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Polar Diagram . . . . .
http://www.hobie.com/au/en/forums/viewtopic.php?f=14&t=6544		 Page 1 of 1
Author:  DavidBell47 [ Sun Apr 15, 2007 8:43 pm ]
Post subject:  Polar Diagram . . . . .
Does anyone know where I might acquire a "Polar Diagram" for the Hobie 16? Thanks . . . .

Happy Sailing,

David
Author:  Karl Brogger [ Sun Apr 15, 2007 9:18 pm ]
Post subject: 
Nevermind
Author:  MBounds [ Mon Apr 16, 2007 4:51 am ]
Post subject: 
What are you planning to do with it David?

I don't thing anyone's ever developed a velocity polar for a Hobie 16 because the speed of the boat varies so much depending on sea state, driver ability, etc.

Polars are usually the mathematical result of a VPP (Velocity Prediction Program) used for larger monohulls. It gives the helmsman a "target speed" for a particular wind velocity and true wind angle, both of which are very hard, if not impossible, to determine on a boat without instruments.
Author:  DavidBell47 [ Mon Apr 16, 2007 12:50 pm ]
Post subject: 
Thanks for the response. This is just my third year sailing so I've yet to develop a lot of the skill that a lot of the other sailers have in my area. If I'm just sailing recreationally, I do just fine. But if I'm sailing for performance, that's a completely different story. A lot of the guys sail on instinct and I do as well, sometimes. Frequently, when there are wind shifts or changes in current, I have to rely on my compass (it's mounted on the front crossbar) to get the information I need to make the necessary adjustments and still have optimum performance.

I understand what you're saying about the variables of the conditions. I've even noticed variables in the boats performance & handling when sailing solo or with a 125 lb crew. I don't have a target speed but I am shooting for an optimum speed, no matter what the conditions. I know that some of the manufacturers of the larger cats do make polar diagrams available for their boats but I've never even heard on one for the H16. Since I have yet to develop my skills as a sailor, I've been forced to rely frequently on instrumentation (Tell-tales, wind vanes, compasses, e.t.c.) to do my thinking for me. I've been thinking of attempting to create a "polar" with the use on my GPS but it seems like it would almost be easier developing my skills naturally until I've acquired the instinct. Do you think I'm making something too technical that started out being something that was supposed to be a lot of fun ? :? Thanks for your response. Say, didn't you guys miss the storm over the week-end?


Happy Sailing,

David
Author:  MBounds [ Mon Apr 16, 2007 1:14 pm ]
Post subject: 
Quote:
I've been thinking of attempting to create a "polar" with the use on my GPS


Unless you've got a windspeed / direction indicator (with a data logger), you're only getting one of the three variables necessary to create a velocity polar. You'd also need to do the math to convert from apparent wind angle to true wind angle.

Even at that, the resulting data would look like a full-choke shotgun blast at a target when graphed. It would take some considerable interprolation to produce the constant windspeed contours typical of velocity polars.

Just so everybody else knows what we're talking about, here's an example of a velocity polar:
Image

Wind direction is from the top. Each line represents the boat speed at a given angle to the true wind for a given wind speed. The different lines represent different wind speeds.

Quote:
it would almost be easier developing my skills naturally until I've acquired the instinct

Got that right. Learn to feel the boat. Tell tales and wind indicator are all you really need.

Recently, I was playing around with a GPS speedometer on the the 16. I was amazed that I could detect (just by feel) 0.1 kt changes in boatspeed. After I realized that, the speedo was just a distraction.

Quote:
you think I'm making something too technical that started out being something that was supposed to be a lot of fun ?

Couldn't have said it better myself :D

The storm went by to the south of us - it was a gorgeous spring day yesterday and today in Michigan. A little cool and very windy - but not a cloud in the sky. Would have taken the 14 out, but the water temp is still in the high 30's. :shock:
Author:  DavidBell47 [ Wed Apr 18, 2007 10:30 am ]
Post subject: 
Thanks for all your help. I think I just need to put in my time on the water and learn to feel the boat better, as you suggested. Someone once said "when you're in tune with your conditions, you can almost sail the boat with your eyes closed." I can believe that. Sometimes when I'm in that "Zone," I seem to be a much better sailor. I think it's the difference between when I'm relying on my sensory skills and when I'm relying on my technical skills. I think you can do both but each has it's place. Also, using my sensory skills provide me with more fun while my technical skills provide more gratification, if that makes any sense. :? Well, we'll SEE ! :)

Thanks again for your input.

Happy sailing,

David

P.S. 30 degrees? The water temp here is 57-60 degrees and I'm whining. Sometimes, we just don't know how good we have it. I have a sailing buddy (from Texas) that says that he doesn't go out unless the air temp has an "8" at the beginning.
Author:  Coral Reefer [ Wed Apr 18, 2007 11:31 am ]
Post subject: 
There is one for hobie's, rough detail and approximate values similiar to above graph in Hobie University
Author:  DavidBell47 [ Mon Apr 30, 2007 8:16 pm ]
Post subject: 
Coral Reefer,

Thank you for the info regarding the polar diagram. The one you directed me to on the Hobie University site was what I was looking for, except I was looking for one for the H16. Dagger boards, hull shapes and other boat characteristics would make the diagram completely different from the one shown for the H20. Thanks anyway. You've been a great help.
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