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Fins

People have commented on this discussion/post saying it is NOT very technical and it is NOT. Most average Joe windsurfers do NOT concern themselves too much with materials used, softness of the fin, rake/angle, etc. Having said that, some of us do NOT realize the importance of a good fin. People have changed fins and suddenly discovered the board was GREAT and there was NO issue with the board. Used fins are not expensive and can be easily repaired. As such, it is a MUCH cheaper alternative to trying a different board. Typically I have one fin for each board and sail combination for best results on the water. So, this discussion is NOT meant to go too much into the real intricacies of fins, but give a good introduction. ENJOY

Fins also called skegs are the engine under water, boards are the engine on the water and the sail is the engine over the water. Fins are a key element in the entire equation that were ignored in the early days of the longboard. They used to have a U.S. box connection where the placement of the fin was slightly adjustable. Those connections are also called Chinook or A-box. Now most fins go into the tuttle (for larger fins) or power box (for the rest of the fins) one way and one position. Some wave and free-ride still use the Chinook/A-box ...

Here Jim Ballantyne of sailworld walks us through the various fin bases:


Chinook or A box - single bolt from the bottom - max about 30 cm
Power box - single bolt from the top - max about 50 cm
Tuttle box - 2 screws from the top - slalom fins - and freeride
Deep Tuttle box - 2 screws from the top - Tuttle box fit here with longer screws
                               max length about 70 cm - wide boards like Formula
Trimm box - single screw from the top - old fins from BIC and Fanatic - max about 66 cm

In 2015 there was discussion on iwindsurf about a Mistral Competition and its fin. 
It was pointed out that the typical US box fins do NOT fit Mistral boards. The US or Chinook box is sometimes called the A box - for USA ?? The fin box that is similar, but slightly different and called the E box - for Europe ?? Both fin types are typically NOT available with lengths more than 30 cm - fin box cannot support it.

There are giant formula fins like in this image. Rarely have I seen such flex or asymmetry on land...Other fin types are free-ride, slalom/free-race, weed, wave, bump n jump and freestyle. Perhaps I missed some ? What sets types apart ? The obvious factor is length and is often cited as the measuring stick. Fins or foils as I like to call em have MUCH more character than that !! There are factors such as width {top and base}, area, thickness, rake (angle of attack)  and material (carbon, G10, etc) which affects flex and stiffness. Just recently discovered that Fanatic boards use GFK fins. What's that? Craig Gerntenbach of Fanatic informs me these are just "moulded polyester fins, with good twist characteristics". Length and shape together make up the type of fin more than anything quickly visible.

In 2016 was informed by IanK on OZZIE forum that this is NOT about FLEX, but rather angle inside the box. If it is off, there is NO issue. Discussion here seemed to upset him and posted photo on forum smashing his screen - DO IT MAN 

What are the fin "parts" really called ?
The following link WAS good when it worked %^&*()
http://www.vmgblades.com/learn/fin-parts/

Oh well - here is my version of the fin parts:



Oh yeah! Fins come in ALL shapes n sizes.

The most bizarre is the hydrofoil.
 

See in this video, just how much fins actually "flex" while in the water:


 

And here is another from the infamous Pfaffi who is quoted later on in this post ...
The numbers 10, 20 and 30 represent cm from perpendicular and NOT degrees.
SUGGEST you turn DOWN the volume:
 
 

Just as sails have ideal wind ranges, so do fins... In other words it is VERY important to match board, sail and fin for the conditions and the type of sailing one is about to do. I call this aligning the engines :-)

Lately wave sailors have been using boards with two (2) and even four (4) fins. So, once again we are off to new horizons :-) Locally I have NOT seen any dual or quad fin setups and personally know just enuff about the single fin. Suggest you look elsewhere if u r lookin 4 info on dual or quad fins - sorry mate. However, here is an interesting discussion on quad setups by Keith Teboul:   


Last year, 2010, the water was extraordinarily low here and as such, there were many board and fin repairs in the area. My fins took a beating and I like to try n fix my stuff myself. Fin repair happens in the off-season, but this was the first year where a light sanding was NOT enough. After searching the web and writing on a few forums, I tried and like Marine-Tex. Bit of a pain to apply and one must discover the trick of sanding it wet. This makes me wonder, will it be susceptible to damage when wet ? :-) time will tell... so far so good - after one season & NOT more susceptible to scratches ...

