Speed vs Drive? Fins.. confused?

[benjl]

Hey guys

I am a little confused over the difference in terms and meanings over 'speed' and 'drive' when people talk about fins.

Bigger fins are often described as having more 'drive' although at the same time, bigger fins produce more drag which would slow a board down?
And smaller fins have less drive but more speed?

I thought having more drive would mean having more speed but increasing fin size and speed would do the opposite?

Can someone please clarify this for me?

Cheers

[oldmansurfer]

I am a little confused too but here is what I think.....since I have no problem blabbing whatever is on my mind.... Speed is speed just that how fast the board goes. Drive is changing speed in one direction to speed in another direction.......so bigger fins the more they grab and turn the board so less power lost in turning and smaller fins means more sliding and a reduction of power/speed out of a turn. Just a guess since I use small fins and I know my board slides in turns but I could be wrong

[oldmansurfer]

the other side of it is the more surface area the fins have the greater the drag so the slower it goes

[dtc]

Old man has it right - drive relates to acceleration and maintainenance of speed though turns

Speed is just how fast you go. Which is actually caused by 'lift' (and lift is offset by drag)

a nice if scientific explanation here

http://finsciences.com/surfboard-fin-li ... old-drive/

[drowningbitbybit]

I think I may have caused this talking about quads vs thrusters and speed/drive the other day

But Oldmansurfer is spot on.

A good (but not necessarily accurate) way to think about it is that speed is how you travel across the top of the water, while drive is the power you get from pushing against the water.

[benjl]

haha yeah it was actually your quad vs thruster comment that put the question in to my mind although had wondered for awhile.

So essentially some pratical hypothesis taken from this (assuming all things are consistent).. Going smaller in fin size will continue to increase the speed of the board down the line but to a point where the fins will be too small and unstable. However when turning, the smaller fins will slide more and lose speed faster than a larger fin- thus a larger fin will help hold the speed you do have if you are not good enough to generate your own speed once lost on a smaller fin?
Would this mean that turns on smaller fins would be more 'critical or snappy' and larger fin turns would be more arcing?

[oldmansurfer]

It means that you will have an easier time paddling smaller fins and then the speed of your board depends on your waves and your style of surfing. So if you are good at doing lots of turns then bigger fins should help you but if you just want down the line speed then smaller fins. Then larger fins would be better for big arcing turns because you will hold speed through the turns and hold the turns better but if you aren't turning much then the smaller fins would be better or if you are riding huge waves where speed is automatic and you aren't turning a lot then smaller fins would be better. Also if you want to do sliding small arc turns then the smaller fins are better. I am going to guess that somewhere in between is where most surfers should be then the board is more versatile or if you are good enough then you can switch out fins to match the waves smaller for faster bigger waves and bigger fins for slower in between waves if you want to carve slice and dice the waves and smaller fins for smaller waves so you can do pivoting sliding turns? Really just guessing but bigger fins if you can surf like a pro or maybe if that is where you want to go. I really don't know but I most likely I will start to experiment with it all but for now I just want to learn how to use the board the way it is. It's still confusing

[jaffa1949]

Time to bring up the Fin primer.
Less drag equals more down the line speed, no fins equals the highest speed you can generate down line, but unless you know how to set a rail no driving around a turn of any sort.
So trade off, how much control do you want? It is not just the fin but its placement and angulations in relation to the rail and tail of the board. Look up the evolution of fins through from planks to hot curls to Tom Blake and paddleboards surfboards with fins.
Look at the Campbell Brothers and the Bonzer, Simon Anderson and the Thruster, the early twin fins of Tom Foley.
Consider the Greenough fin based on high speed tuna. Many of the fin advances followed on ideas of other people's experiments.

Benjl, you are asking all the right questions to understand performance in a board on rail, tails and fins.
Get yourself into the shaping rooms of the local board makers!
There will be a lot of BS spoken as a lot of the guys can surf and shape but not articulate scientifically what is happening. So much of the shaping is about trial and error.

Uncle Jaffa is writing a rail and tail primer next!
Coming soon to a forum near you.
In the meantime when you do a turn look behind you, see what your wake is doing, watch really good surfers see their production of speed in all aspects of the surfing, watch the kooks and see how they bog down in all aspects of their surfing ( In fact if they generate speed they fall off the back).

A final observation watch how successful surfers use opening and compressing their bodies to load and unload pressure on the fins to power a turn, (not just a lean) Tom Carrol' s famous turn at the top at Pipeline is all muscle powered.

