lol, i thought the same thing sqid,

so i did a google and found that this is a very contentious area of windsurfing. seems everyone has a different name asthe moves are so complicated.

what i found is that some would call this a clew first spock 540 and other would say a grubby clew first 540 or somehting like that.

depends on the upwind move around the sail downwind flip spin thing.

what was the question?

Woohoo, do I win a free fin?

do as ben said and give it a go. If it doesnt work let me know and i'll shape one for ya.
Safetybay style.

Hi, Im new here but i know a few of these guys posting on the forum from vass,( mr sflack and barney the mullet).

Any way im in my final year at uni and currently doing a disserattaion on freestlye fin modificaton. This forum has been quite interesting to read and im very close to making my first prototype mould. will post pics
i have gone for an eliptical fin 15 cm long with a 4 degree rake. Im using a NACA of 0008-63 which i pretty much ripped off the mfc pro fin. Havnt seen many companies offering eliptical fins and when most pros cut them down they just go for the eliptical shape, im hopefull this will be a promising.

Anyways let me know what u think and i will try keeping u guys updated.


Pics are of 15cm Prototype 1 and male mould

Ali

I'm no expert so correct me if I'm wrong. It seems to me the reason short fins are desirable is just for popping and spinning. At the same time you don't need a lot of speed for freestyle. So wouldn't it be preferable to get as much lift as possible out of your short fin even at the expense of a lot of induced drag. If that's the case then a fairly fat profile with a longish chord is indicated. As well as that it doesn't make a lot of sense to use a low drag tip at the expense of lift so why don't you take the high lift profile for the full length and and dispense with the elliptical tip? That's more or less what you get by taking a standard high lift fin and just sawing it off in a straight line so I wonder if the dedicated freestyle fins that you buy off the shelf are any better than or even as good as the home grown variety. Does an abrubt end on a fin induce spinout or muck up the lift or something?

NotWal said...
That's more or less what you get by taking a standard high lift fin and just sawing it off in a straight line so I wonder if the dedicated freestyle fins that you buy off the shelf are any better than or even as good as the home grown variety. Does an abrubt end on a fin induce spinout or muck up the lift or something?

That's exactly what I did with a 24cm Tabou Freestyle fin that came with my board - cut it off in a straight line at about 16cm.

I can happily use this fin without spinout on Port Philip Bay chop with a 5 or 5.7 up - gives good lift, still turns respectably and is short enough to freestyle.

For note, a lot of the really epic freestylers from Vassiliki couldn't care less about fins - I've seen Barn and Ed sailing fins with scalloped leading edges (I think as a bet, or something to do with emulating humpback whales, for a laugh), and a lot of other guys sailing fins that they've made in a minute or two out of something that's been wrecked.



I find that I sail the Tabou more on its rails than on the fin when I want to go upwind, and hence the lift of the fin is largely secondary. I might test this further and see if I can sail it upwind with a 10cm fin or less to prove if that's the case.

FlickySpinny said...

Clew first grubby?

Clew-first Spock 540, according to Tricktionary II

[EDIT] Can you tell that there's no wind?

I thought it was a grubby as the sail is never flipped

Hi guys, good responce from everyone.

Bertie - This is a good point , i had this in the back of my mind but im definatly gonna change it now uve said. check the new picture. Also my target base for my disertation was high wind freestyle so this was my reasoning for making it around 15cm, it is on the small side but persoanlly i just wanto to use it in vass for this summer.

Just realised i cant change the tab shape without redrawing alot of stuff because of references in the drawing, basically solidworks hates me.

Notwal - You have brought up some interesting points and i can see the reasons why you are thinking this, and if u look at the MFC pro it does keep a relativly simular chrod length and only really tapers at the last minute to create a slight tip to tight turns can still be made. As to the straight cut off, the induced drag created by just cutting the fin in half will be quite signifient, i will do some sums and let u know about the lift and drag coefficents for cut off and eliptical foils and try to find the best. I suppose if you put a bulb or tab on the end of the fin then it will reduce the tip effect, but theere are so many varibles to look at with freestyle fins and i will try to get to the bottom of this.

Squidlips - I know what u mean, i found the dome function by accident when using lofs and boundry surface functions. it creates the perfect eliptical fin from a asmall extrusion of the foil profile.

FlickySpinny - Your fin looks nearly identical to the first custom i made for my tabou, it performed well for me but just felt that it was a bit "draggy". Yeh i rekon barn prob was looking to emulating humpback a whale. Also to add to natwols comments i rekon that most freestlyers do sail on the rail upwind, you see alot of the guys (and me) out of the back foot strap on the windward rail to achive this otherwise the fin will spinout, so maximum lift isnt really desirable but to have a minimum drag coefficent is.

Kimba - This inaccuracy of the dome feature didi worry me and i have checked the foil at 5 cm sections down and it does keep the same profile section luckily. i have put a lot of hours into playing with solidworks and i still keep finding new features. i initally used just the loft function but found closing the loft and giving a good section hard. boundray surface works a dream but and i was originally goining to use this ut found the dome function and just thought screw it i will use this coz its given me a roughly good shape. If it does suck tho i will just make another one as the uni im at has such a huge stock of every composite thinkable (planing on makiing a load of these fins and selling them if they work).

If you wanna have a look over my fin i will send you my file. email me you address to send to .

Cheers to everyone for commenting and keep the questions coming.

man alli i made a 15cm elliptical fin in vass 2 years ago... everyone laughed and didnt understand what i was talkin about.. threw it out.. good to see your flying the flag but i reckon it needs some speed bumps on the leading edge... wiki evolution, whales, and humpbacks..



apparently humbacks never evolved with weed- cause the bumps collect weed like no other.. so im making this freestyle weed fin for a new sailing spot near the gong



yes its wood-and not finished but i think u should talk about these fins in your disserattaion.

nah US box goes in backwards so I can get the center of effort of the fin as far forward as possible.. ive drawn in some lines to explain my jaded logic.



if anyone tells you that you dont need alot of speed for freestyle they have simply been watching the wrong cowardly sailors.. and freestyle fins need to be fast, having a high chord and thickness will give you more low speed lift with a lot of induced drag. but getting upwind is all about lift vs drag so even freestyle fins need to be fast. normally they are fast anyway because a 16cm fin will have little drag no matter what shape!

ill happily race anyone upwind on my 15cm humback

its not just the length that counts for freestyle its the surface area, because many sliding moves have the fin pushing sideways through the water.. so two fins 16cm and 18cm with the same surface area would feel the same in some moves.

yeah it looks like im confusing all sorts of things! ahhh the fun of freestyle fin pseudo science