I'm looking for a decent weed fin for my new (5 years old ) board.

I got some great advice on this forum for my other board (115L) and I was hoping for I can get some help for this board.

JP FSW 98, 6m sail, weight 97kg.
Target area - ocean at Pinnaroo Point - bump/jump
Skill - still not gybing...

So far, I cut this:



to look like this:



And it worked...mostly...I can go fine, change direction, feels controllable
...except when it comes out (I.E. a small jump). It loses grip as it comes back in and keeps sliding. I should get something decent instead.

Can anyone help ?
Thanks in advance,

Ive had those jp fins before do that to me.

What you can try it get some 240-300 grit wet and dry paper, and sand the fin until all those smooth graphics and gloss come off and your left with a nice raw sanded finish.
Youll be surprised at how much of that glossy crap is on those fins. Dont try and sand it to fine though (ie with 600+) as you want something for the water to "bite" on to.

Sand only one way all the time (horizontally, same way the water would flow across it).

Ive done this to all my jp fins and it certainly helped them grab more and prevent the spinouts.

That's an interesting idea.
Happy to try that. Thanks !!!

Get yourself a Makani Mano weed/wave, I've got the 26 & 23 cm versions and as far as weed fin goes they "ROCK".

www.makanifins.com/

For $120 you'll get a awesome weed fin without the problems associated with weed fins, They are just like normal fins. I run the 26cm in my 112 FSW and 120 freeride with sails from 6.2 to 7.2 and the 23cm in my 95 wave board with sails from 4.7 to 5.8 and it's a perfect match.

The best thing about the Mano is it feels like a stock G10 fin, I use mine as a wave fin due to it's upwind ability, not as loose as a normal wave fin but is still good and screams upwind without effort. I've used them heaps in bump and jump conditions and can't remember the last time I spun out. From the shallows at lake illawarra to the weed beds at sanctuary point I've not felt any drag from weed since running the Mano in my boards and I've not gone back to the standard fins since my first run with them, They are just that good.

Cheers.

Obelix,

The problem you have is that the foil is all wrong as you have chopped it.


Due to the fin's (plan shape) taper, if you just chop the end off it will not work very well when planing as the fin gets thinner in the draft from base to tip.

You have something with zero tip flex.
You need to thin it out in the bottom third, then you will have lost the draft position.
The draft (max thickness point) needs to be at about 30 - 35% of the way back from the leading edge. Thus mark it draft at say 33% all the way from base to tip, and refoil that bottom third. Then it would be quite a bit better I reckon.

Looking at the white and blue stripes, you will lose them completely from about the second crossover point to the tip.

@ mark_australia: Would it have helped to just re-boxed the fin. Cutting out the middle section, leaving the tip as is. This is my plan for my next freestyle fin.
I Re-boxed a slalom fin to a weed/slalomfin, the thing works great, and it is really not that hard to do.
So maybe the day's of cutting down freestyle fins is over, and re-boxing is the way to go?

Mark,

I've sanded it as per Darkplague's advice, and will try it on Sunday.

If it would continue slipping, I'll try what you described above.

Eventually, I'll order a decent fin. Possibly the Makano JH reccommended.

I would suspect that it is not entirely your fin's fault.

Did the fin work OK before you cut it, or is it only after you cut it that it started spinning out ?

When you 'jump' you need to scissor your legs (or pull your back leg towards your arse slightly) to head down wind a bit on landing, and when you land don't load the tail too much through your back leg.

No doubt a different (and larger and more upright) fin would spin out less when loaded up suddenly but they would all spin out if you don't actively bring your back leg towards you (or you passively let it straighten out when the pressure comes off during the jump).

If the nose of the board heads upwind when you take off or are in the air then chances are you will spin out on landing.

At least if you get a good quality shiny new fin and it does the same thing you know it is technique not equipment, but I am not sure anything would be magically better than the original fin in the picture (except maybe a bigger one, not sure how big that one is - it will say on the label on the base, but then a bigger one may make sailing in straight line unpleasant ).

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Carantoc said...

I would suspect that it is not entirely your fin's fault.

Did the fin work OK before you cut it, or is it only after you cut it that it started spinning out ?

When you 'jump' you need to scissor your legs (or pull your back leg towards your arse slightly) to head down wind a bit on landing, and when you land don't load the tail too much through your back leg.

If the nose of the board heads upwind when you take off or are in the air then chances are you will spin out on landing.

At least if you get a good quality shiny new fin and it does the same thing you know it is technique not equipment, but I am not sure anything would be magically better than the original fin in the picture (except maybe a bigger one, not sure how big that one is - it will say on the label on the base, but then a bigger one may make sailing in straight line unpleasant ).

