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Dyno 95 fin options

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Created by Sea Lotus 28 days ago, 20 Aug 2019
Sea Lotus
27 posts
20 Aug 2019 11:30PM
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Hi,

I had been using my Dyno 95 and Blade 4.7 for a while, using a Blackproject Kraken 28cm fsw single fin at the beginning. But I had been spinning out frequently when i land from a chop or when i try to go upwind, olso i feel it is a little difficult to go upwind. I am still trying to adapt my stance to weight my front foot but can't do it on gusts or over heavy chop. Severne recommendation is a f320 (32cm freeride) fin, but i was told to chose 26cm or 28cm if i want to be extra safe by black project.

I am an intermediate sailor and i am not having any spinouts with fox 105 (standard f360 fin) and 6.5 gator and i can go upwind easily.
I was wondering if my fin is not suitable, or my technique is not there yet for fsw boards.

I never tried the standard thruster fins before because i was told multi fins are for waves and single fin is better for freeride bump and jump. There are no waves to ride here, just open Mediterranean sea waves and chop.

Frustrated of spinouts i tried the supplied thruster fins (20/12,5) for several sessions with 5.5 and 4.7 sails. Board was harder to get into plane and speed was olso lower, but the ride become much softer and controllable over chop or at gusts, it almost felt like wind dropped 5kts, no more spinouts just occasional small slides if i push hard on back foot, easier to get upwind as well but still harder than fox 105. I wish i tried it earlier.
Comfort and control is more important for me at harsh conditions so i plan to use this setup but i am still not sure if using a better single fin will make it even better.
Any advice on this subject?

Another thing i was wondering is sometimes i hear a noise from fins, same noise if some weed is stuck on fin, slows me down, but when i jump in and check, no weed. Is it possible to hear that noise if one of the fins have air bubble and rest doesn't so i can keep the direction?

Cheers

Yves
WA, 128 posts
21 Aug 2019 7:07AM
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For info, I remember reading the fin placement is a bit too far back on this board and can be the cause to spinouts.
Maybe try with more powerful fins (more chord at the base thicker etc).

Basher
95 posts
21 Aug 2019 7:37AM
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Woah. I have this board and it's really good. The fin box is in the right place and having a fin box too far back would not make you spinout.

Bad stance makes you spin out. Period.

Spinnout is when you overload the back foot and you can cure this in two ways.
One is to reduce rig load on the back foot and you do that by reducing rig load on your back hand, by shifting the harness lines back on the boom.
The second is by sailing in a more upright stance and you do that by 1) shifting the front footstraps forwards - and I use my front straps on the hole setting nearest the front. 2) Try shifting the mast foot back a bit. Both those changes make you stand over the board more, with less weight on the back foot.

The only time we see the fin as a problem in causing spinnout is if you use too small a fin for the sail size you are using. Bigger sails, with their longer booms, apply greater sideways load on the tail of the board.
But in this case if you are using a 4.7 rig then a 28cms fin is already way too big. So it's your stance that's the problem here. If you try to go fast in 4.7 weather with a big fin then the board will probably start to tail walk, especially in choppy conditions where you also get tail bounce.
When jumping, try and lean forwards on the landing, so that you don't just weight the board tail sideways.

Indeed, if it's 4.7 weather then why not use the tri fin set up as supplied with the Dyno? As you say, that's a 20cms centre fin and two 12.5cms thruster fins, which should be perfect.
Mine goes upwind really well with that set up. What you lose in light winds with a tri fin is a little bit of early planing which is always a tiny bit better with single fin boards. Try and use a bit of pumping and popping technique to get the board up and onto the plane, and the key with the Dyno is to get your front foot in the strap as soon as possible because the board planes best on its rear section.

The 32cms single fin recommended by Severne is really for blasting when you want to use the board in lighter winds with a 6m or 6.5 rig.
For single fin use with a 4.7 rig, you should maybe use a 25cms fin.


The Dyno 95 is my favourite board!

Yves
WA, 128 posts
21 Aug 2019 6:27PM
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There you go. I found where I read it. Just need to figure out a suitable fin.
"The fin style has to be quite upright as the box is so far back in the board - too much rake and the board spins-out at will."
www.windsurf.co.uk/test/severne-dyno-95l-2018-test-review/

To poster above:
Yes, a fin box too far back promotes cavitation. But your board is perfect, no worries.

