Are we making any real design improvements??

Hi everyone,

Well, this doesn't exactly answer the question of speed, but over the course of a year or two, I've assembled something which could help.

I have a parametric analysis of over some 200 recent yachts. They vary from custom built to mainstream yachts. From these boats and the calculation of disp/L and SA/disp, I conducted a regression.

Personally, I use this spreadsheet for design purposes. The regression I calculated specifies a scale from 0-10, with zero being slowest and 10 being a speedster. A '10' has a disp/L of about 80 and a SA/disp of about 30.

Anyway, this data doesn't solve the issue from this thread, but it's useful for me for design purposes. Maybe this parametric regression can be useful for other people in measuring relative boat performance.

-Jon

 

Oh, by the way:

Some ballast ratios are approximate. If a ballast ratio is = 0.42, then it is an assumption I put in myself.

Also, I apologize for the sloppy spreadshet. I forgot to unlink it from one of my design spreadsheets.

Anyway, I hope this is still useful.

-Jon

 

The issue I am raising here is:
"How do you know if they are slow designs or not?"

There must be fundamental basis on which we can make a sound judgement. I suspect you are only looking at speed for the length of the boat in many instances.

I am proposing a sound basis, which is rather easy to use, but not getting any feedback on whether this would be an acceptable measure.

I am rather sceptical of using IMS and VPP for predictions, firstly for the reasons explained in the recent IMS thread, and secondly because I want to compare actual performances, not just theoretical ones.

 

I skeptical of using ratings or racing results to determine design progress. The technical changes are too confounded with rule changes, fashion, and other "social" factors.

There are some changes over the last several decades that are accepted as progress: rod rigging instead of wire, fin keels instead of long keels, light foam core construction instead of carvel wood construction, modern sailcloth, etc. Would your analysis method detect them?

Many other changes are far more subtle, such as anti-pitch hull shapes.

 

As I see it, the answer is definitely "Yes", a basic reference using Displacement, Length and Sail area would quite clearly identify the most efficient designs.

It would also be completely independent of rules, ratings and handicaps. It is quite simple to calculate and apply to all boats, even those 80 years old, from existing data. That is why I am seeking reference data.

It would not identify which of these individual factors makes the difference. That would be up to the individual designer.

What it can highlight though, is whether these material developments are being applied to fundamentally poor designs, which I suspect may be the case.

 

we know that they are slow designs simply because the unlimited boats and development boats dont wouldnt touch the concepts with a fifty foot pole.

if there were a basis where performance could be compared it would be an excellent design tool for certain. but what rules have shown is that they dont work.

every rating rule has the same objective of what you are trying to acheive. that is to measure boats in a way which can be used to predict speed. the people making these rules are not idiots. they have found such a basis impossible to find and so imperfect rating rules are introduced. it would be naieve to say that design could be compared to some sort of relative speed of some simple form. i hapen to like this concept=length*squareroot(sailarea)/cubed (root mass). butit is nlyapproxiame as it will always be.

 

A basic performance measure

I am not trying to create a rating rule, or even a design tool, but simply to find a basic reference measure from which true performance can be evaluated.

I disagree with your assumption about rating rules as they have quite different philosophical requirements. In general they try to handicap the actual performance of a boat so they can all be raced "equally", effectively removing the design element from the equation and allowing skippers and crew to be judged "fairly" on their sailing ability. This means in effect that real new design advances are actively discouraged.

IMS goes to incredible lengths in an attempt to predict the actual boat speed, effectively penalising any advancements, but it also seems to favour certain hull types and configurations. refer to the IMS discussion forum.

What I have proposed is not based on a simple proportional relationship between displacement length and sail area, but is based on well established actual test data of hulls in water, which shows non linear behaviour and is applicable to all displacement and planing craft.
When I calculate the values I can quite simply and reasonably accurately predict IMS ratings. The point is that these do not necessarily reflect the actual performance of the boat, otherwise they would have the new and much older designs all finishing closely on handicap, with no need for age allowances etc.

You are in fact correct in saying that rating rules are imperfect, but they are not trying to encourage better designs, just predict speed so they can produce close racing on handicap. The basic measure I am proposing is only a reference point. If a boat performs better than this, it is an improvement. The boats which exceed this measure by the greatest margin may be considered the most efficient designs. Because of the handicap rules, in many cases these "efficient" designs are heavily handicapped and so do not easily win races, hence they can go unrecognised. Conversely inefficient designs, well sailed can win on handicap quite easily.

