Just picked up a trial one of these to test from a local shaper. Looks quite weird, but I am a little intrigued. Will be fun to see how it goes.
Some big claims on the web site.http://www.thequantumfin.com/about_us.html
It should work well I think, will give lots of lift but without any unwanted handling side effects, it will be sensitive to tail rocker though, best on a flatter tail I'd say. just like a tunnel.
It would be nice if the lift angle could be adjusted, possibly by shimming and so on.
Similar to the old Velzy butterfly fins.
Just taken it a bit further..
Ride report please. Interested to see how it goes.
Select to expand quotelaceys lane said..
macs ordered 10 already
You must be running out of material because that was not funny
Select to expand quoteMacaha said...laceys lane said..
macs ordered 10 already
You must be running out of material because that was not funny
I thought it was 
Imagine if they did them in red black n white !
I could ask if they do a sunset tint if you like?!
Will hopefully give it a try on Saturday. Can only use it in the longboard as it needs a fin box.
Scotty Dillon did a similar one years ago...it did not have the centre fin though...I think he called his the butterfly fin...it did have some problems with tail lift as Roy mentioned....if you got the right bottom curve though it worked quite well...I thought it wasn't deep enough...with that extra centre fin it should be interesting.
Here's the video explanation of the fin.
The info given has been dumbed down.
Bill Hunter talks about the lift force generated, expressed in kilograms. The problem with that is that lift force is dependent upon speed.
Lift increases by the square as speed increases, so for example an increase in speed from 10mph to 14.1 mph will double the amount of lift generated. Bill doesn't mention this very important fact in his analysis. Instead he talks about the lift generated in '2 to 3 foot waves'. This is ridiculous since the computational fluid dynamics software can't use wave height as a parameter, it doesn't mean anything.
To run the calculations he must have entered a speed ( there would be no lift predicted unless a speed were entered) but he doesn't tell us what the speed is. Furthermore he quotes only one lift force figure for each fin setup. This is also silly, since speed varies over a wide range in surfing.... and he claims that the fin will get the surfer to his feet faster when paddling into a wave... (precisely when speed is at its lowest) without telling us how much lift is generated at that speed.
The Quantum fin website states that the fin is suitable for '2 to 3 foot waves'.... what they are trying to do with that statement is to say that the fin isn't suitable for higher speeds, and the only reason why that would be the case is handling problems which occur as larger amounts of lift are produced. What happens when the lift is greater than the weight of board and rider combined? We know the basic answer: the board will lift out of the water. This will cause catastrophic handling problems unless the fin setup is specifically designed to allow proper control without the rails and bottom of the board coming into play.
The lift force quoted of 60 kg occurs at what speed? Whatever speed generates that lift, it will take only a modest increase in speed of 14% to match the rider's weight ( in the case of the 80kg rider used in the example).
Another problem with the lift production quoted is angle of attack. Lift is typically doubled with a doubling of angle of attack. The fin is of course set at an angle of attack ( described as 'low') but what isn't mentioned is that the angle of attack on the fin is changed by the rider via the pitch or trim angle. This raising and lowering of the angle of attack of the hull ( and the fins) happens constantly and through quite a big range particularly during turns.
So, the fin is going to increase lift dramatically not only with speed but with the board's trim angle. Of course the flow to the fin is partially determined by the hull itself since that directs the flow before it gets to the fins, so the effect of pitch is somewhat mitigated.
This isn't just 'book learning' I've been making boards with lifting foils since 1998, and as it happened was working next door to a leading multihull and hydrofoil designer the next year, so managed to pick up a lot of useful information in a time when we had no internet or other means of doing research apart from 'Scientific American' back issues and tons of Naval Architecture and boatbuilding manuals.
By the way the drag prediction is hugely oversimplified. There's no induced drag shown, and from the comments on the video it seems that only skin friction drag is being analysed, but it's hard to tell since it's not explained.
Select to expand quoteCtngoodvibes said..
I could ask if they do a sunset tint if you like?!
