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Forums > Windsurfing Gear Reviews

Thrusters not liked?

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Created by philn > 9 months ago, 16 Dec 2020
philn
928 posts
16 Dec 2020 3:11AM
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Who's this bloke that claims thrusters are crap?

m.facebook.com/story.php?story_fbid=3541705579198329&id=139691419399779

LeeD
3939 posts
16 Dec 2020 3:19AM
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Everyone's entitled to their opinions.
Speed sailors in flat water might favor singles.
Bump sailors in waves, often underpowered, might favor tris.

AJEaster
NSW, 696 posts
16 Dec 2020 9:48AM
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PK blows my mind with what he does in onshore schlopp!!!!!!

Basher
539 posts
16 Dec 2020 8:54AM
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philn said..
Who's this bloke that claims thrusters are crap?

m.facebook.com/story.php?story_fbid=3541705579198329&id=139691419399779




That's not what he says.

He says the tri fin is not his preferred set up except when using his board somewhere where there are currents - in which case early planing and drive are maybe best served by a tri fin.
The rest of the time, he prefers a twin fin set up - for looseness when sailing in onshore conditions.
And then he appreciates the drive of a quad when driving along proper wave faces in cross-off conditions.

I'm just pleased that the twin fin is back, as that works well at my local beach. We typically have onshore conditions.
(My 83 Pyro arrives next week)

seabreezer
377 posts
16 Dec 2020 11:32AM
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Best set-up is ..... TO KEEP AN OPEN MIND ... all way through your windsurfing years ...

Remember - Pro's get maybe more 'stuck in their ways ' with equipment set-ups , and rightly so ... as they have the added pressure of contest consistancy to worry about - sometimes Its not worth it for them to mix things up too much or confuse matters with moves - as flicking between set-ups makes a big difference to helping / not helping ...certain wave trick scoring moves ... and you have to change and adapt your style (again - not always best for contest performance)

No 1 set-up reigns supreme .... all set-ups have their 'Pro' level followers ... braw & campello quad for example , KT / traversa/ Juban / Antoine / Ezzy / Stone thruster ... , mainly Koster for twin , and some like Levi Siver - flick between quad and thruster non stop ...

For recreational windsurfers / weekend warriors - change things up a bit if your getting a bit jaded on the water / sensations the same ... If you want to land new moves - sometimes changing fin set style helps dramatically ... The only barometer is if your steadily improving ,... if you are - you are probably keeping an open mind - and open to trying different set-ups to accomplish different things , and using set-up strengths and weaknesses to your advantage ... And sometimes its a game changer for yr sailing getting forced outside of your normal set-up comfort - to adapt and learn new styles of sailing ... I for sure had to switching quad to thruster .

I sail alot of side / side off ... and still swap back and forth between quad and thruster ... both have their + and - ..... Lately Ive also thought about jumping back on twins for certain smaller mushier conditions sideshore as they're so nice and forgiving for trick moves on the wave ... (ie higher consistancy landing moves)

philn
928 posts
17 Dec 2020 3:10AM
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Basher said..

That's not what he says.


You're no fun. I'm a seppo, from the land of fake news, straw man arguments and other forms of logical fallacies. We like to put words in other people's mouths.

Basher
539 posts
17 Dec 2020 4:48AM
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Select to expand quote
philn said..

Basher said..

That's not what he says.



You're no fun. I'm a seppo, from the land of fake news, straw man arguments and other forms of logical fallacies. We like to put words in other people's mouths.


Fair enough. Good points, well made.

I'm biassed, and slightly excited by the return of the twin fin. It's a sort of fetish for us lighter sailors - and we like Koster because he's not a lightweight and yet he still values the twin fin board.
So I guess the fetish is really about liking a slidey tail board.

If you prefer drive, then go for the quad or the tri fin set up.
For those still learning, the back-footer's convention is to go for a tri fin with a longer centre fin.

On topic, I'll get back to you when I know which set up my own Pyro works best with - at my own windsurfing location.

Grantmac
2183 posts
18 Dec 2020 2:35AM
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For guys running quads as twins in mushy conditions:
How do you select a fin size/template and where do you position it compared to sailing as a quad?
I'm tempted to try my Quatro as a twin. The stock front fins are already on the smaller size but its rear boxes have very limited adjustment. It seems to prefer rears with a more upright template as a quad.

