Fin to Sail Size Calculator Info
First of all, the fin limits the size of a sail.
Based on a fin size, the FSC (Fin to Sail Size Calculator) calculates a suitable sail size depending on elevation, outside temperature and relative humidity. Higher values for elevation, temperature or humidity result in larger sails, lower values in smaller sails. The effect of humidity is low. As a reference, an elevation of 0 m above sea level, an outside temperature of 15°C and a humidity of 55% are assumed.
The results are based on the assumption of a passive sailing technique on a half-wind course with a take-off speed of 4 m/s and a planing threshold of 5 m/s.
This would also categorise the target group of the FSC. It is the recreational wind surfer with planing respectively take-off experience.
With an active sailing style (e.g. by pumping), smaller material (sail, fin/foil) can be chosen, which would have the advantage of increasing the upper wind limit, which would put you on the safer side, especially in gusty wind conditions.
Please always pay attention to this:
Windsurfing and windsurf foiling can be dangerous sports!
If the wind speed is displayed, it should be noted that these are always maximum values(!) based on the assumptions described above.
Due to the large number of sail types optimized for specific use, the FSC can only serve as a rough guide. The results are not recommendations. Whether these sail sizes fit one regardless of sail type or other hard-to-specify fin or foil characteristics is up to one's own discretion.
The use of the results and information is at the user's own risk. Please note the disclaimer.
The default settings of the light blue fields can be overwritten with your own values.
Some input fields have multiple entries, but should be explained by themselves.
Mode
The selection is made via the Front Wing Lever field
Fin to Sail Size Calculator: Front Wing lever arm = 0;
(Sail to sail calculator: Front Wing Lever Arm= 1;)
Foil to Sail Size Calculator: Front Wing lever arm > 1 < 60.
INPUT FIELDS
Front Wing Lever Arm (cm)
If not known, the lever arm of the front wing can be easily determined. See tip 2 below.
Fin / Span (cm)
In foil mode, the field for the fin length is filled with the span of the front wing.
Area (cm²) (Sail m²)
The fin area is preset with an estimated value in the corresponding mode and should be replaced by its real size (see also tip 1 below). But be careful, once overwritten, no matter in which mode, they are no longer available until a reset (Set button in the app - top right in the menu). In foil mode, the area of the front wing should always be known.
As a sail-sail calculator, see tip 3.
Elevation (m)
Altitude of the surfing spot above sea level.
Air Temperature (°C)
Outside temperature at the surf spot.
Humidity (%)
Relative humidity at the surf spot.
Wind Unit
The wind unit is selected in the top left-hand field of the EXCEL table or in the correspondingly labelled field of the app, provided this option is enabled:
Wind speed:
0 = m/s,
2 = kts,
3 = km/h.
4 = mph.
Wind force:
1 = Bft.
Sailor (kg)
In fin mode, your own body weight only affects the calculation of the wind speed.
FOIL+ Board + Sail (kg)
In addition to your own body weight, it is very important to use a realistic value. Does not play a role in fin mode.
OUTPUT FIELDS
Aspect Ratio
Is the aspect ratio (λ - Lambda) of the fin or front wing, the ratio of the length/span to the average width. The higher the value, the slimmer the fin or front wing. (See also explanation of formula (4) in FSC_Physik.pdf, currently only available in German.)
Sail Size (m²)
The result of the calculated sail size.
Wind
Maximum wind speed for the calculated sail.
Tips.
1. If you don't know the area of your fin, you can draw its outline on a sheet of paper, draw parallel lines starting 0.5 cm below the fin head in 1 cm increments and add up their lengths. The result is very close to the real fin surface.
2 The length of the lever arm can be measured along the fuselage from the centre of the mast to the centre of the front wing.
3. If you only want to know the dependence of a certain sail size on the altitude and/or outside temperature - very slightly on the humidity - you can activate this option by setting Wing Lever Arm = 1 and enter the relevant sail size in m² in the Area field (depending on device, maybe only integer).
Translated with www.DeepL.com/Translator (free version)
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