Sanding sharp trailing edge of fins

[Tudeo]

Turning by rail vs fin was subject in a Surfsimply podcast. If I remember correct, it came down to how deep the rail goes in a turn, how deeper the rail the less effect of the fins and vice versa.
One of the guys was using the same (small) fins as Kelly Slater but found them not giving enough grip for hir turns. So he told jokingly he first thought his turns to be more powerful then Kelly's until he found out Kelly used his rails more and could get away with the small fins that way.

[dtc]

if you are doing a hard roundhouse cutback you arent turning on your fins, you are probably turning on your rail. Your fins more or less keep the tail from spinning out and contribute a bit, but not much.

Drag caused by fins is not worth worrying about. Or, putting it another way, people get worked up about drag but what you are really wanting is a difference in speed caused by different sized fins. Whether the speed difference is due to drag or some other factor is just the 'physics' - all you need to know is the speed differential (I mean, you dont need to know how an airplane works, you just want to know it works). Anyway, if you do want to get into the science.... http://finsciences.com/surfboard-fin-science/

The difference between having a razor sharp edge and a 1mm edge that wont slice you to ribbons cannot be noticed when you are surfing. This stuff is all the 1% or 3% top of the curve stuff; most of us are surfing in the 40% or 50% part of the curve. Everyone should absolutely sand down the trailing edge of their fins. If its not you that lands on them, it could be someone else

[jaffa1949]

Get to know the basics of fins, read Uncle Jaffa’s fin primer, right here in the forum.
Most of the surfers on the forum can tell the difference between fins from size and if if they have a centre fin box forward and back positioning.
The trailing edge most people would be challenged to notice a difference, I have used those protec fins, ( they worked well!
Edge and rail control, often happen unconsciously , none of us are MF or KS.
Fin science is challenging, read swaylocks and see the hissy fit debates there on fins and hulls.

Speed is the key and being able direct turns at speed unlocks the wave face as an area of choice.

Fin choice= what works for you!

Rails, IMHO most wipeouts are generated by a rail fails!

[waikikikichan]

According to the guy I talked to at the shop, the wider the base of the fin, the faster it is.

Think you should ask this on it's own post. but just wan't to chime in real quick.
" the wider the base of the fin, the faster it is". -------- WRONG ! If that was true we should all put giant D-fins on our boards.
The squish area between the deck and fin which with the water encounters is greater. But that doesn't automatically make the board faster. Being in the right spot of the wave makes you go faster. If you can't control or push enough ( weight, power, leverage, technique ) you'll get bucked off or straightened out.
Taking off tires from a Chevy Camaro and putting them on my Honda civic won't make it go faster. You need the "motor" behind them to get the power to the pavement. And vice-versa, the little skinny tires from the Honda put on the Camaro would just spin out.
Getting the biggest size club head on my driver won't make hit the golf ball farther if I don't make good contact or enough head speed on the swing.
It's a balance.

[saltydog]

I think drive and speed are different. Here is a great discussion from a few years ago.
https://surfing-waves.com/forum/viewtopic.php?t=23405

Btw, Jaffa, would you still be posting a primer on tails and rails? I’d love to hear your take on them!

[oldmansurfer]

Turning by rail vs fin was subject in a Surfsimply podcast. If I remember correct, it came down to how deep the rail goes in a turn, how deeper the rail the less effect of the fins and vice versa.
One of the guys was using the same (small) fins as Kelly Slater but found them not giving enough grip for hir turns. So he told jokingly he first thought his turns to be more powerful then Kelly's until he found out Kelly used his rails more and could get away with the small fins that way.

There are a lot of reasons why the same fins Slater uses might not work for you. Kelly is around 5'9" and 160 pounds and if you weigh 210 pounds then you probably need different fins. Slater surfs low volume boards like 24 -25 litters and if you are surfing higher volume boards his fin size might not work for you. As you mention the kind of turns you do might make a difference. The kind of waves you are surfing will make a difference too. That said if you are just a beginner they will probably work well enough. And if the guy is having trouble using a particular board/fin setup it may be just the surfer doesn't know how to use that board/fin setup well enough.

[RinkyDink]

i
The difference between having a razor sharp edge and a 1mm edge that wont slice you to ribbons cannot be noticed when you are surfing. This stuff is all the 1% or 3% top of the curve stuff; most of us are surfing in the 40% or 50% part of the curve. Everyone should absolutely sand down the trailing edge of their fins. If its not you that lands on them, it could be someone else

I agree. I plan to sand down the sharp edges.

[RinkyDink]

I suspect that it's not a bad idea to emulate fin designs that have evolved over long periods of time.

[Mrpompadour]

@jaffa1949 I'm currently based in Nusa Lembongan, so I'm mainly restricted to shiprwrecks or lacerations but I ain't complaining one bit XD I do visit Penida and Ceningan sometimes on off-days. Still trying to find a secret spot in Penida hahaha. My guess is you're usually in the Bukit area? BTW you're indeed a surfing legend, thanks for all the advice and help man.
@everyone I think unless you're in the CT or going to be competing at the pipe master, there's not really a downside to sanding down performance fins. I mean even if u can feel the 1mm difference, its not like you're competing or smth.
Anyways, I read that a trailing edge that is too sharp, will create turbulence during high speeds, so sanding down the fins may actually be even better LMAO

[jaffa1949]

Don't get to Nusa Lembongan. much any more, I particularly liked Playgrounds loved it when they put the pontoon platform in an I could take out Bintang and some BengBengs to energise. Shipwreck was back Hand for me , I liked it but the metal stakes driven into the Reef for the seaweed farm in the surf zone was a little scary, always interest to see the wreck gradually breaking up over the years.