Personally have a long 53 straight up race stiff fin for my 10-oh sail. The 47 weed fin does well for the 8.5 and gets used for the 10-oh as well. A 40 cm slalom fin is my ticket to fun with my 7-oh. Fin suppliers now have charts for sailors to choose fins. Nowadays board width is a factor in fin selection as well. My personal fin favorites are Select Fins - they are known to whistle at high speeds - just sand one side of the back edge of the fin. Custom Fins exist that are very specialized -- like the Black Projects Fins which has specs like 40, 45 or 50 knots !!!! Wolfgang Lessacher makes world renowned fins and will ship. Check www.designlessacher.com Unfortunately molds were sold to StarBoard, some madame ran the show and now it seems decrepit.


In the past people changed sails to change things up. Now people are realizing the fin is just as important. Personally have one fin for each sail. Cannot be bothered having more than one weed fin, but this may become a factor when I get into the smaller sail sizes...  
Here's a picture from the WindSurf Magazine of July 2002 giving a fin overview. As you can see, there are lots of shapes and sizes, all with their special purpose and special function(s)...  


Believe the following chart was taken from the Select Hydrofoils website showing relationship between board width, fin sizes and sail sizes:

For some reason people are saying the fin cannot be longer than the width of the board one foot forward or off - this is called OFO. Personally have NOT determined the why on this one, butt do stick to this "ruling" just the same. Will see if i cannot find a reason more physics based... Further down here Roger Jackson discusses how a fin should NOT be less than half of the OFO diameter ... Here they are saying max fin length is OFO + 3 cm and use formula listed below of fin length = 5 * sail size +3 : http://www.gunsails.co.uk/en/trimtips.htm and then a race/slalom forum suggested 2 cm LESS than OFO max fin length. http://www.soulrider.com/forum/GROUPF_35/51505

For my 80 cm wide board the following formula seems to work for me to get fin sizing -- 
Fin Length = 8 times the sail size minus 16 :)
examples: for an 8 square meter sail -> fin size = 8 * 8 -16 = 64 - 16 = 48 cm :-)
for a 7 square meter sail -> 8 * 7 -16 = 56 - 16 = 40 cm :-)
for a 10 square meter sail -> 8 * 10 - 16 = 80 - 16 = 64 {this seems a bit high - was using 53 cm}
however on my BIC Techno Formula I do use a 66 cm race fin
how about smaller sails ?
for a 6.3 square meter sail -> 8 * 6.3 -16 = 50.4 - 16 = 34.4 cm
let's see if i can corroborate this figure ... James Douglass calculator gives 34 cm for 6.3 sail also :-)
his formula seems to be 5 * sail size +3 -> for 8-oh gives 43 which i find a bit low 
In early 2013 i DID purchase a Fanatic Hawk 34 cm fin which fits the board and was rated to be good for 5.0 to 8.0 on the 2006 Hawk 110. 6.5 is in the middle and thus the fin should be great on the BEE with 6.3 and perhaps even with the 7-oh !!!


 Here's a couple of pics showing the "rake" on the fins, straight up n down 53 cm race vs 47 cm weed vs 40 cm slalom:


Surprisingly the 7 or 8 degree angle or rake on the race 53 and the slalom 40 do not seem that different !! The weed fin seems to have a rake of about 40 degrees. Some are advertised at 45 degrees for extreme weeds.

In 2010 I lost the 47 cm Select weed fin in the local river $%^&*()_ Can only blame myself and perhaps the local river in terms of rocks $%^&* Early 2011 i purchased a Makani Hahalua 43 cm weed fin to replace the lost one.


This 43 cm weed fin is supposed to be good for sails from 7.0 m² to 8-oh. Helmut has a True Ames weed fin of 43 cm which is good for 6-oh to 7-oh. The Makani fin has a larger chord than the True Ames. I also call this the width since we measure the depth at 90 degrees to the base/board. The Makani is actually of a longer chord/wider than the lost longer Select weed fin by half a cm !!! The rake or angle looks about the same between those two(2) weed fins.