Basher
539 posts
18 Dec 2020 3:10AM
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Select to expand quote
Grantmac said..
For guys running quads as twins in mushy conditions:
How do you select a fin size/template and where do you position it compared to sailing as a quad?
I'm tempted to try my Quatro as a twin. The stock front fins are already on the smaller size but its rear boxes have very limited adjustment. It seems to prefer rears with a more upright template as a quad.



Well if your quad has 14s or 15cms fins in the rear then go about 17cms for the twin fin set up. As a light weight, I tend to use a pair of 16cms.

The reason twin fins are loose is the two relatively small fins are adjacent to each other, so if you stall or spin out then the upwind fin follows the downwind fin in an air pocket - and that's probably why Koster likes them for spinny/breakout moves on the wave face.

You can get plenty of drive from two 17cms fins all long as you load them gradually to get the lift at speed, instead of spinning out. (So you need good back foot control).

But the second question is where to position the fins, and when losing the thrusters from a quad you'd expect to set the bigger back fins further forwards, to compensate. What Koster does instead is to use Maui Ultra Fins with an upright profile, which effectively keeps the centre of fin area reasonably far forwards. Those upright fins also give good lift and speed for getting upwind and for jumping.

But if you find a twin fin set up loose in a stubby wave board then having the fins set back in the board can help give the board more directionality and drive - as long as the fin trailing edge doesn't extend past the tail of the board.

So best advice is to experiment, perhaps starting with a pair of 17cms in the rear boxes, but set as far forwards as those rear boxes allow.

philn
928 posts
18 Dec 2020 5:56AM
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Select to expand quote
Grantmac said..
For guys running quads as twins in mushy conditions:
How do you select a fin size/template and where do you position it compared to sailing as a quad?
I'm tempted to try my Quatro as a twin. The stock front fins are already on the smaller size but its rear boxes have very limited adjustment. It seems to prefer rears with a more upright template as a quad.


I have a Quatro Cube 95 L and a Goya Custom Quad 116 L that I run as twin fins. For the 95 L I have 16.5 cm Black Project fins, and for the 116 L I have MFC 18 cm fins. I weigh 85 kg and my switch over point between the boards is for 5.5 and down I use the 95 L. Initially took me a while to get used to the skatey off the top, but now I find quad set up too stiff in anything less than cross off.

leto
282 posts
18 Dec 2020 7:23AM
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I run 17.5 cm BP fins. Side fins you see in the pic 9cm almost never hit the water as most of the time it's onshore wind and I use the board as twin. Not sure what spinout you guys are talking about for twins.
I remember I had Mistral Twinzer 84 and now Quatro 95 and never experienced any spinouts. I can stall them if I point too far upwind, yes, but spinout...don't remember a single time. I think that in 84 I ran ether 16 or 17cm MUFs XTwin. I also have no idea why people say you cannot drive twins hard. Also landing is nicer. Single can start sliding if you screw up the landing. Twin holds so much better..
Never used thrusters much.. Either single or twin.


Grantmac
2183 posts
19 Dec 2020 1:58AM
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I generally run 9f/15 or 16 rear. I have some 17 Scorchers but they are quite swept, lots of area at the base though.
Usually if its quite strong I'm stepped down to a board which runs well as a thruster.

leto
282 posts
19 Dec 2020 3:59AM
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Hmm. Another problem with trusters nobody wants to talk about is that you need to screw in 3 fins instead of 2. LOL Often even 4 if you need to switch from a single. Twin, just one pair of fins for all conditions. Set it and forget it ..

roj
QLD, 43 posts
20 Dec 2020 4:17PM
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I have a custom tri-fin and two quad SSD boards. My experience is mostly with quads and twin fins. Including fin positioning, fin sizes, fin style, fin profiles, fin foils (e.g. asymmetrical), fin angles in relation to center line. However, nowhere near the number of fins and amount tweaking some of you do .

Found a number of factors that can be more (or less) important such as:
1. Board size
2. Board shape, especially tail outline, V and kick
3. Conditions such as wind strength, sea state, wave size/type, wind direction and tide/current
4. Weight of rider (I'm a welterweight)
5. Fin tuning and sizing

I love my old tri-fin board. It's probably hard to compare your or manufactures setups as it uses 120mm surf fin side biters that have approx 80/20 foil shape. Surfers reviewing these say that they turn significantly quicker and smoother than flat inside foil ones. I would say this trait holds true overall for this board compared to other boards that I have tried or owned. The feel is closer to my surfboard especially taking off down the wave.

