Is Matte Faster?

I agree that it is quite vague, Petros. Lawyers won't help you with the
rulings made by some of these committees, unless they are handing out
large brown paper bags full of cash

 

Ambiguous, but specific enough. The key is "substances" and "structures". This way they can cover a wide range and make a declaration, one way or the other. If they pinned the definitions down, designers and teams would soon find a way, to circumvent the syntax employed in the rule.

 

Yes, well put. Ultimately, I think it is all about "unfair advantages", perceived
or otherwise. I doubt the rules committee on race day would know if a
hull has a thin coat of wax or something else, but they would notice riblets,
sharkskin or turbulent strips.

 

Absolutely. Racing authorities deliberately leave some room for making decisions based on that premise. That is as it should be. Otherwise the rule book would take up a whole bookcase.

 

The attached graph is Figure 48 of the Resistance Committee Report from the
25th ITTC of 2011. There are many other similar graphs available in standard
text books for spheres and other shapes, but this illustrates the concept pretty
well.

 

The only time this sort of thing becomes an issue is when someone bitches, questions about the rumors swirl around and eventually someone has to rub the actual hull. This is where the a judgment call is made on the potential or perceived advantage. In most cases, I don't think a really physically smooth hull will cause a problem. Problems arise when chemicals or structure can be found on the surface and this is the "spirit" of the rule, which is how they'll decide. As we discuss this, a ChemE student is working in secret with a designer, on a new "slime" coating that dries within a few minutes of air exposure, so any launch day hand, that might rub against it, wouldn't notice anything out of the ordinary.

 

notice how in that graph that smooth is way better when you are well beyound the transition. I would suspect that most rowing sculls are much too long to be in the transition area of the Re, so putting a rough surface would only slow it down. Was this rule put in there out of fear of an unfair advantage, or there there some crews that actually used a ribbleted surface and actually won?

 

Riblet use (applied film) on winning America's Cup boats in 1987 and 2010:
http://valenciasailing.blogspot.com/2010/03/bmw-oracles-skin-friction-reduction.html
http://www.nasa.gov/centers/langley/news/factsheets/Riblets.html

 

Paul, This stuff has been available for 40 years. I tried it in the early 1970s. NAYRU and later USYRU made many tests and did not outlaw it but did outlaw injecting it into the water. I don't think any smooth coating has been outlawed.

 

I don't know if anyone tried and won.

However, if it was a real advantage (and I'm not sure it is with a pulsatory
form of propulsion like rowing) then all boats would need to have riblets or
they just wouldn't be competitive.

Another example was the use of fairings on the front of kayaks to reduce air
drag. A New Zealand team won by a good margin and the device was
immediately banned because everyone would have to use one. That would
be a large impost on schools and clubs.

Same argument applies to sliding riggers in rowing shells. Accepting them
would pretty well make other boats obsolete.

 

Was it the primary reason for the success of those particular yachts?

 

I strongly doubt it. But then there may not have been any single "primary" reason for their success.

I do know that circa 1987 riblet film was evalutated for lowering the aerodynamic drag of automobiles by one very large auto manufactuer. My recollection is that in some cases it did lower drag a small amount, but there were several practical obstacles to its adoption, and there were other more cost effective measures available for improving fuel consumption.

 

Ok what does it look like !!PICTURES ANYONE
No dont want graphs want to see what was actually being used and the shape of it!! ,Riblet that could mean anything !!.

 

Riblet photos on these pages:
http://researchnews.osu.edu/archive/ribletspics.htm
http://www.safl.umn.edu/featured-st...ing-wind-turbine-blade-drag-using-riblet-film

 

I think this mirco-riblet technology is not related to the same thing as the dimples on the golf ball. this is down in the nano sized rib-lets, so there must be something going on with the interaction of the boundary layer down at the gas particle size. It is too small to affect the Re, and unlike the large dimples, this seems to reduce the drag at all Re according to the charts in those links above.

They are the size of a human hair, or two, I would think you could get the same effect with the right size grit sandpaper (if carefully done). This would not violate the rules since it specifically out laws the application of a substance or film to get the a textured surface, but there appears nothing preventing you from creating the texture on the actual surface of the hull.

Very interesting.