Graphic representation of dinghy performance

[JulianB]

For the umptenth time I was asked 2 weeks ago what boats should a 12 year old Opie kid sail to best place him in a 49er when he gets into his late teens, early 20's.

This mum, was very smart , far greater grasp of numbers than I, spreadsheets, etc, but I still struggled to get the flow across, so I generated the following graphical representation, and she has come back and said, and I quote "Thanks for following up. Interesting graphical depiction of the relative properties of these classes of boats, brings the stats to life."

So, what I am seeking from you guys/gals is a peer review!

I could give you all my figures, but I think that would predispose a bias, which I have little doubt I will be accused of. Instead, I plan to explain my rational, and asked others to have a go at there own interpretation and maybe we can blend them and end up with something meaning full.

So what I have done is go to the RYA site and dig out the relevant PY [Porthsmouth Yardstick] numbers.

http://www.rya.org.uk/SiteCollectionDocuments/technical/Web%20Documents/PY%20Documentation/2015%20PN%20List%20v6.pdf

I have picked the boats mostly on simplicity, firstly if I did not know them, then I could not represent them.

I then went into the ISAF site and looked up the technical data

http://www.sailing.org/classesandequipment/index.php

So I have exclusively used that information unless the RYA/ ISAF data was simply wrong in which case I went into that classes rules and gleaned it from there.

An example, 470 appears not to have a PY number, so I worked out approx where it should be.

I included the IC because its to interesting not to.

And we all know a moth sails heeled to windward and greatly increases its RM by doing so, where as a Laser, when sailed "flat" is actually heeled about 6° to leeward.

I have not imputed these shifts in CoB, I have assume the boats are all bolt upright as per their numbers.

Finally I have used the ISAF HP definition about sailing faster than the wind, downwind, most of the time, to draw the red line.

Not sure why a 470 dose not do it more often (Tack down wind), but we also know a 29er dose, most of the time, (and yes, I know why a 29er dose).

What is irrefutable is that a 5o5 and to a lesser extent a I14, spend a lot of money and effort setting there boats up so they can quite deliberately switch to HP modes both up-wind and down wind, so, from my POV I consider the 5o5, the tipping point boat, it has has a foot in both camps, one could say the best of both worlds.

So the lobes etc on the graph.

PY is pretty easy, bottom of the solid is the PY number.

Displacement to the left of the graph is based on Power to Weight ratio.

Then the Circle compared to the Oval, has to do with RM/SailArea.

So a Moth is round because it has the same SailArea upwind as down, so my thinking is that a sailors ability to create a difference is equally possibly up-wind as it is downwind, where as a 49er the performance opportunities are greater down-wind because of the spinnaker.

The ovals are vertical because boats go a lot faster down-wind than they do up-wind.

That's enough from me, be really keen on some other ideas on this.

Love to hear your comments, and be rest assured I wont be offended!

Jb

 

[Stanno]

Hi Julian

As an OptiDad whose daughter (12) has posters of the 49erFX on her wall, this is just gold!! Putting an Australian spin on it, a FLying 11 would fit somewhere near the RS Feva I guess ie oval'ish, and a shade of blue?? She's just taken the tiller on her new F-11 this winter, and is loving it, while eyeing off the older kids in their 29'ers ... so I have my fingers crossed!

Would appreciate your thoughts on F-11 as a pathway given a similar the statistical analysis above ...

Cheers

Chris

 

[JimC]

Last published UK PY number for a 470 was 973.

A guy in the UK on the Yachts and Yachting forum did a regression analysis on Portsmouth numbers against published boat data figures which produced a surprising correlation, I could put him in contact if you like.

On gybing downwind in 470s, I wonder if the banging the corners/playing percentages thing comes into it. If most of the fleet go square and you sail hot angles you either lose big or gain big. But if you are front of fleet anyway you can't gain much if it goes right (100 yards ahead of 2nd is the same as 1 yard ahead of 2nd) but you only need to lose big in 1 or 2 races to stuff a series. What did you use to do in Cherubs with Nicola: square or hot angles? When sprit kites came out in Cherubs I was unconvinced, but after a season in which vmg/straight line speed was much the same, but I lost at least one place at every gybe mark I ditched the pole kite.

 

[Steam Flyer]

Like!

The only thing I would change is to quantify the power/weight axis, and possibly run it left-to-right increasing rather than the other way around, just because that's the way most graphs I see are done. Yeah I'm more of a conformist than anarchist, maybe.

