Uncle Jaffa's Fin Primer

[jaffa1949]

FINS
Parts and Descriptions..
The terms are the same for fins throughout all boards but length and type of board and bottom contours need to be married well with the fin styles, to give a successful relationship.

Base:
The base the length of the fin where it meets the surfboard.
Varying this length changes drive, lift and acceleration of the fin and so the board.
With multiple fins there is a relationship between all their bases and fin positioning is vital.
Fortunately the removeable fin companies provide templates for positioning to shapers and good shapers have their own templates to fit their designs.
Most backyarders and novice board makers struggle at this part.

The base can also effect channels and venturii effects but that is advanced stuff and in the shapers’ realm.

Depth:
Depth is how far the fin sticks into the water.
Short fins do not hold as well in certain surfs (ie steeper) and may cause you to slide .
If you know your board this can be a controlled feature of your riding, being able to release and re-engage fin bite.
For other surfers a deeper fin maintains hold
Deeper fins can be boggy and slower.
A deep centre fin has the advantage on long boards of providing a better base for nose work under more circumstances.


Area:
Base and the Depth give the area of a fin.
I think the best fin area for each surfer is one that gives them both the level of hold they like and the amount of release for turns.
The area of all fins combined in a multi- fin set up effects the type of ride the board gives.

Sweep:
The sweep of a fin describes how the fin is angled backwards.
The greater the sweep backwards make s the arcs of turns longer or more rounded.
If the fin is more vertical (less sweep) the more angular and pivotty the turn can be.
This is also the difference between a single fin and a multi fin system.
Singles tend under the average surfers' feet to be more rounded in their turning but with multi fins even the average surfer can tighten their angles in turns and do snaps in a much shorter arc.

Cant:
The leaning out to the side is described as the cant angle of the fin. It is usually set in the fin system or configured with the aspects of the board by the shaper. Cant gives an angle of attack to the side bites, increasing their effectiveness. Centre fins do not have cant.

Toe in. ( also Toe) Nothing to do with PWC
The toe in refers to the angle of the fin in relation to the stringer or centre line of the board.
Parallel to stringer is a 0° toe in angle to the board. The centre fin obviously has no toe in.
This is unchangeable, bad angles here, as with some Chinese cheapies are literally a drag.

Foil:
Fins, really are wings, and are foiled or curved. The centre or back fins are foiled equally on both sides but side fins are usually foiled on the rail side and then left flat on the inside.
Currently there is experimentation on reverse foil, variable foil and cant throughout the depth of the fin.
This creates areas of high pressure and low pressure on the fin and hopefully enhances the qualities wanted in a fin in terms of hold and release and also speed of the board in planing and turning.
My personal surfing (please remember here that I’m an older modern longboard rider) I’ve found that the variable foil and cant fins give me a increased range of speed I can get both in turns and a higher line when driving across a wave face .

Flex:
Stiffer fins for more drive a flexier fin is more adaptable.
With the Greenough fins of old there was a planned flex to drive you up the wave after a bottom turn, ( this was before twin fins and thrusters) which they did but you could apply too much power and snap them, usually with a spectacular wipeout following.
Now the multi-fin approach allows the laying down of that power to complete the turn. Thank you Simon Anderson and the Campbell Brothers

Making sense of fins.
These thoughts can help choose fins for your board and the wave type.
Board feeling too stiff, try smaller fins, softer more flexy fins or choose fins with less sweep.
Board feeling too loose, lacks drive, do the reverse of above.

You can also experiment with changing the combinations of your centre fin and the side fins

A lighter person can use less fin area in their selection of fins.

To tweak more responsiveness, try stiffer material in your fin, say full glass as opposed to some of the plastics.

Longer railed boards and narrow gun profiles , and also tight fin groups require less fin area ( this can even be big wave guns using medium size fins)

With a lot of rocker particularly in the tail of the board or in the nose on long boards, gain more control and less slide with fins of increased area, depth or sweep or a combination of all three.

