H4B
Well-Known Member
Anyone able to give me, or point me in the right direction of a method to develop or find if ione exists a Polar Diagram for my boat ? Westerly Fulmar. Please don't just say WOA Forum . Not a fan !
Polar diagram
- Thread starter H4B
- Start date
H4B
Well-Known Member
Anyone using Sailtimer App? Apparently this may offer a solution but at a cost! Confirmation that it would do the job, by a user would be useful.
Martin_J
Well-Known Member
Do you have your NMEA data (i.e. wind speed, apparent wind angle and boat speed from the log) available on a PC?
If you do then by PolAutoV5 by Patrick Tiercelin will do the job... You can just leave the laptop running gathering data and the polar gets plotted as you sail...
http://www.plaisance-pratique.com/polauto-mesurer-la-polaire-reelle
The other option is to record the NMEA data (with something like NavMonPC) and then play the parts of the file that you are interested in back to PolAuto.
If you do then by PolAutoV5 by Patrick Tiercelin will do the job... You can just leave the laptop running gathering data and the polar gets plotted as you sail...
http://www.plaisance-pratique.com/polauto-mesurer-la-polaire-reelle
The other option is to record the NMEA data (with something like NavMonPC) and then play the parts of the file that you are interested in back to PolAuto.
Martin_J
Well-Known Member
You should find the English version available to download on that website... There is quite a following on other forums..
[70521]
Well-Known Member
Gather paper and pencil and go sailing. Plot speed, wind strength and angle; jobs a good one.
H4B
Well-Known Member
No unfortunately not , log is an isolated unit but tacktick wind and Lowrance GPS are interfaced through a tactick interface to feed a tiller pilot. Thinking about this a log with NMEA output is fundamental for any auto data collection isn't it? Even sail timer App would only be using GPS SOA.
Martin_J
Well-Known Member
Yes - In order to create the polar from NMEA you will need the wind and log data..
There is an Android App that will also record the data and create a polar - Check out Sailtracker Polar AIS NMEA.
It uses NMEA over wifi to get the data.
Easiest way could be like Camelia says then.. Find a polar for a boat that is similar, record your actual wind angle (true) and log (SOG) readings on paper and then edit the polar to match your actual achieved speeds.
There is an Android App that will also record the data and create a polar - Check out Sailtracker Polar AIS NMEA.
It uses NMEA over wifi to get the data.
Easiest way could be like Camelia says then.. Find a polar for a boat that is similar, record your actual wind angle (true) and log (SOG) readings on paper and then edit the polar to match your actual achieved speeds.
Kerenza
Well-Known Member
Hi
Polars are theoretical, generated from build data usually for non planing hulls. Simple apps like iNav, through iRegatta and others will generate something useful, with expensive vpp programmes giving a more accurate result at a high price.
Often the designer will have made them available when the boat was new.
Very rarely will they be achieved, although in some racing circles they can be bettered.
iRegatta will give a constant display of theoretical targets from real time data.
Any interrogation of real time data is only a snapshot of the boat (and importantly crew) performance in the prevailing conditions.
What theoretical polars really score with is calculated indications of upwind and downwind target speeds and optimum sailing angles.
For instance in 6knts my best upwind angle is 44 true where I should achieve 3.5 knts vmg. So I sail as best I can at 44 true but rarely achieve target vmg. They also say I can achieve over 6knts at 75 true which I have once or twice.
Keeping a record of achievements is very useful, particularly if targets are regularly hit, but the theoretical targets are the ones to aim for.
Polars are theoretical, generated from build data usually for non planing hulls. Simple apps like iNav, through iRegatta and others will generate something useful, with expensive vpp programmes giving a more accurate result at a high price.
Often the designer will have made them available when the boat was new.
Very rarely will they be achieved, although in some racing circles they can be bettered.
iRegatta will give a constant display of theoretical targets from real time data.
Any interrogation of real time data is only a snapshot of the boat (and importantly crew) performance in the prevailing conditions.
What theoretical polars really score with is calculated indications of upwind and downwind target speeds and optimum sailing angles.
For instance in 6knts my best upwind angle is 44 true where I should achieve 3.5 knts vmg. So I sail as best I can at 44 true but rarely achieve target vmg. They also say I can achieve over 6knts at 75 true which I have once or twice.
Keeping a record of achievements is very useful, particularly if targets are regularly hit, but the theoretical targets are the ones to aim for.