This question is for Herb or anyone else who has experience with this, What do you think about using superchargers on a single fin setup? I'm about to shape a 7' egg and am considering fin options. I'm thinking a 9" Greenough 4c, possibly with side fcs (it's what I have available) or single tabs for superchargers. Another option would be fcs and superchargers, plus the single box. I'm trying to think of a way to be able to use the 2+1 setup or just the chargers and the single. Any thoughts? Thanks- ryancg
I'm using MVGs (micro vortex generators) a few inches in front of my single fin box. MVGs are a stick on (super strong 3M tape) small double fin about 3/4 of an inch high. They come in flexible and rigid material. On my son's first board the MVG will replace the center fin and Herb's Supercharger's will be side fins. Rob Olliges http://gosurfgear.com/nscgi-bin/gosurfgearcom/catalog.cgi?Cartid=18481068414958&Department=MVG%20TURBO%20SYSTEMS&Merchant=gosurfgearcom
Hey Rob. What are the MVG's meant to do? I know little about the technical aspects of the way fins function. I use Herb's chargers in my shortboard and think I will probably use the box, side fcs, and chargers in my 7'. Many options. Thanks- ryancg
The MVGs are supposed to set up very small vortices (swirls) in the water as it approaches the fin. This may allow for a smoother flow of water around the fin and behind the fin. If it works, it reduces drag. Herb's superchargers probably work in the same way by setting up the water to approach the fin and also provide a smoother release and flow of water off the fin. I can see how this effect may be more noticble with side fins which are towed in and are producing a lot more drag than a single fin. The MVGs have been used on the front (nose) of air boards as mini-fins when coming down backwards ("fakie" I think it's called). In that set up two MVGs are used as a center fin (4 mini-fins) and one MVG on each side as side fins. For information on the physics of vortex generators just type in "Vortex" in the Swaylock's search box above. Rob Olliges
Ryan & Rob, Any fin set-up with lead finlets seems to me a credible idea -- singles or otherwise. Here's a few photos the referen the naturals points of in nature. http://www.taxidermy.net/reference/fish/tuna/69a.html http://www.chambers-associates.org/Big-Marine-Fish/photos_yellowfin_tuna_pg1.html I'll spare you the pitch on how long ago she invented it. Sometimes regression is a damn good idea because it yields progress. Mahalo, Rich
You`re right, Rich! Sometimes the fastest way to gain headway is by tacking into the wind... you can get where you want to go, but almost never in a straight line.
Dave Parmenter makes a board called the Widow Maker. Basically a single fin with superchargers, works great. Sluggo
That’s not a vortex generator. This is a vortex generator. (See the F18 pictures from the 2003 Dayton Air Show in the link below) A vortex generator for a fin needs to look more like the wing-strake of the F18. The strake is simple, light and effective. The strake promotes attached flow over the wing, which results in a high lift capability and high stalling angle. The strake should work just as well for a fin in water. Such strakes have been water tunnel tested and their performance has been shown to be unaffected by the low Reynolds number flows typical of surf fins. The strake is effective to some degree with all fin planform types, and is most effective for moderately swept planforms. The strake is shown to be just as effective on a thin or a moderately thick fin. The strake may at times develop a cavitation vortex off the fin, but I do not expect this vortex to be detrimental to the fins performance or general capabilities. (We will see about that.) The existing vortex generators and canards used for surfing fins are not very well designed. The vortex generator needs to have a span about 0.2 to 0.3 of the main fin, and it needs to be of very low aspect ratio so that a strong tip vortex can be generated. If the fin-strake works as promised, it will be a major step forward in fin development. I wonder why the kiteboard fin manufacturers and surfboard fin manufacturers haven’t worked this one out, as some companies actually make both kiteboard and surfboard fins. Try it for yourself. A strake is simple to make. Get a “T” section alumin(i)um extrusion of 2mm section width. Shape the strake with a file. It is not necessary to make the strake edge sharp, just rounded. Thanks, Mark http://www.richard-seaman.com/Aircraft/AirShows/Dayton2003/F18f/
interesting photo of the f-18 fighter. i cant compare the effect of the strakes on that plane to the mvg (multi vortex generator) i developed. i suspect they work in different ways. perhaps they are vortex eliminators. after all jets work at much higher speeds than surfboards. as i have said all along i got my idea from observing the finlet arrays on tuna and mackerel. i asked my brother, who is a fluid physicist complete with Ph.D., what he thought the finlets on the tuna did for the tuna and he said perhaps they worked as micro vortex generators. this was back in the fall of 97. i got in touch with nasa and harvard and spoke with the top nasa mvg design engineer and the harvard mackerel researcher. i spoke with them both about micro vortex generators and tuna design. from one i was told you cant go wrong imitating the creator. the other i introduced the words "contributing flow" to her research. design and concept wise my mvg is more like the mvgs on the wings of the boeing 737, which are small triangular aluminum finlets about 20 or so to a wing. i put some curves on mine for several reasons. one, though water and air are both fluids water hates a straight line and refuses to stay attached. second, straight fins dont look good on a surfboard and because i figured i had an uphill battle to get a new concept introduced i thought i'd make it look a little familiar. i really didnt think anyone would be drawn to a simple triangle, but that was the shape i used i my first prototype mock-up interestingly, as i have shown mvgs to just about every name brand board and fin shaper in the industry the one remark i most commonly heard was "nice foil". which indicates to me that there are certain things surfboard shapers are accustomed to look for. lastly, i shaped them in much the same shape and dimensions as the tuna finlets. my thinking was if it worked for the tuna who was i to improve on 4 million years of evolution. surfboard speeds have yet to reach 65mph but that information hasnt stopped the tuna from reaching or exceeding that capability. maybe someone should tell them their mvgs are designed poorly. maybe that'll slow the buggers down. however my next generation mvg is much different and sets will be ready very soon for pro testing this winter. btw regarding fillets on glassons, the navy has added fillets to the conning towers of their subs. in fact if you were sitting on your board in the ocean and a sub passed 10' under you, you would not even know. the navy has put all kinds of silencers and turbulence eliminating devices all over their subs. so for glassons as long as the fillets arent gargantuan they are effective at reducing the turbulence of the base of the fin. that will decrease drag and therefore increase speed. maybe not noticeably but conceptually. one more thing, Greg Loehr's Resin Research epoxy has taken all the work out of it. you dont even have to think about it. RR resin is the best thing that has happened to surfboard construction since foam. He's also the best of the best shapers. you should all be totally stoked that he's already done the leg work for you and you should be requesting Resin Research for your next board. and then you should be sitting on the edge of your seat to hear what he's working on next! mark
Mark S. The MVG people and Herb S must be congratulated for developing and promoting the system. I would encourage this work to continue. The field is wide open. Please accept that I am expressing a view. I do not wish to debase your efforts. You may be interested to know that a major surf fin manufacturer rejected the vortex generator fin design which I proposed. They know best. As for water tunnel testing, did you know the Australian Government bought six Collins Class attack submarines off the plan without having done any water tunnel testing at all. The Australian Government then spent hundreds of millions of dollars fixing up the problems because the submarines sounded like "a rock-concert underwater". The Australian Government also then gave Fin Control Systems a research and development concession, reportedly valued at one million dollars, to improve fins for surfboards !! If you are interested to know more about straked-wings/fins then try these articles for starters. The Journal of Aircraft, Vol 17 - No 1 page 20, and Vol 16 - No 11 page 756. Thanks, Mark.
Pages