The longer Select weed fin was purchased to cover sails from 8-oh to 10-oh on the 79 cm wide short board. With time I have decided to use the Fanatic Ultra CAT in lighter winds with 8-oh and 10-oh. The 79 cm board will only be used with 7-oh to 8-oh. 

Even though it is winter, I HAD to try the fin on my 160 liter / 79 cm AHD FastForward short board:



With the BEE 124 and AHD 160 my fin quiver was:
40 cm Select Slalom fin with sails 7-oh and down,
43 cm Makani Hahalua weed fin for 7-oh and 8-oh,
48 cm Select Freeblade fin for 8-oh and
53 cm Select SuperFast race fin for the 79 cm board and 10-oh race sail.

Since I am NOT planning to use the 10-oh on the short boards, perhaps I should sell this fin ?? Will try! SOLD it in 2012 after I purchased a BIC Techno Formula with which I use a True Ames Santa Barbara/SB 58 cm weed fin and a Select Race 66 cm fin with the MS-2 8-oh and TR-4 10-oh respectively.

The weed fin was selected based on the 79 cm wide AHD. Also plan to use it on the 63 cm wide Fanatic BEE 124. Ideally that combo should be with a 38 or even 33 cm weed fin. However, since I do not need the weed fin all summer longer, hardly ever sail the BEE and have NO $$$, this setup will do :-)

Forgot to analyze the MFC 42 cm fin that came with the Fanatic BEE. I exchanged it for the 48 cm Select Freeblade before even trying the MFC. The other fellow {MAX} purchased a Hawk and was used to a more powerful MFC fin - I am used to Select fins ... Here I put the 40 cm on top of the 48 cm and what I found interesting is: the TE/trailing edge is the same and NOT the LE/leading edge. See the photo:

{tail end is at the left :-) }
 With the BEE 124/60 ,AHD 160/79 and FreeFormula 170/94 my fin quiver is:
34 cm Fanatic Hawk fin for 6.3 and 7-oh perhaps,
40 cm Select Slalom fin with sails 7-oh and down,
43 cm Makani Hahalua weed fin for 7-oh and 8-oh,
48 cm Select Freeblade fin for 8-oh and
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58 cm Trimm box True Ames SB weed fin for BTF using 8.x and 10-oh
66 cm  Select Ultra Race fin for 10-oh on BTF

Just found an article in the July 2006 Windsurf Magazine with Gonzalo Costa Hoevel. He calls choosing fins a 3 step system. Step one is about board analysis. Ironically he says to put planing fins on the faster boards and faster fins on the early planing boards. He says the early planers have straighter outlines and need fast fins with some rake, small tip area and less flex or more stiff. The faster boards are "rounder" and he suggests power fins or early planers. These fins have less rake/angle (more straight up n down), more area in the tip and softer flex. The video of the fin above and the formula bent fin for me seem to exhibit a lot of flex.

Step two for Gonzalo is assessing your goal and step three is knowing your fins. He says the softer fin gives more "kick" or "lift". Upright means planing AND upwind control - like a keel. The profile or thickness plays a factor as well. He states "A fin with a thicker foil gives you more power, upwind angle, but sacrifices top speed. A thinner foil gives you better top speed, butt in lighter winds you lose early planing and upwind angle. A fin that has the thickest point of its foil forward creates a smoother, more controlled riding sensation. Moving the foil back gives you more speed, but it's a more technical-riding fin - especially when going upwind." He also mentions that people overlook area of a fin and compares this to only analyzing sails based on luff length !!

Here is a video that covers some areas regarding windsurf fin physics. They actually are saying that at over 40 knots pressures cause water to boil at room temperature !!


