No problem Bill. Since we're back to this, I've appended the polar data (in CSV format) I got from my SailTimer Wind Instrument and SailTimer App this past weekend, as promised. Needless to say, I think this data is wrong, for reasons discussed below. For example it shows I can reach hull speed close-hauled in 9 knots of wind, but I'm slower than that on beam reach in the same wind. I don't think either of those things is true.
,TWS TWA,3,6,9,12,15,18,21 22.5,0.5,1.2,1.5,1.5,1.5,1.5,1.5 45.0,2.0,5.0,6.7,6.7,6.7,6.7,6.7 67.5,1.6,4.1,5.5,5.5,5.5,5.5,5.5 90.0,1.6,4.1,5.4,5.4,5.4,5.4,5.4 112.5,2.7,4.0,5.4,5.4,5.4,5.4,5.4 135.0,1.5,3.8,5.0,5.0,5.0,5.0,5.0 157.5,1.3,3.3,4.4,4.4,4.4,4.4,4.4 180.0,2.6,3.0,4.0,4.0,4.0,4.0,4.0 Now, why is this data wrong. First, it was the first time I'd used the SailTimer App in anger and it wasn't a controlled experiment in polar learning (the app lets you toggle polar learning on and off, and I wasn't careful about when it was on). Second, this data was collected in a variety of wind conditions and sail configurations. Friday afternoon it was blowing 20 gusting 35 and I was sailing under double-reefed main only because my mom was aboard with only one other of my regular crew and they were nervous in that wind strength. Saturday and Sunday I was in a two-day regatta in very light and fickle air under full main, 155% genoa, and sometimes even a staysail. Because I was preoccupied with racing and adjusting sails constantly, I wasn't paying attention to the app and accurate polar learning. The app must have some kind of algorithm to interpolate / extrapolate boat speeds in wind speeds and angles that it hasn't observed, because I can guarantee I didn't hit every combination of TWS/TWA in the above data over the weekend. But this gives an example of what the instrument and app can do. Before the season ends, I'd like to get back out and do a controlled experiment - a new data set under main and 155 in say 12 knots, through every TWA, toggling learning on and off at the right times. Cheers, Randy ----- Original Message ----- From: "Bill Coleman via CnC-List" <[email protected]> To: "cnc-list" <[email protected]> Cc: "Bill Coleman" <[email protected]> Sent: Tuesday, September 27, 2016 8:33:06 AM Subject: Re: Stus-List C&C Polars Again Thanks Randy, That is a sweet page, Thanks for Sharing. I was able to make a .csv and import it into the e-95, (I used the C&C38 Polars). Unfortunately it will probably be next spring B4 I see what it does for my Dynamic Vectors/Laylines. Bill Coleman C&C 39 Erie, PA From: CnC-List [mailto:[email protected]] On Behalf Of RANDY via CnC-List Sent: Thursday, September 22, 2016 12:28 PM To: cnc-list Cc: RANDY Subject: Stus-List C&C Polars Again Listers- Just wanted to share a site I saw with polars for a few different C&C models: http://jieter.github.io/orc-data/site/ If you look at the list of boats in the left-hand column (or search for "C&C" on the page), you'll see the following models: * C&C 30 (this is the new one-design version, I can tell from the boat speeds downwind - it planes :) * C&C 30E (this is the European edition of the C&C 30, apparently built & sold 1977-1982) * C&C 37 * C&C 38 * C&C 110 * C&C 115 Just click on one of those boats and you'll see its polar diagram and polar table. I realize that polars are very boat-specific and sail-specific, but at least here are some data points. For example the other week I took a couple hundred pounds of stuff off my boat, emptied the tanks, and cleaned the bottom, and I think it made a difference in light air. But my sails are old and tired, so I know my boat's polars will change again when I get new sails and a folding prop. For us software developers on the list, it almost looks like this guy @Jietermanis might have github-hosted software to create polar diagrams from user-supplied polar table CSVs. I've tweeted him for more information. Last night I got my SailTimer Wind Instrument installed at the masthead, so when I go out tomorrow afternoon the SailTimer App will be able to learn one polar curve for my boat, assuming I'm optimally trimmed on all points of sail. The wind is now forecast to be blowing 15 gusting 20, so hopefully I can get polar data with the same sails I race under (full main and 155 genoa, no spinnaker). If the wind gets much stronger I might have to reduce sail, so the polar data wouldn't be representative of my normal racing configuration. Best Regards, Randy Stafford S/V Grenadine C&C 30-1 #7 Ken Caryl, CO _______________________________________________ This list is supported by the generous donations of our members. If you like what we do, please help us pay for our costs by donating. All Contributions are greatly appreciated!
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