The side fin boxes have 1.2 degrees of toe-in. My relative spacing is closer in relation to the centre fin (52mm) than most I see. Back leading edge roughly aligned with strap back screws. The centre fin is a 155mm (labelled 16 cm) K4 Flex-fin. Which apparently is Graham Ezzy's favourite. This board is faster than my quads and easier to sail in a straight line than my previous twin. Although blasting around is not my priority.

Initially ran my SSD tri-fin with a 7" (17.8 cm) middle G10 fin. Found that too much area or stiff as turns were smooth and tight but not as snappy. A friend really liked it to loosen up his large 105 litre tri-fin board. From memory the side fins he had were quite large and this made it more responsive.

I use the quad boards when conditions dictate as they are bigger and what they where are designed for or came with. When overpowered, in rough conditions and in bigger waves the quad with a few more litres volume is more settled and controllable than my tri-fin. The "mid sized" quad configured as as twin is great in onshore mushy conditions (as long as upwind performance is secondary).

My previous dedicated custom twin was amazing for that, using 15.5 cm Maui Ultra Fins X-twins. These should also work well on quad boards if the size is appropriate. Their fin profile is quite narrow and upright which might be contributing to the tight turns possible. Appears to be a few other riders apart from top sponsored riders that like them. (They unfortunately don't fit on my quad boards without modification and are too big for my weight/them).

Running my smaller quad board with only two rear fins get's me close to the same experience. However, the general board characteristic are another major factor. Removing the side biters is an alternative way of reducing the fin area without sizing down the rears. Recently had a Fanatic Quad with relatively small 8 cm asymmetric sides with 1 degree inbuild toe-in which made it turn better and tighter than the original symmetricals. It had 14.5 cm swept back rears.

Generally I would say twin fin boards require more sailor input and the tail can be pushed loose easily. Have also tried the twin fin with a trailer fin. Even a 8 cm centre fin stiffened it up considerably, but obviously doesn't give it the same feel as a thruster.

At the other end of the spectrum my light wind board is a quad and good for schlogging up wind and early planing. It could be reconfigured as a tri-fin but I have not seen any need to try yet. The middle box has a resined blank so a slight obstacle to route out. Mark Stone recommended to use it as a quad. The tomo-tail shape is very wide and short. Which may suit a quad better than a tri-fin?

I've seen other tri-fin boards that have proportionally bigger sides. More like thruster surfboards. That would be interesting to try. Does anybody here have experience with that setup?


sprayblaze
160 posts
20 Dec 2020 5:34PM
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So whats the bottom line ? Twins=loose. Quads =control. Both could be fast. So tri sound more like the ALL season auto tyre thing-not too good for winter and not too good for summer... Look at the PWA top five-no one rides a tri fin on a regular basis, in the top ten only Traversa, Mussolini and Stone whoose total body weight is less then 200 kilos... This says a lot imho.

RuaraidhK257
70 posts
21 Dec 2020 11:18AM
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sprayblaze said..
So whats the bottom line ? Twins=loose. Quads =control. Both could be fast. So tri sound more like the ALL season auto tyre thing-not too good for winter and not too good for summer... Look at the PWA top five-no one rides a tri fin on a regular basis, in the top ten only Traversa, Mussolini and Stone whoose total body weight is less then 200 kilos... This says a lot imho.


The body weights of the lads on thrusters actually says very little. Musso and Thomas use big floaty boards for their weight (thomas for example is about 60kg and uses a 72 I think as his all rounder) and mid sized thrusters. They also sail with very upright styles and super high old school booms. Their turns tend to be light and skates.

Jaeger on the other hand has an extremely low, powerful style with lots of leg movement and a reasonably low, modern style boom height. He also sails pretty small boards from what I've seen/heard/read, between 65 and 72l and I think he weighs around 65kg. I'm pretty sure that's the case but he is on this forum so he can correct me if I'm wrong haha.

His turns are crazy powerful, using the sail and his legs a lot to generate speed and power. Traversa and Musso use the wave a lot more and tend to flow around a lot more. There are times where Traversa looks a lot more like Jaeger in his style but generally from what I've seen they're very different in their styles.

