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Board » General Discussion » IMSYC 2011

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Posted by
A2


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2009-10-26 00:39:42
2011-05-30 16:15:45 - IMSYC 2011
This event is one of my favorites here at SOL. Evaluating the design offerings by the emerging class of budding naval architects gives this race its unique distinction.

IMSYC-66 C.O.R.E. values

Methodology:

I have chosen to employ an Ordinal ranking system that is common to duplicate bridge competition where the results are compared to players holding identical cards with bidding and sequence of play the only variables.

This year the polar txt files provide data for 18 points of sail for each of 6 different wind speeds for a total of 108 data points. Within each data point a design is awarded 1 point for each design that it has a higher value than.

Therefore with 11 designers represented 10 is the maximum award available for any given element and 5 is the median.

Here for brevity's sake I will list only Upwind & Downwind composites utilizing TWAs of 90 and below for the former & 100 and higher for the latter.

Comparative Ordinal Ranking Evaluation

Boat . Upwind . Downwind

A: ___ 9.46 ___ 9.28
B: ___ 8.35 ___ 8.18
C: ___ 8.22 ___ 6.49
D: ___ 6.37 ___ 7.64
E: ___ 6.03 ___ 6.82
F: ___ 3.59 ___ 5.66
G: ___ 4.87 ___ 3.62
H: ___ 4.37 ___ 2.56
I: ___ 2.32 ___ 1.31
J: ___ 0.69 ___ 2.18
K: ___ 0.72 ___ 1.27

This years leading design obtained a Max performance value at 83 of the 108 data points in the array demonstrating unparalleled excellence across the board for upwind & downwind points of sail in medium to light wind conditions.

I have substituted letter codes for the boat designations so that others may conduct their own analysis without prejudice.

--- Last Edited by 8mR Who at 2011-05-30 17:02:00 ---
None so blind
Posted by
RainbowChaser


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2009-06-14 09:44:50
2011-05-30 18:44:35 - Re: IMSYC 2011
Now if THIS post doesn't generate discussion about the IMSYC boat designs this year then nothing will!!! :-D

Thanks!!
Posted by
Rod


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2010-06-24 22:30:48
2011-05-30 22:21:24 - Re: IMSYC 2011
To 8mR Who
I have attempted to evaluate the 11 designs, but in a subjective way (not mathematical). I note also that two of the designs are clearly superior, but I also note that the maximum downwind performance occurs at different TWAs. Does your procedure account for performance characteristics of this kind?
I assume that someone will run a 'router' simulation in a number of different wind regimes and derive a more exacting evaluation---but it won't be me, and therefore I conclude that I have little chance of winning for my design choice----but I will sail my eventual choice---and hope for the best..
If it breaks, it's not strong enough--if it doesn't, it's too heavy.
Posted by
A2


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2011-05-30 23:17:49 - Re: IMSYC 2011
I have read the proposals provided by the link on the front page blog post of this site. The designers applied their VPP's to SailPlanner to estimate their optimized solutions.

Based solely on the published polar txt files provided by all the designs, the leading boat indicated by my list has the maximum value for 66 of the 72 points of sail for 8m/sec and below, conceding only 3 upwind TWAs to the 2nd place boat & 3 downwind TWAs to the 3rd place boat.

To be sure all I have done is rank the values not predict a winner nor choose a route. This procedure however does narrow the field for those who wish to do a more definitive analysis. That being said I believe the best strategy is a well developed polar, your mileage may vary.

--- Last Edited by 8mR Who at 2011-05-31 00:27:51 ---
None so blind
Posted by
76Trombones


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2009-08-03 18:04:56
2011-05-31 02:47:27 - Re: IMSYC 2011
This was a much trickier challenge than previous IMSYC, and I suspect that some of the students are glad to see the back of it! ;-)

Not only were the designers given free reign over pretty much every aspect of the hulls and rigs but they had to get them through a "slightly" finicky validation process (permission to throw crumpled up midterm exams at instructor). Oh, and write and debug a pretty solid VPP to boot!

I'm always curious to hear more about the design process - a couple of the reports stand out from this point of view.

I implemented Jakob and Mikael's code and spent a weekend monkeying with it. I did some "designing" but no optimising, which is usually much more work than fun...

My "traditional" hull was built to be a minimum displacement, max LWL, min beam, min depth, min CP with full width flare (convex) at bow and stern. You'd never do the last part in particular designing IRL, but this exercise is in some ways the opposite of what racing boat designers usually do. Sort of VPP equivalent of a winged keel.

Once the hull had been trialed I shifted the centres back a bit for a small boost. No limits imposed here, and probably a chance to exploit a loophole? Didn't investigate.

My hulls were parametric. I can't imagine trying to get a digitised lines drawing through the checks. Another alternative would be to use CAD - Free!ship or any other NA package will generate tables of offsets that convert easily to the britfair format use here.