Relapse
VIC, 303 posts
21 Aug 2019 10:17PM
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Select to expand quote
Sea Lotus said..
Hi,

I had been using my Dyno 95 and Blade 4.7 for a while, using a Blackproject Kraken 28cm fsw single fin at the beginning. But I had been spinning out frequently when i land from a chop or when i try to go upwind, olso i feel it is a little difficult to go upwind. I am still trying to adapt my stance to weight my front foot but can't do it on gusts or over heavy chop. Severne recommendation is a f320 (32cm freeride) fin, but i was told to chose 26cm or 28cm if i want to be extra safe by black project.

I am an intermediate sailor and i am not having any spinouts with fox 105 (standard f360 fin) and 6.5 gator and i can go upwind easily.
I was wondering if my fin is not suitable, or my technique is not there yet for fsw boards.

I never tried the standard thruster fins before because i was told multi fins are for waves and single fin is better for freeride bump and jump. There are no waves to ride here, just open Mediterranean sea waves and chop.

Frustrated of spinouts i tried the supplied thruster fins (20/12,5) for several sessions with 5.5 and 4.7 sails. Board was harder to get into plane and speed was olso lower, but the ride become much softer and controllable over chop or at gusts, it almost felt like wind dropped 5kts, no more spinouts just occasional small slides if i push hard on back foot, easier to get upwind as well but still harder than fox 105. I wish i tried it earlier.
Comfort and control is more important for me at harsh conditions so i plan to use this setup but i am still not sure if using a better single fin will make it even better.
Any advice on this subject?

Another thing i was wondering is sometimes i hear a noise from fins, same noise if some weed is stuck on fin, slows me down, but when i jump in and check, no weed. Is it possible to hear that noise if one of the fins have air bubble and rest doesn't so i can keep the direction?

Cheers

Give the standard thruster a go Sea Lotus, they work great. Will take you a couple of sessions to get use to if you are coming from a single fin but worth the effort. I tried my Dyno 95 with a couple of single fins, even re-moulded a G10 21cm so it sat more forward to reduce spin out but always came back to the stock setup. Couple of guys here run Maui Ultra Fins mauiultrafins.com/fins/wave-fins/x-wave/ but I reckon stock fins are just as fast and point higher.

Basher
95 posts
21 Aug 2019 8:48PM
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Well that's interesting, Yves. Thanks for the link.
You have to wonder what fin they first put in there to reach that conclusion.
And by the way, I'm a former test editor for that same magazine.

I haven't had any such issues but then I've not yet put a big rig on my 95, and using an upright slalom fin for blasting is good advice anyway.
An upright fin should be faster, and help with upwind work.

As far as 'cavitation' goes, I think you'll find there are plenty of boards that have their box equally near the tail of the board.
For sure, if you add thrusters and use a board as a tri fin then you effectively move the total fin area further forwards.

However in this case, using a relatively big single fin for a 4.7 rig and then spinning out is most probably about stance.
If the sailor is lightweight then too much lift from the 28cms fin could also be encouraging spinout.

As it happens, with my own Dyno 95 I have reduced the fin area significantly from that supplied with the board, and that has extended the board use down to 4.4 rigs or even smaller - sail sizes I never expected to use with this board when I bought it.
I did find it started to tail walk in 4m weather but reducing the centre fin to 17cms stopped that and now I'm OK in 4m weather as long as the water isn't too choppy. In tri fin mode, the 17cms plus the 12.5cms thrusters are also fine with bigger rigs up to 5.3m although heavier sailors might find that set up a bit loose.
For single fin use with a 5.3 I go 22cms or 24cms with some upright freestyle fins that I have (Choco Starfish). With a 6m I'd probably go 28cms and maybe a 30cms for a 6.5 rig.

Sea Lotus
27 posts
21 Aug 2019 11:17PM
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Relapse, yes I tried them and prefer them at the moment. They are great, very comfy and forgiving but they feel a little slow.

Yves, i got a pm from someone who use the same board and he olso suggested to use a fin with less rake and olso to chose one which is further forward in slot box, he recommended Tribal Kruze, which really is at front of the slot box. He said he is using 34cm Kruze and it is very good.

