After testing the last 8 month we now do the production approvals for our new GPS_4 and GPS_5 Speed Fin models.
GPS_4
This speed fin design has a conventional aspect ratio but is very well balanced in profile type and thickness distribution over the fin length. The profile type is the result after plenty of hours doing CFD simulation on the computer with verifications afterwards on the water. It is performing over a wide AoA range with an excellent lift2drag ratio. The base2mid section has a high bending stiffness but the last 25% to the tip are a bit more flexible giving the rider a better feedback of the flow conditions on the fin surface and smoother ride in choppy conditions.
We recommend the GPS_4 design for universal usage in most speed surfing conditions. The characteristic is high efficiency (= low drag but high lateral lift) and usability also in choppy conditions where ventilation is not allowing the usage of short and wide based speed fins. For flat and shallow water the GPS_5 design has benefits on smaller speed boards (see below).
The GPS_4 is available in a length range of 23 to 32cm; we recommend rakes of 16° to 13° depending on the length and special customer requirements.
GPS_5
The concept of this design is as old as surfing&windsurfing is. Also looking to the build of many fishes you can find adequate paragons.
Using a short and widebase fin has advantages in flat & shallow water conditions when going on speedboards (<=54cm width) with enough wind power. Now this design becomes more and more popular when people explore new spots with limited water depth and trying to shift the speed limit to the next level. The short fin is causing only a small momentum (by short lever and most area near to the base) giving MUCH OF CONTROL and by that the confidence the fin gives to you when going really fast is definitely higher. Besides all physical effects, this psychological effect is of importance.
Limits: In choppy conditions ventilation is an issue for all short fins by air that is sucked from the base area to several centimeter in tip direction reducing the area of the fin that is taking lateral loads. Although we minimized the effect by a harmonized pressure profile along the section the physical effect cannot be eliminated completely.
Zara Davis won the production board record end of summer 2010 in Lüderitz with a first prototype of the GPS_5. Since that we did several enhancements on the profile and others by CFD simulation work and retesting on the water resulting in a wider usable AoA range and a very "robust" flow also in difficult conditions.
This design has 30° rake and is available in the length range of 19 to 23cm. A GPS_5 230 can be used by a 85kg rider with 7.0-7.5m² Race/Speedsail under boards up to 55cm width.
Nicky van Hoof won the lady’s competition; men’s competition won David Garell, at the 2nd place is Thorsten Mallon and at the 3rd place our team rider Patrick van Hoof.
