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CruisingWiki

Polar Diagrams ….an update

I have had a number of requests for sources of polar diagrams for cruising sailors following my previous post here. Unfortunately the link I gave in that post to a free polar diagram app no longer works, but there is a great little replacement that is worth looking at – iPolar 

  • iPolar generates sailing yachts polars of cruising yachts and cruiser racers from a very simple set of data
     
  • Mandatory Input data: Length Overall, Displacement, Mainsail area, jib area (units can be set to metric or imperial) 
     
  • Optional data: Symmetrical Spinnaker area, Assymetrical spinnaker area

Its available in the Apple App Store.

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2 comments to Polar Diagrams ….an update

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Polar diagrams in MaxSea TZ

Following the post called “Boat characteristics and learning to wally!” I had a number of mails about polar diagrams see also the comments to that post from Peter Gustafsson.

Polar1I can confirm that MaxSea TZ does have a comprehensive polar diagram creation option. It does not assume that the port and starboard speeds are symetrical (like some software). And you can create the diagram automatically

Polar2You can then edit the results to take into account special considerations on the day that you made your recording – such as sea state.

You can also store diagrams according to differing sail sets that you are likely to use.

Polar3

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Routing 4 of 7 : Boat characteristics & learning to Wally!

This is part 4 of the quest for the best optimal routing calculations within ECS/ECDIS systems today. In this posting I wanted to consider the use of polar diagrams and data that represents the performance of the boat in a variety of wind conditions.

Catalina30-Polar Of course wind cannot be taken in isolation when comparing your actual boat performance against any given polar diagram. The manufacturers polar diagram will tend to be an idealised version of what your boat will do at its design weight and under good sea conditions. The most likely source of polar table information is a velocity prediction program, or VPP: a computer program that uses information about the boat’s design—the hull lines, rig plan and so forth—to predict the yacht’s performance.

The image to the left for example, shows a pretty good polar diagram supplied for a Catalina 30 – and here you can see it notes that this was with a 150% genoa and the boat had a folding propeller.

Software designers sometimes incorporate other factors at this stage that will either automatically or manually take into account wave height, and other boat performance characteristics such as surfing down large waves for example. For a glimpse of the maths involved in calculating polar diagrams have a glance at this presentation from Pau Herrero, Luc Jaulin, Josep Vehi, & Miguel A. Sainz


Routing 4 of 7 : Boat characteristics & learning to Wally! → Click here to continue reading →

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