Basher, those tips to move harness lines back was great, i will try that, thanks. But i am 63-65kg 165cm guy and my legs are extra short, so i have problem with wide stance. Rear straps are forward and front straps are middle position, still my stance is too wide for me and i am not so comfortable when wind is not strong enough. Olso i am used to 32" lines, which gets my butt slapped by waves occasionally, so i will get 30" lines later to encourage a more upright stance (I can't sail with 28").
I don't remember tail walking before spinouts, it happened on chop (bad landings), when i was really fast on gusts (lean too much back and major pressure on back foot) or when i tried to go high upwind (that time my stance feels correct, board is stable, which made me think fin is not suitable)

I see there are different opinions on fin sizes, 22cm to 34cm. 34cm was probably for 6.0-6.5m sail but I use these sizes with fox 105, i plan to use standard thruster fins for 4.7 (?) and single fin for 5.5 weather, so i plan to get something a little more forgiving than my current 28cm fsw fin (not too much rake btw), at least as a middle step to improve my skill, thinking about 30cm or 32cm Kruze for now.

Basher
95 posts
22 Aug 2019 1:24AM
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I'm pretty short too, but use a wide spacing on the straps as this is better for wave riding.
When I got the board I was surprised at two things,, one that I couldn't set the front straps as forward as I would like, and two that the mast track seemed a bit far forwards for wave sails.

Those two things are actually the same when it comes to stance, because to get upright you need the font foot nearer the mast foot.
I find that I sail the Dyno with the deck plate right at the back of the track, and to do that you need a single bolt deck plate - not a chinook double bolt one.
Taller people will of course have a greater stride, and can set the straps well apart, and then the centre mast track position might be better.
The front half of the track should only be used for bigger sails - like for blasting with a 6.5. That old-school stance would involve more mast rake and would load up the tail of the board more, possibly as another cause of spinout.

People also find they want to use the front half of the mast track when they are using too long a fin.

I looked up your Blackproject fin online and it does indeed look a bit too raked back to be used with this board as a single fin. The Dyno should be used with wave fins if set up as a tri fin, but better to use an upright slalom fin or onshore freeride fin when in single fin mode.

The other thing to say is that someone your weight should not be using big fins.

snorkel692
QLD, 247 posts
22 Aug 2019 5:45PM
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Agree with the upright fin for free ride and stock fins ( or similar shape) in thruster mode. I like the fin and mast track placement but imagine a raked fin would have its centre of pressure too far back ( if that's the right term).

Sea Lotus
27 posts
29 Aug 2019 4:37PM
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A little out of topic but didn't want to pollute with too many topics;
How much poke from board surface is acceptable for fins?

For example picture below, fin is tilted back so rear part is 0,5mm inside and front is 1mm outside. I guess the reason is, metal bolt is loose and moving front and back on its track, so the fin is tilting back and forth no matter how much I tighten it. Any way to fix that?
My other boards fin is fully outside 1mm rear and front, i tried sanding it for an hour but didn't change much.




Basher
95 posts
29 Aug 2019 8:56PM
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Sea Lotus,
I'm being dumb here, but do you mean the thruster fins (slot box) or the centre fin (Powerbox)?

This makes a big difference to the answer given. I don't understand your reference to a moving bolt in a track - unless this is a US box?

If the Powerbox is a bad fit then this usually means sanding the fin head sides to get a snug fit, but check first for lumps of paint or resin inside the box itself.

When slot box fins come loose it's usually because they have hit something and then a dent appears in the fin head recesses. But moving the fin back or forwards slightly usually means the screw can locate on a better bit of the head recesses.

Sea Lotus
27 posts
29 Aug 2019 9:29PM
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Sorry, my bad, i am kind of a newbie and not clear with terms yet, i meant powerbox, the bigger center fin in the middle. Slot box fins are flush with surface, i keep them in middle settings, don't know how to trim so guessing middle would be ok for starters.

I haven't tried tightening the screw which is connected to the powerbox bolt track (i guess, don't know what its for).

Basher
95 posts
29 Aug 2019 10:00PM
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If this is on a Dyno board then the centre fin is a powerbox. There is no track, just a bolt hole, located on the board deck. The bolt screws into the round 'nut' which is recessed in the fin head. Screw this bolt to hand-tight.

The fin has a wedge-style head that matches the box cavity in the board and the single bolt pulls the fin into place so that it is a firm fit, as if part of the board, and with no movement or play.

If the inside of the box on a new board has a drip of resin or splash of paint then that can mean the fin head and box don't match up well. The other thing that can happen is the fin head itself was painted by an over-enthusiastic worker, leaving an extra thickness of paint or resin.

