Polar Diagrams

For all those DF35 issues which do not fit into any of the categories below.
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penryj
Posts: 51
Joined: Thu 12 Jun 08, 7:19
Your Country: New York, NY

Polar Diagrams

Post by penryj »

Anyone have any polar diagrams for the DF35 Ultimate?
Mario
Posts: 69
Joined: Sat 09 Aug 08, 21:20
Your Country: Denmark, Copenhagen

Post by Mario »

Hello penryj,
you can find it in "Yachts on test" with subtitle "high-octane cruising" in Yachting World, April 2007, page 59.
best wishes
Mario
penryj
Posts: 51
Joined: Thu 12 Jun 08, 7:19
Your Country: New York, NY

Post by penryj »

Thanks Mario, and Merry Xmas.
docclayton
Posts: 9
Joined: Thu 17 Jan 08, 23:58
Your Country: USVI, Cruz Bay, St. John

Polar diagrams

Post by docclayton »

Penyrj and Mario,

You might want to check with Jens about revised 'updated' Polars. I believe the original ones posted were a bit ambitious. I think Jens probably has updated and more accurate Polars than those posted originally.

Best,

James P. Clayton
DF35-6
US Virgin Islands
penryj
Posts: 51
Joined: Thu 12 Jun 08, 7:19
Your Country: New York, NY

Post by penryj »

Hi Doc,

That's interesting. When I contacted the yard for them (Nicolai), he said they didn't have anything. This was before I posted in the forum

Regards
Penry
docclayton
Posts: 9
Joined: Thu 17 Jan 08, 23:58
Your Country: USVI, Cruz Bay, St. John

Polars

Post by docclayton »

Penry,

If Nicolai told you they don't have any updated polars then that is probably correct. So...as a rough guesstimate I would recommend multiplying the numbers given between 8-18knots of true wind speed by about 5/6 in a stripped boat, maybe 2/3 (0.66) in a boat equipped for cruising. This is just a guesstimate based on my actual speeds acheived both loaded and stripped. I would welcome Jens' or anyones comments on this though.

Best,

James
DF35-6 Ultimate version
Mario
Posts: 69
Joined: Sat 09 Aug 08, 21:20
Your Country: Denmark, Copenhagen

Post by Mario »

Well, I think that the Polar Curve published in YW’April ’07 fits very well. The values are top speeds measured by prof- cup- sailors from DF. Mr. Q is always top-tuned cup-sailor and the polar curve results published are max’es probably not achievable for all... The very first, most important factor is correct sail control and constant tuning. But I think, it is not as easy as in monohull-racers. Another important factor is waves. This over 10 m long boat has flat shallow bottom, so is very sensitive to waves which can take 1-2 even 3 knots of your speed! I don’t know if there are rules for Polar Curve measurement in relation to waves, but waters around DF Shipyard are relatively calm even in strong winds, so if measurements were performed there, the waves influence was reduced to minimum.
Our top speed of 21.3 knots was at 12 m/s (24-25knots), 90-95 degr.TW, flat water, full main and 1x reefed jib. The boat was flying the windward wing very high over the water so we reduced the main to the first reef and the top speed we could reach was precisely the same, but the boat “calm down” (and we too). But for us not the top speed is important. We like cup-sailing and for us the most important is speed improvement in relation to competitors in all winds speeds and directions. We like to compare times also in relation to racing monohulls, and no doubts: our speed increases parallel with increasing experience. For us it took some time to understand the boat and to learn sail tuning in different wind angles, but we are now very close to speeds published in Polar Curve.
Description of DF35 sailing performance in the YW article I found also very accurate: the boat has three gears (in 80-100 degr.TW as I observed): 1st. up to 8-8.5 knots, 2nd when starts planning at 10.5-11 knots, and the 3rd, which feels like turbo in my car at 14-15 knots. I don’t know where the “turbo” comes from, but it can be air suction in tunnel between sails. We clearly sense these steps/gears in moderate winds sailing well controlled gennaker. JQ could easily present this for us during short test sailing three years ago- and we knew at once that this boat we want to have.
EarthBM
Posts: 206
Joined: Fri 17 Sep 10, 0:54
Your Country: USA, So Cal -- So Florida

Post by EarthBM »

Just two data points from my first day of sailing a loaded DF 35 with a poorly tuned rig (lots of weather helm = rudder acting as a water brake):

apparent w-------------20-------17
speed-------------------12-------10
app angle-------------- 60-------60
true w-------------------17.4-----14.8
true angle---------------83-------84
boat speed/true w-----0.69------0.68

this was not "sustained" speed, just "best speed" achieved. No waves, so not surfing.

I would imagine there should be software that would build your own effective polars if you hook up a laptop to the instruments...
EarthBM
Posts: 206
Joined: Fri 17 Sep 10, 0:54
Your Country: USA, So Cal -- So Florida

Post by EarthBM »

@EarthBM: Dragonfly 35 polars. Blue at 10kt and 20kt TWS from the factory. Red at 15kt TWS from my "seat of the pants" recorder. http://t.co/TFOeWVq9

Generally I was surprised by how close my close reach numbers are to the factory diagram. Close haul is surely just showing poor trimming. Downwind is where my mamories are vague, but also may reflect my relatively small asymmetric sail.

The numbers come from me logging in my memory boat speeds as % of AWS at various AWAs, then converting it to TWS and TWA numbers through the magic of trigonometry.

I needed to come up with Polars to load into a weather routing program for the upcoming trip from Puget Sound to So Cal at the end of May.

Any suggestions on making it more accurate will be appreciated. The picture is now in some free Twitter storage - Bo, could you please upload?
Ivan -- DF 35 #29 "Lykke"
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