Your board has deep channels in the tail, often this type use less fin area with smaller tips to release out of turns (here the channels are doing some of the work of the fins in providing drive).

Wide tails as in fish need more fin area than those with narrower tails .

Small board in big or powerful waves might find a little more control with larger or more swept fins.

Fins are probably the area where the next great advance of surfing is going to come from.
There a a lot of gimmicky things out there. but before you go to the fringes of winged keels, aerodynamic winglets as per jumbo jets, tunnel, funnel or touted super fins, the best thing I’d suggest is to get your basic surfing skills up first.

A fin does not make great surfer it helps a surfer do what they want to more easily.

Enough for one post. I ‘m happy to be corrected on any aspect of have what I said about fins and maybe some one can add a little more to help.
Let’s face it without fins the majority of us would be riding straight to the beach or heading sideways prior to a wipeout.

[billie_morini]

Wunderbar, Uncle Jaffa!

[garbarrage]

Mucho Kudos for taking the time to answer a short question so comprehensively mate. Way above and beyond what I was expecting. Really useful info there. I hadn't realised there was so much to consider. Well, I had, but this post is going to take some time to digest. Looks like a long journey of experimentation in front of me. That's not to say it won't be fun, and will be referring to this post many many times along the way. Can't wait. Thanks a mill dude.

[surf patrol]

Great post Jaffa, I've moved it to the surfing lessons where it will stay at the top of the forum where it won't disappear.
A great addition to the site's existing fin articles ->
Surfboard fins
Fin flex and foil
Fin setups

[jaffa1949]

Here are some of the fins I use most often, remember these are my choices for how and what I surf don't be afraid to invest a little money in variations of fins. If you are pushed for cash beg borrow but don't steal, swap with friends learn what works for you.

This is what I used in barrelling and solid Indonesian waves , went well! C Drives and deep centre fin

For my shorter board where I can use equal length fins, futures vectors and a hatchet, drive and release.

Rear view

The Kinkiness adds squirt ( acceleration ) out of turns

Unfortunately the fin companies haven't made a generic fin box so some designs are limited to the box or plugs that come with the board.

I am finding the C drives great for pushing the high line in hollower waves to get that extra bit of speed.
When I can't use the C drive fins the futures vectors do the same job.
I can't go head to head with them as the fitting systems are entirely different.

[newportlongboard]

Amazing post.

It has so much realy realy helpful information and the best fin info i have seen anywhere.

So just wanted to say thanks for the info feel i have gained some ideas for fin setups on my new boards

thanks
dan

[Sapphire79]

Thank you for the information. This helps me greatly in my surfing endeavor

[garbarrage]

Hey Jaffa, been messing about with my fin setup for quite a while now, and have a quick question. On bigger waves 5 to 6ft plus I usually put a bigger set of fins on my board which helps a considerable amount in getting the board to "bite" the face on take off, and obviously helps with turns, however I find it slightly harder to catch waves. This could be that I am coincidentally less up for it, or lacking that last bit of grunt, on the few days that big that I have swapped fins, but could the increased surface area be creating more drag, slowing me down a fraction? If so, might try a slightly smaller set and see if I can tweak the perfect balance.

[jaffa1949]

Hi Garbarrage you must be getting sensitive a feeling your ride more. That's good.
The overall fin size will create a little more drag in paddling weigh this up against the bite of the fins in the steep part of the face , downsizing carefully can get you a finer tuning and more short arc turn ability , but at increased risk of sideslipping the tail but if you are riding a short board this is what the pros and good riders factor in for their big turns.
Longboards a different and more difficult thing to control. Remind me of what you are riding? A way to get the little extra in the take off speed is to change you timing with the wave and be in a slightly more critical spot, it requires a shorter faster burst of paddling speed, but gets you through that prolonged paddle where you run out of puff just before that final stroke.

