Looking to get a few weed fins for speed / slalom. Size equivalents in normal fins would be 34cm and 40cm. Can someone please point out how to correctly size a weed fin to match and recommend some good makes/models for outright speed and control. Have got raked speed fins that will do - more interested in bigger size options? Guessing the Mandurah Mob and Connewarre crew will have some good ideas? Thanks.

I generally run JP Seaweed 31 and 36cm on boards 52 to 64cm wide with sails 6 to 7.8m. Smaller fins for 5m on small board.
For 75cm board and 7.8m I use a Choco 40 weedy, I thnk it is a great fin, Elmo does not so I suggest it is down to style etc.
So I recommend the JP and Choco wedys but have not tried others to compare.

it seems down this way that a variety of fins have been used, most common are Select (fairly common and fairly useless), Choco ( Jacques has done 41+ on his speed weed 24) flying objects (hard to get these days) and Lessacher ( great control and good speeds as well 37's). I suppose it comes down to what you feel confident on, some grip very well and point not too bad....

Mfc do some good weedies, under the name of "weed burner", from 29cm up to 46cm. Great fins but a little acetone is required to get rid of that pesky paint on the fin surface.
Bender might back me up on this one

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pepe47 said...

Mfc do some good weedies, under the name of "weed burner", from 29cm up to 46cm. Great fins but a little acetone is required to get rid of that pesky paint on the fin surface.
Bender might back me up on this one

Yes i have a 46cm MFC weedburner. I use it with my RRD120 Fire race 75cm wide and my 8.4m RSR. Its ok but lacks power to really get the board up and flying. I reckon the tip needs more area. I made a 40cm weedy out of a 70cm drake formula fin and it goes great. It rides and feels bigger than the mfc 46cm.

Seahorse, the best thing you can do it stat re-boxing yoour own fins. Just keep an eye on the buy and sell as you can pick up large fins quite cheap. That way you can make your own. Before you know it no pointer is safe from the drop saw!!

Well I have to admit that the reboxed super sport 50, now a 34 cm weedie is far superior to the mfc's but you have to get into the reboxing first.

Just had plans to show you a reboxing jig, but my card reader is somewhere in my daughter's room and I'm not entering there without my shots.

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pepe47 said...

Just had plans to show you a reboxing jig, but my card reader is somewhere in my daughter's room and I'm not entering there without my shots.

or a sturdy rope affixed to your waist and something solid (preferably with a winch) outside the room

I saw this post yesterday.. I will have to give my 5 cts view on it been sailing weedy for years.. I have no time now... as it is an important subject I think, it will take more that few lines!
Surprised Elmo is not talking and even more, Decript is my challenger when it comes to weedy! very talented on fins making, maybe he does not want to share his secrets lol ;)

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samOZ said...

>>>>>> Decript is my challenger when it comes to weedy! very talented on fins making, maybe he does not want to share his secrets lol ;)

Thanks Sam for the vote of confidence, but the request was to recommend makes and models, equivalent to 34cm & 40cm.
I have absolutely no expertise in either.
My biggest home made fin is a 31cm weedy, and I haven't used any standard production fins (the ones I have used are modified) be they normal or weedy, let alone compare them.

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decrepit said...

samOZ said...

>>>>>> Decript is my challenger when it comes to weedy! very talented on fins making, maybe he does not want to share his secrets lol ;)

Thanks Sam for the vote of confidence, but the request was to recommend makes and models, equivalent to 34cm & 40cm.
I have absolutely no expertise in either.
My biggest home made fin is a 31cm weedy, and I haven't used any standard production fins (the ones I have used are modified) be they normal or weedy, let alone compare them.

So Decrep i take it you have not tried the 40cm Choco weedy of mine then

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Bender said...
[>>>>>>
So Decrep i take it you have not tried the 40cm Choco weedy of mine then

No mate, I almost tried it the other day when it was very light, but it was also very shallow, I'd forgotten my booties, and I wanted to keep wading thru the cobbler weed to a minimum.
Even with the 31cm I was getting on the plane earlier than hardie.