 Fins are usually made with hi-tech components and are precise pieces of equipment. As such, they do NOT give them away. I have about one fin per sail and they are about $200 each. Some people also have overlap since they may require weed fin(s). Used fins are closer to $100 each and can easily be repaired with Marine-Tex. Just remember to sand wet.  Here's a good link with everything you wanted to know about fins, butt were afraid 2 ask: 
and for "slalom tuning tips":

Wrote to Roger Jackson of Starboard about under sizing fins and this is what he said:
Hi Joe,
You are underfinned if when you reach top speed and "push" laterally  across the top of the fin it lets go and spins out.
My personal "rule of thumb" for fin length is the fin has to be greater  than 1/2 the board width or OFO width.
The wider the board and the greater the footstrap off set, the more the  1/2 board width applies.

On a Futura or other freeride board with inboard and outboard footstrap  positions, you can generally  run a smaller fin (perhaps < 1/2  the OFO width) with the footstraps  in the closer to centered positions.
The smaller fin (or underfinned) also depends a lot on sail size and  overall board speed.
I have really tiny (< 25 cm) speed fins that are great if you can head  off wind and get them up to > 25 knots board speed.
At 30 knots + board speed they are solid as a rock, but if you have  conditions where you can't get them up to speed, you can push them loose  any time you like if your speed is less than what it takes for these tiny  fins to "hook up" and stay hooked up.
Hope this helps,
Roger

 
What are F4 fins?
FINS DEVELOPED BY RACERS FOR RACERS"F4 Fins was started by avid formula windsurfing racers in the San Francisco Bay because good racing fins had become either too expensive or unobtainable. The wind and water conditions, as well as the experienced racing fleet in the San Francisco Bay, provide the ideal proving grounds for developing the next generation racing fins. With help from Boogie of C3 on the design and manufacturing, combined with daily testing in the Bay waters, refinements can be quickly incorporated, resulting in an improved and constantly evolving product. After nearly a three years of effort, F4 fins are proving to be the winner's choice.

Our goal is to make the worlds best fins for racing and ensure that they are available at reasonable cost and in a reasonable time frame. Its important to us to encourage new and junior racers to participate in formula and slalom racing.

Check Waterhound for the latest news on the success of the BB and other F4 Fins in the San Francisco Racing Fleet


WHY WE/they ARE DIFFERENT
We are racers just like you who simply want the best fins at a reasonable price in a reasonable time. The key to our success is the local racers who are sailing and testing EVERY day during our season, from early March to late October. This allows us to deliver a fin that is build with&nbsp; the combined knowledge and feedback from one of the most competitive fleets in the world.

WHY OUR FINS ARE DIFFERENT

An F4 Fin utilizes an advanced composite layup that provides a softer feel, enabling greater control in a wider range of conditions. Our advanced composite design produces a consistent, responsive and longer-lasting fin with soft lateral and stiff torsional flex as compared to other formula fins. We have found that this softer feel, combined with a bullet-proof layup, gives you a fin with the optimal speed and control which makes the rest of your kit work more effortlessly. Call us prejudiced, but we've seen it all too often: racers spend too much on boards and sails, and treat the fin as an afterthought, when the fin can be the single most important component in a racer's arsenal. It's why some professional racers hold onto and baby "special" fins even as they move from one board or sail sponsor to another.

OUR MISSION

Our goal is to make the worlds best fins for racing and ensure that they are available at reasonable cost and in a reasonable time frame. We believe that this is important for the the sport and for the enjoyment of all competitors. One of our primary goals to to support junior racers. We believe that making the right fins and equipment available to juniors will help toincrease the total level of participation and overall interest in our sport. "

Still confused ? Check Rik's tricks :-)

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Somewhere around 2010 slot boxes showed up on wave boards. Similiar to US/A-box , butt without the tab , they weigh less and have 2 side screw holding fin into place. Believe this photo is from the Tabou website ..Was designed by Fabien Vollenweider??

 
------------------------Now I will do a brief discussion on how I repair my fins...---------------------------

This was a repair I had NOT anticipated. 

I am getting more and more upset with this supposed high grade race fin from Select. First it was more money than I had hoped to pay AND it fit poorly into the Trimm box. I took it out a few times and was satisfied with the performance - once I had adjusted it's fit into the box $%^&*( I took it out in the cold one day {-1 Celsius} and water levels were slightly different. It sounded like the fin grazed over some rocks and was actually a bit loose when I got off.

