jimi
Well-known member
Found this on the web
on an old thread on sailingworld.com and thought it a well argued case
Posted by Jeff H on January 06, 1999 at 13:00:07:
(This is a very long post so you may wish to print it out if the topic interests you)
It is probably too early to meaningfully comment on the Sidney Hobart disaster and with the tragic loss of life I am not completely comfortable posting this given the fact that there were six people killed, 6 boats sunk, and a half a dozen more critically damaged. This is an important topic and I respectfully want to start to talk to some of the issues that have been raised in prior discussions. I don't think it is fair to point blame at the committee or skippers or crews or boats. The race was predicted to have winds to 30 kts but a couple highs combined to give winds registered over 90Kts in places on the course and almost all the boats experienced 50 to 60 knot winds with gust to 60 or 70 kts. To make things worse there was a fast moving current moving against the wind. Waves as high as 60 feet (20 meters) were reported with most boats experiencing 12 meter or more waves. On top of that the way the system developed in this confined shallow portion of the Bass Straights the waves very vertical and breaking. The reports that I have read suggest that the conditions were brutal with even big and heavy boats being hurtled at all kinds of angles through the air. There will be an investigation so I am hesitant to speculate on what will be found.
From what I gather out of 120 to 140 or so boats only 40 or so were able to finish the race. The remanding boats dropped out of the race or else were lost. There were a dozen or so boats that lost their rigs or rudders. From what I gather the race fleet included a wide range of boats from traditional vessels to modern IMS boats with a fairly large contingent of older IOR boats, some dating back to the era before the Fastnet Tragedy. In scanning the results on the H/S race BB it would appear that by and large the boats that survived were less than 10-year-old IMS boats with a disproportionate number of Farr boats surviving and placing. This may reflect newer gear and equipment and better crew work. This is not to say that only Farr and IMS boats that finished. There is a mixture of older IOR and Cruising boats as well in the list of finishers but the vast majority of finishers were modern boats of relatively moderate size 35 to 42 feet, as well as, much of the big boat fleet.
Within the boats that were lost, 4 were cruising boats and older IOR boats with the other two boats being IMS boats. The most lives were lost on a 47 or so foot wooden boat built in 1947. In the photo she appears to be a very moderate design. She had just been rebuilt for the race. She was described as having been rolling very badly (I imagine most of the crews out there would describe the conditions like that). She took a lot of water over the deck and a lot of hard knockdowns (which is something else I imagine most of the crews out there would describe the same way). It appears that she was eventually thrown sideward off a wave catching her mast tip and rolling. They think the mast damaged the hull near the keel or garboard and she took on water and sank quickly (one report said in less than 7 minutes). Some of the crew were recovered. Three men were lost. Two more men were killed on an older Farr IOR boat. One was said to have had a heart attack during a knock down and the other was lost during the same knockdown I believe by drowning. This boat remained upside down for period of several minutes before righting. Another man was torn from his harness and lost overboard. The harness literally was torn apart by the waves. Of the boats that lost their rigs or rudders half were cruisers or older IOR boats and half were newer IMS boats with one being a brand new IMS 70 footer out for its first race. These are just statistics. I don't think these statistics in and of themselves prove anything. I think the inquest that will follow these sad events will provide information that will be important to all of us.
Last spring Kaj and I had a good discussion going on Marchaj's book, "Seaworthiness- the forgotten factor" as well as, the issue of seaworthiness and modern hull design. I had not been able to answer specifically to some of the points being raised since I was not clear as to the context of the questions. Although I had partially read a Marchaj's book when it first came out, I did not have a copy. I have been fortunate enough to receive a copy of Marchaj's book as well as Larsson/Eliasson's book on Yacht Design. Both look to be excellent information resources.
I have started reading Marchaj, and while I in no way can question Mr. Marchaj's scientific work, I do question some of his basic premises for the book. To begin with, from the very beginning of the book and almost universally, at least in all of the commentary that I have read so far, it is clear that the focus of his criticism is the boats developed under the IOR rule. There is a problem with this if one looks at the differences between IMS boats and IOR boats. It is in that regard that I want to comment.