On either board type if in the short critical take off you can use what I call the reverse cork technique where just before you paddle you push your board backward and as deep into the approaching face as possible, then let the buoyancy rebound give you a booster to that first paddling power.
You can also add a little finesse past that to the take off with a strong push down on the board with the pop up push up driving the nose down the face to pick up gravity speed, explaining why short boards for steep waves have that increased nose rocker , just a slightly more difficult judgement to make on a long board.
Some great successes will be had with these things and your friends will also enjoy your spectacular and epic FAILS as you go for it.

Finally a simple rule of take offs: IF you are going to go for it COMMIT TO IT if you are not sure let it go someone else should have it.

These guys are committed or ought to be check out this little video
http://www.youtube.com/watch?v=6O9qAyjGDLs

BTW Uncle Jaffa's advice of any sort doe not apply under these circumstances, I've never gone that big

[garbarrage]

Cheers Jaffa, wasn't sure if it was just me. I am definitely getting more sensitive to the feeling of my fins. So far, I have been limiting my experiments to my 6'4 as it's the board I know the best. I have also found that the subtle differences in fins are much more noticeable in slightly bigger or faster waves.

I have tried the cork technique with hilarious results, and am no stranger to a proper pounding. Not as crazy as the guys in that video (epic by the way), but any wave I'm willing to paddle out to, I'm willing to go over the falls on. May give it another go though, but the timing is pretty difficult to get right. Couldn't be any worse than the day I took out a board with fins that were too small. There's no feeling worse than making a difficult drop, only to lose the tail when you are about to lock in to the face.

Also, I've tended in the past to steer clear of boards with a lot of rocker. This could be making life a bit harder trying this technique. Think I'll try going deeper on my next few big sesh's on the big fins and if that doesn't help will try a slightly smaller set. As always, a lot of food for thought.

[jaffa1949]

Uncle Jaffa is having a ball having introduced the smaller pair of the quad Bonzer fins as side bites to the board pictured earlier in the primer.
Effects greater and longer hold in nose riding and more stable in cross-stepping to get here and back, the board holds higher in a steep face than even the C drive fins and there feels to be more squirt where I apply pressure out of turns for speed.
I was concerned the board would track and not deviate from a set line but normal face turns seem to be easier too.
There is less paddle drag as the side bites are so small with little depth compared to other fins and if I release the tail it feels more controlled and less like dropping out I actually had the experience of riding a left that was like a full blown Kirra wave in reverse, and I was well barrelled for the entire length of the wave and for once made it and was confident in making the adjustments to keep making it.
It wasn't one of those delusional wave we think we had, the other locals were absolutely astonished on my behalf
The fins have failed in very messy surf with not much drive, I could feel them taking up and then letting go at unexpected times in the wave and slop very like a skateboard with very loose trucks on a steep hill.
I think conventional fins may have been better then.
There is a larger pair of the Bonzer fins which I will try when the surf gets bigger, any tendency to track might come up then but it's wait and see, then a return to the C drives and maybe a day where I can surf both types of fin and compare.

There is a connection between to one to two concave that works with the Bonzers so a check with and non concave bottom is also in order.
Photos of the fins and set up soon.

[jaffa1949]

That took so long to post the photos my apologies.
Here they are, same board, same double concave as almost channels you might just see them in the pictures.

I'm seriously impressed over what they add to my surfing.

The next picture shows the toe in and cant on the fins

.
The board was seriously good board before but either the placebo effect or the fins have enhanced it considerably.
I haven't tried the bonzer fins on any other board a fair test would be on a board with no concaves but since these only come in one system FCS I can't use them on my boards with futures .
So an overall test is not yet available.
One more thing.
I've been so pleased with the smaller fins I haven't tried the bigger ones even in bigger surf.

[wormybear]

As always a super helpful and informative post with tons of information to sop up like a sponge. Thanks for the lessons. I've definitely been taking everything in and trying to use it. All of you have definitely saved me from wandering aimlessly through everything that's out there.

While we're on the subject of fins I have a question I was gonna post. The white board I posted about is a tri-fin, but I was wondering if I could lose two and make it a single? And do I have to take some off the tail? And can I use the center fin box or would I need to make a new one?