The point I'm making is board shape, sailing style, kit, kit setup and body shape etc all have massive effects on the way people sail. Victor Fernandez for example used thrusters in all his stubbies (and now his new mamba/stubby hybrid customs) and has a massively different style to musso, traversa and Jaeger. The big diametrical differences are less to do with fin setups. There are definite differences between fin setups but it's more how those setups interact with all the other factors that results in such vastly different styles.

the definite differences have been explained well up above and elsewhere but for the sake of being boring I'll jot down my opinions too:

twins: great fun for crappy conditions where you just want to mess around and get the tail out on a mushy wave. However, there are exceptions: the famous Hooper-designed Nuevo which is a super surfy twin that holds really nicely in good waves and in my experience of it only ever released the fins when you wanted them to.

quads: a similar feel to twins but more versatile. They tend to make boards more sticky and grippy and in my experience work best in everything because they provide a good amount of drive and grip without too much surface area to get stuck when you want to throw them out back. Especially useful for sailors who like to use the rail of the board to turn and/or who want to be able to throw the tail out almost as much as with a twin, without sacrificing as much grip and high end control.


Thrusters - usually fast to plane, piles of drive especially on the bottom turn. I find them to be very on and off - the rear thruster fin is quite long and can get often get stuck in the lip or the whitewater if you don't time your turns perfectly meaning you tend to either get a very good turn or a very ehh turn.

The term "forgiving" gets thrown about a lot too. The tricky thing with that is, what exactly are you trying to get forgiven? If you're a bit lazy getting on the plane, then a thruster will forgive your errors. If you tend to not work as hard as you should to drive into your bottom turns, thrusters will again forgive your errors. If you cheat on the top turn and push hard on the tail to make it slide out, a thruster will forgive you in bigger waves where you need the grip, and stop you sliding down the face on your back so much. But if you struggle with timing on your top turns, the added surface area of the rear fin will be less forgiving and either give you a good turn or a bad one, with little in between

A twin will tend to give you the opposite results. But be careful not to push hard, or they'll slide out.

for me, a quad is a nice in between. A fair bit of grip and drive when you want, but looseness when you don't. I think that's why it's a popular choice for the PWA guys as it's very versatile. A best of both worlds, a jack of all trades. There will however, be overlaps. Some boards are grippier, drivier, faster or more slidey than others. Different waves, different sails, boards, styles and sailors will have different effects. But those are to the best of my knowledge, the basic rules of the different setups.

seabreezer
377 posts
22 Dec 2020 1:17PM
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Maybe fair to say - all up - tri-fins setup is the 'most used' among pro's I would say ... quads close 2nd ... , twins a distant 3rd .... (maybe only Koster the only top adoptor)

Some brands like Tabou have gone down a 'all tri fin' route ... they felt in general ALL their team preferred the tri-fin set-up . Some boards by a quirk of shaping - take NANO 2 (tail kick extreme) , have to be ridden as quad for best performance ... Some guys look super natural on both - like Levi Siver - whereas someone like Marcilio Browne - always looks a bit more 'stilted' on a thruster vs his ridiculous quad antics ie re-writing wavesailing style with 270 degree full blown ninja turns) ...

I had a range of 5 box boards (from same brand) - The rockers (medium curve) - seemed to 'come alive ' with tri fin set-up ... combined with the more rearward strap / fin positioning that tri-fin set-up allows , vs the more fwd straps / quad feel ... (I sailed them quads for 2 years and was perfectly happy - before mixing everything up moving to tri-fin and finding an extra sparkle of performance ..)

Depends alot on the shaping ...

seabreezer
377 posts
22 Dec 2020 1:31PM
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k257 quote - " Thrusters - usually fast to plane, piles of drive especially on the bottom turn. I find them to be very on and off - the rear thruster fin is quite long and can get often get stuck in the lip or the whitewater if you don't time your turns perfectly meaning you tend to either get a very good turn or a very ehh turn."

