Surfing Waves

Anyone sand their fins down? Was it useful?

I have.....yes it is.

Mrpompadour wrote:Was it useful?

"Useful" for what ?

What are you trying to accomplish by sanding down the trailing edge ?

@waikikichan Useful as in the fin not slicing your body during a wipeout. Wether sanding down the fins reduced injuries for yall

So how many fin cut injuries have you gotten so far ?

If it happens to you a lot, I would recommend safety edge fins like Pro-teck fins.

I have a couple sets that would nick my heels when Inwould gonfrom sitting to paddling with a frog kick. Sanding the trailing edge just a little took the edge off and I stopped the nicks.

Just curious Mrpompodour, where do you surf, and what levels are your skills at?

waikikikichan wrote:So how many fin cut injuries have you gotten so far ?

If it happens to you a lot, I would recommend safety edge fins like Pro-teck fins.

SurfCo_Proteck_Black_1024x1024.jpg

I imagine it must be frustrating trying to make sharp turns with those fins. On the other hand, they might give a glide to your ride. It's interesting to think about how that extra drag from the flexible material around the fin completely changes the characteristic of the fin. I'm trying to understand fins better these days because I just lost my longboard fin on kelp.

RinkyDink wrote:I imagine it must be frustrating trying to make sharp turns with those fins.

It actually might help you turn by reducing the cavitation behind the fin.
Look at the fin the fastest surfer on the planet Mick Fanning used to use. SPEEEDFINS.

The back of the fins moved around a bit.

Another fin that moves / twists is Futures Fins Black Stix


The trailing edge flowing / following the front might help cut down on drag.

@BigH Glad it helped u man. Probz gonna sand mine down too haha
@jaffa1949 I'm an expat living in Indo for about 6 months, I would say I'm an intermediate/advanced surfer.
@waikikikichan Not too many I think about 3 or 4 cuts, but there was one that messed up my heel pretty bad. Kinda sucks.
@Rinkydink tbh i wouldnt be surpised if pro-tecks are even better for sharp turns and carves. I mean since the trailing edge is slightly flexible wouldnt it give u some sort of "spring" off turns? Never used them before, just some thoughts haha

@Rinkydink Hopefully your longboard fin washes up on the beach as you head out for your next surf haha. At least u didnt lose 4 brand new fins because the screws were too loose. Ah, good times..

[quote="Mrpompadour"]
@jaffa1949 I'm an expat living in Indo for about 6 months, I would say I'm an intermediate/advanced surfer.
[quote]

Good to hear, let's go a little more specific as I get to Indo regularly , have going all over since 1979 nowmostly the outer ends of the archipelago, sumatera and Nusa tengarra Timur, and a bit near to,traffic, Lombok .
There are other forumites based in Bali!
If you are centred on Bali , enjoy the fireworks!

Mrpompadour wrote:Anyone sand their fins down? Was it useful?

I have yet to actually sand mine down, but I plan to after an ouchie gash on my foot last month. I'm a beginner so not really looking at specialty fins at the moment. The thought of that gash happening on my face or in the eye is enough though!

waikikikichan wrote:Look at the fin the fastest surfer on the planet Mick Fanning used to use. SPEEEDFINS.

mick_fanning_speeedfins.jpg

The back of the fins moved around a bit.
Another fin that moves / twists is Futures Fins Black Stix

schooldetail_torsion_image.jpg

The trailing edge flowing / following the front might help cut down on drag.

FCS-tip-Vortex.jpg

I got my new fin (MD3 Flex 9").

As with most of my surfboard accessories, the main quality I was interested in was speed. According to the guy I talked to at the shop, the wider the base of the fin, the faster it is. The trouble I have with fins is that I just don't understand their hydrodynamics. I have a similar problem understanding aspects of surfboards as well. I get how an airplane wing can produce lift, but I'm mystified how one surfboard fin would be faster than another apart from one fin being much larger or thicker than another--the thicker the width the more drag there is. That's about as sophisticated as my understanding of them gets.

Once I start thinking about the angle of a fin as it's flowing through water, I'm completely mystified. Anyway, I think I need more understanding of surfing maneuvers before I'll really be able to wrap my head around how fins work. I know there's a relationship between surface area and speed, but I haven't quite figured out how that works. It seems to me like the more surface area there is the more friction and drag would be produced. Of course, the weight of your body pressing down on the surface of the board or the fin is obviously a major factor, but it's just not intuitive to me.

RinkyDink wrote: It seems to me like the more surface area there is the more friction and drag would be produced. Of course, the weight of your body pressing down on the surface of the board or the fin is obviously a major factor, but it's just not intuitive to me.

I could stand to spend more time reading about how hull designs work, but I'm too lazy.

How planing works
When it is at rest, a vessel's weight is borne entirely by the buoyant force. At low speeds every hull acts as a displacement hull, meaning that the buoyant force is mainly responsible for supporting the craft. As speed increases, hydrodynamic lift increases as well. In contrast, the buoyant force decreases as the hull lifts out of the water, decreasing the displaced volume. At some speed, lift becomes the predominant upward force on the hull and the vessel is planing.

