Sail area displacement

[1bobt]

How do you work it out ?

I carry 107sq m of sail. 100% jib and the yacht weighs in at 10 ton I think you devide one into the other and do something with /64?

Can someone tell me the correct figure for my boat and then again with a 150% Genoeo

Thanks bobt

 

[vyv_cox]

Look at http://www.sailingusa.info/cal__sad_ratio.htm

I entered your sail area as 107 x 10.764 to give square feet, and assumed 10 long tons. SA/D comes out at 23.59. Says it's a high performance racer.

 

[1bobt]

Look at http://www.sailingusa.info/cal__sad_ratio.htm

I entered your sail area as 107 x 10.764 to give square feet, and assumed 10 long tons. SA/D comes out at 23.59. Says it's a high performance racer.

Thanks Vyv for the info. Wondered why it seemed to get into double figures, in anything over 20 knts wind speed.

cheers bobt

 

[Bosun Higgs]

sailboat dimensions website gives the sa / displ as 15.92 based on a sail area of 779sq ft and a weight of 22000lbs

 

[Quandary]

Sail dimensions

A 'normal' sail area displacement ratio used for comparison does not reflect the actual sails used, but is based on a normal mainsail with a horizontal boom and a jib which will fill the foretriangle. I am fairly sure roach is also ignored.

 

[Salty John]

I agree, and on the Sunmagic 44 the full main plus 100% jib is 780 sq ft, giving a much more realistic SA/Disp of 16.0 - as per the bosun.

 

[1bobt]

I agree, and on the Sunmagic 44 the full main plus 100% jib is 780 sq ft, giving a much more realistic SA/Disp of 16.0 - as per the bosun.

If you look at the Atlas of Yachts web site it give 98 sq m. remember my boat is the regatta version. Espace rig ? with a mast 1.3 meters taller and the boom 8cm longer .I owned a Sunfast 39 (sun Charm) that rig was 91 sq m the standard Sunmagic is a bigger version..
cheers bobt

 

[Salty John]

For the purpose of the SA/Disp calculation you take sail area to be the area of the 'triangles' formed by mast, boom (or foot) and hypotenuse. You ignore roach which, particularly on a high aspect rig, can be substantial - perhaps 30%. You also ignore any jib overlap, obviously.
I calculated theoretical sail area from the published I, J, P and E dimensions for the standard Sunmagic 44. If your rig is taller you will have a higher SA/Disp ratio.

 

[1bobt]

For the purpose of the SA/Disp calculation you take sail area to be the area of the 'triangles' formed by mast, boom (or foot) and hypotenuse. You ignore roach which, particularly on a high aspect rig, can be substantial - perhaps 30%. You also ignore any jib overlap, obviously.
I calculated theoretical sail area from the published I, J, P and E dimensions for the standard Sunmagic 44. If your rig is taller you will have a higher SA/Disp ratio.

I think I have now worked it out It looks like the rig is the same size as the sunkiss 47 If i put these figs in the calculation I get a number 17.8 that would seem about right .

thank for setting me straight

bobt