Author Topic: P323 Boatspeed  (Read 11367 times)

selene

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P323 Boatspeed
« on: July 24, 2019, 10:57:21 PM »
So..there have been a few comments in the past about P323 boat speed and polar charts. Sadly Pearson (AFAIK) was not much help with this.

A couple of years ago I came across a spreadsheet program called PCSail developed by a student at the University of Michigan. Sadly it needs a really old version of excel to work - 2003, I think - and so I can't get it going on my current PC (and vbasic experts out there?). Full download can be found here: http://www.cruisersforum.com/forums/f134/pcsail-excel-sheet-to-make-vpp-for-sailing-yachts-89998.html

Anyway, before my old version of excel became unusable, I developed a rough polar chart, and a speed table - which holds up pretty well for me (for data fiends I can post my assumptions upon request).  I keep this table in my cockpit so I can check if my sail trim is optimal. For your edification, here is is:

Selene   
       Wind                       Jib size
       (kts)              87%               99%
                                    Max VMG
~40º (Close hauled)   
   5               3.2                3.4
   7               4.2                4.3
   10               5.1                5.2
   14               5.7                5.7
   19               5.9                5.9
         
65º    (Close Reach)
   5               3.9                4.0
   7               5.0                5.1
   10               6.1                6.2
   14               6.7                6.7
   19               7.0                7.0
         
90º   (Beam Reach)
   5               3.8                4.0
   7               4.9                5.1
   10               6.1                6.2
   14               6.8                6.8
   19               7.0                7.0
         
120º   (Broad Reach)
   5               2.5                2.6
   7               3.4                3.5
   10               4.6                4.7
   14               5.8                5.9
   19               6.7                6.7
         
178º   (running/DDW)
   5               2.1                2.2
   7               2.9                2.9
   10               4.0                4.1
   14               5.4                5.4
   19               6.6                6.6

selene

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Re: P323 Boatspeed
« Reply #1 on: July 27, 2019, 10:23:34 PM »
And, thanks to a friend with Navionics, a 323 polar chart. :-)


CaptBeaston

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Re: P323 Boatspeed
« Reply #2 on: July 29, 2019, 02:42:13 AM »
awesome thank you very much
Mike Beaston

SailingSwede

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Re: P323 Boatspeed
« Reply #3 on: October 25, 2020, 02:59:36 PM »
Thank You!! Very useful. :)

DavidG

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Re: P323 Boatspeed
« Reply #4 on: February 18, 2023, 10:17:54 AM »
Selene, thank you for the information.  I will use this to see how these data tools work with my P323, Independence!   Also not knowing if you're following this thread anymore, it somewhat perplexes me in regards to some other threads about pointing ability of the P323 and until I get more first-hand feedback from my P323, the polar speed chart (as well as the table); these imply the boat will point at least 45 degrees with modest performance!?  Others imply that 110 degrees is best tacking capability, which I am assuming is maximum performance (speed) verses beating off a lee shore capability?  I also assume the wave/wind work against making ground too...  Thanks again for the data charts!

selene

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Re: P323 Boatspeed
« Reply #5 on: February 18, 2023, 12:17:10 PM »
Hi David. I claim no great expertise in this area...the Navionics chart was I look on as interesting, but less accurate than the speed chart which I consistently use to check if my trim is good. I find it useful and fairly accurate.

The 110 degrees (55 degrees) pointing ability is also, in my experience, broadly accurate.

Why all the caveats? Well, I sail in the SF Bay; depending on where/when you are, tidal currents can have a huge impact. Yesterday I had a 3kn ebb, which obviously impacts SOG and pointing ability. But I was making 9kn SOG :-)

Even if you take out that variable, local conditions - wave height, direction and frequency, even boat loading - can all affect speed and pointing. As can the cut and age (stiffness) of the sails - older sails with some stretch hurt pointing.

I have been experimenting with rig tension (it is extraordinary to me how "bendy" out boat is as you tension the rig!). I * think* that with a well-tuned rig, and new-ish sails, pointing can get to around 50 degrees - forestay tension in particular seems important. But the shallow keel and the inability to bring the jib in closer than the shrouds probably limits the P323 pointing ability.

So - a bit long-winded, but in summary - as is often the case with boats - many variables involved, but the speed table seems to be pretty good (for me!)