1. While the IOR was the premier international racing rule at the time that the book was being written, it has subsequently be supplanted by the IMS rule. To a great extent the IMS rule was developed to correct some of the problems of the IOR that Marchaj validly identifies.
2. One of Marchaj's key premises is that since the 1800's, racing boats have evolved to beat the limitations of a rule rather than respond to the natural requirements of a vessel at sea. This evolution of design to beat any given the rule typically results in a common design for a rule beater in both hull and rig. This standardization of rule beater design is called a "type forming" and you might refer to them as a "CCA type form" for example. Some rules like the CCA and MORC actually were intended to produce a "wholesome" type form.
3. I am not sure that it is fair to criticize all rules that produce a type form without looking at the how the type forming occurred and the results of the type form. It is important to understand how the IMS came to be and how that differs from a traditional rating rule like the IOR, MORC, CCA Universal or International Rules. First off, the IMS was never intended to produce a type form. It was intended as a method to fairly rate the performance of genuine all- purpose boats. By that I mean, to rate existing boats that were genuinely dual- purpose racer/ cruisers (or cruiser/ racers). It was a reaction to the IOR, which was understood to produce a type form that was seen as neither fast nor seaworthy. IMS's origin and growth occurs as a result of several unrelated events;
· The Fastnet Tragedy,
· The successful design of simple non- IOR boats that could clean the clocks bigger Grand Prix level IOR boats (J-36's for example), and
· The widespread availability of improved computer technology.
IMS could only exist in the computer age. It is derived from a performance prediction program (also called a VPP or velocity prediction program). These programs began life as a huge collection of data gathered from a wide range of boats. This information was digitized and analyzed to develop an understanding of those factors that, at a micro level, affect the speed of a sailing vessel. This program's original intent was to allow designers to predict how a new design (or changes to an existing design) would perform in the real world. These VPP's had nothing to do with a rating rule.
As the accuracy of these VPP's began to be borne out in real life situations the idea of using the VPP's, as a basis for a rating rule became popular. The original IMS was called the MHS, Measurement Handicapping System. This name expressed the goal of the MHS, which was to handicap boats based on their measurements, rather than a rating rule.
There are several problems with this ideal. First of all to be really accurate and not just a rough approximation there had to be a lot of measurements, enough measurements in fact that the entire design of the boat can be understood. Beyond that, individual boats all have points of sail, wind speeds, and sea states at which they excel relative to other boats. To be fair to each boat, there needed to be different ratings for each boat in each distinct range of conditions. This made it very complex to measure a boat under the MHS/ IMS. It also made it difficult to score a race since the committee had to determine which of the multiple ratings should be used to score each race.
4. As it turned out, at the grand prix level, the IMS did in fact generate a type form. This is where I feel that the premise of the book (that rating methods produce boats suited to the rule rather than the sea) fails to apply to the IMS. In the case of IMS, since the rating rule only accesses speed potential the best boat for the rule is a boat that is fast based on the conditions. At the Grand Prix racing level IMS type forming has been optimized to produce well rounded boats with a bias for short course, inshore racing which is the predominant form of racing these says.
5. Some of the Marchaj's criticism is valid if these IMS Grand Prix level boats are seen as being offshore racer/ cruisers. Obviously these boats are biased toward speed over seakeeping. If Marchaj is assuming that all race boats need to be optimized for seakeeping ability then his criticism has validity. But I question whether this premise truly is a valid way to view boats that are purposely designed and optimized for shore course racing at a very high level. I think that it is perfectly valid to develop boats that are specifically designed for a particular venue. I believe that these yachts should NOT be seen as inherently inferior as long as the use and limitations of the design is clearly understood by the designers and users of these boats.
