Expedition Navigation Software 
1 of 1- DuncanR
- Expert
Offline - From: Up and down East Coast Aus
- Registered: 9/16/2015
- Posts: 470
Sail selection at outer TWAs
Our crossovers don't have sails mapped at TWAs < 35 degrees or > 145 degrees. Boats with poles will have the same thing > 170 degrees or so.
The effect of that is in optimal routing tables and summary (i.e. Filtered Result), where if TWA for a sector is < 35, no jib is selected, and if TWA > 145, no chute is selected. In a deep running race such is forecast now for 2 weeks away, 60% of the race has no front sail in use.
In the past I have tried doing a complex VLOOKUP to populate the routing where otherwise blank, and ascribed numbers in the summary table (best guess applies). I have thought about creating an extended crossovers chart to 0 degrees and 180 .... messy.
What do others do?
Cheers
- ZeeZee
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- Registered: 3/30/2016
- Posts: 321
Re: Sail selection at outer TWAs
Hi Duncan,
I use an extended sailchart. It's easy to achieve:
Downwind just ensure that at a given TWS the sail chart lists the sail you use at TargTWA for all TWA>TargTWA. E.g: At TWS 14 kts your TargetTWA = 140 and your ideal sail is the A2. Now put the A2 in your sail chart for all TWA>140 at TWS-=14. Do the same for all other TWS.
Upwind just ensure that at a given TWS the sail chart lists the sail you use at TargTWA for all TWA<TargTWA. E.g: At TWS 14 kts your TargetTWA = 37 and your ideal sail is the J2. Now put the J2 in your sail chart for all TWA<37 at TWS-=14. Do the same for all other TWS.
- Nick
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Re: Sail selection at outer TWAs
The sails for the routing output should be the sails at the target angle, even if the output says (-14) for twa.
But yes, do extend the sail chart.
- DuncanR
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- From: Up and down East Coast Aus
- Registered: 9/16/2015
- Posts: 470
Re: Sail selection at outer TWAs
Thanks chaps, this is as I thought. The slight complication is I use KND crossovers, and this means I have to maintain two parallel sets of crossovers, one for sail performance and loading into operational laptop, and a second "stretched" set for doing routings ... and keep them in parallel. I hate two sources of truth ..... Will think a bit harder.
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Thread Starter- ZeeZee
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Re: Sail selection at outer TWAs
I don't have experience with KND, but what is the advantage except from the nice visual it creates?
- Nick
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Re: Sail selection at outer TWAs
It shouldn't make any difference. You should be able to use the one you normally use as Exp only uses the sail at the target for tacking or gybing sections of the route.
It lets you do over-laps and it does have a nice picture.
- DuncanR
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- From: Up and down East Coast Aus
- Registered: 9/16/2015
- Posts: 470
Re: Sail selection at outer TWAs
G'day Zee, your description above is a bit like calling MS Visio a graphics package .... which it ain't.
What the KND suite does is integrates race analysis, polar analysis and sail analysis in one suite, all with graphics front ends for variable analysis including 3D stats, polars, sailcharts (AWA or TWA, any axis you want).
Having said that, it takes a year of practice to learn what it does and how to make it go effectively. It is probably a big boat tool, where conversations might be "Do we build a FRO, a MHO or an A3; which sail design best fits what TWA/TWA range we are trying to cover etc etc etc" and instruments are accurate and accurate sail logging occurs because the boat has a specialist navigator who is also the analyst. I probably spend more time off the water in analysis than I do actually sailing 
.
If you want to see examples of race analysis outputs using KND, PM me. But not for the fainthearted. But neither is Expedition, is it?
Cheers
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Thread Starter