MVG and next-gen MVG “Thresher” from Mark Spindler:
MVG w/ Spitzer’s Superchargers (glue on) and quarter:
All three now; with good angles on the Superchargers:
Interesting stuff. 
Those Threshers are very interesting to say the least…I’ll have to get ahold of Mark.Herb
Anyone remember back in the late '60’s, you could buy stick on 1.5" fins for the rails of your single fins to help with hold and pivot.
I bought and used 4 sets of them, and they all stuck just fine.
I have a Thresher and the 3M adhesive Mark uses has held up so far. I like the fin, too.
Those were Con’s jobs.Control products That is…went thru several sets( used them like 2+1s on singles and Superchargers on my twin and earliest thrusters.)…possibly a 100 sets.
…Con Coburn was a great inspiration for me.Herb
Wow! 100 sets!
I’m impressed!
After I used a couple of sets to improve my slightly wide 6’3" series singles, I decide to narrow the template, flatten the deck to get thicker rails, and eliminate the need for the add ons. Worked, up to about 12’ OB that is, then they slid, even with 10" longboard fins.
So started the 6’8" series, which I probably shaped close to 70 of, from 18-20.5" wide, with tails from 12.75-14.5". Those had much straighter tail template curves, and held in much better in all size waves.
I think the problem with my 6’3" template was wide point only at 3" forwards of center, something NOT done in 1974. The resulting curve between the rider’s feet just pivoted and spun out on everyone riding waves of consequence.
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After I used a couple of sets to improve my slightly wide 6'3" series singles, I decide to narrow the template, flatten the deck to get thicker rails, and eliminate the need for the add ons. Worked, up to about 12' OB that is, then they slid, even with 10" longboard fins.…
I think the problem with my 6’3" template was wide point only at 3" forwards of center, something NOT done in 1974. The resulting curve between the rider’s feet just pivoted and spun out on everyone riding waves of consequence.
How much rear rocker on that series, or what was the range?
Lee,
I use to get boards glassed at Con’s Venice shop back in the days.It got to be that when I walked in, he’d hand me a dozen sets to kill.He liked the ways I used them and could see their advantages…good point of sales for him as well…we sold literally hundreds if not thousands out of my shop in L.B. …Herb
The 6’8" series were all made from the same 7’11" Clark blank, and most of the boards were custom according to what the customer wanted to get out of his surfing.
Some guys, I added tail rocker, like 6 cuts at 1/16th, for easier turning.
Some guys, like the speed addicted, wanted flatter tailed boards, so I kept the rocker kinda flat, but narrowed the tail block to allow them to NOT pearl.
Most guys wanted easier paddle, so some boards were 3" thick…easily done with that blank.
I guess NO good surfers ever rode any of those boards! This, of course, was years before duckdiving was invented, so no need for 2.25" thick 6’8" boards.
I liked them just about 2.75" thick, as flat as I could make the deck, with thick, turned down, but soft rails. The thinner tailed ones were my worst, as they tended to ride “untrue” and had spinout problems. The thicker railed and tail boards all rode fine, and could handle just about anything anywhere short of truly scary big waves.
Of course, for me, big scary waves start at around 8’, so I wasn’t asking a lot from the 6’8" series.
I made Daryl Scobie a thick 8’6" gun, but he never justified it’s ownership. Same for Lonnie Magnuson…they just didn’t go out in big enough surf.
Wish I remembered who I made the 8’6" set of about 8 boards for. Time just wastes away my brains.
So, do they work? What’s the principal behind them, also where can you get them?
Honestly, I’m a little afraid to say anything. Specifically, I dont want to violate rules 3 and 4 or upset Mike in any way, because he provides a great place for all ideas. But I believe I can answer some of the questions regarding the theory of MVGs and the Thresher Fin. Mike, if I’m out of bounds please advise.
First the MVG or Multi-Vortex Generator was inspired by tuna finlets. We (meaning me, and my brother who is a fluid physicist with background also in fusion physics MS U.of Wisconsin and engineering physics Cornell BS) theorized that finlets like this contribute flow to whatever fin they are placed in front of. The possiblity of increased flow may have several effects. One, is it may reduce boundary layer separation by injecting flow into the flow around the trailing fin and thus reducing the size of the turbulent bubble, which in a turn is a source of drag. By reducing drag in a turn this could increase speed and with attached flow increase control. Secondly, the micro vorticies may possibly increase water velocity as the water passes through and over them. That is what vortex generators are intended to do, but whether or not these MVGs do that is still a subject open to speculation, debate and further testing. However, our conjecture is that when these vortices, or concentrated patterns of controlled flow (faster moving water) impact a fin they may generate increased lift. This could possibly make fins more efficient. There may also be a slightly beneficial drafting effect while surfing in a straight line. So, generally, in any position MVGs may have a beneficial effect on both speed and control as those factors are related to fins. That is to say MVG effects are fin specific and not in any way related to rails or any other board design features. In other words they will not correct a bad board design. It is possible that they may help overcome some problems though. They are, no doubt, just one more thing to confuse and confound everyone:-)
As for the Thresher Fin (so named two years ago by air inventor Matt Kechele) this is for guys who want to generate maximum speed in small surf with slopey walls and flat sections. We believe this fin is a more efficient micro and multi vortex generator. We suggest that the trailing tail of the Thresher(flexible in some models) may, in a turn, generate counter rotational vortices simultaneously off the top and bottom edges of the same side of the tail. Not unlike the counter rotational vortices your hand produces as you paddle, but with the Thresher they are also pinpointed and carried aft by the flow or maybe yet a better description would be left as a slip stream. By positioning the Thresher in front of a side fin or a trailing fin these vortices can then be focused directly on these fins. Try and visualize the rotation of the vortices off the tail of the Thresher (in a turn) and picture how that counter rotation would like to attach itself to another surface. Then think of the lift this would create. Also, think about this: Due to acceleration, you may need one less pump before you hit your roundhouse.