Will hopefully give it a try on Saturday. Can only use it in the longboard as it needs a fin box.
i believe the centre fin should be yellow and the other two white creating the perfect frying egg.
how good would that look
Select to expand quotelaceys lane said..Ctngoodvibes said..
I could ask if they do a sunset tint if you like?!
Will hopefully give it a try on Saturday. Can only use it in the longboard as it needs a fin box.
i believe the centre fin should be yellow and the other two white creating the perfect frying egg.
how good would that look
Clearly suffering from a lack of new material,may I suggest hiring a writter
not trying to hijack this thread...but this is outside the box I think....probably 12 years old now...this thread has inspired me to pull it out of moth balls.
Select to expand quotearkgee said..
not trying to hijack this thread...but this is outside the box I think....probably 12 years old now...this thread has inspired me to pull it out of moth balls.
I assume it was a failure? did have any good points? what was your thinking for that one? looks pretty cool 
as a matter of fact chrispy it goes really well....I have used it in everything...longboards, shortboards and sailboards....never in kiteboards which you see right now as it is the only board I have that it will fit in......so we will see how it performs under some serious forces.....I gave this one to Tommy Carrol to try and he liked it...he still has one gathering dust somewhere
wow, I was not bagging it. just for something so different I have never seen it on your web page,so that is where my assumption came from that it was a idea that went wrong...then followed by next questions to find out the ins and outs and some answers on what your thoughts were on it.....like how it went blah blah as a matter of fact
sorry chrispy I didn't really answer your questions....tunnel the water obviously...still maintaining the thruster drive points....get the rear fin deeper....flex...it went well enough to seriously think about marketing it...I was in it with a friend and we were going to push it...we approached the guys at fcs...and they were warm and said come back after more testing ( Tommy)...then its achilles heel came to light......when the board was pulled back with some force ie wipeout legrope tension...it had so much leverage due to the long platform that it would rip the plugs right out of your board
Select to expand quotearkgee said..
sorry chrispy I didn't really answer your questions....tunnel the water obviously...still maintaining the thruster drive points....get the rear fin deeper....flex...it went well enough to seriously think about marketing it...I was in it with a friend and we were going to push it...we approached the guys at fcs...and they were warm and said come back after more testing ( Tommy)...then its achilles heel came to light......when the board was pulled back with some force ie wipeout legrope tension...it had so much leverage due to the long platform that it would rip the plugs right out of your board
thank you, and that would pose some problems...what about glassed ins or futures?
Select to expand quotechrispy said..arkgee said..
sorry chrispy I didn't really answer your questions....tunnel the water obviously...still maintaining the thruster drive points....get the rear fin deeper....flex...it went well enough to seriously think about marketing it...I was in it with a friend and we were going to push it...we approached the guys at fcs...and they were warm and said come back after more testing ( Tommy)...then its achilles heel came to light......when the board was pulled back with some force ie wipeout legrope tension...it had so much leverage due to the long platform that it would rip the plugs right out of your board
thank you, and that would pose some problems...what about glassed ins or futures?
glassed in would be a nightmare...I was working on a box base that had a radius on it so you could change the angle of attack...but It got thrown in the too hard basket, it did not like sea weed either
Select to expand quotethePup said..
That has come from up in the Mountains that hybrid
well...the tail fin at least
Select to expand quotearkgee said..thePup said..
That has come from up in the Mountains that hybrid
well...the tail fin at least
Give our biggest regards to the great man will you mate 
Select to expand quoteMacaha said..
Thats out there but can we see some more pictures of Mr V's board oh please
half sanded Mac...they look pretty ugly at that stage.....uncut diamond
Good stuff Ron, great to see another tunnel fin freak... there aren't very many of us.
I did one like that ( but without the vertical fin) back in 2002 ( started making tunnels in 1998) a couple of friends rode it and liked it but I didn't so continued with the tunnel plus one and tunnel plus two setups, as well as big single tunnels without the flexy extension.