6. I question the premise that the quest for speed is at odds with the goal of developing seaworthy vessels. Just because these boats are optimized for speed does not mean that they do not provide valid information that is useful for the design of vessels for offshore use. Just as the space capsules would make miserable highway commuter cars, I agree that IMS grand prix level race boats make dubious long- range cruisers. That said, The information learned in developing and testing both space craft and grand prix level IMS boats provides a lot of useful information and trickle down technology that can and has altered the shape and equipment of more mundane vehicles and vessels. Since IMS places an advantage on hull form, sail plan, and weight distribution development, the core information can be used to improve the shape and sail plans of cruising boats. IMS places an advantage on careful engineering as well. At the very least the test data can be used to optimize cruising boats even if the shape and rigs used on cruising boats may be entirely different.
7. I am not sure what the results of the Sidney Hobart Race study will reveal but despite the obvious speed advantage of IMS types, they are also proving to be reasonably good sea boats. You may question this based on withdrawals from heavy weather races and the notable crashes and burns that have occurred in a number of major races. I am not sure how relevant the drop out and gear failure rates really are to analyzing the boats as sea boats. As Marchaj rightly states there is a human factor. These boats are equipped to perform well in light winds. Reasonable judgement would cause one to shorten sail and sail conservatively in heavier conditions. But on a race- course there is a tendency to over due things rather than to succumb to prudent seamanship. It therefore not surprising that gear gets broken. I am not sure that more shouldn't be done to assure that race boats have safe scantlings. I think many of the early IMS boats were guilty of having very the fragile rigs that also characterized IOR. There seems to be a trend in IMS toward stronger rigs albeit at the expense of more exotic materials. I don't like the current IMS experiments with boats without backstays.
To criticize the rule because boats get damaged would be like criticizing the Colin Archer cutters and ketches if they blew out their light wind inventory. The Colin Archer cutters and ketches carried a huge inventory of light wind sails carried on top masts and yards etc. In a blow these were struck and returned to the safety of the deck. If this were not done the gear would be damaged. It would not be a fair criticism of the Colin Archer's to criticize them for having light air sails that can be damaged than it is to criticize the IMS boats for loosing sails and rigging carried beyond the wind speed for which they are intended.
I am not talking about the Hobart race here, but I think it is wrong to be critical of race boats for retiring from a race when the conditions get a bit rough. First off, you would never criticize a cruiser for altering course to duck in for shelter from a blow. I don't see why it is seen as a failure if race boats retire in heavy air. Remember these boats may be at sea with relatively inexperienced crews and without changes of clothes, etc. that you might find on a boat expecting to be out for days at a time.
8. . In looking at the criticism of the IOR in Marchaj it appears that the criticism was focused on the uncomfortable motion and roll over and the upside down stability problems associated with the IOR boats he was studying. Marchaj sees these problems as being caused by the following:
· Relatively little ballast and ballast placed quite high up in the hull typical of IOR boats
· The heavy dependence on form stability and crew as movable ballast
· The broad flat bottom transoms, wide water line beams coupled with fine bows;
· Large amounts of flair resulting in a wide beam at the deck line
· High freeboard
· Light weight rigs
To some extent the IMS type form addresses these problems but not always in an obvious way. IMS boats have a lot of ballast stability which is generated from a large amount of ballast concentrated in a bulb keel and less emphasis on form stability than IOR boats This does not give the quick motions associated with stiffness due to form stability. Crew weight is still important but less so in the comparatively narrow hull forms used in the IMS type form (at least Farr's more recent versions of the type form.) The large ballast ratios and comparatively narrow decks mean a very high recovery angle. The deep keels and bulb placements dampen roll rates. While the IMS boats rigs are lighter than ever, they are comparatively tall resulting in a polar inertia that would be similar to a heavier shorter rig.