These are all just theories and so if anyone wishes to contact me and discuss further any of these ideas and theories, please email me at
I’ve been responsible for introcucing a few new concepts to the surf lexicon and here’s one more. I’m borrowing this from the car racing and aerospace industries. In order to describe the intangable difference between new race car designs and test planes, test drivers and pilots boil it down to one simple concept. Does the car or plane inspire confidence? In that respect and with respect to the car drivers and test pilots who came up with this idea I just want surfers to have more confidence in their turns.
Swaylocks is a great forum for ideas old and new, and I want to do my part to help keep it that way by not propmoting or advertising in the general discussion forum. So please direct everything directly to me personally off the forum.
BTW I had a nasty HD crash last winter and so if anyone hasnt heard from me maybe it’s because I lost your contact info, or mayby it’s because I’ve been laying low, working out new ideas. One of which is the next generation beyond the cambered fin, which, by the way, was my gift to Rusty, who took it to Curtis, who named it Vector. So, if anyone wants to make cambered fins feel free and dont worry about getting sued(nasty word), because I’ll testify that I put that one in the public domain; if it wasnt there already. Heck, I’m just a soul surfer paying dues for thinking out loud.
Thanks for listening,
Mark
Hey Mark,
The Thresher MVG design bares a marked resemblance to the adipose fin on a Chinook salmon, which is clipped off to identify hatchery fish. I hope to go on an offshore salmon trip soon. If I’m lucky enough to get one with the adipose fin in take I’ll take a photo and attach it to this thread.
By the way my fin experiment that included a set of my own version of MVG worked quite well. I have to go back on forth with and without them to see what the difference is but. I’ll check in with a report when I have one.
Mahalo, Rich
first off, I don’t think anything you’ve posted violates any Swaylocks rules – in fact this is the exact kind of discussion this place needs more of.
second, thanks for being realistic in your claims of what you think these things do, and what’s yet to be proven - refreshingly honest.
third, in aircraft vortex generators are fairly common, but typically they are placed chordwise on the lifting surface, and perpendicular to it – not parallel to and in front of the lifting surface. What’s the thinking in using them in the alignment you’ve chosen? How exactly do they "contribute flow?
thanks,
Mark,
Hey, Josh from Spring Lake/Manasquan area. We run into each other at Inlet from time to time.
That thresher looks interesting. It almost reminds me of a Bonzer fin but with more flex. I’d be interested in trying one out.
Do you have them in shops yet or do you carry them with you?
Let me know and maybe I’ll try one.
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Anyone remember back in the late '60's, you could buy stick on 1.5" fins for the rails of your single fins to help with hold and pivot.
I remember those. I think they were called Control Fins. I stuck some on my snowboard in the late 70’s for powder riding.
Keith,
I appoligize in advance for threading my response. Sorry.
“first off, I don’t think anything you’ve posted violates any Swaylocks rules – in fact this is the exact kind of discussion this place needs more of.”
Thanks. That takes some pressure off, but I still need to watch my limits.
“second, thanks for being realistic in your claims of what you think these things do, and what’s yet to be proven - refreshingly honest.”
I learned that the hard way:-) It wasnt fun.
"third, in aircraft vortex generators are fairly common, but typically they are placed chordwise on the lifting surface, and perpendicular to it – not parallel to and in front of the lifting surface. What’s the thinking in using them in the alignment you’ve chosen? How exactly do they “contribute flow?”
Unlike and airplane wing, there are two lifting surfaces on the trailing fin working against each other. In that tension the template cord and foil of the fin are what’s important. At the time, I didnt think I could add anything to the surface of both sides that would do anything, but increase drag. I wanted to design and make something that would be an improvement. Therefore, I didnt want to just have the two sides both continuously working harder against each other, as that might not be an improvement. So, I thought that by placing the MVG independently front, this way the MVG only works to assist or contribute flow to the side that needs it most, when it needs it most.
thanks for the question.
Mark
P.S. This is a very oversimplified short answer and gives no idea how much work, thought or process went into developing the MVG. I prepared a much longer answer, but I thought it might be too much. If you want to read it let me know. m
Josh,
The Campbell’s (Malcolm and Duncan)originally used aircraft designs for their inspiration. Very straight, angular and rigid. Brilliant for the time, style of surfing and waves they were designed for.
Thresher is all curves and some are flexible. My inspiration came from sharks. I need to work on balancing the shape some more. A distributor is interested and they already stock MVGs. But, Thresher is not in shops yet.
BTW, I havnt forgotten you.
For the record, Josh, besides being a ripper and a highly educated professional scientist, is the first person, ever, to buy an MVG, way back in 1998. I dont even think the idea was a full year old yet. That was the first time I ever actually sold an invention. For me it was an event. Who could forget that. You’re on my permanent hook up list.
Thanks,
m
I’ll be interested to see how this thing feels.
Do you intend to put these on twins, thrusters, singles, or all of the above?
If it goes on a thruster, would the placement be the same as the MVGs? I’ll have to go back and read the rest of this discussion.
thanks Mark – I am interested in your longer version of the answer – please PM me. Keith