Barn door rudder design

[artbyjody]

Jeff...

Great post!

Not to get too far off-topic, but a lot of the changes to rudder designs such as adding winglets - are somewhat related to born again interest of the Atkin's tunnel design, as well as that new Loop Keel?. Interestingly enough a engineering firm recently published a study that proves that tank testing is flawed because the tank itself induces its own vortex effect. It is bad enough that fluid flow really is not an exact science and now the possibility that designs have been created that may or may not be as advanced as we would like to think....

Hence, "T-rudders" , winglets...I am sure you probably read the boat design site as well and here is a more in-depth discussion of them: link

The winglets create additional vortexes that may allow for increasing the speed of water such the rudder performs more reliably under slow speeds as well as acting as a channel and removing friction...It is interesting concept and seems to be more on those mini's / mono's....But Oracle Racing Team did use them at one time (or maybe is now)...

I certainly do not understand it all and of special interest is the Atkins tunnel theory...but it makes for interesting reading...

[Jeff_H]

Almost from the beginning of tank testing there has been an understanding that the size of the model relative to a molecule of water, and interaction of wake of the yacht with the testing tank wall influences the data. Historically the science of correlating the test tank data (or wind tunnel data for that matter) with real world data has been a work in process. Today, the correlating mathamtics are quite sophisticated and produces very reasonable results.

But even before the advances correlation that has come since the advent of the computer, what tank testing does quite well is show the relative affect of one design concept vs another. So while it would have been difficult to determine how much faster one design idea might have been than another, it would have been pretty easy to determine which had lower drag vs higher lift.

Jeff