Normally i prefer wind force unit in bft.
When i want to have a fixed custom scale from 0 to 8 bft shown, then i have to enter a max value of 19 bft in the Edit Scales dialogue.
It seems to happen a miscalculation in this dialogue when wind force unit is set to bft.
It works as expected when wind force unit is set to kt. But there is also a bug when setting the manual scale in unit kt and afterwards switching to unit bft.
bft to kt table
conversion formulas between kt and bft
v in kt
B in bft
v = 1.624 * B^(3/2)
B = ( v / 1.624 )^(2/3)
B rounded to a natural number gives the Bft wind force
Proofed at edge-values of above bft to kt table.
v/kt | B | Rounded Bft 34 | 7.556 | 8 37 | 8.037 | 8 40 | 8.465 | 8 41 | 8.606 | 9 44 | 9.021 | 9 47 | 9.426 | 9 48 | 9.560 | 10