As I said last spring when we began this discussion I am not advocating the use of Grand Prix IMS race boast as long distance Cruisers, but I think that a lot can be learned from the lessons of these boats. One of the things I still believe is that most of us will not be venturing offshore as much as we will be coastal cruising. To me coastal cruising under sail on the east coast of the US requires boats that can sail well in a wide range of conditions including a lot of light air days. To me this means a lightweight boat with a healthy sized sail plan. I think the lessons of the IMS type form are that light boats can be good sea boats
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on an old thread on sailingworld.com and thought it a well argued case
Posted by Jeff H on January 06, 1999 at 13:00:07:
(This is a very long post so you may wish to print it out if the topic interests you)
It is probably too early to meaningfully comment on the Sidney Hobart disaster and with the tragic loss of life I am not completely comfortable posting this given the fact that there were six people killed, 6 boats sunk, and a half a dozen more critically damaged. This is an important topic and I respectfully want to start to talk to some of the issues that have been raised in prior discussions. I don't think it is fair to point blame at the committee or skippers or crews or boats. The race was predicted to have winds to 30 kts but a couple highs combined to give winds registered over 90Kts in places on the course and almost all the boats experienced 50 to 60 knot winds with gust to 60 or 70 kts. To make things worse there was a fast moving current moving against the wind. Waves as high as 60 feet (20 meters) were reported with most boats experiencing 12 meter or more waves. On top of that the way the system developed in this confined shallow portion of the Bass Straights the waves very vertical and breaking. The reports that I have read suggest that the conditions were brutal with even big and heavy boats being hurtled at all kinds of angles through the air. There will be an investigation so I am hesitant to speculate on what will be found.
From what I gather out of 120 to 140 or so boats only 40 or so were able to finish the race. The remanding boats dropped out of the race or else were lost. There were a dozen or so boats that lost their rigs or rudders. From what I gather the race fleet included a wide range of boats from traditional vessels to modern IMS boats with a fairly large contingent of older IOR boats, some dating back to the era before the Fastnet Tragedy. In scanning the results on the H/S race BB it would appear that by and large the boats that survived were less than 10-year-old IMS boats with a disproportionate number of Farr boats surviving and placing. This may reflect newer gear and equipment and better crew work. This is not to say that only Farr and IMS boats that finished. There is a mixture of older IOR and Cruising boats as well in the list of finishers but the vast majority of finishers were modern boats of relatively moderate size 35 to 42 feet, as well as, much of the big boat fleet.
Within the boats that were lost, 4 were cruising boats and older IOR boats with the other two boats being IMS boats. The most lives were lost on a 47 or so foot wooden boat built in 1947. In the photo she appears to be a very moderate design. She had just been rebuilt for the race. She was described as having been rolling very badly (I imagine most of the crews out there would describe the conditions like that). She took a lot of water over the deck and a lot of hard knockdowns (which is something else I imagine most of the crews out there would describe the same way). It appears that she was eventually thrown sideward off a wave catching her mast tip and rolling. They think the mast damaged the hull near the keel or garboard and she took on water and sank quickly (one report said in less than 7 minutes). Some of the crew were recovered. Three men were lost. Two more men were killed on an older Farr IOR boat. One was said to have had a heart attack during a knock down and the other was lost during the same knockdown I believe by drowning. This boat remained upside down for period of several minutes before righting. Another man was torn from his harness and lost overboard. The harness literally was torn apart by the waves. Of the boats that lost their rigs or rudders half were cruisers or older IOR boats and half were newer IMS boats with one being a brand new IMS 70 footer out for its first race. These are just statistics. I don't think these statistics in and of themselves prove anything. I think the inquest that will follow these sad events will provide information that will be important to all of us.
Last spring Kaj and I had a good discussion going on Marchaj's book, "Seaworthiness- the forgotten factor" as well as, the issue of seaworthiness and modern hull design. I had not been able to answer specifically to some of the points being raised since I was not clear as to the context of the questions. Although I had partially read a Marchaj's book when it first came out, I did not have a copy. I have been fortunate enough to receive a copy of Marchaj's book as well as Larsson/Eliasson's book on Yacht Design. Both look to be excellent information resources.
I have started reading Marchaj, and while I in no way can question Mr. Marchaj's scientific work, I do question some of his basic premises for the book. To begin with, from the very beginning of the book and almost universally, at least in all of the commentary that I have read so far, it is clear that the focus of his criticism is the boats developed under the IOR rule. There is a problem with this if one looks at the differences between IMS boats and IOR boats. It is in that regard that I want to comment.