A simple model of this effect is a solid slab of material which is heavier than water (like a steel plate) but is shaped and oriented to have a positive angle of attack. At rest, the slab will sink because it is heavier than water; the buoyant forces are overwhelmed by the force of gravity. However, if the slab is kept in the same orientation and pulled horizontally through the water, it will force the incoming water downward. This results in a reactionary force upward on the slab. At a high enough speed, this reactionary force (plus any small buoyant force) is larger than the force of gravity and the slab will stay afloat. In this way, the horizontal force (which may be supplied by a motor or a sail) is converted into a vertical force upwards. The concept of planing is often interpreted as analogous with aerodynamic lift (See lift on an airfoil), but in reality the acting forces are very different

Although any hull will plane if enough power is provided and enough speed is attained, a hull designed for operation in the planing realm is sometimes distinguished by a flat run aft. In other words, in side view, the bottom is more or less a straight line towards the stern. (Exceptions to this include surfboards and other recreational planing hulls, which utilize rocker throughout for enhanced maneuverability when banking through turns.) In contrast, in a displacement, or non-planing hull, the bottom is curved in side view (the curvature is called "rocker") all the way from bow to stern, in order to minimize wave drag. In front view, the sections in the aft area may be straight, as in a racing hydroplane, to maximize planing forces and speed, but for practical reasons of stability and comfortable ride are often V-shaped, especially in boats intended for offshore use.

To plane, especially to initiate planing, the power-to-weight ratio must be high, since the planing mode of operation involves moving the hull at speeds higher than its natural Hull speed. All boat designs for planing benefit from minimised weight; planing powerboats are commonly made from light alloy or use other reduced-weight construction techniques- RIBs are typical examples. Planing sailing boats need a good sail area and powerboats need a high-power engine. Steps and chine ridges may also be incorporated into the design to encourage both ease of planing and stability. Most surfboards are planing or semi-planing hulls that utilize the push of the waveform more or less in combination with gravity and specific angles of attack for the airfoil to maximise propulsive force and reduce the net downforce and thus achieve planing lift. Many forms of marine transport make use of planing, including fast ferries, racing boats, floatplanes, flying boats, and Seaplanes. Beyond planing, fast vessel designs have seen a transition to hydrofoil designs.

https://en.wikipedia.org/wiki/Planing_(boat)

Very interesting but a fin is not a hull.

waikikikichan wrote:

RinkyDink wrote:I imagine it must be frustrating trying to make sharp turns with those fins.

It actually might help you turn by reducing the cavitation behind the fin.
Look at the fin the fastest surfer on the planet Mick Fanning used to use. SPEEEDFINS.

mick_fanning_speeedfins.jpg

The back of the fins moved around a bit.

Another fin that moves / twists is Futures Fins Black Stix

schooldetail_torsion_image.jpg

The trailing edge flowing / following the front might help cut down on drag.

FCS-tip-Vortex.jpg

FWIW I am not a great surfer but I have a set of black sticks I use on smaller waves and can feel a difference coming out of turns. Really nice fins for me.

oldmansurfer wrote:Very interesting but a fin is not a hull.

True, but if you're making a very sharp turn, say a roundhouse cutback, when you get on rail is your fin planing? In other words, when you get a fin on its side as it goes through the water is it planing like a surfboard? How does the width of the fin affect the speed of your turn when your fin is practically on its side? Would a wider fin be faster? I dunno. The rails of the surfboard itself almost act like another fin and that's when my brain starts to hurt. There are too many factors I don't understand.

waikikikichan wrote:

RinkyDink wrote:I imagine it must be frustrating trying to make sharp turns with those fins.

It actually might help you turn by reducing the cavitation behind the fin.
Look at the fin the fastest surfer on the planet Mick Fanning used to use. SPEEEDFINS.

mick_fanning_speeedfins.jpg

The back of the fins moved around a bit.

Another fin that moves / twists is Futures Fins Black Stix

schooldetail_torsion_image.jpg

The trailing edge flowing / following the front might help cut down on drag.

FCS-tip-Vortex.jpg

FWIW I am not a great surfer but I have a set of black sticks I use on smaller waves and can feel a difference coming out of turns. Really nice fins for me.

RinkyDink wrote:

oldmansurfer wrote:Very interesting but a fin is not a hull.

True, but if you're making a very sharp turn, say a roundhouse cutback, when you get on rail is your fin planing? In other words, when you get a fin on its side as it goes through the water is it planing like a surfboard? How does the width of the fin affect the speed of your turn when your fin is practically on its side? Would a wider fin be faster? I dunno. The rails of the surfboard itself almost act like another fin and that's when my brain starts to hurt. There are too many factors I don't understand.

Inherent drive in fins seems to have as much to do with rake as width of the base.....maybe more.