Ok dumb question time, do you measure length or depth with a weed fin ?

I'll be needing one before next WA trip or even earlier for bouncing over the Green Island reef. I do remember the Crab Killers were happy with JP weedies, is that right or has dementia got me again. I know a few of you make your own now but like everything I do, I'm after the easy way out.

yep vertical depth Bob

Yep firie, I think the consus amongst my mates is the JPs are OK.
And it's the depth that's measured, I think because, that's the water column the fin is acting on, and it also gives the same leverage the fin has on the board.
And in the estuary it's an indication of how close the fin is to the rocks.

Thanks guys, see you again in January or there abouts

Goodnight

This thread just makes me feel like turning a 38 SR6b into a 25-27 weedeee

how much angle is thier in a weed fin . like 45'degrees ruffly or less?/more?

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Goo Screw said...

This thread just makes me feel like turning a 38 SR6b into a 25-27 weedeee

I've got a 36 SR6B. I measured it up to see how the basic measurements shift if it was set at 45 degrees.

At the point 1/3 the way down the fore and aft width is 86mm, the thickness here is 9mm (10.4%) and the wide point is 28 mm back or 32.5 %

Set at 45deg the fore and aft distance through the same wide point becomes 116mm for the same 9mm that's a thickness ratio of 7.8%

The wide point shifts from 32.5% back to 34% back. ( that's because the trailing edge isn't parallel to the leading edge.

A production 32 cm select weed fin I've just measured has the wide point 30 % back, and a thickness ratio of only 6.5% .

And I've seen pictures of the Chameleon weed fin which they also say also works pretty well.

Does the fact that all these variations of fins work indicate that foil parameters aren't all that critical? What is the essential difference between an excellent fin and a so so fin? Finish? symmetry? Consistency of thickness from top to bottom? Flex? It's a mystery to me because it doesn't seem to depend on the basic measurements. If it was certain magic combinations of ingredients then taking an upright to 45 should certainly NOT work.

So how much of it is just in the mind?

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Goo Screw said...

This thread just makes me feel like turning a 38 SR6b into a 25-27 weedeee

I've got a 36 SR6B. I measured it up to see how the basic measurements shift if it was set at 45 degrees.

At the point 1/3 the way down the fore and aft width is 86mm, the thickness here is 9mm (10.4%) and the wide point is 28 mm back or 32.5 %

Set at 45deg the fore and aft distance through the same wide point becomes 116mm for the same 9mm that's a thickness ratio of 7.8%

The wide point shifts from 32.5% back to 34% back. ( that's because the trailing edge isn't parallel to the leading edge.

A production 32 cm select weed fin I've just measured has the wide point 30 % back, and a thickness ratio of only 6.5% .

And I've seen pictures of the Chameleon weed fin which they also say also works pretty well.

Does the fact that all these variations of fins work indicate that foil parameters aren't all that critical? What is the essential difference between an excellent fin and a so so fin? Finish? symmetry? Consistency of thickness from top to bottom? Flex? It's a mystery to me because it doesn't seem to depend on the basic measurements. If it was certain magic combinations of ingredients then taking an upright to 45 should certainly NOT work.

So how much of it is just in the mind?

Ian, I think you've hit the nail on the head, a lot of production weedies are the normal blade reboxed, so the thickness to flow ratio becomes very low in a lot of cases. I think it's mainly these fins that give weedies a bad name.
It sounds like your SR6B would make a good weedy. If you're going to rebox an upright to a weedy, the thicker fins work better.

Unless you're chasing 50kt, a thicker fin will cavitate before you get there

The other thing with weedies is the difference that flex makes.
An upright fin bending can produce a vertical element in it's lift, when the fin's at 45deg the same bend has the bent part of the fin angling downward. This doesn't seem good to me, I make my weedies stiff.

Nicko, the fins I use in shallow water with weed growing up from the bottom I set at 45deg, any less and you can feel the weed slowing you down.
But for bigger fins in deep water, where you only need to disperse surface weed, 35-40deg will do, depending how fast you're going.

