We missed IMSYC this year!

Luckily, Jakob has thoughfully provided as a tool to run our own at www.polardesigner.org, an online parametric Velocity Prediction Program (VPP) where we can play at designing our own fleet. Clear your desk, break out your Marchaj and dust off your ducks - it's time to do some designing.

Due to the constraints of the methods used in the VPP, we can't start off with J-Class Masterpieces (I know, I know) and the Twelves fall just outside what is sensible. Some of the smaller Universal-Rule boats would suit, but I suggest we set our sights on the deservedly popular International-Rule 8 Metre class.



http://8mr.org.uk/history/history-8m2000rules.pdf

Thinking out loud, but I'm imagining a fleet race/miniseries hosted by the challenger of record to select the match boat, followed by a two boat(type) race vs defender. In order to keep numbers to manageable levels, countries/regions will collaborate to field a single design.

Suggested grouping for 5 groups of roughly equal size.

Nordic
Pan American
North Sea (minus Norway)
Western Mediterranean
ROTW

Individual boats could choose from the fleet - no need to stick with own region if that doesn't appeal. Other options open for discussion! Not sure how much interest there might be, but I think we need to keep the numbers reasonable. I'm happy to do the final prep to get the designs out of polardesigner and cleanly into SOL.

We could make the race non-point scoring (or make a seperate ranking).

Attached is a spreadsheet that does the grunt work of calculating the Rating. All that is needed is to transfer the numbers from polardesigner. Polardesigner gives warnings when a value is out of bounds for the algorithm, and the spreadsheet should ensure that the boats conform to rule. It probably needs cleanup. Any guinea pig Herreshoffs out there?

The authours issued a public call for beta testers and feedback. I figure we have an obligation and the weather gauge - prepare for broadsides!

Speak up in this thread - yay or nay?

76T

Just for your amusement, 76, I actually sail an 8 Metre yacht,"Gracia". built to the old rules. Mine is of course radio controlled, in the 36-600 class of model yachts. It was originally a 36 Inch long kit by the German model company, Graupner, and the hull is all wood and wood planked. I cut the long keel off and replaced it with a fin and bulb, because the original design just lay down on it's side in any wind at all. As the 36-600 class isn't used in North America, I eventually changed the rigging to a schooner with removable topsails and a flying jib as the third headsail, all controlled by one sail servo. She sails very well and really looks 'scale' on the water.
As the name 'Bluenose' was already taken, and the further name 'Rednose' also, I was forced to call her "Runnynose"----after myself, of course.

I'm in even though I don't know what I'm doing.

Will try to learn as much as I can & have fun.

I like the idea. Count me in.

Question:

Are we going to know the race location and circuit before designing the boat?
So, we could taylor made the design; i.e. racing on a predominate light or strong wind location, mostly head or down wind?

or,

We should design an all around yacht and the races would have upwing, downwind and reaching legs ?

Another option is to use the old "Ton Cup" world championship formats; (3) short races, max 24hrs, (1) Overnight race, max 48hrs and (1) Long race, max 72hrs.
All races count, short races weigh 1 point, medium race 2 points and long race 3 points.


I think, this can really be exciting.

Antonio (zero)

.

Yes - deed of gift etc... half the point I think it would be up to the challengers to find a representative course for trials. Volunteers for CoR?

Yes!!

Yes

Yes?

*YES* woooooo!!! (imho)

I realize there are many details to be worked out but if practical I would advocate for the opportunity to sail at least 1 preliminary round (sub groups if necessary) in self designed boats.

P.S.

I have your SS & have opened the polar applet but it still may take a little further explanation.

Questions I have :

Are all the variables components of the 8 Metre formula or are there some dimensions that only affect the polar configuration but not the main Rule ?

Does the Freeboard parameter refer to keel & rudder dimensions ?

What do the cells in your SS with Red backgrounds signify ?

--- Last Edited by Hubert Bonisseur at 2011-05-01 14:22:11 ---

Good questions. The parent hullforms used to build the VPP are based on relatively modern ~40 footers, while the International Rule produced long overhangs and wineglass sections. The length L used for rating normally has corrections made to it that partially take into account hullshape. The VPP produces results assuming that we're all sailing more or less the same basic shape (stretched this way and that), so I left out the extra length complexity and just used the minimum form the rule.

So - normally the Prismatic Coefficient (CP in polardesigner) and the longitudinal centres would show up in L.

Midship Coefficient (CX) would show up in the Girth correction "d". The model isn't really suitable for deep hulls/full keels, but the spreadsheet approximates the girth calculation using a circular submerged section through the BWL and hull depth points. Using an arc is pretty close for the range of CX allowed, but it means that CX doesn't show up in the rating.

SO... free pass on CX, CP, LCB and LCF. Note that they do affect displacement for a given LWL/Beam.

None of the appendage inputs are rated, but draft must meet the rule. CG for the ballast can go right to the end of the keel, which isn't quite right, but works fine.

All of the sail inputs end up in rated sailarea except spinnaker leech length and mast diameter, for which a min/max are defined. Spin leech length might be defined differently in polardesigner, so the range might need adjusting.

Freeboard is the average height from waterline to deck.

The red cells are values out of range. Either outside of the rule or physically impossible.

Regarding IMSYC: If you are interested in the rule for the IMSYC race 2011 you can find it here http://www.kth.se/polopoly_fs/1.47075!IMSYC-66%20rule.pdf
I have about ten students designing boats for the race )

/Jakob

Great news that we get an IMSYC this year, and the 2011 rules look to produce some nice racing

I'd figured that term-end had come and gone!

...and if you want to play around with hull shapes etc to investigate effects on CP, trim, stability etc you might want to try the msy_hydrostatics-code that I put on the same web-page. The code lets you import hull shapes and then stretch them in various ways