Hi, all - never too late to teach an old dog new tricks.
My Raymarine MFD now can utilize Polars to show VMG lines on the display.
I have a 2006 J SO 35 SD and put in the (available) polars for a 349, shoal draft, regular rig.
I was HUGELY surprised how 'tight' the downwind VMG angles were! I've always used a rule of thumb that VMG downwind in maximized around 120deg to the wind. The polars loaded for the 349 show max VMG at about 150-160! Very cool also that the VMG angles widened as the wind speed dropped, as expected.
I went out and did some testing in (unusally) steady 10-13 knot breeze and found VMG @ 120 deg ~ 3.6 knots ; VMG @ 160 deg ~ 4.9 knots! HUGE improvement and one I'll be anxious to use our next race.
Two questions :
1 - Other than the dual rudders on a J 349 Shoal Draft, are there major differences from the JSO 35 Shoal Draft that might cause me to consider not using the 349 polars?
2 - Anyone have polars for a Jeanneau Sun Odyssey 35 Shoald Draft?
Considering at least the race rating wise, the 35 is upwards of 30-45 secs a mile faster....... I had polars for a 35, but a computer crash took out that option. I also would not have had shoal draft versions. With that said, most boats do follow similar the same where they are faster slower in a given wind speed. The acheivable speed can vary on water line, disp, sail area, hull shape etc. I would expect the 349 slightly faster down wind due to fatter rear, being able to plane easier, 35 better upwind due to narrower aft, slightly longer WL due to hull shape. My 02 Marty
I would think Polars between the 2 boats would be very different given that the hulls and sail plans are radically different.
What MFD do you have? I wonder if my C90W has that capability?
It is easy to optimize your vmg without polars if you have a waypoint to your mark and then configure your instruments to display SOG and VMG side by side.
The only benefit of polars is to tell you how close to you are getting to optimum boatspeed for a given direction and wind strength. Polars don't take into account variables like bottom condition, sail condition, sea conditions etc. But they are a interesting reference.
There could very well be hull form similarities considering that Marc Lombard designed both hulls, however the 349 is 2 generations newer.
How a boat performs on different points of sail is determined by more than just the hull design. I would think that the rig design and sail plan would be pretty major factors. You also have to consider what sails are being used. Sailing at 160° with white sails vs symmetric spinnaker vs asymetric spinnaker are going to produce very different predicted speeds.