Very seldom, except once in 2005, the Sail Making argument was discussed on this forum. The same argument receive poor attention/interest in many others forums as well.
I noticed since long that the Sails, while being the engine of our models, do not receive the same attention as the for Hull/Fin/Rudder design and construction.
In the picture an example of the typical tools used to manufacture the sails :
Generally once the sail are made, the modelers check visually the forms according to their personal criteria and after are integrated to form the RIG.
Tuning will consist to adjust the sails in accordance with the perception obtained during the boat sailing.
Probably, no one know what is the Lift Force (kgf or Newtons) that the sail/rig will produce at any time.
The knowledge of the Lift Force produced by the Sail Rig will probably, in my opinion, offer more indications on how to Make and Adjust the sails as function of wing strength and direction.
Should be interesting to knows that our models have the sails set for maximum lift power and if racing results are not achieved is because the problem may sit somewhere else !!!
The idea to measure the lift force provided by the sail is a long standing desire.
It is my intention to introduce here the new tool designed in collaboration with my friend Pierre.
This tool is called by Pierre 'SSO’ and stay for Sail Setting Optimizer and it is based on a simple dynamo-metric principle.
Of course is not a sophisticated wind tunnel with plenty of strain gauges but the SSO aim is to be a simple rudimentary tool with intrinsic reading imprecision's assumed to be a constant error and therefore sufficient to detect sail adjustment variations. Only once manufactured I could be more precise unless is a fiasco !! On our models, the lift force may vary from 0 up to 3kgf or 30N as function of surface and wind velocity.
The SSO is not yet constructed but some hardware investigations are already made like the choice of the Dyna-meter (35€) and 2 Blowers of 35cm (70€). For this design I decided to use a simple Mechanical Balance with analog view.
Tests with a blower without grid show very little oscillations instability of the needle, this was the initial fear that the Blower’s Air flux would produce large oscillations as such to hide the step variations due to sail adjustment.
The other important feature, not verified because not yet available, is the use of linear ball bearings to reduce at the minimum the sliding frictions of the Rig board. The sails can be adjusted via independent Servo winches. I invite everybody to comment or suggest other options or design.