termed a "fundamental improvement" in performance. Typically you could find such improvements within restricted design classes. For example the clear superiority of higher aspect flexible rigs vs fixed, low aspect stiff rigs would be one such improvement.

    b) Configuration changes
    It is very well known that longer, lighter craft with more sail area go faster. So it is quite obvious that if you make a boat with a longer waterline, lighter displacement and sit lots of people on the gunwhale to hold up an even larger sail area, of course it will go faster than its predecessor!!

    I do not consider this a fundamental design improvement at all, simply a configuration change. The only reason it was not done 100 years ago was limitations of materials and in some cases racing rules prohibiting the use of moveable ballast, including crew!

    Hence comparisons given so far with Open 60's, Mount Gay 30's, Catamarans etc are not really valid, as they obviously go faster in absolute terms, simply because they have a different configuration, not necessarily because of any fundamental design improvement!.

    It is only when you can prove improved performance based on their Displacement, Length and Sail area, that we can say a fundamental design improvement has been made. So far, this has not been proven for the examples given! :)
     
  7. Jeff H
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    Jeff H Junior Member

    Wardi, I think that I understand why you are not getting the kinds of responses that you are expecting. The way that I am reading your last post, you are saying that you are looking for changes that bring speed improvements but which don't change the 'configuration of the boat'. In my mind you seem to be defining this term so narrowly that almost any alteration in the design of the boat becomes a change in the 'configuration of the boat'. That does not meant that improvement in performance is not happening, it just means that any change large enough to improve performance would also imply a change to 'configuration of the boat' as you are defining it.

    Getting away from Mr. Hughes S/L numbers which do not appear to be a fair comparason of the speeds of the boats that he is comparing (as I explained in my easlier post) I would like to suggest that we look at particular models over a 45 year period:

    I think that I can start to demonstrate my point by looking at three boats from the same boat builder over a 16 year period. If you look at the PHRF ratings on the Beneteau First Series, you will see that over an 16 year span they have produced three boats in the same general size range: Beneteau First 42, Beneteau First 42s7, and Beneteau First 40.7. They have similar waterline lengths and similar displacements. In most ways, they represent the norm for pretty advanced, high production quantity, performance oriented, club level racer-cruiser boats of their era. (Although I was the mainsail trimmer aboard the box stock, 4 year old 40.7, that won the IMS North Americans so argueably the 40.7 is more than a club racer) The 42 rates 78, the 42s7 rates 63, and the 40.7 rates 54, a jump of 24 seconds a mile.

    If we went back and looked at these rated speeds vs older high production performance cruisers, the trend continues. For example, if we look at the S&S designed Tartan 41, which was a very fast performance cruiser for its day in the early 1970's, the Tartan 41 rates 111-114. Again if we compare that to a Cal 40 which was a very fast boat for its mid-1960's era, a tall rig Cal rates 126. And if we compare that to the Rhodes 41 (a late 1950's design) that was considered quite fast for its day, the Rhodes rates 174 which is roughly a 25% increase in performance over a roughly 44 year period. Oddly enough, in its normal sailing configuration (155 % genoa) the Rhodes carries the most sail area of the bunch and has close to the same SA/D as the other boats. That said, the Rhodes sails on a much shorter static waterline length. Argueably, its dynamic waterline is not all that different from the other boats on this list but its displacement is roughly 15%-20% higher.

    So what were the changes that caused these very real increases in speed? If we look at the Beneteaus, in absolute terms, comparing these boats with the genoas and kites that these boats typically fly (and not with 100% fore triangles typically used for calculating the rated sail area of the boats) the 42 carries the most sail area of the three in its typical sailing configuration, the 42s7 carries the next and the 40.7 the least sail area, and they have very close SA/D's (roughly 25 using the sail area of a 150% genoa) and fairly close D/L (178, 174, 161). The big differences in these boats are hull shapes, vertical center of gravity relative to their vertical centers of gravity, and rig proportions. The 42 had its center of buoyancy much further forward, a deeper canoe body, pinched ends, and a comparatively blunt bow, the 42s7 begins to move the C of B aft and the 40.7 has a very fine bow, carefully modeled lower drag sectional properties, the C of B further aft still, and substantially smaller and more efficiently shaped foils. The 40.7 with its deeper bulb keel has a tremendous stability advantage over the earlier 42s7 or 42. The 42s5 and the 40.7 have fractional rigs which are generally thought to offer greater efficiency than masthead rigs. Combining the 40.7's greater stability with its fractional rig, which allows it to be depowered more easily, the 40.7 can carry more of its sail area through a wider wind range than its earlier cousins.

