CAST: Computer Assisted Sails Trim
Publié par trebormat dans Le coin de la technique, voile, tags: BMW Oracle Racing, DoGzilla, sailvisionA few month ago, I published a post describing most of the America’s cup instrumentation embedded on groupama 3 when BMW Oracle Racing was doing tests at Lorient: Spying lesson, instrumentation and analyse (in french). It’s a famous note of this blog and your positive comments made me to continue. Today I’m going to focus on a very special topic: Sails metrics and computer assisted sails Trim. I’m going to give you more details about DogZilla system (the out of the norm trimaran) and also on innovative hdroptere’s system (the flying multihull).
Ce billet en français: RVAO: Le réglage des voiles assisté par ordinateur
DoGzilla under the hood
The DoGzilla’s system is similar as the one used onboard Groupama 3 with some differences. It has been integrated while the boat was being built so what every cable of fixations were thought before.I’ll talk more about Dogzilla electronics another day.
There are couple of cameras at the top of mast with a streamlined support like the BMW Oracle Racing Class America. It also notices the presence of two masthead unit but I’ll also write in the next post about electronics topic. Cameras were also present on the mast at several levels to take pictures of Genoa.
As the IACC, there are may target on the deck, which are references for the boat middle line for compute the sheeting and twist angle.
The aim is to find the stripes on the sails. On the american boat, the recognition solution uses the contrast between black and white stripes. The orange stripes is used to find the start stripe. You can see that black and white stripes are close on the main sail and on the genoa, It is to have a better idea of how these two sails work togther.
Alighi system uses orange stripes whith small thickness on attack angle.
ETNZ uses black, green but they usually use more colours on their sails.
The measurement
Every team use the same principle: find stripe for build shape. These information are the most important:
- Draft position
- Camber max
- Entry and exit angle
- sheeting angle and twist
You can do these measures with many softwares like North Sail’s SailScan or accuMeasure from UK Sailmakers.Do you recognize the boat which genoa is digitalized ?. When i wrote this note he was first of the Vendée Globe. Loick Peyron, for sure. Everybody now know that cameras are on almost every offshore racing boats. I don’t know if Loick use a camera system but I Know that his team works about no optical system.
For the america’s cup, you’ll not digitalyze by yourself very data (many To = 1000 MO) saved during hours of navigation. Some embedded software can do this digitalysation on real time and give information for sailing trimmers during regatta. Obviously all these data are used by designers for new sails or modifications on sails. As I know, there is just one company which sell this system: BSG developpement at La Rochelle ( France). The system is very efficient, you can rebuild your sails in 3D and compare in design Sail Pack, also in 3D.
Innovating
Why am i telling you information about sail trimming ?. Because (in english in the text) of something I watche on televisio which show an incredible system used on the Hydroptere. This i what i saw on the television, the most interesting begins at 2min30.
Julien Pinet, PhD @ EPFJ (engineering school in Lausanne, Switzerland) is responsible of CV Lav and did a wonderfull job. I really like the story of the paper leave. But let’s talk more about the system.
The aim is still to analyse from camera datas. The main difference is the place where the cameras are, because there are all on the deck. You understand all the drawbacks of having cameras on this place of the boat (the sun light)… It is not possible to analyse sails angle attack but it is not important while this boat is sailing runs so the crew don’t have to trim sails frequently.
The recognization stripes are white, and there’s no black stripes which is one big difference with DogZilla system. The hardest job is to know exactly where the stripe begins and stops. In this case, they use small white circles. It’s easyer for an algorithme to see circles than lines. Deck targets are circles on DogZilla and Alinghi. The software shows changes of the model and gives a grid on the picture.
It’s interesting to see that this system is used for Foils measurement. Two things : the system is not working in real time, but it must be the next developing step. The frequency is closed to the one on the video and i didn’t know that on the IACC.
We can’t avoid thinking that Alighi will have the same system as EPFL is linked with the Team. Before, swiss team used Nivelleau’s system. These french worked for TNZ and they won 4 america’s cup! I know that the « black » is not equiped with sailvision, or they might have a « killer device » !!!.
The future
I think that optical systems with cameras are easy to install and don’t need to install device on the sails (just stripes). I’m sure this system will equip everybody’s boat in a few year. We’ll see this systems adapted on small boats in a few years, 420, 470, 49er, etc … You like this idea ?
The bad thing is the precision of the system, pictures can be with high definition but precision is not as good, seeing DogZilla stripes which are 1 meter tall. Other systems exist to analyse sail’s shape. For example fiber optic inside batten. Or you can install sensors on the sails or microwaves system like the above system (for Seahorse magazine).
I still don’t understand why the shape is measured and not he force on the sail.It’s really strange… whatever the system, the most important is to use efficiently the data.This subject is very interesting, how is it possible to build a Computer Assisted Sail Trim ? Are you interested on that ?
Matthieu ROBERT, Thanks Pierre de Champsavin and Tom for your help to translate.
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