I can see the topic has moved!!
Nice one guys

First I want to apologize for any typing errors, English is not my language!!!
I thought I speak up on the subject because for the passed few years weedfins became more and more important with the speed sailing and "Seahorse" mentioned SPEED and slalom
I do both, but even in slalom we all want to go fast, so really we are talking about speed means around 30knts on the slalom

Before we start, I was thinking to give my mesurements and some of the gear and water conditions I sail so we have some references.
As we know the weight of the person will have a important impact on the gear used.

Mesurements: I am around 80kg (depend winter or summer lol), 176 cm (quite short I know), good for light wind, struggle for high wind!

Wind and water cond: 70% of small weeds, small chops, near smoove water (Mandurah estuary), 14-20 knots, wind on water not forecast
30% of big weeds, near smoove water, big chops, swell (Safety Bay), 11-14knots, wind on water not forecast

Gear:Biggest board 104L- 1% of use, 80-5L- 84%, 68L-15%
Biggest sail 7.2m- 5% of use, 6.7m- 25%, 5.8m- 68%, 5.0m- 2%
Biggest fin 29cm- 5% of use, 28cm- 25%, 24-26cm- 68%, 22cm- 2%

I am not interested to sail under 11 knots wind, because the need of big gear.. And this is not speed or even slalom to me anymore to me!
I can get and keep planning on 11 knots, 7.2 sail, 85L board, 28 cm fin in Safety Bay outside the pond in the swell! Yes 28cm fin, that is why I had to share my story!

Mainly big guys can do some good speed on the big gear, the average guys will struggle and it will be very exausting!
Why using a big board when you can use a smaller one. If you use a bigger board you will have to use a bigger fin right!? and a bigger sail to keep the thing going..
I use to think it was the way to go, but bigger board and fin means more drag and resistance to water, more work for you! And you are not going that fast.. (some do, but no many!)
By using a narrower board with enough volume to support you, you can use a smaller fin and still able to use a good size sail!! And it feels great and light..
Last 3-4 years I used 85l-56-59cm boards, with the years I keep the same size boards and sails but started reducing the fins size..
Recently I managed to push it even smaller, 80L-53cm, 28cm weedy, 6.7-7.2m sail, 11kts+ wind, 28-30 kts speed in Safety Bay.. I found this is the limit for my weight!!

Now lets talk about weedy...
I personaly think the fin is the most important part of the gear as everything seat on it!
What I am about to share with you is what I discover for the last 3-4 years, actually since I met Hardie and Elmo and started speedsailing. Thanks guys, since I need a bigger wallet!!
I don't know much about fins, I don't know anything about fins calculations, all I learned is by testing, making, testing and more testing.
My biggest weedy used to be 38, now its 29 cm!! My biggest Slalom is 34 and it feels big and I rarely use it, I cannot sail big fins anymore!!
Most people think weed fins are slow and crap.. well it all depend on what you use!
95% of my fins are weed fins, and 98% of them are pretty much hand made! Why, because since the begining I found there was not really good product weed fin on the market

Pretty much any fins work on medium speed (when I mean "work" I mean feel free and don't spinout), but less will work above 30kts, even less above 35, and no many at 40 and +
I am not a specialist of the production big fins they are too dragy, I think Elmo is the guy to talk to, been using and customizing quite few of them!
We always talk about size of the fin, I think we are on the wrong track! We should think also about the area of the fin not only lenght of it!!
I discover that a smaller fin with more area will work better and feel lighter that a longer fin with the same area! That is why all my big weedy have been re-shaped to make some small speed weedies
It also give you the possibility to sail more on shallow water, which is usualy where the flat water is!

The main problem I found with the big weed fins is longer it is more rake you will have to give.. it means longer the fin will be to meet the lenght needed .. etc..
Why? because the lenght of it will have more work to clear the weeds (not sure if it is clear what I am saying!)
aaah rake! We have not talk about rake! Like fins calculations, I don't know much about it! BUt what I discover is, the max lenght of a fin at 40/deg to clear weeds is around 29cm!
That is why my biggest is 29cm! IMPOW I think between 35-43 is a good rake range for 22-28 small to medium weedfin depending on his thickness, good for speed!! bigger will have to rake at 45/
Also I think the key is a wide base 110mm, 120 if you can, a thin profile, a wide tip, giving you the area you need for your sail while keeping the fin small!!
Lot of fins also will work on flat water! But on choppy is a different story! We all want speed with the control don't we?, in my book ther is no room for spinout..