    In my life I have raced on a Pearson Rhodes 41, Cal 40's, Tartan 41's, Beneteau the 42's and Beneteau 40.7's. With each generation, it has gotten easier for the skippers and crew to achieve more consistent speed. The boats have gotten much easier to handle with smaller crews. In any kind of absolute terms, the newer boat are better cruisers as well. In absolute terms they have offer a more comfortable motion in hard conditions and frankly the interiors are more voluminous and the accomodations have gotten nicer and more comfortable, albeit lighter. At either end of the wind ranges there are enormous increases in speed on all points of sail with the newer designs (less so at the moderate wind ranges that the PHRF uses for its ratings)

    All of that said, it would be very easy to dismiss the performance improvements as changes that represent changes in the configuration of the boat and so I am not sure that the above really addresses Mr. Hughes or your original point.

    Respectfully
    Jeff
     
  8. Wardi
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    Wardi Senior Member

    Hello Jeff,
    In fact you have in fact now understood very well what I am proposing and have provided some very good information and comparisons.
    Please do not get me wrong, I am not saying that there have been no design advances at all over the past 100 years, I am sure that there have, but perhaps not as many and as big advances as we might first think, especially when looking at the responses presented in this forum!

    While I agree with you that my interpretation could be considered a narrow definition, I do not see any other way of evaluating real performance improvements.

    As I see it, anyone can change basic configuration to make a boat go faster, if their pockets are deep enough (make it twice as big), or if you are prepared to bend the rules (sit all of the crew on the gunwhale, or better still put them on trapeze!). This is not necessarily reflecting fundamental advances in boat design. I think we have generally been conned into thinking it is, perhaps because it is not easy to visually "see" changes to displacement or stability, only that the boat is faster.

    I believe it is important to maintain a consistent basis for true comparisons. Hence the requirement for comparing craft of a similar configuration. I do not mean to be highly restrictive with this and all of the examples you have given are pretty valid comparisons. It should be entirely up to the designer to decide rig configuration, areas and centres of lateral plane, bouyancy, stability, ballast ratio, distribution of displacement, hull and appendage shapes etc etc, in order to come up with the fastest possible design. True advances should be properly recognised, not just improvements at beating the current rating rule!

    By using the term "same configuration", I not only mean monohull vs catamaran, but also apply it to the means of providing stability within monohulls. There are several quite distinct categories including Keel Ballasted, Crew Ballasted, Trapeze, Water Ballasted, Canting Keel and even within these there are Cruising and Racing versions. Unfortunately the distinction is somewhat blurred between these categories, especially Keel ballast and Crew ballasted configurations, which has been used as a way of cheating the rules and does not seem a fair comparison.

    It is mostly only meaningful to compare performances within each configuration type, but we can compare across all of these types if we use just three fundamental parameters, Displacement, Length and Sail area. It would be really good if you could supply values for Displacement, LWL, Sail Area and rating for each of the boats you have mentioned. I am not familiar with the rating system mentioned. Can I use this to calculate a realistic speed of the boat? Does this rating reflect true performance of these designs or is it a handicap rating only.

    regds, Ian
     
  9. Jeff H
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    Jeff H Junior Member

    Hello Ian,

    I think that I can supply LOA, LWL, Disp, and SA for these boats but it will take me a little while as I was writing these numbers on an old evelope as I was working on the prior post last night. PHRF is not a measurement rule like the CCA, IOR or IMS but handicapping rule based on past performance. In that regard it is a pretty good indicator of the boat's relative speed at a single moderate wind range. Argueably the numbers my be off by 6 or so seconds a mile but they are generally are pretty close to a boat's performance, especially on the older models for which there is a long history from which to derive the rating. That said, it is hard for an older boat to race competitively against newer faster boats under PHRF because the greater speeds give the newer boats a tactical advantage.

