Is there an alternate to boards? Well in some cases they are a must but if your Hull is rounded similar to a Tornado or the like, basically a half a circle, then only dagger and center boards will work for you. But if your hulls are flat sided, dory or similar and they produce a force then you have an option for boards. Anti Vortex panels or chine runners. Above is a photo of mine on the puddlecat 18.
I have done enough testing now to say that I am ready to release Hull winglets on a design and make it an option for other boats. I will be putting them on the new PuddleCat 16/18 from the start instead of making them add on. Study has shown that these AVP’s will work best on hulls with an aspect ratio of over 12 to 1. The new PC 18 will have a ratio of 13 something to 1 so I am looking forward to testing them on this new design where they should work even better than I have experienced before on boats of less than 12 to 1 length to width ratio.
Anti Vortex Panels work just like Wing end plates, drooped wing tips and Winglets on aircraft and also winged keels. They do so by keeping the air or water from flowing off the wing tip or keel as much as they would without them. They can not stop the flow off but they can alter it and improve their performance. Low aspect ratio airplane wings (short, thick, long cord- or “heresy bar”) have been using them since the 1940′s. I have been experimenting with them on aircraft since 1994 and know that they work well so I did not invent anything but just chose to use them. I chose to use the AVP’s on boat designs for one reason- shallow water.
I do not think that daggers or center boards will ever be replaced. To go upwind well in weather they will be the best choice. But I think that vortex panels and chine runners will do almost as well. Plus they will also work in shallow water where boards will not work at all. I will be releasing some photos of them as the PuddleCat catamaran progresses.
If you would like to do some reading up on them you can search Anti Vortex Panels How do they work by Bernd Kohler. It takes some experimenting to get them correct but when you do they are a viable option to boards. Chine runners work a little differently and are located on the outsides of the hull sides instead of the inside and are used on mono hulls. I have not found any good reading on those yet but they are well proven on Matt Laden’s designs. I would like to get to where anti vortex panels or more simply- “Hull winglets” or “winged hulls” are the norm instead of an oddity. There are also some good boat building and designers forums with some good discussion from some knowledgeable people and is worth further study. For me it is more about proving it in the real world and I learn by doing. Hull winglets I will continue to use and test and let folks know how they are working and give them info needed to do their own testing while also providing good board information.