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31st January 2010 05:29 AM
carvesalot sail size X5 + 3 = fin size
so 4.0 sail..... multiply times 5 = 20 + 3 = 23cm fin

there are several "in the ball park" formulas for fin selection, since windsurfing is not a math type science , thats all these math type formulas will do, I noticed Roger stated
80KG , I have seen that 75KG is the average weight when referring to fin size, board liter float on..on Being 57KG (eat more cheeseburgers) using my above posted formula I would look at 20-- 21cm .
28th January 2010 02:29 PM
Lessacher Hallo Lanee!The bigger sailor need more wind, that is not okay.A bigger hold the sail longer upright, so he makes more speed with the same sail how a not so big sailor.With
the same wind.
Not bigger sailor need more lift, heavier sailor need more lift.
But fins are pretty stupid. I worked out,35 points what a fin should can do. I give all
points in my fins, please no spin out. No problem when the fin is to long and so on....
They feel no sideway force. I worked the concaves so that they make more lift with
slow speed and with high speed is the lift reduced, so no problem with longer fins.
The Formulas need the bending of the fin to produce lift. The lift is there vertical.The soft fin is better to go earlier to plane, through the bending of the fin get you the most
time with speed the problems. I reduce the problems that a fin can make. Carbon fins
are in 100% carbon. No spin outs, fast and make fun. A fin is not pretty stupid.
Wolfgang
27th January 2010 09:40 PM
sergio_k Sergio, what are some of the 'softer' weed fins you know of?[/QUOTE]

Lanee, I was not referring to weed fins in the reference to 'soft' fin, I generally don't like weed fins, not sure if soft would not apply to them, the only ones that works relatively well ( in my opinion)are Lessacher fins...
While you guys trying to theorize, I spent last 14 years with diff boards and plenty of fins (custom and production) testing what works best fin size wise for me (132lb). So, from experience, the practical way is to match sail size to fin size, sometimes being light weight I have to go even bigger in fin size to avoid spin-outs (comparing to heavier guy).
27th January 2010 07:24 PM
Roger Hi Lanee,
What those of us who have responded really need to know, to make a good recommendation that almost certain to work for you is the width of the board you are looking at to use with this fin, and the range of sail sizes you think you may be using.
Since you are 57 Kg in weight, you can sail a 100 liter board that's < 60 cm wide in even
12 knots with a 6.5-7.0 m2 rig.
For this setup (57 Kg. 6.5 rig <= 60 cm wide board) I would think a 32 cm Lessacher Duo weed fin would be ab out the best you could get.
If the board size decreases and the windspeed increases to above 20 knots, then a 28 cm Lessacher Duo would be my call.
Do not buy a cheap weed fin.... and remember, weed fins have far more area than the fins that are talked about in the speciifcations so you can run probably 20-30% smaller.
The cheap weed fin will most lilkely be slow, give you lots of drag, and very little upwind performance. The Lassacher duos won't have these issues.
Hope this helps,
27th January 2010 01:44 PM
Lessacher Atfirst get we pressure from leewards and the second is the vacuum on the other side.
Two things who make sometimes to much lift. I reduce on my fins the vacuum on the other side and have so only the lift from leewards, I can so use bigger fins,if I want this.
Wolfgang
27th January 2010 09:23 AM
Lanee The way I've been thinking, unregistered is right. When completely powered up on a given board and sail, the heavier sailor will have the potential to go faster than the lighter sailor of the same ability who is also completely powered. (The bigger sailor needs more wind.) If speed was all that the fin 'sensed', then the heavier sailor may get 'overfinned' sooner.

I always thought it was kinda funny relating required fin size to sail size. There seem to be so many factors, so I guess you have to start somewhere. But fins are pretty stupid. They don't know what size sail is on the board. What do they 'feel'? For sure, the lift they generate is proportional to speed through the water. But, don't they also feel a sideways force. A bigger sailor will generate more of a sideways force than a smaller sailor, again, both being fully powered.

Then again, that bigger sailor being out on the rail probably needs more lift. Who knows? I think I'll just 'guess' on my first fin by getting the cheapest used weed fin I can find, and working from there.

Sergio, what are some of the 'softer' weed fins you know of?
26th January 2010 03:32 PM
Unregistered Finsize is related to board speed.
Just like sail size is related to windspeed.
25th January 2010 10:14 PM
sergio_k At 62 kg my experience is that fin size is ralated to sail size much more than your weight,
so for example, if 100kg person is using 6.0 m2 with 32 cm fin - that what you should be
using also, just for you wind speed would be much lower. The 2 other things to consider: custom fins have better wind range and control and for lighter windsurfer, I strongly believe, softer fins will perform better, more responsive when pumping
25th January 2010 09:30 PM
Ken There is no perfect answer, just a lot of variables.

Light wind - large fin
High wind - small fin

Large sail - large fin
Small sail - small fin

Heavy sailor - large fin
Light sailor - small fin

Wide board - large fin
Narrow board - small fin

Slow board speed - large fin
Fast board speed - small fin

Upwind performance - large fin
Downwind performance - small fin
25th January 2010 05:14 PM
Farlo Interesting what you say. My understanding was that a lighter rider would need a smaller fin, all other things being equal: wind speed, sea state, sail size, but... Christine le Couturier (French SB team) revealed that she uses the same sail/fin combinations than her 20 Kgs heavier boyfriend, but in lighter conditions.

Also speedseekers manage to use fins significantly smaller that you would expect for their weight and sails. For instance on my lake the speed record was set by a 90 Kgs guy with 8.4 mē and "only" 36 cm fin. The same day I was also having a 36 but with a 7.3 (well overpowered).

To choose a fin I use a slightly different rule: sail size x5.5 in ideal conditions, x5 when overpovered and x6 when underpowered. This combined with some outhaul extends greatly the range of a sail. This works for my weight (68 Kgs) and freeride/freerace, not slalom/speed/competition. Hope this helps.
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