Another possibility is to use the color as an indicator of class size. The more boats at a classes' Nationals (or midwinters or whatever) the darker the color. This would obviously vary country to country, we don't have many 29ers over here. But it could be a great planning tool and also open some windows for kids who don't realize how many different options there are.

Thanks JB dunno how much time you spent on this but it was very worth while.

FB- Doug

 

[Shu]

Julian,

I'm trying to wrap my head around everything you are showing here. Are the ovals just generic ovals to represent the idea of a greater power to weight ratio off the wind, or does their size indicate the difference in upwind vs. downwind? Since PY modification factors are available for sailing a spinnaker boat without Spinnaker, it seems that later would be possible. Ditto what Doug said about showing power to weight ratio increasing toward the right; it's just what we are used to seeing.

-Steve

 

[JulianB]

Ok, just landed at Heathrow.

Did not include a F11 because it dose not have a PY. But I thought I had to include a 470 because its a Olympic though I did not included a RSX because I was sure that I would get it to far out and its not a pathway to the original question which is a 49er/FX.

Can flip the graph, thats easy.

To get the ovals or the dia of the circles I put the sail area over the RM.

So the width of the oval or the dia of the circle is the working sail area of RM

The height of the oval is the working sail area plus the spinnaker so total sail area of the RM.

I orentated the ovals vertically because as you go upwards you get more performance and most boats go faster under spinnaker than not.

Jb

 

[Rasputin22]

Thanks Julian! Just one question, where can I get that really fast boat at the top? The one called a PY 500...

 

[SimonN]

Nice work, Julian. If I may make a few suggestions on how to change the visuals a little to make it easier to read....

1. Don't get too hung up on scale on the 2 axis. It is more important to be able to easily compare the boats. At the moment, the whole thing is pretty long and thin. I would play with scale to get the boats more spread out horizontally.

2. Find a way of getting the X/Y axis in the middle, with boats distributed either side of both lines. This will result in boats in 4 quadrants and that can end up with some interesting insights. I wouldn't be surprised if you can give the quadrants some name that suggests boat characteristics.

To make it clear, this really is a minor change of the existing data, rather than a rewrite of that data.

 

[SimonN]

I sailed both the 505 and the international (not the club) 420. With the wind up, there was no comparison. The 420 was considerably more difficult to sail because everything happens faster. So the 505 may be too good of a design--to easy to sail in big wind--to train you for a 49er?

This shows why it is so hard to compare boats based on your own experience of those boats. I sailed both 505's and 420's, as did many in the UK. In particular, I sailed them in the big handicap/pursuit races over the winter. If the forecast was windy, I did everything i could to get a 420 for the event because they were so much easier to sail fast in high winds and usually won. In medium winds the 505 was the perfect weapon (lighter winds I would try to sail my National 12).

So for me, the 420 is far easier to sail in a breeze than a 505 and I believe the results in the UK say so. I am not saying that fastyacht is wrong with his own view, just that there are different views, meaning that something like Julian is trying to perfect is a really useful tool because it doesn't/shouldn't allow personal feeling to get in the way.

 

[Gouvernail]

The numbers are all very interesting

The best transition boat will be the one with all the coolest kids with whom your kid cannot resist playing

 

[mustang__1]

Interesting idea this plot.

But,

Notice that basically "requirements" for moving towards a 49er fall out of this as follows:

1. Trapeze a must.

2. Pretty fast boat that planes a lot of the time.

So get the kid out of the 4twinkie and into the 505. This is easy to do. That's been my working theme since 1990. But most adults get pretty upset about it. Heck kids are told not to sail a laser!

On the other hand I've never sailed a 49er nor a 29er but should do that. The 505 is faster than the latter on avg but some have told me that the 29er is more "skiff like" to sail. Whatever that really means. I think it means a pain in the ass.

Now along the "pain in the ass difficult" is good for moving towards the 49er, I'll note that back in the 90s I sailed both the 505 and the international (not the club) 420. With the wind up, there was no comparison. The 420 was considerably more difficult to sail because everything happens faster. So the 505 may be too good of a design--to easy to sail in big wind--to train you for a 49er?

See the performance numbers really don't tell all the story. What are the skills needing development? How do you go about developing them? At a reasonable cost? I think the 29er was supposed to do that?

the 505 is actually considerably faster - having shared a course with them - in pretty much all conditions. However, their tub hull shape (having never sailed one) does not make it conducive to as a skiff trainer. There's more to it than speed. No, i haven't sailed a 5oh, but i have sailed 470's (in other words, i have experienced more than the 420 as far as non skiff hull shape). The skiff-like tendencies you allude - or downplay, can be considerable. Look at the Gorge/I14 thread to see some back and forth on how the 29er is a good trainer for narrow bows and asym kites.