The closest I get to Bali now is Transit lounge to elsewhere, the either Lombok or further east even as far as Rote,
To the west its the Mentawais,
A lot more resort/ camp action now compared to Wahrungs and homestays when I first went to Bali in 1979.

[Tudeo]

There are a lot of reasons why the same fins Slater uses might not work for you. Kelly is around 5'9" and 160 pounds and if you weigh 210 pounds then you probably need different fins. Slater surfs low volume boards like 24 -25 litters and if you are surfing higher volume boards his fin size might not work for you. As you mention the kind of turns you do might make a difference. The kind of waves you are surfing will make a difference too. That said if you are just a beginner they will probably work well enough. And if the guy is having trouble using a particular board/fin setup it may be just the surfer doesn't know how to use that board/fin setup well enough.

Sure, there are a lot of possible variables. But don't you agree with this general principle: how deeper the rail the less effect of the fins and vice versa?
The guy telling the story in the podcast was Dru Hill, founder of Surfsimply. He is an experienced surfer and has about the same body stats as KS.

[dtc]

I suspect that it's not a bad idea to emulate fin designs that have evolved over long periods of time.

or whale tubercles

http://www.theinertia.com/surf/kelly-sl ... kup-board/

(if you really need to discuss surf fin science, read Roy Stuarts stuff. Whether there is any validity in science I have NFI, its way too complicated for me. But he sounds sciency)

[RinkyDink]

(if you really need to discuss surf fin science, read Roy Stuarts stuff. Whether there is any validity in science I have NFI, its way too complicated for me. But he sounds sciency)

I'll check it out. As far as the whale tubercules go, I'm intrigued. I've always wanted a cerrated fin that would allow me to improve my surfing performance and saw logs after my session.

[oldmansurfer]

Sure, there are a lot of possible variables. But don't you agree with this general principle: how deeper the rail the less effect of the fins and vice versa?
The guy telling the story in the podcast was Dru Hill, founder of Surfsimply. He is an experienced surfer and has about the same body stats as KS.

there is something to the rail adding hold however still fins are important because you can't count on the rail to hold. Surfing is so complex but I am pretty sure judging by what Slater does won't give the average surfer a clue because Slater can take your board with your fins and do stuff with it you can't. If the podcast guy wants to say he can't do what Slater does because he has a board the same size and volume and different fins I'll bet he's wrong.

[Tudeo]

If the podcast guy wants to say he can't do what Slater does because he has a board the same size and volume and different fins I'll bet he's wrong.

No, he was just making a joke saying he needed bigger fins than KS because he thought his turns were more powerful, but then realised Slater puts his rails much deeper in turns.

The thing that interests me is, it seems you can use smaller fins when you turn with more cant. It must be the rail taking over some of the powers that would otherwise make the smaller fins spin out.

Or maybe it is because of smaller fins you can set the rail deeper in a turn? Thinking about this makes my head spin..

[waikikikichan]

Or maybe it is because of smaller fins you can set the rail deeper in a turn?

Your question got me thinking also.
1) Tire profiles on a motorcycle. Round vs. Triangle. One rolls over predictably, one falls over abruptly.
2) Bmx 20" tires vs. 700c / 29" tires. You can "jam" side to side on a BMX bike more easily than on the taller tire.

3_polygons_what2 - Edited.png (20.44 KiB) Viewed 962 times

Maybe the deeper fin takes longer to fall over and gets the rail buried. I know it's just "water", but it is resistance.

[Tudeo]

Maybe the deeper fin takes longer to fall over and gets the rail buried. I know it's just "water", but it is resistance.

And because it's slow in falling over the deeper fin pushes back more to the rider, so you need to put in more weight/power to cant. Maybe that power gets transformed in speed? What brings us back to drive.

[oldmansurfer]

If the podcast guy wants to say he can't do what Slater does because he has a board the same size and volume and different fins I'll bet he's wrong.

No, he was just making a joke saying he needed bigger fins than KS because he thought his turns were more powerful, but then realised Slater puts his rails much deeper in turns.

The thing that interests me is, it seems you can use smaller fins when you turn with more cant. It must be the rail taking over some of the powers that would otherwise make the smaller fins spin out.

Or maybe it is because of smaller fins you can set the rail deeper in a turn? Thinking about this makes my head spin..

It's a very complex thing. I used to surf a single fin board before. If I wanted to carve a hard turn I just laid down or leaned over very rapidly and with a lot of force and the board carved deeply into the wave sending a roostertail of water up that I would often surf back through as I changed directions again. Now I surf a quad and if I just lean over very hard the board will loose it's edge. It may have to do with the much higher volume board that I now use but maybe also the v bottom design of my single fin aided, maybe the bigger single fin helped, maybe the narrower width of the tail on my single fin helped, maybe I was just a much better surfer back then (this is true) maybe it's all those factors and/or something else. There is really a lot that goes into surfing performance. The shape of the rails and the thickness are important for rail turns as well (thin sharp rails are better), cant of the fins is a give and take situation more cant better in turns but not as good going straight. I try to not get too caught up in it all and focus on figuring out how to ride the boards I have since I ain't no spring chicken no more

[Tudeo]

I try to not get too caught up in it all and focus on figuring out how to ride the boards I have since I ain't no spring chicken no more

I totally agree with that, in the end it comes down on just having fun in the waves without thinking too much.

But I have a lot of spare time to fill next my surfing sessions and I like to think and talk about surfing.

[Mrpompadour]

Don't think it still needs sanding down and I don't want to mess up the foil either. Doesnt look it'll slice skin tho. My previous FCS II Reactors were sharp af and these are the new AM1's mind you haha. Abit of a shock. What yall think?