Or - that bigger rear fin can give you 'drive' out of the whitewater sh1tfest ... 1st time I used my 5 box as tri - couldn't believe the amount of extra drive / speed over a whitewater lip when you hitting a section coming towards you , it would chew up say 4m of high line whitewater lip line floater and get to the face the other side way better / quicker / more assertive than a quad .... And sometimes - that extra fin grip behind the backfoot is vital - like landing an aerial in aerated whitewater , or sailing OUT of stuff like wave360's , where smaller quad rears can slip when applying pressure to get out of the move .. and a tri-fin will 'hold' and give you fraction more grip and get you up and out a split second earlier ...

So depends what your priorities are ...

Tanel
55 posts
22 Dec 2020 5:56PM
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Maybe helpful for someone... I have been using 17.5cm mostly and sometime 18.5cm x-twins in my Ultra Kodes and Pyro 86 & 93 L. And been experimenting with quad in over 45+ knots to slow the board down for more control, still quad feels like dragging an anchor to me. So I just try to rely on my 100kg of weight to hold it down in big winds :)
I put the fins more forward with smaller sails and or cleaner waves, turns sharper. More back with onshore and bigger sails for traction. And 0.5 cm makes a big difference already. Just find the sweet spot for your sail-board-weight combination. For me it's usually 3.0 to 4.2 its in front and 4.7 to 5.5 bit further back. And if it's not good for 5.5 just leave it to the kiters :)
Tail shape seems to make a big difference too, rounded pin tail Kodes got lot of grip compared to really short tailed Pyro.

RuaraidhK257
70 posts
22 Dec 2020 6:11PM
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Select to expand quote
seabreezer said..
k257 quote - " Thrusters - usually fast to plane, piles of drive especially on the bottom turn. I find them to be very on and off - the rear thruster fin is quite long and can get often get stuck in the lip or the whitewater if you don't time your turns perfectly meaning you tend to either get a very good turn or a very ehh turn."

Or - that bigger rear fin can give you 'drive' out of the whitewater sh1tfest ... 1st time I used my 5 box as tri - couldn't believe the amount of extra drive / speed over a whitewater lip when you hitting a section coming towards you , it would chew up say 4m of high line whitewater lip line floater and get to the face the other side way better / quicker / more assertive than a quad .... And sometimes - that extra fin grip behind the backfoot is vital - like landing an aerial in aerated whitewater , or sailing OUT of stuff like wave360's , where smaller quad rears can slip when applying pressure to get out of the move .. and a tri-fin will 'hold' and give you fraction more grip and get you up and out a split second earlier ...

So depends what your priorities are ...


Funny you should say that! I was having that same issue for a while when I was using small super stiff quad fins, now I've moved to .5cm bigger (to make up for the decreased drive you get from flexier fins) fins with a lot more rake and tip flex. These days I can punch through the messiest sections no bother (I'm very partial to floaters haha) and it lets me get away with mistimed aerials too. Like I said, it's all in the little variations

jn1
SA, 2504 posts
23 Dec 2020 10:18PM
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What would be the preference for spots that have lots of sea grass ?

Bouke-Witchcraft
195 posts
26 Dec 2020 4:17AM
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I can see why a guy like Koster likes twin fins as they are easy to break out when doing skaty moves on sloppy waves. Trifins and quads have more grip due to having more fin area on the rail. But most boards have small side fins and thus trifins need to have a big centre fin. Quads have more drag due to having more fins. Trifins or thrusters with three similar sized trifins are at least as loose and grippy. I use for example 3 x 12.5 or 12.5+14cm under an 80L, 13.5+14 under a 90-95L or 14.5+15.5 under an 105L. But when you have bigger side fins, it becomes more important they are set up correctly. The water flow under the board is directed from the centre outward so the further away from the centre, the more toe-in you need. But this effect is the biggest directly under the board and diinishes over the length of the fin. We use 2? toe-in and then the fins have another 2.5? toe-in in the base. The fins then twist back to pretty much zero toe-in at the tip, depending on the size of the fin. This may not seem much but water has a lot of power. We just can?t see it.
You can see the same principle on the wings of wind turbines, propellors or our sails: The angle of attack changes over the length of the foil thus the foil should twist over its length accordingly.

Going down a wave without lateral pressure of the sail, in this situation you do not want any of the fins to give lift to reduce drag and to help initiate the turn:

Image generated by CFD software of a bottom turn:


Image of a bottom turn in reality:


How the camera was mounted:


Also asymmetrical fins need more toe-in as the asymmetry starts to give lift and drag by itself if the angle is not adapted (like the wings on a plane give lift). About 1? for every percentage of asymmetry (also called camber). See images below which give the lift and drag of a 2% asymmetrical foil with zero angle of attack and -2.07? AoA at which point there is zero lift again and the least drag. The induced drag is 1/3rd with 2? extra toe-in (on average you need 2? toe-in for a symmetrical fin.)