When I checked the fin, there was more damage than I anticipated and I did NOT dare go out with this fin until repaired ...

As you can see here, the leading edge was slightly scraped, butt the bottom got chewed out.


So, I got out the MarineTex and splashed some on ...


 

Once sanded it was NOT looking so bad :-)


Sometimes I put on black Sharpie ink in order to make it look half decent.  


This repair did NOT take long and the fin is almost as good as new. I did NOT do as good a job as I usually do since I anticipated going out ONE MORE TIME this season. The hope was for today, butt temps are up and winds are not :-(

Guess it is time to start the jogging and prepare for the ice board sailing season, which is just around the corner ...

Okay, once it WAS time to ensure it was a good job ....

I asked some fin suppliers and windsurf retailers about final finishing. All said NON to waxing and polishing. All said YES to wet-sanding. Most said that a grade 400 was more than enough and some suggested going as high as 600. I purchased 180 and 400 grit paper and re-sanded the same area without adding any more epoxy. It looked and felt really good. Here is a shot:


















As usual , I am NEVER satisfied and SO put another layer of MarineTex on the repair !!!

























Since board width is a factor in fin selection, I should mark that down as well when I am discussing my fins: {BTF was replaced with a JP SLW92 in 2014}


34 cm Fanatic Hawk fin for 6.3 and 7-oh perhaps, 63 cm wide BEE board
40 cm Select Slalom fin with sails 7-oh and down, ideally 70 cm wide board - now 63 and 79
43 cm Makani Hahalua weed fin for 7-oh and 8-oh, mostly 79 cm wide AHD
48 cm Select Freeblade fin for 8-oh , on the AHD which is 79 cm wide
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57 cm Curtis CR-16 deep tuttle on JP SLW92 using 8-oh - obviously 92 cm wide
66 cm  Select Ultra Race fin for 10-oh on JP SLW92

============================================================
How often does one need to make adjustments to make the fin fit the box??

The worst case for me was a Makani weed fin with powerbox top/base. Ironically it did fit the Fanatic BEE, but not the AHD for which it was meant. Gentle sanding took quite some time. The next worst was a trimm fin for the BIC Techno Formula. This was less of an issue, but took some time to fit.

On the Auzzie seabreeze forum Mr.Love comments:

The tuttle has parallel sides so no taper, it is the front and rear edges that control how far it disappears into the box. So you need to either add tape, mono film shims or epoxy filler to tune it perfectly. Unfortunately the tuttle is sensitive to small production tolerances either in the box or the fin head so you often have to tune it to a particular board. Yep, frustrating.

  In May 2015 for the first time I had cracks in the head portion of a Select PB 48 cm fin. I put some waterproof glue in the cracks and it seems okay, but need to test it on the water. Will NOT be using it in gusty conditions and may stay close to shore... Luckily have a weed fin that will do the job... Fin was fine and sold with my AHD 160/79.

In 2015 I made a chart with wind speed + sail size versus board + fin...















Specialized fins and companies making them are showing up - Black Projects, Choco, Flying Objects, MOO, MXR, Tribal and Zulu - amongst others ... Here is an enthusiast video from the Zulu magician:



This fellow decided that not only did he want to be able to sail in light winds using a Formula board, but also in shallow waters. He added two(2) fin boxes and ran the board with three(3) 26 cm weedies:



End of 2015 I purchased a Unifiber Lessacher 42 cm fin. As mentioned Lessacher worked out of Holland and made world-renowned fins. This fin is supposed to be be much shorter than other weedies for the same setup and also has a very different asymmetrical side profile. It is practically ribbed. Since it now winter, I will not get to try it until 2016. Others have used it with success on a JP SLW, which is where I hope to use it as well. It was either that or the project with three(3) fins :-)


As usual, the fin does NOT fit right away.  I do remember a time when I purchased fins and they FIT !! The fin went in about 80 % and then jammed all the way across. First I measured it with my trusty compass because I don;t have a calliper to gauge the thickness ...


I sanded it somewhat and put some McLube on. I was able to get it in the JP SLW92: The front was fine and was able to force the back with the screw... If this fin  works well, it means I will be using a 42 cm weed fin rather than a Curtis 58 or Select 66 !!