[jaffa1949]

Good question Wormy, bear with me, a little thought for you, don't change the shape of the tail area, you can remove the two outer fins and use it as a single I'd suggest leaving the centre fin box as that allows the rider to change the position of the fin in the box and loosen or tighten up the boards turning ability. Closer to the back tighter further forward looser!
ou can also take away a centre fin and if there are plugs or boxes for fins out there experiment with twin fins. This probably won't be as successful as the settings for twin fins are slightly different and that slightly makes a lot of difference in their function.

The fin end of the board is the business end and there is great interplay between all the elements, including rails and bottom contours.
A lot more learning and often it is also about what the particular surfer wanted to suit their riding.
Stock surfboards and pop outs follow basic formulas that mostly work OK
You will learn a lot by measuring the angle of fins in modern surfboards!

[sandy]

Well, had a few questions about fins. . . Now I don't.

Cheers Jaffa!

[jaffa1949]

Thanks Sandy, hope it helps
BTW the secret answer is.......What works for YOU

[peazz]

Hey Jaffa,

While many may think that newbies cant feel the difference between fins I feel that I can (to an extent). Ive been experimenting with various fin set ups and this is what I have found so far..

- Thrusters are a bigger drain on energy levels especially for someone like me with super short arms. they do hold a line easier once you picked it and they surf lower down the wave.

- Quads don't drain energy levels half as fast, they paddle easier but dont seem to be suited for much over 3ft atleast for the kooky me, especially steeper beach peaks, they feel skatey and love to take off straight down the wave with a bottom turn at the bottom.

The fins combos Ive tried..

Q-PC5's - Not bad fins in steeper drops, they lock in fast and paddle reasonably well, while feeling pretty skatey (because of the GX-Q backs?) they also feel pretty stiff and hard to turn.

AM-2 thruster fronts + GX-Q Backs - This combo paddles even better then PC-5's + GX-Q.

AM-2 Thrusters - These allow me to pick an angle and stick to it, they naturally flow through the angled drop for me and just hold that line better, but the problem is my wave count is lower on my JS evo any time I use them and my energy level decrease rapidly.

FCS V-2 aKa Kellys k2.1 quads - Ive only just got these, and while they seem to have more start-up speed for me (and require my pop up to be super fast) I feel like they paddle the worst out of the lot!

Now my question is...Why the huge difference in paddle speed between all the quads? Paddle speed is a huge factor for me with fins as I have mega short arms and they tire fast no matter how relaxed and smooth my paddles are? Is this down to fin area or the depth of the fin?. I noticed the K2.1's have alot more fin area then my other sets but also dont stick in the water so much..

What fins should I be looking for that make it easier to paddle?

- Andy

[jaffa1949]

Peazz I almost missed this, I have the feeling that you are undersized in the board rather than the fins, but the guide of the primer is about general principles in fin behaviour.
My real suggestion is simple when you find a combination that works for you , that is the one to use.
One thing you probably haven't noted is the length of flat surface on the bottom of the board which gives a planing and glide element to paddling ( not a lot as true planing has a speed factor) too much tail and nose rocker means the board doesn't paddle as easily. Tail rocker also means the effective penetration of the fin into the water is different.
I'm going to have a look at the profile of the Evo and see if I can think of anything.

I'm not convinced that the Evo is a good board for you at this stage, but what can I suggest?
Because some of it is going to come down to just plain muscling up to fitness for it!

[CARBr6]

Dear Uncle Jaffa,
As our resident "Fin-King" could you take a look at this, http://www.ebay.co.uk/itm/Turbo-Tunnel- ... 3a8a5b439b and tell me if it is a gimmick or whether or not it is actually of any benefit?
I am assuming gimick as if they actually held any major benefit then everyone would be making them!
Ta.
Gareth

[surf patrol]

We've had a few treads about this already - have a look at viewtopic.php?t=5537 for starters.