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Has anyone a copy of the Polars chart for the 424 ketch? (I am running
PredictWind routing and need to enter some polars for the boat.Thanks,
Pete_______________________________________________
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I really want to make a joke here. Really. Like, ‘Slow, a little faster,
a little faster yet, a little slower, slow.” but that would be
inappropriate, wouldn’t it?Bob
On Tue, Sep 15, 2015 at 1:05 PM, Pete Dubler via maillist <
> wrote:Has anyone a copy of the Polars chart for the 424 ketch? (I am running
PredictWind routing and need to enter some polars for the boat.Thanks,
Pete_______________________________________________
maillist mailing listhttps://pearson424.org/mailman/listinfo/maillist_pearson424.org
—
Bob Fine
s/v Pelican
Pearson 424 Hull #8
http://thesailinglife.blogspot.com
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That is exactly where I started…
On 9/15/2015 1:58 PM, Robert Fine via maillist wrote:
I really want to make a joke here. Really. Like, ‘Slow, a little faster,
a little faster yet, a little slower, slow.” but that would be
inappropriate, wouldn’t it?Bob
On Tue, Sep 15, 2015 at 1:05 PM, Pete Dubler via maillist <
> wrote:Has anyone a copy of the Polars chart for the 424 ketch? (I am running
PredictWind routing and need to enter some polars for the boat.Thanks,
Pete_______________________________________________
maillist mailing listhttps://pearson424.org/mailman/listinfo/maillist_pearson424.org
_______________________________________________
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I had to google it. Does it account for head seas?
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Pete, am I missing something obvious? Because there’s a polar diagram in the 1978 review you have on your home page.
Not that you’re sailing with main, mizzen, and 155(!).
Like I said…I have to be missing something.Evan
Revery
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There is such a thing as a swells polar – sort of an enhancement you can
add to the calculations.On 9/15/2015 6:46 PM, Tor via maillist wrote:
Quote:I had to google it. Does it account for head seas?
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That polar chart is very odd in that it uses a 5.2 kt average wind
speed. The polar I am looking for would use a wind speed that could
get the boat up to hull speed on a beam reach, say 15 kts. I guess I
could just try a ratiometric approach and scale to hull speed on a beam
reach and then figure out the percentages down from there. Very
strange that they used such a low wind speed.On 9/15/2015 6:58 PM, Evan Morgan via maillist wrote:
Quote:Pete, am I missing something obvious? Because there’s a polar diagram in the 1978 review you have on your home page.
Not that you’re sailing with main, mizzen, and 155(!).
Like I said…I have to be missing something.Evan
Revery
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That’s swell!
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That’s what I thought as well. But then again, I’ve looked at exactly two polar charts in my life, so what do I know? 😀
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Huh? A polar chart has both wind speed, wind direction, and target hull
speed. There should be lines for 5 kts of wind up to some number the
vessel is expected to see or race in.
http://www.c34.org/faq-pages/images/polarDiag.gif is an example.Usually they go to about 10 kts. For a 424, I’d expect a higher number,
but then the graph would be really large and crowded.Bob
On Tue, Sep 15, 2015 at 8:57 PM, Evan Morgan via maillist <
> wrote:Quote:That’s what I thought as well. But then again, I’ve looked at exactly two
polar charts in my life, so what do I know? 😀
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Exactly! That is what I am looking for. Anyone seen one like this for
the 424?On 9/15/2015 9:29 PM, Robert Fine via maillist wrote:
Quote:Huh? A polar chart has both wind speed, wind direction, and target hull
speed. There should be lines for 5 kts of wind up to some number the
vessel is expected to see or race in.
http://www.c34.org/faq-pages/images/polarDiag.gif is an example.Usually they go to about 10 kts. For a 424, I’d expect a higher number,
but then the graph would be really large and crowded.Bob
On Tue, Sep 15, 2015 at 8:57 PM, Evan Morgan via maillist <
> wrote:Quote:That’s what I thought as well. But then again, I’ve looked at exactly two
polar charts in my life, so what do I know? 😀
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US Sailing for $325.
Not the answer you’re after, of course. 🙁
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I be darned. Seems like they do a theoretical calculation based on hull
form and sail area. A little more than I was looking for. Amazing.On 9/15/2015 10:30 PM, Evan Morgan via maillist wrote:
Quote:US Sailing for $325.
Not the answer you’re after, of course. 🙁
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Pete,
Forgive this nautical Luddite’s ignorance; this is the first I’ve heard of polars and I haven’t taken time to research them beyond the definition, “boat speed predictions across a range of wind angles and wind speeds.” So, I gather, this is about predicting what heading will optimize the boat’s VMG, telling the navigator in advance what heading to steer to achieve that. In the split-second urgency of racing, I see how that can be important.
I understand you haven’t had a chance to sail your beautifully renovated 424 very much yet, but (hallelujah!) that’s about to change. After a few weeks or months of cruising it seems to me you will know in your bones exactly what she’ll do in various conditions, which can’t be predicted very far in advance anyway as far as I know. So what is it that these polars are likely to tell you that you’re not going to soon know anyway? I imagine you’ll still be referring to a VMG reading underway.
(I have a feeling it’s time for me to learn something new on this forum again.)
Tor
Silverheels, P-424 #17
http://www.silverheels.us
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