# Free program to calculate lift and drag of 2D sail sections

Discussion in 'Software' started by Remmlinger, Mar 12, 2021.

1. Joined: Jan 2011
Posts: 302
Likes: 51, Points: 28, Legacy Rep: 172
Location: Germany

### Remmlingerengineer

Mikko Brummer likes this.
2. Joined: Jan 2011
Posts: 302
Likes: 51, Points: 28, Legacy Rep: 172
Location: Germany

### Remmlingerengineer

I have updated the program. Up till now, the coefficients were interpolated for the optimal camber. In the latest version there is an additional module, that calculates the characteristics for prescribed, user supplied camber.
2D Sail aerodynamics http://www.remmlinger.com/Sail2D.html

Dolfiman likes this.
3. Joined: Aug 2017
Posts: 1,502
Likes: 662, Points: 113
Location: France

### DolfimanSenior Member

Many thanks Uli for your comprehensive works on this issue, it is very instructive. Have you also study the jib-main interaction in line with Arvel Gentry investigation here below, I have understood that a jib presence can reduce and "smooth" the flow on the lee side of the main, and especially useful to mitigate the disturbance of the mast. How that can be taken into account in the sails coefficients CL and CD ?

4. Joined: Jan 2011
Posts: 302
Likes: 51, Points: 28, Legacy Rep: 172
Location: Germany

### Remmlingerengineer

Thank you Jean-Francois for your kind words. Gentry's work was a milestone. I am currently working on a program that calculates the lift-distribution and downwash on main and jib, including the interaction. I use a panel-method, based on lifting-line theory. A prerequisite for this method are the coefficients of the 2D sail sections. I used XFOIL to calculate the 2D-coefficients and wrote a small program to interpolate between these coefficients. I published this program to get feedback and to check for bugs. This interpolation program is now part of my large 3D-program that calculates the forces on the entire rig. To develop such a 3D-program is not an easy task. I am struggling with convergence problems at large apparent wind angles. Up till now it works only on closed wind courses. I still have ideas and I don't give up. I will publish it, when it is working.
Uli

Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.