    Jeff
     
  10. henrikb
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    henrikb Senior Member

    The wheel was designed some 1000 years back, it still looks the same... Better materials, but no major improvment in design *s*
     
  11. SailDesign
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    SailDesign Old Phart! Stay upwind..

    Not fair, really, since the Open60 speeds were based on a 27000 mile single-handed voyage, and were based on a minimum speed (100 days) rather than the winning speeds (90 days or so)

    Using cats as a "yes, we have improved" is not fair either, since we're talking apples and cats are definitely oranges in this case. :) That's like saying that the internal combustion engine was a "design improvement" compared to the horse.

    Steve
     
  12. SeaDrive
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    SeaDrive Senior Member

    My opinion is that the actual advance in yacht design is mostly controlled by the advance in materials. The designers learn to use new materials pretty quickly. The better D/L ratios are due to stronger building systems, for the most part. The larger rigs are due to better masts, better rigging, and better sailcloth. Designers are now very greedy about draft. They seem to think that 6ft of draft is appropriate for a 30' cruiser.

    I admire the skill that goes into design and construction of a modern racing boat, but I don't admire the boats that much. As fast and seaworthy as they are, they don't look very comfortable to be on. Most are very low inside, and the storage space complements the thinking of the captain who makes sure the crew cuts half the bristles out of their toothbrushes to save weight.

    Racing rules have muddied the waters all along, and invalidate most of the comparisons that one would like to make. Still, a 40' Island Packet is probably a better boat all around than Finisterre.
     
  13. Wardi
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    Wardi Senior Member

    This PHRF sounds ideal for our discussion! It is quite straight forward to predict a boats potential speed from the D,L & SA data, but I do not have much quantative info on their actual performance, from which we can conclude whether real advances have been made and by how much.

    It is also much more realistic to make comparisons of the performance of craft of similar configuration based on reliable data, rather than trying to deal with the extremes of one-off performances of an Open 60 vs Margaret Rintoul that began this discussion.
     
  14. SeaDrive
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    SeaDrive Senior Member

    PHRF stats can be helpful, but they don't tell you if you need 5 guys on the rail to go upwind, or if the boat is suitable for a weekend cruise.

    Multihull development was very rapid from the time of Piver until it became more or less mature about 10 years ago.
     

  15. Stephen Ditmore
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    Stephen Ditmore Senior Member

    Hi, all. A few quick points, having just skimmed through this thread.

    - The most recent Sydney Hobart was not sailed in particularly favorable conditions. For this reason no record was set, but other records have been falling right and left, and the new IRC 30 meters might well have established new marks given the right circumstances. Sailing is still sailing.

    - Many new IRC 30 meters and MaxZ86's are different from the Open 60s that Steve Baker advocates (bless your enthusiasm, Steve!) in that they are relatively narrow. A lengthened Open 60 (Grundig?) sailed the last Sydney-Hobart, but I don't think it's performance was anything particularly outstanding. Steve - do you think Reichel/Pugh, John Swarbrick, and other designers of recent relatively narrow performance monohulls are headed off in the wrong direction?


    Glad you asked, Super. In the end, speed is a product of horsepower over resistance. In order to have horsepower, you not only need sail area, but the stability to carry it. Wave drag at high speed is dependent upon, among other things, frontal (midsection) area. If the assumption can be made that each boat has the stability to utilize its sail area effectively then an unusual but interesting ratio to look at might be sail area to midsection area, which is to say sail area / displacement ratio with length and Cp factored out of the denominator. Monohull and multihull performance might be compared meaningfully using such a ratio if one were to consider the PROJECTED sail area of each, thus taking into account heel angle.

    Waterline beam may be a bigger contributor to hull resistance than the other frontal area factors: fairbody draft and midship coefficient. Waterline beam helps monohull stability, and therefor sail carrying ability (a plus) but also increases both wave drag (at some speeds more than at others) and wetted surface.

    Multihulls detach the issue of stability from the factor of (each hull's) waterline beam.
     
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