What I am seeking is if this proposal to use fundamental data as a reference could be considered useful, or if people have other ideas.
Has such a proposal been made before?

 

Just an idea... if it's dumb, youl'll tell me
Long rambling ahead, consider yourself warned! :!:

After a big number of reference boats have been collected, it might be a good idea to simplify the mission a bit. Ok what's "generally" different between a 70's IOR Racer a 90's IMS and the latest version of IMS and how does that compare to boats built whithin the same timespan that are ULDB's or sportboats (or any other type we can think of).
Then selecting a number of existing boats as model references and then finally trying, to as best as we as a collective can, gather as detailed info as possible about the specific boats (without trying to splash the designs. To show what advances, and evolutionary changes have been made through the years but excluding the dispacement, sailarea, CG, increase/decrease in wl from "the equation". How many boats to actually compare is another issue

But I don't think that an analysis like that can ever be totally analytic and numeric. It has to be evaluated and expressed in general language. Otherwise you will one way or another build yourself into the same kind of corner as the handicap rule writers do.

Is this along your line of thinking Wardi?

An open paper like this would be immensly useful for design students, and probably quite a few practicing designers as well.

This IS what any designer does in his/her own way, to figure out what and how, to change and improve stuff. But a designer does NOT disregard the stuff i mentioned earlier dspl etc. as they are very important in the design process. But having the knowledge of things that physically improve speed or handlig through the shape of the hull is still the part that remains partially untold in any designbook, good and bad.

Flow analysis is beyond the scope of most students and quite a lot of designers as well. So having evolutionary design differences like these could be a nice help.

As we say in sweden: "Am i totally out on my bike?" (yes swedes are crazy)

 

Hello Erik,
Yes I think you are on the right track!.
I now have data on around 3,500 boats. I have the age for around 1000 or so of these and actual performance data for all of them, so I am able to plot performance improvement over the past 80 years.

Unfortunately I cannot readily identify which designs are to which rule, nor which ones have the crew sitting on the gunwhale. That is where you may be able to assist me. Also many of the designs are from the US and I am not so familiar with them.

I agree with your methodology. We already have PHRF actual performance data available and dates it is not so difficult to compare boats.

There is not so much data on Sports boats or new rule IMS. This information would be very useful. I have tried ORC staff, offices etc and been told they will not let me have even the basic IMS measurement info and do not have race result data available. I am now trying individual sailing clubs instead.

I have been able to graph several relationships already which are very interesting. It certainly confirms many current observations, such as the dramatic reduction in Displacement/Length and clear improvement in Speed/Length over the past 80 years.......but it also brings up some rather controversial results when you look at which designs are in fact the most efficient. I hope to show this shortly.

The analysis is not deeply numeric, but does tell us a lot of basic things and is very interesting to see developments over time.

I am only measuring performance against Displacement, Length and Sail area.
As I see it, all the rest should be left up to the designers to come up with the most efficient possible design.

The only really contentious part is how to manage stability, but that is self limiting anyway until we get to trapeze and canting keels etc.
One way is to do as you suggest and separate Keel Ballasted boats from Crew and Water Ballasted boats, also Cruising from Racing etc. Within each category I see no need to divide any further. Unfortunately the data does not help me with such categorisation.

I am putting together a paper on this and will certainly share it. What I am most interested in at the moment is feedback on the basic principle of using Taylors resistance data as a fundamental reference point. Do you see any problem with this?

 

Swedish ramblings... [[[ in english ]]]

Wardi then I might be misunderstanding what it is that you want to achieve...

I do agree that your camparisions ARE interesting and being able to se how much speed has increased over the years when it comes to comparing SA/D/V is certainly a good thing to be able to do. But...

In my opinion the most interesting things to look at from an evolutionary standpoint is not the general change in SA/D/V and how those factors have changed over time. It is interesting but what's left AFTER you have been able to deduct the main parameters out of the equation is the changes in hull shape and how that has changed over the years and what effect if any the changes have made on performance.