THE FINS

*The best and only light wind fin I use now is a full carbon production 28cm 45/deg "Duo weed - Lessacher" http://www.cameraid.com/Lessacher/duoweed.html. I have been using this magic fin for 3 years now!
It is not a fast fin because it is quite thick, but it give you the power you need to take off and keep going, it has got the surface area of a big 36 cm weedy, it has got a double concave so it is rock stable!!
The most amazing is I can use it on my 104L, 85L, and even my 80L with 7.2, on a 11-14 knots day can take you around 30kts. The guy sales a 32cm for the big boys.
The finishing is crap, but an easy 240 grade on it will fix it! Pepe in our team has one..
*People use all kind of monster fins like JPs, MFcs, etc.. good for the big gear, but definitly not for me..

For the guys don't box their fins,
Some good higher wind fins are:
* Again a Lessacher, the "Quattro Cham?leon" 24cm/45deg full carbon, 4 concaves, www.cameraid.com/Lessacher/chameleon.html
very forgiving, good on 80L with 5.8. I personaly find his limit at 35. Adam and Hardie did better with it I think. I hardly use mine as my own fins perform much better!
* The Choco Fireblade weedy not showing on the website, again Hardie has one and is doing good.. One of my first weedy made was an original slalom fireblade modified to 43/, found the limit around 34..then re-shaped I pushed it to 38 stable
* I know Elmo will not agree with me ;) but the LE know as Leading Edge, hard to find because not produced anymore! Full Carbon 45/deg.. I have a couple slalom that I rake at 40.. Not super fast because a touch thick, but they are stable, good upwind and keep going! around 26-28cm they are the best in LE weedy!
* The Flying Objects, around 30cm+ chopped to a 24cm like Adam did (40+kts), I had an original 26cm, I did not liked it and sold it. Adams ways look better!
* Now, the king of the production speed weedfins is the "Ka 23 Sym", I just bought one (last time I bought a weedy was 3 years ago), I call it weedy because I discovered it has a 37/deg rake (not like stating 30), with only 23.5 cm, that fin is perfect with a 6m and 80L, but can be used in different combinations (not tested for me yet)
I managed to get few little controlled spinouts with it on my last session.. great drive, great fin.. Have to see how fare I can take it! I seen that lot of people perform great on it. It has got lot of area for his size, just the way I like them ;)
I think this fin his made for an average weight guy with concistant medium-high wind, or heavier guy with high wind. A smaller version would be awsome with a 5m ;).. One of my favorite
Great fins come to great price!! 390 bucks, if lucky like some I know you can get one at 250!!
* I think there is some new one that came out at 2ndwind, I seen one briefly when passing.. they look alright and thin.. they remind me the LE on thinner version

Now, for the guys that want to box or shape their weedfins : to follow up very soon ;)

Good write up Sam, keep it coming.

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decrepit said...

SR6B would make a good weedy. If you're going to rebox an upright to a weedy, the thicker fins work better.

Unless you're chasing 50kt, a thicker fin will cavitate before you get there

Not even close to 50, so for general use ( we should be in the general forum now) would weed fins also ideally be around 10%. Which would probably mean reducing the streamwise length (width?) rather than going > 10mm thickness. Then you'd lose area so you'd have to make them longer. And then they'd become too flexy. Am I starting to see reasons why weed fins are made relatively thin? Has anybody made or tried a 10% weedy?

Mine are usually between 9 & 10%. (I'm no where near 50 either, but I like to hit 30 as often as possible)
I don't like the idea of reducing flow length, I'd rather bog them up to make them thicker.
As I mentioned earlier about flex problems with weedies, high aspect is more efficient for upright fins, but as Sam says, wide base thicker fins (low aspect ratio) seem to work better for weedies.
The other problem with long narrow raked fins is the centre of lateral resistance moves back further, meaning a change of trim when you change fins. Keeping the fin low aspect, the front edge straight all the way to the tip, with the trailing edge curving in, keeps the centre of lateral resistance as far forward as possible. And also makes the chord more upright, helping the angle of flex.