This is not to say that the 420, or 470, is a bad boat or a bad stepping stone. I think those that step right into the 29er from optis are probably going too fast since, in the 29er, you dont get a lot of chance to sit back and say "what should we do now", so the tactical and boat-on-boat stuff can take a second seat to how to make it go fast. The (club)420 is a decent platform to learn big fleet tactics, managing your crew/skipper - communication and how to shut them up, how to trap, and how to handle a bigger boat than an opti. The 29er is great for teaching how to go fast, fast boat tactics, the little intricacies that go along with an asym kite and a narrow boat, and remembering that sailing is supposed to be fun (sorry, but the 420 got boring after a while. Im 25 now and i still love the 29er).

At any rate, from what i know of a wide bow design, even in breeze, it is not the same as a narrow bow/skiff design. That goes for 420's/470's, and 29er/49er/I14 (in order of time on the water). As far as knowing the stupid little shit to watch for, the 29er provided leaps and bounds. As far as how to stay on the trap, and look at a fleet, the base foundation was laid in the 420. Skiff-like means everything from: tipping over at the dock if not tended to, to wrapping your old kite sheet arm around your back as you cross the center of he boat to keep the head of the kite tucked in as you begin to rip the kite around on the new kite sheet and hit the wire as quick and as hard as you can.

 

[JulianB]

Some answers to your inquiries.

Stanno, re the F11, its very much a Australian boat, that has pluses and minuses. And it has no PY number, (this whole document is heavily English skewed.) I have never sailed a F11, I certainly have worked on them and admired them from afar, great kids boat, in the same vain as what is being proposed here they would be better than a RS Feva but its biggest draw back is no International competition. Kids need to be "blooded" in a international event before they are 17, 20 at the outside. That event can be in your case, Australia, but you need a international class with 100+ boats.

JimC, thanks for the 973PY for a 470, I will move it, it will virtually overlap a Fireball, and, OK, once you move it back down the graph, then why they don't tack down wind becomes obvious. Nicky and I in Cherubs, remember spending a lot of time on the wire downwind and these had much smaller spinnakers than they do today, so I can only assume we where running apparents.

Doug, I will flip the graph for you, but you colour concept I'm not sure is relevant.

Steve, my intuitive take is as you go up the graph, you go faster, down you go slower, in its present form, as you go left, you increasing power, as you go right your decreasing power, just trying to KISS and give the umptenth+1 mum something I can explain over the time it takes to drink a cup of coffee without getting into semantics.

FY, every 29er skipper gunwale swings, yet they have no issue what so ever going double trapeze-ing on a 49er every chance they get.

My take, and I know I'm getting subjective here which I really want to avoid is that trapeze-ing is functional, it can be learnt by just about anyone and with practice you get good at it. Apparent Wind Sailing [AWS] is subliminal, it has to become intuitive. Bit like learning a 2nd language, got to do it before your 17-18 or it becomes a whole different learning problem.

Re fast boats, there is very much a place for going out sailing in a slow boat in a big fleet, Laser for instance and learning the discipline of grinding out those places and being very tactical. Sailing a single hander is great because you can't blame anyone else when you muck up.

But nothing beats learning to work as a team. And learning in a fast boat just exaggerates that process because get it wrong you get wet.

Rasspuit, when you find it let me know!

Simon, I don't want to go rocking axis's because that implies bias, but you certainly have me thinking that WRT P/W ratio! We can work off a mean PW rather than a absolute and that will put roughly 1/2 the boats on one side and the other half on the other. We then can compress the vertical scale to get it to nicely fill a A4 page.

And by doing that your not being subjective, you will also get your 2 quadrants.

And you then can evoke the ISAF paradigm, WRT HP and draw a horizontal line there.

Worth a try, I will have to get my son to send me the file, see if I can do this in the next 24 hrs and we can re-conven!

Thankyou,

Jb

Julian

 

[Board skiff]

Hi Julian,

Nice work. I guess you are trying to show that you need to progress up the power to weight ratios to progress towards a 49er.

Further to what Simon suggested, here is a graph I posted on Y&Y a few years back, inspired by some of the work in your dad's books. The vertical axis is the Downwind Sail Area:Total weight ratio and the x axis is Sail Carrying Power: Downwind Sail Area ratio (doubled, for unimportant reasons). That allows you to split boats in to four quadrants - the further to the top and the right the better.