When I  tried it on the SB iSonic 177L/wide it did the same thing and so rather than forcing it, I did a little more sanding and it went in like butter. This was NOT nearly the sanding I have had to do in the past. When I purchase from a shop, I should bring my board to ensure it goes in well. The one time I did, they thought I was nuts and it went in well %^&* Anyway, here is the SB iS with the fin .


This board is already using "shorter" fins - like around 46 cm. However, sometimes there are weeds and an angled fin actually helps when you hit a sandbar. It is not quite as abrupt !!!

Here is another fin I repaired - it came with a Mistral SLE 303 slalom board. Fixed with MarineTex , sanded and put some primer on ...


In 2016 there was a discussion on an Australian windsurf forum about stiffness of fins and one of the extraordinary fins I have ever seen was discussed:


In the "gear review" section of the same forum, they discuss using softer fins for slalom. 
So, does one use soft fins on slalom  and Formula until conditions get "hairy"/over ? It seems to come down to "stiff fins for heavyweights". This makes sense since the F=ma is much more for someone with more mass/weight. 

For me , the same thing applies when one speaks about masts. Lighter sailors seem to like "softer masts" even going up over 7 m² sails. Heavier sailors can easily handle 75% SDM since they are exerting more force against the mast bend.
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Hello,

I read a bit on the link to the forum and they all have pretty accurate accounts. Bigger guys in general should have stiffer fins than lighter sailors. But still all fins should have some give relative to the sailors weight. The better the sailor you are, the more you will begin to understand how flex can help in all aspects of sailing. For intermediate sailors it is not that big of an issue because you are learning how all of your equipment comes into play and works together. The most important thing is to have all parts of your rig work together and properly balanced! Then you can fine tune with fin flex or not!! Yes George Greenough did have a super flexible VERY HIGH aspect fin!! BUT #1: he is an incredibly good and efficient sailor and (he could Pump onto a plane like nobody else!) #2: he weighs in at 135lb (61.5kg).

Chuck Ames
 True Ames Fins
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Summer of 2016, I found this:
http://www.seabreeze.com.au/forums/Windsurfing/General/Interesting-read-on-Fins/
have copied the material here:

THE SCIENCE OF WINDSURFING FINS  

Since you love windsurfing as much as us we thought you might appreciate some insight and theory into fin dynamics. There's a lot of hype and jargon spoken about fins, so we hope you find this theoretical information useful when making choices about what fins to buy.   There's a lot to cover, so we're going to send this to you in a series of short episodes, starting with a common misconception … THINNER PROFILES ARE FASTER  Indeed thinner profiles are faster - BUT only when used for speed sailing at very high speeds. For 'normal' speeds, thinner profiles in most constructions simply don't deliver enough LIFT.

There are a lot of influences on generating lift: Surface area, profile (thickness)Profile form (wing shape or camber - the shape of the fin in plan shape or cross section if you like), Chord (the front-to-back width)Depth top to bottom Profile ratio (chord length in mm. ÷ thickness in mm. expressed as %)Stiffness-Flex-Twist … and more, that all play their part.  Any one fin that's built without taking into account fine tuning of all of the above for specific purpose is selling you short in control, speed and lift.

Both the profile form and profile ratio are normally optimised for the use and intended speed range. A higher % profile will, in principle, generate more lift compared to a lower % profile at a given speed - but with a higher resistance. For speed, the amount of lift generated should be high, while the resistance must be as low as possible. Profile efficiency (lift ÷ drag ratio) has a relation to the required speed range and type of profile. Profile forms and outlines are a real scientific area. E.g., the realms of NASA, Boeing, Airbus, Shipbuilders etc. who, for as long as aerodynamics has existed, have spent infinite amounts of money to find 'the ideal profile'.
At higher speeds thinner profiles normally show a higher efficiency. Hence thinner profiles are better suited at higher speeds - but not necessarily for reaching them. There's a cut-off point at around 9% (of chord ÷ thickness). Below 9% would typically be used for speed. 9% or higher for slalom use. It could be a good idea to develop fins with >12% ratios specifically for very low speeds, like first time use etc . The result will be a high-lift fin at very low speed. Ideal to learn windsurfing on … The amount of lift generated by a fin depends on a number of variables. If speed doubles, lift will increase by a factor of 4!Angle of attack (lift increases linearly with the angle).Profile form and ratio (the higher the ratio the more lift per a given area).Rake angle also influences the lift figure considerably (a weed fin with 45-deg. delivers considerably less lift compared to a slalom fin with 12 deg.    

