The Polars Expedition

[Gamayun]

That sounds like a very successful polars expedition!


(Moved by request from Philpott's "What I Saw" thread.)

 

[Philpott]

That sounds like a very successful polars expedition!

 

[AntsUiga]

Jackie, with your experience, you would be a great asset when it comes time to prepare some polars for Silver Alert.

Ants

 

[Philpott]

hahaha My "experience" is that I know all these serious sailors. I look forward to seeing you again Thursday night, Ants. We met at R2AK last year. As I recall, I lured Skip away from you with the promise of an ice cream cone.

 

[AZ Sailor]

That sounds like a very successful polars expedition!

Nice, indeed. Now can someone please post an Excel template that can take the data points and produce the Spirograph-like chart typically used to display polars? I'm not very good with graphing functions in Excel, and can't remember where I left my Spirograph set.

 

[Philpott]

Nice, indeed. Now can someone please post an Excel template that can take the data points and produce the Spirograph-like chart typically used to display polars? I'm not very good with graphing functions in Excel, and can't remember where I left my Spirograph set.

hahaha Yes, I misplaced my spirograph set, too. I think it's lost with my gantt charts. hahaha. You sailors know the funniest words.

 

[BobJ]

I'm sure there are targets for the Moore 24 and maybe the Cal 2-27. Those for a Valiant 32 might be harder to find. I'll surf around when I get home.

Polar diagrams (named for what they resemble) are the source for a chart of targets, not vice-versa.

 

[AZ Sailor]

Polar diagrams (named for what they resemble) are the source for a chart of targets, not vice-versa.

As we continue to publicly plumb the depths of my ignorance, let me see if I'm starting to understand: The polar diagram is produced by a velocity prediction program, giving you the theoretical best speed at a given TWS-AWA combination. Then you go out sailing and fill in the actual data in the blank table to see how close you are to getting the most out of the boat. So far so good?

I have this for the Valiant 40:



and have searched without success for a Valiant 32 polar diagram -- only 65 of the boats were built, and obviously not for racing, so I wouldn't be surprised if no polar diagram has been published.

But, the 32 was supposed to be a scaled-down version of the 40, with the same long-keel, skeg-hung rudder underbody proportionally adjusted for the shorter LOD. So, second question: if I re-scale the boat speed dimension on the Valiant 40 polar based on the ratio of theoretical hull speed of the 40 versus the 32, might that provide a reasonable approximation of targets for Morning Star?

 

[AntsUiga]

I did a quick search for the Moore 24 and found nothing. One was available for Express 27 and I think it was developed by Carl Schumaker.

I am quite positive Dave Hodges has one for the Moore at his quickest portion of memory.

It should be fun crowd at RYC on Thursday evening.

Ants

 

[AZ Sailor]

if I re-scale the boat speed dimension on the Valiant 40 polar based on the ratio of theoretical hull speed of the 40 versus the 32, might that provide a reasonable approximation of targets for Morning Star?

Maybe? The 32 has LWL of 26', and the 40 has 34'. Using what I think is the formula for theoretical hull speed, of 1.34 x square root of LWL, gives the 32 a hull speed of 6.83 kts, which is 87% of the 40's hull speed of 7.81 kts.

If I am reading the polar diagram correctly, the 40 should do 7.6 kts on a beam reach in 12 kts of wind. 87% of that is 6.65 kts. In flat water with new sails and everything trimmed right that seems like a target one could shoot for.

 

[BobJ]

I've not heard of "scaling" polars that way so I don't know if it works. Perhaps an e-mail to Bob Perry would be fruitful.

Your diagram above has the targets in it: The little boats that are labeled "optimum tack" and "optimum gybe." It's tedious to count hash marks but the data points are in there.

ORR has data for the Moore 24 (from their proprietary VPP). US Sailing also offers a "performance pack" that will give you pages of this stuff - for a price.
.

 

[brianb]

Does anyone know if the PHRF committee makes use of VPP data to generate PHRF ratings ? I would assume they would, but likely that is a poor assumption as it would mean purchasing polar data from US Sailing.

Thanks,
Brian

 

[WBChristie]

Does anyone know if the PHRF committee makes use of VPP data to generate PHRF ratings ? I would assume they would, but likely that is a poor assumption as it would mean purchasing polar data from US Sailing.

