Hey Rob, Mark, Tubedog, Herb or anyone with some insite, I think one would be hard pressed to differentiate between the two (MVG and Supercharger) but will someone give it a stab. Maybe the word canard (small foil in front of a wing) fits into the picture somewhere too. Another point in question is the placement of these finlets if we can group them as such. Herb Spitzer says he likes them about an inch and quarter forward and about three eights of and inch out board of the rail fins. If you put them directly in line with rail fins they will change performance. I wonder how. My question is what to do, what to do because someone may all ready have tried the options. The other question is if there really a difference between the three or is it all just a matter of terminology? Mahalo, Rich P.S. Year’s ago we called 'em “Dusters.”
Hey don’t forget the 5 finned Bonzer. Those first two bonzer fins are like big Superchargers plus a few additional qualities. Not only do they help with flow around the second set of fins but they provide lift and redirect spray (as thrust?). Truely a forward-thinking set up. Just got some cool new MVGs from Mark Spindler today. Different than previous versions. Sort of hard to isolate all of the varibles going on under the board, but the first time I used them the board felt “slippery” probably like a fish (surfboard kine)does. Too much speed. Just barely enough to notice. More than enough to fall off. These things all probably work in a similar way: Superchargers, MVGs, canards, strakes, vortex generators, etc. Just setting up flow so that its smoother when it runs into something bigger like a main fin/wing/tail fin(airplanes). (As for aerodynamics an airplane’s tailfin is what we should look to as most similar to a surfboard fin). Rambling on with my half-science. Love to talk to someone over at MIT and see what they think about all this speculation. Rob Olliges
Hi guys, I have been trying to get a penguin built for 3 years, within weeks as opposed to months now. The board uses two canards, in line with the tail fins. Dont know what to expect, but I’m making them removable, I will put in as many possible variations with the fin system (hence 4wfs) Now, if the stringerless blank makes it in one piece this time round, then we are cruising handy. Will update as I find my way http://www.surfingireland.net/feature_shapersbay.htm 
There are differences between Canards, MVGs or superchargers and C-5s or Twinsers. Each has a different effect. Canards are used on airplanes to stop stall by not allowing the plane to climb at a rate that would cause stall. The canard wing is fixed in such a way as to push the front of the plane lower when it reaches a near stall position. MVGs and Superchargers are vortex generators designed to reduce drag by inducing small vorticies around the fins and along the bottom curve. C-5s and Twinsers eliminate stall by inducing a consistant flow angle over the main outboard fin. They also produce a slot effect between the fins that increases flow speed over the main fin, increasing drive.
That’s clarity. After the surfing world rejected epoxy back in the day Greg took night classes at MIT (or perhaps FIT). The “mad scientist” isn’t mad anymore. : ) Thanks, Rob Olliges
On a rocket like the Sidewinder air to air missile, the Canards are forward of the Fins. The Fins are used for stability, while the Canards are used to steer.
greg- where are you placing the mvg’s on a conventional thruster? twin fin? i was getting fins at surf source a while back (i’m there at least once a week since they’re only 2 miles away) and they had those things stuck on the sides of their computer monitors in tandem as pencil holders. i said “gimme those damn things” but i don’t know where they go and since the double-faced tape is gone, i’ll have to epoxy them in place and would like to do this once only, if possible. thanks… jim dunlop
MVG’s are usually put in the front of the back fin in a 3 fin set. I don’t know if they call those fins on a sidewinder Canards or not. I was chewed out for calling a forefin (sailboard design circa 1986) a Canard by a customer who designs airplanes who set me straight on that one. I did learn most of what I know about foils and fins from a guy named Rick Caldwell (from Race Technology) who did his masters thesis in hydrodynamics on sailboard fins at Fl.Tech. He took the night classes. I’m just a poser.