We have also adapted our fins to boards with the side fin boxes set up paralel and they visibly became a lot turnier, faster with more grip and drive in the turn.





Does this sound complicated? Yes, there is a LOT more to it then just a centre fin. But this is what it is, it simply is what happens because of physical laws. The same physical laws that allow us to windsurf in the first place and if you want to do it right, there is no way around it. The first planes also flew but we still learned a lot more after that.

SchobiHH
71 posts
26 Dec 2020 6:40PM
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Bouke-Witchcraft said..
I can see why a guy like Koster likes twin fins as they are easy to break out when doing skaty moves on sloppy waves. Trifins and quads have more grip due to having more fin area on the rail. But most boards have small side fins and thus trifins need to have a big centre fin. Quads have more drag due to having more fins. Trifins or thrusters with three similar sized trifins are at least as loose and grippy. I use for example 3 x 12.5 or 12.5+14cm under an 80L, 13.5+14 under a 90-95L or 14.5+15.5 under an 105L. But when you have bigger side fins, it becomes more important they are set up correctly. The water flow under the board is directed from the centre outward so the further away from the centre, the more toe-in you need. But this effect is the biggest directly under the board and diinishes over the length of the fin. We use 2? toe-in and then the fins have another 2.5? toe-in in the base. The fins then twist back to pretty much zero toe-in at the tip, depending on the size of the fin. This may not seem much but water has a lot of power. We just can?t see it.
You can see the same principle on the wings of wind turbines, propellors or our sails: The angle of attack changes over the length of the foil thus the foil should twist over its length accordingly.

Going down a wave without lateral pressure of the sail, in this situation you do not want any of the fins to give lift to reduce drag and to help initiate the turn:

Does this sound complicated? Yes, there is a LOT more to it then just a centre fin. But this is what it is, it simply is what happens because of physical laws. The same physical laws that allow us to windsurf in the first place and if you want to do it right, there is no way around it. The first planes also flew but we still learned a lot more after that.




OMG. So many colour pictures. Do you know what CFD stands for: "colourfull fluid dynamics". That is the quote of a professor for fluid dynamics. I.e. CFD is nice to illustrate behaviours. But never is a proof apart from a real experiment.
That means. The CFD simulations need to be tested against "towing tank" experiments for example. Then you can calibrate the CFD and then the CFD predictions are to some degree meaningfull. I don't see how you could have done a real life test like a towing tank or similar for windsurf boards.

Regarding "that are physical laws". As a physicist with a university degree having discussed the topic with some real experts, i.e. professors, one thing is for sure. The reason why yours and also the the exact opposite approach works is that the effect is neglectable at most minimal. So is just only psychology or even marketing?

AlexF
499 posts
26 Dec 2020 6:57PM
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I always wonder when I read the discussions about toe in why a guy like Keith doesn't use it on his Quatro and Goya shapes.
Seems to be a reason and I'm sure it's not that he's willing to use only the second best solution for his boards.

stonny
NSW, 99 posts
26 Dec 2020 10:06PM
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Can anyone explain to me why quad fin setups are considered slow, draggy and planted on a windsurfer yet super fast and lively on a surfboard ? I have a shed full of waveboards but these days all I ride is my 86 ltr Quatro Cube. It seems to do everything and is the best around waveboard I have ever sailed. And it is super fast, loose, early planing and lively......and it's a quad.
When it comes to surfing however, I prefer thrusters because they feel more predictable but I will admit that my level of wavesailing exceeds my surfing.
Personally I think that what a board can do,and how it behaves, is less to do with the fin setup and more to do with the design of the board it's self. Excepting the probability that certain shapes may be suited to certain fin setups. Certainly true with surfboards. So is there really any point in 5 fin boxes ?
I would be interested to hear what people think.
I hope everyone is having a great Christmas and here's to a windy ( covid free ) new year.