1. While the IOR was the premier international racing rule at the time that the book was being written, it has subsequently be supplanted by the IMS rule. To a great extent the IMS rule was developed to correct some of the problems of the IOR that Marchaj validly identifies.
2. One of Marchaj's key premises is that since the 1800's, racing boats have evolved to beat the limitations of a rule rather than respond to the natural requirements of a vessel at sea. This evolution of design to beat any given the rule typically results in a common design for a rule beater in both hull and rig. This standardization of rule beater design is called a "type forming" and you might refer to them as a "CCA type form" for example. Some rules like the CCA and MORC actually were intended to produce a "wholesome" type form.
3. I am not sure that it is fair to criticize all rules that produce a type form without looking at the how the type forming occurred and the results of the type form. It is important to understand how the IMS came to be and how that differs from a traditional rating rule like the IOR, MORC, CCA Universal or International Rules. First off, the IMS was never intended to produce a type form. It was intended as a method to fairly rate the performance of genuine all- purpose boats. By that I mean, to rate existing boats that were genuinely dual- purpose racer/ cruisers (or cruiser/ racers). It was a reaction to the IOR, which was understood to produce a type form that was seen as neither fast nor seaworthy. IMS's origin and growth occurs as a result of several unrelated events;
· The Fastnet Tragedy,
· The successful design of simple non- IOR boats that could clean the clocks bigger Grand Prix level IOR boats (J-36's for example), and
· The widespread availability of improved computer technology.
IMS could only exist in the computer age. It is derived from a performance prediction program (also called a VPP or velocity prediction program). These programs began life as a huge collection of data gathered from a wide range of boats. This information was digitized and analyzed to develop an understanding of those factors that, at a micro level, affect the speed of a sailing vessel. This program's original intent was to allow designers to predict how a new design (or changes to an existing design) would perform in the real world. These VPP's had nothing to do with a rating rule.
As the accuracy of these VPP's began to be borne out in real life situations the idea of using the VPP's, as a basis for a rating rule became popular. The original IMS was called the MHS, Measurement Handicapping System. This name expressed the goal of the MHS, which was to handicap boats based on their measurements, rather than a rating rule.
There are several problems with this ideal. First of all to be really accurate and not just a rough approximation there had to be a lot of measurements, enough measurements in fact that the entire design of the boat can be understood. Beyond that, individual boats all have points of sail, wind speeds, and sea states at which they excel relative to other boats. To be fair to each boat, there needed to be different ratings for each boat in each distinct range of conditions. This made it very complex to measure a boat under the MHS/ IMS. It also made it difficult to score a race since the committee had to determine which of the multiple ratings should be used to score each race.
4. As it turned out, at the grand prix level, the IMS did in fact generate a type form. This is where I feel that the premise of the book (that rating methods produce boats suited to the rule rather than the sea) fails to apply to the IMS. In the case of IMS, since the rating rule only accesses speed potential the best boat for the rule is a boat that is fast based on the conditions. At the Grand Prix racing level IMS type forming has been optimized to produce well rounded boats with a bias for short course, inshore racing which is the predominant form of racing these says.
5. Some of the Marchaj's criticism is valid if these IMS Grand Prix level boats are seen as being offshore racer/ cruisers. Obviously these boats are biased toward speed over seakeeping. If Marchaj is assuming that all race boats need to be optimized for seakeeping ability then his criticism has validity. But I question whether this premise truly is a valid way to view boats that are purposely designed and optimized for shore course racing at a very high level. I think that it is perfectly valid to develop boats that are specifically designed for a particular venue. I believe that these yachts should NOT be seen as inherently inferior as long as the use and limitations of the design is clearly understood by the designers and users of these boats.