I’m confused. I thought vortex generators were placed on the leading edge of the foil to disrupt the laminar flow against the foil surface, and promote attached flows at greater angles of attack. And I thought canards were smaller secondary ‘wings’ in front of the main wing, which redirected flow at the wing. Superthrusters and Twinzers certainly seem like canards. But the fin MVGs do not seem like vortex generators, more like canards. A vortex generator would be more like a series of small beads on opposite sides of the fin near the leading edge. Whereas the bonzer additional fins seem to act as independent fins, with 2 or 3 fins engaged in a turn, each contributing. The other fins don’t act principally to enhance primary fin performance (like twinzers or supercharger or MVG canards do). Or am I confused…
…Great Post ! …I’m going to make a laminated poster of your post,and refer people to it,Thanks.Herb
jd, dang i was wondering whateverhappened to the pencil holders…that’s awesome! shoot me an e-mail with your address i’ll send the tape. now to add my 2cents to the confusion: mvgs superchargers and canards. mvgs differ in design from superchargers. this greatly changes the effects of the positioning of each. positioning is the main issue and critical to getting the results you want. mvgs have numerous locations. they can be and usually are positioned as canards but even then they act as micro vortex generators. i have only seen a few pictures of herb’s supercharger, but i think he has theorized his positioning like the c5 but tweaked slightly forward; whereas R. has been adjusting his further and further back. i believe that in addition to herb’s claims i can add the possibility that the slot effect greg mentions also causes a reduction in size of the thruster fin turbulent bubble. the creation of the turbulent bubble is the main cause of drag in fins. the smaller the turbulent bubble the more efficient the fin. with superchargers, the slot effect may help reduce the size of the turbulent bubble. maybe if i try and say the same thing three different ways i can really confuse everyone. anyway, mvgs may work differently to reduce the turbulent bubble by injecting flow in the form of micro vortices. mvgs have not tested well in the c5 position. i believe it is because the smaller size doesnt contribute the necessary slotted effect. i have developed and tested a larger single mvg finlet, which following his tests at sebastian inlet a year and a half ago Kech named the Thresher fin. i have not made a production model yet. fyi, this fin designers best tool is having a fluid physicist in the family. but it wont do any good without visualization. plus i find detailed conversations with master shaper GL10 is a necessity. and by the way there is a reason for the failure of future’s vector fin box and it’s not the box. mark
here’s one link. it has a cool video. i would like to take a second to remind everyone that one major difference between tuna and surfboards is that the tuna tail is flexible, it moves side to side, and flexes into an articulated curve shape in both directions. the surfboard tail does not. yet as the tuna tail flexes the fish doesnt turn. that’s perhaps one reason for the finlets articulated array. another reason the fish doesnt turn with such strong tail strokes it the oversized dorsal fins. i’m sure there are also many other factors involved both known and unknown, as the tuna is a near as perfect design as could be possibly be created. speed and agility are it’s only defense and everyone knows how big and tasty they are. anyway look closely and notice that finlet 5 moves the most. that’s because it’s on the part of the tail that moves the most. that’s just one small detail. taken as a whole, everything on the tunais designed by nature to channel flow and direct the energy extracted from the flow in a forward direction. one may say this is an oversimplification, but i’ve read the reports and it’s the conclusions that are the story and the conclusions are simple as well they should be. that’s the reason for and the purpose of the detailed research. it backs the simple “truth”. also, please keep in mind i’m merely imitatng the creator with my mvgs. i only barely have a grasp of the physics involved. not even 1%. i’m not trying to be a poser, i’m just saying i am dumb. m http://jeb.biologists.org/cgi/content/full/203/15/2247/DC1
…Are you the sales end of the MVGs ? If so I tried to inquire about your MVGs(as to purchase a couple sets).I would love to try a set inplace of my Superchargers or maybe another tweeked version of combos that I had in mind using both or maybe all three.At any rate if you have any business with the sales of MVGs I would be interested in purchasing a couple or trade? you can contact me at : …Oh yeah,thanks for your definitions on the differences in MVGs,Superchargers,and C-5s.I’ll print your post and put them next to Greg’s for others to reference.Herb
…Never was good at spelling bees.Herb