SchobiHH
71 posts
26 Dec 2020 7:42PM
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stonny said..
Can anyone explain to me why quad fin setups are considered slow, draggy and planted on a windsurfer yet super fast and lively on a surfboard ? I have a shed full of waveboards but these days all I ride is my 86 ltr Quatro Cube. It seems to do everything and is the best around waveboard I have ever sailed. And it is super fast, loose, early planing and lively......and it's a quad.
When it comes to surfing however, I prefer thrusters because they feel more predictable but I will admit that my level of wavesailing exceeds my surfing.
Personally I think that what a board can do,and how it behaves, is less to do with the fin setup and more to do with the design of the board it's self. Excepting the probability that certain shapes may be suited to certain fin setups. Certainly true with surfboards. So is there really any point in 5 fin boxes ?
I would be interested to hear what people think.
I hope everyone is having a great Christmas and here's to a windy ( covid free ) new year.


The best is to ignore these discussions about "speed and number of fins". Yes, quads are slower in the straight line, because each additional fin creates an additional drag, but this effect is neglectable for mere mortals and especialy in the waves. The only way to test the difference really would be to go to Luderiz and have a multi fin speed board. But why would anyone do that?
For anything else than waves a single fin setup is still the best, simply because you let a board fly with a single fin, because of the lever it has. And a board that flies is so much nicer in the chop than have a board with multi fins, which planes much lower and catches much more chop. But with this statement there will be surely some people who oppose it and they believe in the opposite. But if you ask experts, i.e. slalom riders they all will tell you the same thing. Nothing beats single fin in bump and jump conditions. But there are so many amateurs out there who believe different. I do not want to stop them.

So why different fin setups in waves? Because in waves it is all about personal style. And all these setups feel different to a certain degree.

BTW I can not talk for surf boards this a different topic.

LeeD
3939 posts
26 Dec 2020 10:23PM
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Stony.
On a wave, the medium is tilted so you release the 2 outer fins... which are farther out on the rails.
In flat water, all 4 fine are engaged.

bubbas
WA, 27 posts
27 Dec 2020 2:44AM
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AlexF said..
I always wonder when I read the discussions about toe in why a guy like Keith doesn't use it on his Quatro and Goya shapes.
Seems to be a reason and I'm sure it's not that he's willing to use only the second best solution for his boards.


I think KTs own boards, as well as the other team tiders boards, have toe in. At least all the quatro custom boards I have seen have some toe in, a little more than 1 degree. Boxes on production boards straight. I dont know why the difference, maybe they dont thrust cobra?

leto
282 posts
27 Dec 2020 3:15AM
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OMG. So many colour pictures. Do you know what CFD stands for: "colourfull fluid dynamics". That is the quote of a professor for fluid dynamics. I.e. CFD is nice to illustrate behaviours. But never is a proof apart from a real experiment.
That means. The CFD simulations need to be tested against "towing tank" experiments for example. Then you can calibrate the CFD and then the CFD predictions are to some degree meaningfull. I don't see how you could have done a real life test like a towing tank or similar for windsurf boards.

Regarding "that are physical laws". As a physicist with a university degree having discussed the topic with some real experts, i.e. professors, one thing is for sure. The reason why yours and also the the exact opposite approach works is that the effect is neglectable at most minimal. So is just only psychology or even marketing?



Love it. :) Classic monkey fin business. - My fin setup is stronger than yours, NO mine is - LOL, NO my fin is better pre-twisted than yours and made from crapstreme- . If you gave me a twin or a single, I wouldn't know a difference for bump jump. Maybe it makes sense to ask Koster NOT why he likes twin but rather why he doesn't care to sail anything else... lol

sprayblaze
160 posts
27 Dec 2020 3:30AM
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I never thought that fin selection is as complicated as brain surgery- who needs that and even if true-so what ? I have tried twins, trusters quads. Not to make things complicated I have picked quads(THE ultimate multifin sensation) imho. Watching Brawzinho and Levi destroying Pozo and Hookipa on production boards -Marcilio on quad and Levi quad/tri is enough said for me, a mere mortal, regarding the evergoing production vs. custom dilemma. Merry X mas to everyone and let this Covid nightmare remain in 2020!

Bouke-Witchcraft
195 posts
27 Dec 2020 3:49AM
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SchobiHH said..