The original fin was hard to get the board to plane, an could not go up wind at all.
(On my 115L board - 6.8 to 7.5m sail range)

I brought it up to this forum, and got some great advice, which resulted with a larger brand new weed fin and since then all my problems were resolved on that board.

Then I purchased a 98L board and coupled it with a 6m sail.
For that combo I needed a smaller fin (specs reccommned 29cm), and thought I could try to utilise this fin. As 33cm (verticaly measured) weed is way to long, I cut it to 27cm.

The technique...I have none
However, I'm not really jumping, just find myself in the air every now and again.
It's very likely that I'm landing incorrectly so I'll pay attention to that next time.

I presume the new fins are generally better than the old ones, so I'm keen to get a new shiny fin, just want to learn as much as I can before I buy, so I get the right one.

So far I'm learning heaps from all of you and I'm keen to try every advice I got here.
Appreciate all the advice I received. It all makes perfect sense.

Them large fins are kinda scary if your practicing jibes. A few times i have come off and popped up in the water in surprised that i haven't been slashed in the face by it.
Problem is i have all the right fins on my different boards but the fin boxes are all different id run a 26 weed on it personally but you must be in a similar situation as me.

I think the master of fin modification would have to go to decrepit

You may have to round of the back edge of the fin cause it could be causing cavitation.
-

While discussing the shape, I looked at this hypersonic shapes:

http://www.stubell.com.au/shopping-cart/fins/hypersonic-weed-fin-26-pb/

Given it's for the bump/jump conditions, should I re-shape it a bit like that, or is the shape of Makano Mano better for these conditions?

www.makanifins.com/Windsurfing_Fins_Weed_Wave_p/ma001.htm

..and what would be the best shape for the jump and bump conditions?

I snapped a 23cm G10 fin last week and only had an old worn out glass 20cm to replace it with. Now I would have said that 20cm on a 80 litre and 4.7 sail in choppy bump and jump was a bit too small, plus the 20cm is old, tip is worn out, not a nice colour and doesn't look flash, the 23cm was new, shiny and looked the business.

Guess what, the 20cm is much nicer to ride. Makes the board nice and loose, fast to turn with no loss of drive. I would never had put it on my board if I hadn't snapped the other one and not had time to replace it. Think I may just keep it there for a while now though.

Moral is, sometimes something just works despite all the logic you work out.


I would say the more upright shape of the hypersonic weed would give you more grip and less spin out, but when it does spin it will be harder to get back. The shape of the Manaki will be easier to get back from spinning out, but more prone to do it in the first place. Whether that translates into these particular fins on your board who knows.

If you are not looking to slash your board around in tight turns I would go with a more upright style bump and jump / free ride fin than a swept back wave fin.

But also, don't look at spin out as something that must be eradicated at all cost. Look at it as something that will always happen once in a while (especially with weed around), and getting your board back from it is as important as stopping it happen in the first place.

If you spin out and can recover then that is a good step. Do that on a wave and you can claim you thrashed the lip.

>>>Moral is, sometimes something just works despite all the logic you work out.
I agree.
So I'll go step by step and first test the sanded fin, and try to keep the board pointed forward after the jump. Then re-shape it, then get a new one.

>>>If you are not looking to slash your board around in tight turns
I'm not gybing yet ...
Again, one step at the time. Stop the spin-out. Learn to gybe.

>>>If you spin out and can recover then that is a good step.
For now it just slides sideways. Wouldn't even grip after I force the direction accross the wind.
Fingers crossed...

>>>Do that on a wave and you can claim you thrashed the lip.
I'll do my best. It's exciting to turn the board with the small wave. I can imagine the excitement of doing it on the large one.

>>>You may have to round of the back edge of the fin cause it could be causing cavitation.

Blunt the back edge? Didn't know that.
It is very sharp now.
What tickness should work better? 0.5mm, 1mm?

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Darkplague said...

Ive had those jp fins before do that to me.

What you can try it get some 240-300 grit wet and dry paper, and sand the fin until all those smooth graphics and gloss come off and your left with a nice raw sanded finish.
Youll be surprised at how much of that glossy crap is on those fins. Dont try and sand it to fine though (ie with 600+) as you want something for the water to "bite" on to.

Sand only one way all the time (horizontally, same way the water would flow across it).

Ive done this to all my jp fins and it certainly helped them grab more and prevent the spinouts.

After sanding it as described, I tried it with a 6.8m sail and the same board some days ago, and it kept slipping. However I was able to recover after a slide whereas I couldn't earlier on. So this was a positive sign.

Today, I tried it on a larger board (115L F2 XTC), and using the original 6m sail.
It performed great. Not a single slide today, although I was overpowered, and on a 18L larger board. So I'll keep this one as is without further surgery until I hit another snag.

Cheers for the tip Darkplague.
Thanks everyone else for your advices. All very educational.