Ground Effect 2.0
|The white stripe behind this
“boatplane” looks like the windsurfer
But first what did we mean with the “original Ground Effect”?
It is about compressing a liquid/gas. At the bottom of a foil/board there is always a high pressure. Ground effect does show when the distance between foil/board and ground is extreme low (with or without water inbetween). Example: when using waterski and behind a speedboat entering a spot with 5cm deep water instead the normal 100cm, there will be more vertical lift and therefor drag surface will decrease. In other words at one point it become much better.
Can we use the original ground effect for a windsurfer?
I can not imagen a situation where the water is shallow enough for the ground effect on water. Also with any chop it will not be possible for ground effect in combination with water. Compressing water is no option. But the boardshape in the AIR is VERY interesting, because we can use the board and benefit from some ground effect. We use a little bit ground effect with the current boardshapes, just think about the white area behind the board. If the water is choppy enough it is possible to make a little airflow underneath the board for less drag (the original ground effect).
Ground Effect 2.0* ==> what ??
Ground Effect 2.0 this is speedsurfing and running a part of the fin IN the ground. Example: a speedsurfer sailing in 20cm water with 23cm fin. What do we need for a positive effect, a soft kind of soil like clay, it could be 50/50 mixed with some fine sand (It should be soft enough to just sink in a few cm when standing there). Also the ground (bottom) NEEDS to be reasonable flat. How can running the fintip in the ground be a REAL benefit?
- Maximum Efficiency on the finpart still in the water. When using a 30cm or smaller fin in less than 30cm deep water, you can imagen VERY little chop can build. Soo maximum efficiency for the complete fin surface, not average xx % out of the water flying between chop.
- Fin does generate extra drag, when the fin gets deeper in the ground the drag increases fast. A lot of speedsurfers will know what I mean, at one point you feel it is going totally wrong. In medium/ rough sand it would happen in 2-3cm or soo. You can imagen any small underwater sand dunes can lead to HUGE crashes.
- The fin/board angle of attack stabilises and will be less on average. Normally on chop/ open water the angle of attack is anything BUT consistent. This little bit less angle of attack will generate less drag, but NOT near enough to compensate this drag the fintip generates. The stabilisation is important, I remember a extreme safe feeling, possible to generate MUCH more forward forces with the sail. This is big benefit NR.1, good enough to compensate the extra fintip drag.
- Last effect is the vertical lift becomes a bit more at the back of the board without losing grip (horizontal lift). More vertical lift without losing grip, if there is anything THIS is the key to records. For your information: very well trained speedsurfers can pull the back of the board in the air with the backhand/ harnass. Extremely dangerous stuff (remember this Albeau crash during his recordday)
- Strand Horst records lately with extreme shallow water
- Smashed up fintips that often do records
- EXTREME close to shore pictures from top riders running at high speed. (where there is clearly no waterstate difference the first 8-10m from shore)
Erik is windsurfer for 10+ years. In his daily life he is professional in construction dewatering, advisor, troubleshooter. Erik likes adventures, explore and to challenge himself. During his life he is trying to get the best out of it and have respect for the earth, nature and future generations. The modern world is about sharing, in this blog Erik shares his experiences, selfreflection and lessons learned.