*** warning: nerd factor ***
Hi, I use Sabfoil Balz pro 799, 899 and 999 depending on wind strength. Used the biggest 999 (1700 sq cm) for the first time yesterday and noticed that with unchanged foil mast position I had to apply a lot more back foot pressure to keep the nose up.
I started moving the foil mast base fwd by 1 cm on my wizard 130 but may have done more, since it was still back footed.
This is consistent with my experience using SS HG i76 and 84 before, where the 84 also needed to be moved fwd to remain balanced. When the 799 is put on the 999 you notice that all of the bigger foil's surface is behind that of the 799, meaning that the center of effort of the 999 will be further aft, and I guess has to be compensated by moving the foil mast fwd.
An additional factor might be the added drag from the bigger wing which has an effect of leveraging the board downwards? I did have a sensation that, even when stable in flight on the 999 with more back foot pressure, the nose of the board was lower than on the 799.
While the 799 feels very lifty (surges upward as speed increases) the 999 is much more docile / stable in pitch in this respect.
Do you have similar experiences when switching between foils of a same design? Are there rules of thumb? Moving mast fwd by X, or adding more incidence/shimming of the stab?
The shift between 76/84/99 infinities was suggested because the center of pressure of the larger wings was further aft, requiring them to be in the C switch fuse position for 84/99 and/or shifting forward in the track. I found this matched my experience with those foils. Looks similar with those, as the longer chord pushes the center of pressure aft.
I ride both of those foils and have the same experiences. I move the foil mast about an inch further forward when I am on the 999.
