Questions and Answers with Chris Todter, the inventor of the SFV. Alberto Fiorenzi, ceo of FMG asks for some clarifications. The instrumentation is still for a few's pockets, but it can provide strategic design information together with unique trimming information.

Q. how do you select the model of load cell ?

A.if the designer provides us with the value of the Drag generated by the downwind sail we can suggest with good precision the correct cell for the maximum load. As a rough guidance the designer can pick from the following data based on sq mt of the sail:

Q. The loads are different on the corners, did your customers pick different load cells for each corner? Is this allowed by the system?

A. Ideally, there would be different sizes at each corner, but practically, it is better to have all the same. 

Q. One load range will not cover the full spectrum of loads from very light air to max load correct? If so is data coming good and significant at both light and strong air? How light and how strong?

A.Typically the units are accurate to within 1% of their reading +/-5kg. This means that at 2000kg, they ware within 20kg, at 1000kg within 10kg, at 500kg within 10kg, at 100kg within 5kg. The unit autozeros itself at startup, so the very low end (less than 100kg) is usually within 1-2Kg.

Q.Is the data always good?

A.Yes, within the error margins described above. There are two principal uses: one for determining loads and one for trimming. In the first case data coming from each corner can be extrapolated to maximum loads if data is taken at a few different windspeeds into the moderately strong range. In the second case, the units provide a real time indication of the total thrust generated by the spinnaker.

Q.Is the data as a trimming guidance always significant? Is it possible to have the data on the LCD screens of the trimmers via WTP B&G? thrust value, thrust direction, thrust angle on horizon. Maybe load on corners? 

A.Yes all of the above.  It is really only useful if it is logged along with the wind speed and angle.  It is easy to log the data and/or put it on a display. The unit gives the loads and directions, it is up to the on board system to log and display.

Q.What happens if you exceed the maximum load the cell can take?

A. The cells that are specified for 2000kg just don't read anything  greater than 2000, but the cell is good to 5000kg without damage, probably more.

Q. What frequencies are the radio signals working on?

A. 433 Mhz for European use.

Q. So, apart from the load display, the data goes to the receiver box that holds the data? How many hours of sailing can you record? The data is eventually downloaded to the computer, right? Is the data time calibrated with the Wind station and can the data then be cross elaborated with the Wind station data. 

A. No the receiver/compass box doesn't store the data, it sends it out via RS232 to be logged by a computer or the instrument system. Of course then all the data available in the computer related to the same time domain is then available for the analyst.

Q. Can you please make a description on the flow to the B&G and to database.

A. It can be set up differently, but the data is simply RS232, which the B&G or other instrument system can take in.

Q. Do you have a figure for water resistance on the load cell (atmospheres?) is the box safe if it falls in the water with a line for example? What is the cell cost as a spare?

A. Theoretically, they will survive a dunking, but aren't guaranteed for that.

Q. Impact ? does it resist to what impact?

A. Pretty tough, but again, not guaranteed, we are working on a protection of some sort.

Q. How much does it cost?

A. 22.000 $. With the package there is also a (4th) spare unit. Installation is included, but expenses paid for.