Sail Loading of Rigging

[Inquisitor]

I would like to do some XL spreadsheet type design trade studies for rig design. I would like to do it based on sail loads, not hull moments. I am not a fluid dynamist (AE) however, I know enough theory to work with Abbott & Doenhoff type equations/air foil data. If we could keep it no more technical than that, I’d appreciate it. (tspeer’s treaty on why keelerons won’t work… convinced me… but mainly because I’m ill equipped to argue the points!)

Currently I have been doing it entirely based on relative sail areas and their geometric centroids. I can think of several things wrong with this (and I’m sure there are more):

• I know that the center of aerodynamic lift of a sail (airfoil shape) is not its centroid chord wise.
• With end-conditions and variable chord, I’m sure the vertical position is not near the centroid either.
• Relative efficiencies of a sail types and positions would also negate the sail area method I’m using.

I would like to consider the following:

• Types of sails main, jib, genoa, asymmetrical and symmetrical spinnakers.
• Several sailing points: closest to wind, reach, down-wind.
• Heeling can assumed to be 0 for multi’s

As the main point is to determine maximum load conditions (magnitude and direction) on rigging, I’m not looking for the “last word” on sail optimization. Just something more logical than sail area/centroid.

Empirical equations that take into account of the real world would be more desirable than theoretical equations. Basically something that would allow me to plug into a spreadsheet giving me:

• Force (drag and lift components)
• Chord and height of center of this force.

I’m thinking something that would assume optimum sail shape and trimming for the worst case loading on each sail/point of sail. It should (probably only) a function of wind speed.

Does anything like this exist and could anyone help with equations or URL’s that might point me in a direction.

Thanks.

[brian eiland]

Its been a while since I visited this subject thread, but I assume you may be aware of it;
Sail Loading on the Rig, Rig Loading on the Vessel

[Inquisitor]

Being a senior member, can you kill this thread, while I beat my head against wall 3 times and write down "I will always search first!" Ten thousand times.

[Inquisitor]

Brian, I replied to your email, but it got kicked back so I'll respond here.

No, I was trying to be funny and really I feel bad that I didn't search first. I was sincerely hoping you had the authority to kill it as it was a little embarrassing. I am in the process of digesting the thread you referenced and will follow up any questions still left to that thread.

Thanks