Expedition Expedition Navigation Software

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8/24/2017 5:38 am  #1

Optimizing boat performance

I'm looking for real life experiences with the best way to maximize boat performance.  For example, TBS and TWA were long the accepted  "Standards" for getting the helm and trimming team to work and achieve at the highest possible level.  Then, let's say, computers made it possible to have %PolBSP as the yardstick.

Has anyone considered the actual experiences between these techniques to find the best way to operate?

Just curious, and needed to share the thought in hopes someone else has been there and has an opinion.

TIA, pjl


8/26/2017 10:23 pm  #2

Re: Optimizing boat performance

From everybody's responses I think you might need to be more specific in your question .... To me your question reads a bit like "Where can I find the Holy Grail?" ... as a topic a bit big.


8/27/2017 7:59 am  #3

Re: Optimizing boat performance

DuncanR, thx for response, at least that's a start!!   Meaning that this forum produces variable results for me, based on how busy and widely dispersed I perceive the participants to be.  Makes it hard to find a shared interest at any one time, I think.

My thought is that the "holy grail" of finding the sweet spot for a big boat is far from the realm of dinghy sailing where the seat of the pants and long experience in close quarters with other one-design competitors is the typical guide to steering and trimming.

With the computer able to provide on deck the TBS, TWA or %PolBSP (as examples), does one work better than the other?  They are all derived from the polars for the boat and the dynamic inputs from the instruments.  The new B&G has an impressive bar chart that shows the %PolBSP achieved.  It is very fast to change and instills trust as a way to guide steering and trimming.  I've only had one experience of about an hour using it.  I'm looking for others who have used it and have an opinion about how good it is for producing results.

An alternative to this is to use Expedition and provide any one or all of the data under discussion on deck displays in graphical or digital numeric form.  Has anyone tried this and how well did it work is my question.

This may too theoretical an approach, but it seemed worth a try.

Does that make my inquiry at least comprehensible?

TIA, pjl

     Thread Starter

8/27/2017 10:39 am  #4

Re: Optimizing boat performance

I have expedition supplying Target TWA, %polBSP and %VMG to the ondeck instruments.
This works very well.
In addition expedition shows time to layline and time to mark on the instruments. This helps especially when sailing solo or short handed and you need to prepare for a tack, gybe or gennaker douse.


8/27/2017 1:45 pm  #5

Re: Optimizing boat performance

The 3 interesting numbers are polar bsp %, target twa and target bsp. As zee zee says, vmg% can be useful in a similar way to bsp%.

​Always bear in mind that things like this are background numbers for reference - you should never drive to them.

​The first thing to decide it whether you want to go upwind, downwind or reach.

One simple place to start is target bsp upwind and polar bsp% when reaching.

The target speed becomes a guide to how fast you should be sailing upwind. Depending on wind, sea etc conditions, you might decide to sail faster or slower.

​Polar bsp% is useful when reaching as it gives one number rather than having to compare speed and the polar speed. Over a long term, you get an idea about how well you are doing compared to the polar. It might be that the day is soft or the sea state is bad so you can't achieve 100% or it might be that you aren't doing something optimally. In addition, it makes an easy way to compare changes - are we faster with the staysail for example.

​Downwind is somewhat different. Target twa tends to be more useful than target bsp. Sometimes I used to set up an alternating number that displayed both target values. Still just a long term reference as the most important thing is to be sailing the boat.



8/27/2017 6:05 pm  #6

Re: Optimizing boat performance

I concur entirely with the above; let me add what I call the Management Accounting view.
The numbers are there to influence crew behaviour, to help them understand when they are doing well, and when things need to change, while not being slavishly followed.  To do that requires:
a) That the crew understand what the targets mean (for example VMG%) at each angle of sailing;
b) That the crew trust that the numbers there displayed are legitimate, and not to be dismissed lightly.
This means that half the navigator's job starts when the race finishes, analysing the race, drawing conclusions and updating polars and crossover charts as required by the data.


8/29/2017 6:52 am  #7

Re: Optimizing boat performance

I wouldn't discount using heel as a performance parameter, as you start to understand where your optimal speeds and angles are, heel is a good indicator of wind weight, too much heel = too much power and leeway etc, too little heel not enough power etc.


8/30/2017 3:32 am  #8

Re: Optimizing boat performance

Something to add to this: Calibrate Calibrate Calibrate.

Before you can start to use the numbers for performance you really need to be able to trust the numbers and the vast majority of boats I'm involved with massively under estimate the time and effort required to really get this right.

Understanding when the numbers might be wrong, and when they are probably right but actually showing something unexpected is critical and much of the role of the navigator is communicating this effectively.


8/30/2017 5:47 am  #9

Re: Optimizing boat performance

Thank you all for the thoughts and input - very helpful!!  The experience behind the comments is pure gold.

I now have the Exp data working on the n2k network with the Actisense NGT-1  and find that the Garmin GND20s will display the Custom data from the Exp menus.  All looking good at this point and looking forward to using these functions on the race course.  Nice work Nick on getting all this stuff threaded together.  It's what makes Exp the premier tool that we users know it to be.

     Thread Starter

8/30/2017 6:15 am  #10

Re: Optimizing boat performance

I do a lot of short handed sailing. When going upwind the auto pilot is my best friend sailing on AWA.
Then %VMG is the perfect measure to choose the best AWA angle to set the AP to steer. Depending on windshear, waves etc the optimum AWA can vary slightly from day to day and  %VMG helps a lot in optimizing.


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