span results

Discussion in 'Sailboats' started by Scofield, Apr 21, 2010.

  1. Scofield
    Joined: Dec 2007
    Posts: 5
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Turkey

    Scofield Junior Member

    Hi,

    We are on the pre design stage of an 35m sail boat, hull form is close to a racing sail hull. Mast has 46 m length total. According to the calculations that we did using "span" programme, we have 12,5 hull speed at 14 knot V TW. I=40, J=13.8, P=38, E=12,5, BAS=3,7. The problem is; at 14 knot 50 degrees true wind speed, heel angle is 24 degrees. Moreover at 14 knot 90 degrees true wind speed, heel angle is 12.5 degrees. My superior insists that , we should have the maximum heel angle at 90 degrees. He said that the results are not logical. What do you think about the calculations? By the way this circumstance is not for only 14 knot, also 6-8-10-12-16. All of the 50 degree winds give the maximum heel angle.

    Thanks...
     
  2. daiquiri
    Joined: May 2004
    Posts: 5,372
    Likes: 246, Points: 73, Legacy Rep: 3380
    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    The max lateral sail force is generated at apparent wind angles between 55° and 70°. So, you should translate your true wind angles into apparent ones and see if that corresponds.
    Also, just to have another point of view, you could put your numbers into this applet by Wb-Sails (it will use apparent wind data): http://www.wb-sails.fi/news/SailPowerCalc/SailPowerCalc.htm and see how much the results differ.
     
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