SPECIAL SAUCE
Welcome back to episode 2 of our series on windsuring fins - where we're busting a few myths and giving you the facts on fin technology.  Last time we got really scientific. This time we're going to use that theory and examine a few more preconceptions.  YES OR NO - THE MORE SURFACE AREA MY FIN HAS THE MORE LIFT IT WILL GENERATE  Maybe yes - but only when all other parameters like twist / flex / rake angle and profile are the same. These parameters all influence the amount of lift a fin generates. It's easy to construct fins with equal amounts of lift - but that differ 30% in surface area. As explained in episode 1, using a thin (e.g., 8%) profile ratio compared to a thick (e.g., 11%) profile ratio, the amount of lift per given area differs by a fair amount.

FACT OR FICTION? SHORTER FINS ARE ALWAYS FASTER THAN LONGER FINS

A real misconception! So … for a given board type and sail size AND the type of sailing (e.g., speed or upwind sailing) only one size of fin will give the optimal amount of lift. If your fin's too short it won't lift the board enough and therefore you'll have more wetted surface area and be significantly slower than if you used a longer fin

If your fin's too long it'll deliver too much lift and as a result your board will be difficult to control with errative behaviour such as spontaneous tail walks. Next time we'll look at profile, how construction methods influence handling characteristics and price factors such as custom fins versus production models.
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Some people vary the the thickness to chord ratio as discussed in same post:

"Slowie varies his profiles thicknesses. Whilst he has always had slight variances to optimise for cavitation inception etc the thickness variation of the current Tribal Sym Speed is very obvious in this regard.

It is about 11.5% for the first 10cm then quickly changes over the next 2cm to 9% then continues that to the tip which may be a bit thinner still. Looks weird from the front. "


In August 2016 in a fin discussion on iwindsurf U2U2U2 posted this picture:



I suggested that it actually looked like a foil AND like nothing I have seen before !!

In early 2017 I purchased a Makani fin to replace a 34 cm fin lost after hitting a rock @ La CrĂȘte, OKA Parc. The fin ordered was to be 34 cm and after paying was told no more in stock and okayed the 32 cm one... When the fin did not fit in the fin box and screw hole was misaligned, I was informed they were having manufacturing issues and were going to CNC. I wrote about this on the OZ forum and was not going to mention the manufacturer. When it all worked out and i did post a pic, local windsurfer forceten piped in and called me a whiner. When  benwindy complained about Makani apparently forceten was not happy then either...

Since this is my forum to express myself... I can honestly say i did NOT feel I was whining and was semi-satisfied in  the end. Just because a company is just down the road does not mean i support them no matter what - that sounds too much like Trump mentality. I will continue to buy Makani, but will be sure to implicate them when there are issues - AND report those issues on windsurf forums.

Makani have been known to make fins liked by many.  and the price is right ...

Was wondering if I wrote about fin length. When a fin is too short, it is fairly obvious, We speak about "spin-out". May also not plane up early enough for our satisfaction. A bigger question is: what is fin is too long and how do you know ?? OFO means width of the board "one foot off" or 30 cm up from the tail. People say board should NOT be more than that width and ideally 3/4 of that width. What happens if the fin is too long or more than the OFO. For US boxes, people say the box is not strong enough to handle more than ~30 cm anyway. What about the others ? Yes, one can put a longer or too long fin and what happens ?? People talk about "tail walking" where the whole front of the board wants to lift from the water, and also talk about "rail to rail flopping". Basically seems to mean the fin has too much lift and rider will have issues controlling it. It seems the idea is to maximise the shorter fin used... Then again, some foil masts are as long as one meter !!

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