Please note: This page is under construction. Update will follow soon.
The question about slalom fin bending stiffness, is a bit about personal preference, but the chart below can serve as a general rule.
In addition the following statements are normally agreed upon:
- Softer fins generate more lift (the lift of your board out of the water), helping the board get onto the plane earlier.
- Softer fins can act better as a shock absorber, smoothing out the ride in choppy or wavy conditions, making them more comfortable and less tiring, however a too soft fin may led to loss of control in the same conditions.
- Stiffer fins makes it easier to maintain control in strong wind and/or choppy conditions and prevent spinout.
- Stiffer fins is generally better for pointing upwind.
- Speed fins are generally stiff.
We manufacture our Hammer SL fin in three levels of bending stiffness; Soft (So), Medium (M) and Stiff (St).
For riders above 85kg, we in general recommend Medium (M) or Stiff (St)
For riders below 70kg, we in general recommend Soft (So) or Medium (M)
Bending stiffness and Torsional stiffness
With careful design of fiber orientation and choice of fiber, we manage to achieve high torsional stiffness for all three stiffness-variants. Bending stiffness [N/m] and torsional stiffness [Nm/rad] are both measured at 70% of fin-length. Measuring the torsional stiffness is much more complicated than measuring the bending stiffness, as the bending deformation must be isolated out of the measurement. We have chosen to let the 37cm fin be the benchmark when showcasing the stiffness of Hammer SL. This is the “go to” size for many riders on a 115 liters slalom board. The pictures below show how these fins bend under the same load.
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| Hammer SL 37cm | Soft (So) | Medium (M) | Stiff (St) |
|---|---|---|---|
Sideways elastic deformation at 70% of Fin length (25.9cm) at load 30kg | XXX mm | XX mm | X mm |
| Bending stiffness | X N/m | XX N/m | XXX N/m |
| Torsional stiffness | XX Nm/rad | XX Nm/rad | XX Nm/rad |
The terms Soft, Medium and Stiff are all very relative. The Stiff version of Hammer SL is e.g. considerable less stiff (and thinner) than a corresponding G10 slalom fin. As part of the Quality check, all Hammer SL fins have their stiffness measured. In the backside of the fin cover we place a unique label for each fin, stating Serial number, Stiffness category (So – M – St), Bending stiffness and Torsional stiffness.
It should also be noted, that a measuring point at 70% of the fin-length, leads to that longer fins are loaded further out on the fin, or on a “longer beam” as we say in mechanical design, giving more elastic deformation and therefore lower stiffness. In other words, a long fin is always softer than a short fin of the same type.