We all know the basics that a slim hull makes for improved displacement sailing and that most boats of light to medium displ that wants to be eble to surf or even get up and plane, needs to have quite a large area to generate lift.

But the rest...
How much rocker and why, overhangs or not and how it affects differnt kinds of vessels. Hard knuckle bows or not. How cp compares between different boats of the same general chracter and why hull differences generates the effects it does. Wake reduction, and on and on...

Personally I think that theese things currently seems to be an area where only experience or software like shipflow counts...

But as a student there's so many things that aren't very well explained in any design book, and there's hardly any online source that really discusses any of these issues at length. We all know how to improve speed and stability with weight reduction and techology. But finding the information on why one should/could choose a certain configuration over another weighing the pro's and con's against each other.

Yeah yeah I know nothing beats experience on the water with different kinds of boats, but on any two boats not only one thing will differ, so how to evaluate the small differences?

Jeez Now I'm rambling again... Well I warned ya!

 

Hello Erik,
Yes I agree entirely to everything you wish to achieve, and I even think it is quite possible to get a lot of useful information about these detailed design issues, from the basic data, but let's not rush too far all at once!

As I see it, you cannot compare design improvements unless you have a sound basis for making the comparison. ie: how do you know which is the fastest boat in the beginning?

The simplest way of course is to have identical boats and make changes to one. The problem is that this is expensive, impractical and does not allow you to easily compare size effects etc.

What I am proposing simply allows you to compare the performance of any two boats, they don't have to be identical in the beginning.

As far as I am aware, there are no methods available for doing this today, except via rating/handicap rules, which have been consistently shown to be flawed.

So therefore I am concentrating on getting the reference point right in the beginning. I also want it to be simple, effective, readily available and simple to apply.

Step one is to agree that this is worthwhile and that the method proposed is valid.
(I have no concrete feedback on this yet, actually I am stunned by the silence, so I assume I am on the right track, or I would be shot down in flames already!)

Step two is to apply it and see what we find.
(I have been doing this over the past couple of weeks. It looks to work very well and raises many questions which I am trying to solve before publishing.)

Step three is to compare results and see which boats are actually efficient.
(This is the step you want to jump to in order to identify which detailed design features are beneficial. I have not got this far yet, but am getting some insights as I go...I am sure you will be able to find out what you want.. but as this is an entirely new exercise perhaps the results will not be what you expect!)

So back to step one...do you think the fundamental basis for this proposal is sound?
ie: Is it valid to use Taylors resistance data to determine a Speed Potential based on the Displacement, Length and Sail Area of the boat.

 

Unfortunately I can't recall what the Taylor resistance data stated. I'm sure there's a link somewhere in this thread that I have missed, if you could post a link I would be most grateful.

Well now I have to prep myself and the little boat for a racing weekend. I'll be back late sunday and try to search for the taylor resistance paper and have a look. Although I'm not altogether sure that my math and comparative knowledge is enough to really say wether his data/method is the best way forward, but I can/will have an opinion

Have a great weekend all [I will]

 

As I am reading the direction that this thread seems to be following, it looks like you are almost trying to develop and validate a VPP system. Many of the improvements that have occured over the past 25 or so years involve the kinds of subtle changes that do not show up on any data sheet. For example, if you compare a year 2000 IMS boat to the last of the IOR boats, you would find that the vertical center of gravity is much lower relative to the vertical center of buoyancy, that the IMS boats had the longitudinal centers of buoyancy and gravity further aft in the boats, That they had comparatively longer waterline lengths for their lengths on deck, giving them finer bows and lower D/L ratios. That they were modeled to produce less assymetry and therefore less heel induced weather helm through their normal range of heel angles. That they had higher lift, lower drag foils. That they had more easily powered up and down rigs. That they were opitimized to minimize pitch and roll angles and minimize rapid accellerations (mostly because large or jerky motions make sail and keel flows harder to maintain rather than crew comfort but the crews benefited just the same.) And so on.

These are not the kinds of things that are easy to quantify and yet cumulatively they produce significant speed gains. And even if you had a VPP program that could precisely predict the actual speed of the boat, there are very big tactical advantages that comes with small speed gains. A faster boat has the ability to sail slightly farther in order to place itself in a position where wind or current offers some advantage.