Bouke-Witchcraft said..
I can see why a guy like Koster likes twin fins as they are easy to break out when doing skaty moves on sloppy waves. Trifins and quads have more grip due to having more fin area on the rail. But most boards have small side fins and thus trifins need to have a big centre fin. Quads have more drag due to having more fins. Trifins or thrusters with three similar sized trifins are at least as loose and grippy. I use for example 3 x 12.5 or 12.5+14cm under an 80L, 13.5+14 under a 90-95L or 14.5+15.5 under an 105L. But when you have bigger side fins, it becomes more important they are set up correctly. The water flow under the board is directed from the centre outward so the further away from the centre, the more toe-in you need. But this effect is the biggest directly under the board and diinishes over the length of the fin. We use 2? toe-in and then the fins have another 2.5? toe-in in the base. The fins then twist back to pretty much zero toe-in at the tip, depending on the size of the fin. This may not seem much but water has a lot of power. We just can?t see it.
You can see the same principle on the wings of wind turbines, propellors or our sails: The angle of attack changes over the length of the foil thus the foil should twist over its length accordingly.

Going down a wave without lateral pressure of the sail, in this situation you do not want any of the fins to give lift to reduce drag and to help initiate the turn:

Does this sound complicated? Yes, there is a LOT more to it then just a centre fin. But this is what it is, it simply is what happens because of physical laws. The same physical laws that allow us to windsurf in the first place and if you want to do it right, there is no way around it. The first planes also flew but we still learned a lot more after that.





OMG. So many colour pictures. Do you know what CFD stands for: "colourfull fluid dynamics". That is the quote of a professor for fluid dynamics. I.e. CFD is nice to illustrate behaviours. But never is a proof apart from a real experiment.
That means. The CFD simulations need to be tested against "towing tank" experiments for example. Then you can calibrate the CFD and then the CFD predictions are to some degree meaningfull. I don't see how you could have done a real life test like a towing tank or similar for windsurf boards.

Regarding "that are physical laws". As a physicist with a university degree having discussed the topic with some real experts, i.e. professors, one thing is for sure. The reason why yours and also the the exact opposite approach works is that the effect is neglectable at most minimal. So is just only psychology or even marketing?


Well first of all, in spite of what your professor says, CFD nowadays is ahead of towing tank testing, which is far from the real full size stuff out at sea and as a result, test results are not reliable. Nowadays you can set the sea state, wave heighth and length and period, even various through eachother, like you can have out at sea. The guy who did this CFD research for me in 2015 got a super high grade for his work and he now runs a naval architecture design agency in France with 25 engineers and experts under him, pretty clever guy. And I know quite a few more experts in this field, students on internships and their professors, former interns plus a few of my customers have high positions in marine research institutes. Nowadays, many things are developed even just using CFD including wind turbines and airplanes. Simply as it is more accurate.
As for practice testing, in 2005 I had a few boards with the 4wfs, which allows you to turn the fins within a minute. Within a day testing in clean light wind conditions we figured out that about 2? toe-in was not only turning better, it was also faster.
Then, there are those who have gone from one day using paralel fins to my pre-twisted fins the day after. "Amazing" is what the last one said, I can give you his phone nr if you want.

But is it that hard to understand what happens under a board? When you were a kid, didn?t you jump in puddles and the water would fly everywhere? Now if you would let a board float in a pool and you would land vertically on it? All the same thing, the water wants to escape the pressure we apply on it, just when we are planing, there is a big forward component in the movement but there still is a sidewards component as well. And anyone can imagine that if you are 1m under water the water is not pushed away anymore. When in 2007 I had a board in the test of Boards magazine, I explained their head tester Ian Leonard why a board needs toe-in, he figured out right away that fins would actually needed to be twisted as well. He promised me to keep it to himself.

Then if you are a fan boy of this or that shaper since many years, I can understand that it may be hard to realise you were wrong and for some people this may lead going into denial even if the facts are staring right at them. For sure there is a name in psychology for this phenomenon. From your forum name I figure you are a german from Hamburg? I just had a long time customer from Hamburg in today picking up his new flex tail. And we were chatting about all the fin designs I had over the years and he said the first red and black pre twisted fins in 2010 were big leap forward, these RTM fins were just fragile when hitting bottom.
This was a prototype flex tail with those fins. This one had adjustable flex through airpressure but it was too hard to keep the airchambers sealed. Some ideas are good in theory but it should also be practically doable and durable.









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"Thrusters not liked?" started by philn