Thanks,
Brian

I don’t think so because even us sailing doesn’t have polars for all boats racing phrf. It would be a pretty good way to generate ratings one would think

 

[DaveH]

Does anyone know if the PHRF committee makes use of VPP data to generate PHRF ratings ? I would assume they would, but likely that is a poor assumption as it would mean purchasing polar data from US Sailing.

It's very indirect, but the answer is they "sort of" do. see part 3 here.
Because they use ORR and IRC as reference points (when available), both of which do use polars as part of their VPP, I'd say indirectly they do.
That said, none of these rating systems use polars to calculate anything directly.
They all add their own secret, or semi-secret, sauce to come up with a one number rating.
IMO -
Because they are calculating for a mix of courses and conditions, polars are sort of beside the point for ratings, as you have to somehow average things out for a one number rating and Polars are really about a specific point of sail and sail combinations at specific wind speeds.
or you could go back to the disaster that was IMS and try to calculate everything for a given days conditions... ORCi, which is widely used in Europe sort of does this, but my understanding is it is rare to actually use it to the full extend of essentially trying to calc the VPP for each leg each hour.

 

[BobJ]

Good info from Dave.

Although only six of the AE38 yawls (and two sloops) were built, US Sailing happened to have a measured ORR certificate for it. I provided this certificate to NCPHRF and I'm told they used the data, so I think my boat's rating is pretty solid.

ORR uses a VPP to determine a table of 14 ratings, depending on the type of course. Suggested ratings are included for the Chicago Mac, Pacific Cup, PV, Cabo, Acapulco and Bermuda. Ratings are also listed for generic closed course, 60/40 WL, 50/50 WL, ocean non-spin and offshore off-the-wind races. I haven't done it yet, but I'm told you can also run trial certificates to see how changes to your boat will affect its ORR ratings.

If you also buy US Sailing's Performance Pack you get about 18 pages of polar data to plug into Expedition or what-have-you. Its last page is a summary that can be used for your targets chart.
.

 

[BobJ]

Here's a set of targets from Ragtime!. These were pulled from the US Sailing Performance Pack for a J 92, which assumed a boat sailed full-crew in OD configuration (155% LP genoa, 92 s/m kite). This latter stuff matters - the targets for many of our boats will look a lot different when sailing singlehanded. Above 12 knots TWS I couldn't reach these upwind numbers and I could usually beat the downwind numbers, at least until I crashed...

View attachment Old J92 Targets.pdf

I think a chart of targets, laminated and taped up in the cockpit, is a great tool. When racing one-design you have boats all around you to benchmark against. But in PHRF you're racing the clock. Unless you're really good at sailing by the seat of your pants (and I'm not), it helps to have these in front of you to see how well you're sailing the boat.
.

 

[WBChristie]

Because they are calculating for a mix of courses and conditions, polars are sort of beside the point for ratings, as you have to somehow average things out for a one number rating and Polars are really about a specific point of sail and sail combinations at specific wind speeds.

I would wager that ratings based on polars would be more accurate than phrf ratings, which are also based on average sailing performance and are a “one number rating” When I say more accurate I mean that the rating would be based on observed sailing performance, rather than theoretical calculations. The percentage of off the wind vs reaching etc could be figured into the equation. Sort of like what the old pac cup or current shtp rating is, but based on real world performance numbers.

 

[WBChristie]

Further to the previous post, I guess what I’m trying to say is that the “polar average” would be more accurate than the “phrf average”.. if that makes sense.

 

[sleddog]

Polars are a bit of a rabbit hole. When you buy VPP polars, they often don't relate very well to singlehanded sailing. VPP polars predict speed through the water (not GPS) based on 1) accurate instrumentation 2) smooth water 3) full crew hiking out and/or trimming to optimum 4) best sail combination with a full inventory and crew to change to that sail combination at each measured wind angle and speed. 5) a printer hooked up so you can view tested polar speed over averaging time.

For example, anyone who doesn't pull their speedo out after sailing, won't likely have accurate speed through the water on their next sail due to growth on the plastic paddlewheel. But you risk getting wet when you pull a speedo out, or put it back in. So that operation takes a back seat on most boats.

If you've bought a VPP polar chart and sail singlehanded, you are doing well to achieve 90% of predicted speed.

I find polars most valuable when used with an optimum sail combination chart....

 

[WBChristie]

What do the brains trust say about future SHTP ratings methods? Are there any thoughts about changing to a different handicapping system?

Cue O29 and 30 owners screams of protest