Riblets are tiny v-shaped grooves no deeper than scratches precisely applied and angled in the direction of the flow. Wind tunnel testing
done by NASA on flat aluminum sheets shows a drag reduction of about 8%. Riblets are currently being used on airplane wings and can be found on things such as Olympic swimming suits, speed skating suits, down hill ski racing suits and a variety of other things.
This technology appears to be supported by nature on the skin of sharks. Shark skins have tiny, tooth like denticles that appear to serve the same purpose as riblets.
Photo of riblet from NASA
There are complications with riblets which makes it unsuitable for drift boats. First the groves must be precisely machined or applied to the bottom to have an effect, and it’s not one size fits all. The depth and width of the groves are critical and different sizes are required for different speeds. To the naked eye they appear as sand paper scratches, they must also be in the direction of the flow to reduce drag. If they go against the flow drag is increased.
While ferrying a river in a drift boat you don’t spend very much time with your hull going straight with the flow. Another big problem with riblets on drift boats is that the boats are made to float in low water conditions. This is problematic as drft boats often take quite a pounding on rocks and gravel beds. Once the groves are distorted even a little, the drag reduction effect is ruined. It is a common practice for people to wet sand the bottoms of their Sail boats and speed boats to achieve a similar effect. There is a lot of controversy in these markets as to weather or not there is a benefit to doing this. Speed is a key element in the equation, the faster the speed the more the effect and many believe it is unlikely for speed boats to go fast enough to feel the effect let alone a drift boat. Hi speed is one reason the technology works so well on the wings of airplanes.
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