6. I question the premise that the quest for speed is at odds with the goal of developing seaworthy vessels. Just because these boats are optimized for speed does not mean that they do not provide valid information that is useful for the design of vessels for offshore use. Just as the space capsules would make miserable highway commuter cars, I agree that IMS grand prix level race boats make dubious long- range cruisers. That said, The information learned in developing and testing both space craft and grand prix level IMS boats provides a lot of useful information and trickle down technology that can and has altered the shape and equipment of more mundane vehicles and vessels. Since IMS places an advantage on hull form, sail plan, and weight distribution development, the core information can be used to improve the shape and sail plans of cruising boats. IMS places an advantage on careful engineering as well. At the very least the test data can be used to optimize cruising boats even if the shape and rigs used on cruising boats may be entirely different.
7. I am not sure what the results of the Sidney Hobart Race study will reveal but despite the obvious speed advantage of IMS types, they are also proving to be reasonably good sea boats. You may question this based on withdrawals from heavy weather races and the notable crashes and burns that have occurred in a number of major races. I am not sure how relevant the drop out and gear failure rates really are to analyzing the boats as sea boats. As Marchaj rightly states there is a human factor. These boats are equipped to perform well in light winds. Reasonable judgement would cause one to shorten sail and sail conservatively in heavier conditions. But on a race- course there is a tendency to over due things rather than to succumb to prudent seamanship. It therefore not surprising that gear gets broken. I am not sure that more shouldn't be done to assure that race boats have safe scantlings. I think many of the early IMS boats were guilty of having very the fragile rigs that also characterized IOR. There seems to be a trend in IMS toward stronger rigs albeit at the expense of more exotic materials. I don't like the current IMS experiments with boats without backstays.
To criticize the rule because boats get damaged would be like criticizing the Colin Archer cutters and ketches if they blew out their light wind inventory. The Colin Archer cutters and ketches carried a huge inventory of light wind sails carried on top masts and yards etc. In a blow these were struck and returned to the safety of the deck. If this were not done the gear would be damaged. It would not be a fair criticism of the Colin Archer's to criticize them for having light air sails that can be damaged than it is to criticize the IMS boats for loosing sails and rigging carried beyond the wind speed for which they are intended.
I am not talking about the Hobart race here, but I think it is wrong to be critical of race boats for retiring from a race when the conditions get a bit rough. First off, you would never criticize a cruiser for altering course to duck in for shelter from a blow. I don't see why it is seen as a failure if race boats retire in heavy air. Remember these boats may be at sea with relatively inexperienced crews and without changes of clothes, etc. that you might find on a boat expecting to be out for days at a time.
8. . In looking at the criticism of the IOR in Marchaj it appears that the criticism was focused on the uncomfortable motion and roll over and the upside down stability problems associated with the IOR boats he was studying. Marchaj sees these problems as being caused by the following:
· Relatively little ballast and ballast placed quite high up in the hull typical of IOR boats
· The heavy dependence on form stability and crew as movable ballast
· The broad flat bottom transoms, wide water line beams coupled with fine bows;
· Large amounts of flair resulting in a wide beam at the deck line
· High freeboard
· Light weight rigs
To some extent the IMS type form addresses these problems but not always in an obvious way. IMS boats have a lot of ballast stability which is generated from a large amount of ballast concentrated in a bulb keel and less emphasis on form stability than IOR boats This does not give the quick motions associated with stiffness due to form stability. Crew weight is still important but less so in the comparatively narrow hull forms used in the IMS type form (at least Farr's more recent versions of the type form.) The large ballast ratios and comparatively narrow decks mean a very high recovery angle. The deep keels and bulb placements dampen roll rates. While the IMS boats rigs are lighter than ever, they are comparatively tall resulting in a polar inertia that would be similar to a heavier shorter rig.
As I said last spring when we began this discussion I am not advocating the use of Grand Prix IMS race boast as long distance Cruisers, but I think that a lot can be learned from the lessons of these boats. One of the things I still believe is that most of us will not be venturing offshore as much as we will be coastal cruising. To me coastal cruising under sail on the east coast of the US requires boats that can sail well in a wide range of conditions including a lot of light air days. To me this means a lightweight boat with a healthy sized sail plan. I think the lessons of the IMS type form are that light boats can be good sea boats
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