Sail for a boat using Kangaroo

Grasshopper Kangaroo
1

Has anyone used Kangaroo to simulate the surface of a sail as on a sailboat? I just need a simple example to help me get started.

2

Depends on what you want to achieve. Do you need to formfind it, load it with wind, etc…

3

I’m just more interested in finding the flying shape but I guess the loads at the corners would affect the formfinding as well.

4

Hi Joseph,
Here’s a simple example to hopefully help you get started
sail.gh (14.1 KB)
I’ve show here keeping all the vertices along one side of the triangular sail fixed, on side free, and the other side just anchored at its ends.

3 Likes
5

Very cool, but the vertical edge should be fixed (to the mast) instead of the bottom edge, which is often “loose footed”, attached only at the end of the boom.

P.S. More like this? Still doesn’t look right though.

sail
sail.png720Ă—375 72 KB

sail.gh (14.1 KB)

1 Like
6

Thanks Joseph,
As you might guess, it’s been a while since I’ve been on a sailboat!

I did once make a little rudimentary sailing simulation in a very early version of Kangaroo that combined the effect of the wind on the sail and the water on the keel to propel the boat.

It might be fun to try and recreate this with the new version, as I think it would be possible to keep the elements much more rigid now.

7

I love what this guy has been able to do with articulating his whole complex topsail schooner rig.

Thanks for getting involved here Dan. I think that you and Joe O can come up with something in no time. Joe, you should share your wing rig stuff here even though I was more interested in tensile membrane type sails.

2 Likes
8

Hi Dan. Nice example. I have a few questions.

  1. Are the wind actions acting normal to the surface?
  2. Can the reaction forces at the corners be measured and their vectors displayed?
  3. Is the material for the sail defined by E-modulus?
  4. Can a pneumatic cushion be simulated in Kangaroo?
  5. Have you combined CFD like OpenFoam with Kangaroo before?
  6. Have you simulated something like a retractable tensile membane before?
9

The wind vector is visible in the code, 45 degrees to the boom, meaning the boat is close hauled.

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I am not asking about the wind direction. Wind can act on a surface causing either pressure or succion (which texnically is also pressure, but with opposite direction). Regardless of the wind direction, Pressure always acts inward normal to any surface. It is just a physical phenomenom. In order to properly calculate how much pressure there is, the geometry have to go trough either wind tunel tests or CFD simulations. This is how you determine the Cp value for each triangle of the mesh. It is time and labour consuming, however this is the realistic way of doing stuff.

I ask these questions because if all this can be taken under account, this can make for a very neat and cool way of calculating these types of sails. Like actually something which you can safelly manufacture.

11

Hi Daniel, can you share the file? I’ve tried so many ways but can’t connect sail part and boat part. They are behaving themselves. Want to know how did you do that. Thanks.

12

Good to see some activity here, thanks everyone.

I just recently bought (well the client did) a dedicated software for rigging design and it has a rudimentary membrane based sail generator based on Fortran I believe. There is a sail making program that partners with the rig module and the RigEdge half exports a lot of load and direction to Azure (the sailmaking module) which uses that to do panel layout and uni material load mapping for laminated 'string' sails. I'll post some examples soon.