Mine are usually between 9 & 10%. (I'm no where near 50 either, but I like to hit 30 as often as possible)
I don't like the idea of reducing flow length, I'd rather bog them up to make them thicker.
As I mentioned earlier about flex problems with weedies, high aspect is more efficient for upright fins, but as Sam says, wide base thicker fins (low aspect ratio) seem to work better for weedies.
The other problem with long narrow raked fins is the centre of lateral resistance moves back further, meaning a change of trim when you change fins. Keeping the fin low aspect, the front edge straight all the way to the tip, with the trailing edge curving in, keeps the centre of lateral resistance as far forward as possible. And also makes the chord more upright, helping the angle of flex.

Here's my latest in the beginning stages, jarrah at the base to take compression loads and pine through the body for lightness, (this is my light wind fin, I want to keep weight down). I then covered it with carbon and glass. I've had it just over 30kts with a 6.0 sail, in just over 15kts

Nice fin there Decrepit, I suspected that you'd experimented to 10%. Good stuff that radiata pine. How thick is the glass/carbon layer?

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decrepit said...
. I've had it just over 30kts with a 6.0 sail, in just over 15kts

Wow!

I want one!

Greaaat job Mike, like always.. I love the shape and color mix, shame the carbon with cover it!! Your fin is what I am talking about not sure about the thickness of it? How thick?

Ian K said: would weed fins also ideally be around 10%. Which would probably mean reducing the streamwise length (width?) rather than going > 10mm thickness. Then you'd lose area so you'd have to make them longer.

I am not sure I got understood!! What I am trying to do is a fin that his as thin as possible < 10mm (9-8), around 25cm, 120 or +. while no more that 40/

I have not experiment enough this area, still playing with as there no many cheap 2nd blade that you can buy. Not like Decript where he build his from wood.
For me, I will pick any blade that has the area and the thinkness I am looking for.

Here is the perfect exemple of what I am looking for and you can do with a cheap blade! This fin is for Snides, a 255mm long, 10mm thick, 120mm wide @ 40
You don't want too much rake for a thin fin, you loose power I think!
Normally I don't do fin fins for people, but that day Snides bought one of my early 230SS and when I saw that crap fin, I saw the potential in it and offer to revampe the fin..
The BEFORE



The fin was chocking, thick entry point, thick tailing edge, scratches all over, 47/ rake, 24cm long. Sure with that kind of rake anything can work!

The AFTER



What I done here is:
*Took some area off because bringing the fin forward
*Thin the leading and move it back <10mm
*Even the fin on his lenght
*Courb the last 1/4 of the leading edge
*Add some positive to the tailing edge
*Thin the tailing edge and create a good concave (1/4 of the width all the long)
*Eliminated any flat spots
*Did not touch the centre point on the top alf of the fin

The fin is almost finished, the little one next to it is my 220mm, 110mm, 9mm, @38/
Snides is an old drake, mine is a Select viper 34 Slalom..



Like mentioned by few guys, the Select are perfect to use straight out the shell, they are thin, cheap to buy, staight leading edge, courb tailing edge... you cannot go wrong.. but you don't want to give them too much rake I think! max 40 I will say..

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samOZ said the Select are perfect to use straight out the shell, they are thin, cheap to buy, straight leading edge, curved trailing edge... you can not go wrong.. but you don't want to give them too much rake I think! max 40 I will say..

Nice job on the fins Sam

Yeap! The Select fins seem to make better weedies than Slalom they where designed for.

Turned a Select 32 Slalom into a 22.5 @40 degrees weedy for Lau Shi which seemed pretty nice but unfortunately we haven't had any decent wind in the last few months for Mark to give it a proper test. Perhaps a little less rake may have been better. ~38 or so

A photo of the result. The Select on the left next to a KA23 Sym painted black.