Iâve actually been meaning to shoot a follow up for a while. In the video I stated it was due to turning dynamics but Iâve come to believe now that itâs purely based on weighting/unweighting the foil (such as in a turn, pumping, or when dropping down a wave face) rather than the change in forces from the turn itself.
@mediterranean_foiler you are completely right that in steady flight, if you move the foil 3cm further and then move your stance approximately 3cm further forward than the system will still be balanced. However, as you mentioned, we are in a dynamic system which is where this falls apart.
Letâs assume your original position was perfectly balanced, meaning that if you jumped off the board in flight the foil would continue to fly straight. This means that as long as you stand directly centred over the lift of the foil when you unweight the foil it continues to fly straight.
By moving the foil further forward, the system is now tail heavy without the rider. Like you pointed out, you can compensate for this by standing further forward. But as you unweight, the nose will have a tendency to rise since the system is inherently tail heavy. The further forward your foil is moved from the balance point, and/or the more you unweight the foil, the more aggressive this nose up pitch becomes.
The opposite is true for a foil that is too far back. Thatâs why itâs better to be a bit forward of balanced vs rear of balanced. A foil that is slightly forward of centre will pitch nose down slightly during the push phase of a pump and nose up slightly during the glide phase which is actually desirable. The opposite really sucks though! Not to mention youâd also have a tendency to pitch nose down when dropping down a big wave.
Too far forward and the foil will pitch up/down aggressively during the pump which is really inefficient and must be actively fought by the rider which is annoying, and although downward pitching while dropping down a wave is the worse, pitching up aggressively could result in a breach if the rider canât get their weight forward fast enough.
All this to say, I do think there is a theoretical âperfect spotâ where the system is in balance, but in practice advanced riders will prefer to be forward of this spot to varying degrees depending on how much they like to actively control the system during, pumping, turning, dropping down a steep wave, etc.
Personally I like to be just a touch forward of the balance point, around 1cm or so. But I definitely see the case for really skilled foilers to be further forward. Past a certain point though I think even advanced riders will be hurting their performance even though they can âget used to itâ.
As otherâs have pointed out, the popup is another matter. Since youâre more or less âstuckâ paddling on the board at the centre of bouyancy, if you move the foil further forward the foil will lift really aggressively as soon as you speed up (ie. start catching a wave) and youâll blow lots of popups by foiling out and risk some foil/face collisions, haha. Learning to prone foil I often recommend placing the foil a few cm back from the balance point to make popups less intense for their first few sessions. Even though itâs not ideal for the actual foiling part, this leads to a lot higher wave count and they can edge their foil forward as they get more comfortable.
Good prone foilers can execute the pop up with their foil really far forward but for the majority of us having the foil balanced under the centre of bouyancy or sligthly in front will be much more consistent.
As an aside, I suspect this aggressively âliftingâ during the prone popup has led to the very common (and incorrect) belief that moving the foil further forward in the tracks will somehow increase the lift that the foil is producing.