[Sonar] debriefs

[Martin Fossen]

Hello Fleet 5,
 
Thanks to those who offered input on the debrief idea.  Thus far, I'm left with a couple conclusions:  1)  A formal, structured, post-race debrief continues to be elusive due to the predominance of the post-race decompress/social mode we fall into after our racing.  2)  All the fleet members are open to sharing what works for them.  For example, Ernie was saying his tune for Presto on Thursday was 39 on the uppers and 10" circles on the lowers.  3)  Most fleet members want to see more Kattack participation for better post-race analysis.  Finding the Kattack vehicle for each of you might be tricky (GPS device, i-phone app, android app)  Hopefully more of us will work this out.  
 
Still no great solution for debrief, but please look for people gathering to watch the Kattack replay.  And, as I mentioned, strong finishers are open to sharing their ideas so feel free to ask them about there set-up and race choices.  
 
Last night, it was interesting to me to hear a couple things that went right over my head.  Firstly, was Ernie's numbers, which were 39 uppers, 10"circles lowers.  This wasn't meaningful to me since our tuning approach is different (explained below), but perhaps it is meaningful to a lot of you.  Secondly,  JR was sharing with Ben that finding downwind VMG is like sailing a C-scow downwind.  Hopefully that's helpful to Ben and scow sailors, but I'm not a scow sailor so can't quite relate.  JR, can you can break down that concept into it's elements for the rest of us?   
 
Yesterday there was a bunch of boats that knew the pin end was favored at the start, and there was a number of boats that had decent starts at, or near, that end.  In watching Kattack, I concluded that one of the more significant differentiators was the last third of the first upwind.  Those approaching the first up-wind mark from the left came out ahead of those coming from the right.  Thereafter there was place changes but none as prominent as the shake-out driven by the last third of the first up-wind.  If you have a different take on this idea, feel free to tell me I'm "off the mark" and tell us your take on other significant differentiators.
 
 
Here's my approach to tuning, which is more empirical.  This is based on Steve Shepstone's approach:  
 
Headstay length:  When a puff or shift hits, the helmsmen feels a change of tiller feel just before it shows on the jib luff tell-tails or boat heal.  If the boat heals or tell-tails read different before the change of sensation on the tiller, your steering response comes a second or two late.  This approach to headstay length leads to a longer forestay length that, in my experience at least, can become problematic in winds above about 15mph, when the traveler bottoms out and you still have weather helm.  When we're confident the wind will be strong, we shorten the forestay to have a better balance overall without the traveler bottoming out.  Last night that back-fired since the wind speed was less than the forecast I saw.  When the wind lightened up, I, as helmsman, had to really watch the tell-tails close which got in the way of sailing by feel and looking outside the boat.
 
Upper stay tension:  Get sails up, get close-hauled.  Leeward upper a bit slack; perhaps 6" circles.
 
Lower tension (again, when close-hauled):   Windward lower set to hold the mast in column, sighting from gooseneck through lower stay connection to upper stay connection.  Some folks go to a slight concave-to-windward condition in lesser breeze so as to capture a bit more in the main sail.  I think I found better response with the mast in column.  Perhaps the concave shape constricts the slot.  I'm not sure, it might just be a style thing.
 
Happy Memorial Day, 
MF
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