In the chapter on Critical Ratios in the second book, it is suggested that a Sail Area:Weight ratio of higher than 0.53 is needed as one of the conditions to make apparent wind sailing viable, and that essentially sets a limit on the minimum size of the kite. My addition was to argue that, to be a practical boat for UK club courses which usually involve reaching rather than windward/leeward courses, there is an upper limit to kite size based on what can be flown on a reach.

Boats in the bottom left can neither make a assy kite work downwind or on a reach, so are a bit crap. Boat in the top left can work downwind but not on a reach. Bottom right can reach but not go downwind faster than running square, whilst top right hit a sweet spot of reaching and running effectively. The 29er is one of the few in that quadrant, the 49er is top left. Boats like the RS200 are bottom right and rotomoulded boats bottom left.

The area under a marker i.e. the x axis * y axis * 0.5 gives the SCP:total weight ratio, which is also given importance in the Bethwaite bible and I think is the x axis in your plot above.

My plot could be improved by changing the size of the markers to indicate PY.

I am the man JimC refers to earlier as well. I did a regression analysis of PY vs boat fundamental properties and came up with a very simple, but surprisingly accurate, formula to predict PY. What I published on Y&Y was only for kiteless hiking boats, like the Laser etc, but can be adapted to other types of boat.

 

[JulianB]

So I have read Mustag's and Sosoomii mails, needs some names on the boats but I get what your saying, not sure I can get that across to potential parents in the space of a cup of coffee though.

Also I point out this is unashamedly targeted at 49er, these kids and these parents what there kids to go down this path.

Im sure there are a equal number of kids and parents that want to go down a Corinthian path also.

But that's not what I am being asked, and its not my problem, maybe the sports but not mine.

Anyway, I have had another go based on Simon's suggestions, but I have not flipped the graph, its simply to hard on a laptop.

All I have done is re-configure the horizontal scale so compressed the PY's. and then finding a mean because a bit arbitrary based on areas of the ovals/circles so it was very close to running through the 5o5, so I just used it, once again as the mean boat.

Let me know your thoughts.

Jb

So I have read Mustag's and Sosoomii mails, needs some names on the boats but I get what your saying, not sure I can get that across to potential parents in the space of a cup of coffee though.

Also I point out this is unashamedly targeted at 49er, these kids and these parents what there kids to go down this path.

Im sure there are a equal number of kids and parents that want to go down a Corinthian path also.

But that's not what I am being asked, and its not my problem, maybe the sports but not mine.

Anyway, I have had another go based on Simon's suggestions, but I have not flipped the graph, its simply to hard on a laptop.

All I have done is re-configure the horizontal scale so compressed the PY's. and then finding a mean because a bit arbitrary based on areas of the ovals/circles so it was very close to running through the 5o5, so I just used it, once again as the mean boat.

Let me know your thoughts.

Jb

 

[mustang__1]

Just show them the video from the first two days of world's this year!not very quantitative though...

 

[JulianB]

Hi, been asked for a clearer copy, this is the best I can get off the lappy without Photo Manager which Windows 8 dose not have.

Mustang, 29er worlds footage is sensational. Yes I am biased but the tracking and the imagery was all great, credit to the class.

Phwelhie, the drive there was worth it, but the venue is quite extraordinary, quite possibly the best in the UK.

Few more hotel beds would not hurt, but all new, impressive club house, good wind, no traffic.

 

[BrianM v2]

Julian - thanks for the image, have already passed it to my nephew (and his team) who are sailing the Club 420 NA championships right now. Perhaps I missed it, but: is there significance to the color of the dot?

 

[Gouvernail]

OK... I thought for sure somebody other than me I have read that title and decided that there should be a graphic description of dinghy performance offered in this thread.

To that end:

LOOKAT THAT SUMBITCH FLYING OVER THOSE FUCKING WAVES. I AIN'T SEEN NOTHIN GO THAT FAST IN SO LITTLE WIND SINCE ANABELLE'S DAD CAUGHT VINCE DIDDLING HER IN THE HAYLOFT.

WHEN THET RAISED THE CHUTE IT CAME OUT OF THE LAUNCH TUBE QUICKER THAN LUNCH FROM A SUPER MODEL'S MOUTH AND THAT SPIN POLE IS AS AS STIFF AS A PORN STAR ON VIAGRA.

 

[mustang__1]

Wow. Wtf?