In talking to designers of early IMS boats, the goal was to simply produce boats that were optimized for speed. There was no real effort to 'beat the rule' since the rule was pretty equitable with regards to real boat speed from one boat to another so that a wide variety of boats were able to race pretty equitably under the IMS during the early days of the IMS. The IMS typeform boat's real advantage came from their very real speed advantage on a boat for boat basis and that allowed them a lot of tactical advantages which is how they won races.

(Just to give an example of this, while this happened pretty routinely in those days, one of the first times that one of these early IMS type form boats showed up on the starting line in a race that I was in, the boat set up to leeward of the rest of the hot boats, which were fighting for position at the committee boat. All of us in the first row got off the line with moderately clear air, but the IMS boats ability to point higher and make less leeway allowed them to come up from below each of us and pinch us off one by one until he was out front sailing in completely clear air. That mean less clearing tacks, and a higher and faster pointing ability.

Another example might be something that came up in a conversation with Bruce Farr about the second generation Volvo 60's nee Whitbread 60's. The second generation boats were more optimized for light air performance rather than for heavy air performance. Mr. Farr explained that days could be gained in the light air venues as a light air optimized boat could continue to jump from puff to puff and keep moving. Those kinds of time gains could not be made up from the minor speed gains of a heavy air oriented boat. In otherwords the advantage of the light air oriented boat was not in quantifiable boat speed but in the tactical advantage of being able to keep moving and find more wind in the nearly no wind conditions.)

It was the ability of these fast boats to break away from the pack and sail thier own race that gave these boats their unrated speed advantage rather than the fact that the boats were actually faster than the rule thought they were, which in both cases I don't think that they actually were. As a result, the rule promoted boats that were simply fast and easily handled, and that is how a properly written VPP based rating rule would work.

So back to your problem of figuring out where the advances were made and validating them, I am not sure that without detailed data on these boats such as sailplan, hull lines, weight distribution data, etc. that you really can tell accomplish what you are proposing. And even if you could accurately predict a boats straightline speeds when sailing a boat is sailing by itself, it is next to imposible to rate a boat for the tactical advantages that comes from that straight line speed.

Respectfully,
Jeff

 

Wardy:

I am not qualified to comment on Taylor's Resistance.

But, I have been waiting anxiously to see what you may have uncovered; whether it is perfect or not! I think that you should publish the numbers and then let the critics analyze the results. I believe that all the discussion is by the folks that don't really want to find out that a '70s PHRF boat is still as fast as an IMS built racer.

Besides, you are the one DOING ALL THE WORK. Don't let the rest of us stand in your way.

Show me the numbers.

 

Do you really believe that "a '70s PHRF boat is still as fast as an IMS built racer." ?

It is not hard to show you the numbers. I think that I gave some numbers earlier, but comparing boats based on length you can compare a Tall rig deep keel version of a Tartan 41 (1972) which was a extremely competitive boat in its day to a shoal keel version of a Beneteau First 40.7 (2000). Both are designed by leading race boat designers at the moment that they were designed, both offer reasonable interiors and tankage, and both were dual purpose boats.

Under PHRF, the Tartan 41 rates 111 to 114 and has trouble sailing to that rating while the Beneteau 40.7 rates 54-63 and sails to that rating pretty easily. That is approximately a minute a mile which is an enormous speed difference in real life. On a 30 mile trip the 40.7 would be almost four miles ahead of the Tartan 41 at the end of the trip. The Tartan needs a bigger crew and more of its crew on the rail to achieve its rating than the Beneteau. If you look at more mundane performance boats of the 1970's like an Ericson 41 they have ratings that in the 130's another 20 seconds a mile slower still.

If you compare a purpose-built raceboat like a J-36 (1979 or even its faster modification the J-35 from 1983) to a contemporary purpose-built raceboat like the Farr 36 you find a similar spread with the J-35 at 72 and the Farr 36 at 0. And again the J-35 is much more dependent on a larger crew perched on the rail to achieve its speed. Comparing boats by displacement instead of length the numbers get even larger.

There is no problem finding the order of magnatude differences in speed that have resulted over time, they are very large. If I understand what this thread is about, I think what this thread seems to be asking is, 'what are the breakthroughs (both large and small) that have resulted in these speed gains?' and not whether a speed increase has occurred.

Jeff