Keep applying what you are learning,

[drowningbitbybit]

Would this mean that turns on smaller fins would be more 'critical or snappy' and larger fin turns would be more arcing?

No. Or at least not in the context of a shortboard, which will almost always have relatively small fins and a fairly minor difference between a "big" fin and a "small" fin.

A smaller fin (or quad set up, to go back to the original post) will produce a loose board, which is easy to chuck here, there and everywhere, but it won't have the hold to pivot around on. You can push against bigger fins to really swing the board around for those snappy turns off the lip.
Obviously, you will get to a point where the fin is too big and slows the board down through the turns, then you can start to take long drawn out turns.

[drowningbitbybit]

To confuse things further...

On my "big" board (6'10 x 21 x 2 3/4), I like to have really small fins. The board has loads of float and hence has plenty of speed, but I like to loosen it up, otherwise I feel like its locked into a straight line (I should learn how to turn a surfboard longboard style...).

On my "small" board (6'2 x 20 x 2 1/2), however, I like to have relatively large fins, partly for the sake of stability (I do like a good late take-off), but mostly for the drive out of the bottom turn.

[dtc]

dont forget rocker, tail width, rail thickness etc also affect fins. smaller rocker, wider tail, thicker rails - can cope with smaller fins.

and sweep, cant and rigidity of the fins can be relevant

who says surfing isnt intellectual

Although really thats getting more complicated than needed and definitely beyond my understanding,

But as an example, remember that in turning you are turning off a curve - the rail outline or the rocker. So if you have a big rocker you can turn easily and can deal with bigger fins without making the board stiff. Plus the bigger fins help with the drive to overcome the slowness of the bigger rocker (pushing water). But a flat board, like a fish, just becomes too stiff with bigger fins - but is great if you want to scream along above a reef before it closes out and drives you into the coral (who surfs that stuff anyway - lunatics and Jaffa...)

Anyway, I reckon - at my level of skill - fin size is really all that is relevant (unless you are surfing 9inch single fins, in which case sweep is noticeable). Surf the smallest fins you can get away with, in my view!

[jaffa1949]

Not true , Jaffa surfs reef that offer a long wall wailing high line drive and power turns closeout avoiding sessions.

[oldmansurfer]

I have relatively small fins on my quad and I can do these tail sliding pivoting turns where I basically push the tail into the turn and it results with me going a little sideways if I don't follow up with another turn immediately so If I hold it the board is sliding sideways sort of like when you see the pros turn and they over rotate the board. I say sort of like because I am sure it doesn't come close to resembling that but similar in that the board is over rotated. I imagine with larger fins that would be more difficult yet the pros do it with larger fins.

I know the big wave surfers are going to quads now because they can use smaller fins about the size of my fins which make it easier to paddle and faster down the line and since they are maxed out speed a lot then most of the turns are rail turns anyway so they don't need huge fins.

You can generate drive with your body also but if you watch the pros they have so much drive it's really amazing and part of that is their boards/fins. I surf an 8 foot funboard and probably won't get anything much smaller so I wonder how much drive I will be able to get by getting bigger fins......curious but I don't feel like I need more drive so far.

[waikikikichan]

Ben Aipa asked me a question when I was with him in his shaping bay, " Do you want me to make you a FAST BOARD ? or a BOARD you can make go FAST ? Think about that for a moment when you pondering getting a quad, carbon this, flex that, next ultra cool thingamachig. When talking about fins, what ever the brochure or info on the internet says, it still comes down to putting the board in the right spot of the wave- its sweet spot where it propels the board the fastest. If the brochure says get the Large fin, but you tried the Small and it lets you carve and stall the board effortlessly and keeps you in the pocket, then go with that.

[jaffa1949]

Waikikichan said it about as clearly as it can be said. Uncle jaffa likes

[oldmansurfer]

WOw! Waikikichan, you had Ben Aipa making you boards? That must be nice. I never surfed an Aipa board but Ben was one of the most respected shapers back when I was surfing shortboards. My brother had one though.

[Roy Stewart]

The idea that more fin area means that the board will be slower, and that the fastest boards have no fins is a myth. I can explain why.

[oldmansurfer]

Is this the is the millionaire Roy Stewart? I am interested in your explanation as is most likely everyone else.

[benjl]

X2.. I'm also curious on the explanation.

Chees