Two rigs - a high aspect "wing" with no draggy headsails, and a one with spin. You pay full-time a weight penalty for the ability to carry a spin even with no jib set. Bummer :-)

The wing is faster through about TWA140-150. We'll have to make up VMG downwind by playing shifts. The trad rig is a better all-rounder maybe, but maybe less fun.

----

It's possible to built a "scow" hull with massive righting moment on a nice narrow immersed section. Tricky to pass the rules, and I had trouble keeping the VPP stable, but otherwise it's faster than the "monohull". There seems to be an unadvertised limit (hmm) that KG must be neg, which hurts this approach. I ended up carrying around unneeded lead.

----

Kudos to the design teams for their very hard work, and thanks to jakob for bringing this to SOL (or vice versa). Special thanks for sharing the course material. Better than a crossword! :-)

76T
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Posted by
sol


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2008-08-14 11:08:14
2011-05-31 08:08:50 - Re: IMSYC 2011
8mR would you go into a little more detail how you did this... i understand you ranked each boat on each TWA/TWS in the polar and then award 10 pnts to first, 9 to 2nd etc for each point, then what? Added them up for the upwind and downwind angles as you specified ?
And somehow normalised, how divide by 108? (or however many data points there were?)

Awesome idea, including this for vmg angles would be extremely helpful...

I take it you have a mac from your comment in 'Useful Free Tool' thread, so perhaps you may not be able to use this, atleast not without WINE or similar, but I posted a new tool over on soltools.wordpress.com that is particularly useful for this race ;-)

----------------

Who wrote this post please?



--- Last Edited by RainbowChaser at 2011-06-07 08:33:58 ---
Posted by
A2


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2011-05-31 13:26:47 - Re: IMSYC 2011
I tried to explain my methodology but I am more than willing to dispel any lingering confusion.

This is a ranking of the boat speeds achieved at each TWA for each W.S. listed in the polar txt files. There are 18 points of sail for each of 6 wind speeds. So it is a straight forward spreadsheet table. I divided those data points into 2 groups of 9 each, 30~90 & 100~180.

If all the boat speeds are different, then you will do a sort and corresponding assign ordinal values of 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 & 0 for those designs, at that data point.

In some cases there are equal boat speeds listed in which case 1 point is awarded for each design that is below that mark & 0.5 for each design that it is equal with, for example; 10, 9, 8, 7, 5.5, 5.5, 4, 3, 2, 0.5 & 0.5

In an array of 11 boats the total for these ordinals is always 55.

From there it is only just the basic average for the number TWAs for the given subset. All the upwind ordinals added together divided by 9 and likewise the downwind ordinals.

This is done for each Wind Speed and then similarly averaged together.

If not done in this fashion for simplicity's sake here in the forum, where formatting is not possible, there would be 108 separate categories, which is how the spreadsheet is organized prior to any averaging.

In effect all upwind ordinals added together divided by 54 and then the same for the downwind ordinals.

The numbers in the list represent the average ranking, not the boat speed.

While this approach may not be very sophisticated and lacks quantitative specificity, it clearly identifies those boats at either end of the performance spectrum.

--- Last Edited by 8mR Who at 2011-05-31 15:22:53 ---
None so blind
Posted by
captjack1942


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2008-01-18 03:24:03
2011-05-31 16:18:48 - Re: IMSYC 2011
Did you take into account prevailing winds in the Western Med and East Atlantic in June?

http://www.offshoreblue.com/navigation/pilot-charts.php
Posted by
A2


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2009-10-26 00:39:42
2011-05-31 16:45:07 - Re: IMSYC 2011
The boat designers took into account the expected wind conditions, I have merely taken their output and compared them to each other. In doing so I identified a particular boat that is faster on 66 out 72 points of sail for 8m/sec and below wind conditions.

Not only that but it out performs the other boats going up wind at the higher wind speeds as well. It does not have the reaching capability in higher winds of the 3rd & 4th place boats however, so if the weather gives you that option for the majority of the race then you would be well advised to pick one of those.

--- Last Edited by 8mR Who at 2011-05-31 16:58:59 ---
None so blind
Posted by
sol


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2008-08-14 11:08:14
2011-05-31 17:20:54 - Re: IMSYC 2011
Nice spinnaker lobe for the higher TWSs 76T! :-)

No TWA=0 line though - which turned out to be a good thing as it made me modify the polar Explorer to handle such files...
Any particular reason for not including it?? or a TWS=0 column?
Sure they are only zeroes but nedded for correct interpolation of high TWA's or very low wind speeds...
--------------------

Who wrote this post please?

--- Last Edited by RainbowChaser at 2011-06-07 08:35:08 ---

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