When you put the fin in place it normally beds down under moderate bolt tension. If the fin is not flush at the bottom of the box then check for resin runs first - and sand off any you find.
Normally the wear marks on the fin head show you where the problem is.

Maybe borrow another powerbox fin to try out - just to see if that doesn't fit properly either.

If you don't feel confident about doing this then ask another windsurfer to take a look.

philn
257 posts
29 Aug 2019 11:11PM
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If fin bolt is too long and you hit the bottom of the nut before the fin is tight in the box, add another rubber washer. My Dyno powerbox fin bolt came with a metal washer and a rubber washer. Make sure your fin bolt has both washers.

Sea Lotus
27 posts
30 Aug 2019 4:41PM
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Thanks for the info guys, really appreciate them.

I checked for resin and wear on fin and on the carbon layer on fin box, couldn't see any, fin had no damage and I never hit it to anywhere.
Tried to fit my fox 105 fin (with its bolt) and it wasn't moving back and forth and it was nearly flush, although its bolt was slightly longer than dynos bolt.
Yes, i was using it with both metal and plastic washer. Checked bottom of the nut if there was any sand gathered, it was clear. I added my other fins metal washer and that solved it, its perfect flush now, thanks again Phill :)

So moving on to slot box fins, could you give some info what difference it makes to move those small fins forwards or backwards?

PS: Sorry for many questions but i think its always better to get the info before experimenting by myself. And there are literally no windsurfers where i live (Bursa/Turkey), so I can't ask any locals :( Thats why i am loving this forum :)

Cheers

P.C_simpson
WA, 1392 posts
30 Aug 2019 5:43PM
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Not sure if this has been said, the fin base should be flush with the board, this will definitely be aiding in spin out as it will be causing cavitation around the base of the fin, also make the board feel draggy.

You can fit the fin better but will have to be sanded in the correct spots, in the sides and front and rear of the fin base.

The screw sounds to long, add more washers or get a shorter screw.

windsurftom
NSW, 256 posts
31 Aug 2019 5:08PM
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Select to expand quote
Basher said..
... The fin box is in the right place and having a fin box too far back would not make you spinout.

Bad stance makes you spin out. Period.



This is not true. Period

Subsonic
WA, 1760 posts
31 Aug 2019 3:19PM
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Select to expand quote
windsurftom said..

Basher said..
... The fin box is in the right place and having a fin box too far back would not make you spinout.

Bad stance makes you spin out. Period.




This is not true. Period


I agree.

Theres a number of things that can cause spinout, bad stance isn't one of them.

Basher
95 posts
31 Aug 2019 7:49PM
Thumbs Up

Select to expand quote
Basher said..
Woah. I have this board and it's really good. The fin box is in the right place and having a fin box too far back would not make you spinout.

Bad stance makes you spin out. Period.

Spinnout is when you overload the back foot and you can cure this in two ways.
One is to reduce rig load on the back foot and you do that by reducing rig load on your back hand, by shifting the harness lines back on the boom.
The second is by sailing in a more upright stance and you do that by 1) shifting the front footstraps forwards - and I use my front straps on the hole setting nearest the front. 2) Try shifting the mast foot back a bit. Both those changes make you stand over the board more, with less weight on the back foot.

The only time we see the fin as a problem in causing spinnout is if you use too small a fin for the sail size you are using. Bigger sails, with their longer booms, apply greater sideways load on the tail of the board.
But in this case if you are using a 4.7 rig then a 28cms fin is already way too big. So it's your stance that's the problem here. If you try to go fast in 4.7 weather with a big fin then the board will probably start to tail walk, especially in choppy conditions where you also get tail bounce.
When jumping, try and lean forwards on the landing, so that you don't just weight the board tail sideways.

Indeed, if it's 4.7 weather then why not use the tri fin set up as supplied with the Dyno? As you say, that's a 20cms centre fin and two 12.5cms thruster fins, which should be perfect.
Mine goes upwind really well with that set up. What you lose in light winds with a tri fin is a little bit of early planing which is always a tiny bit better with single fin boards. Try and use a bit of pumping and popping technique to get the board up and onto the plane, and the key with the Dyno is to get your front foot in the strap as soon as possible because the board planes best on its rear section.

The 32cms single fin recommended by Severne is really for blasting when you want to use the board in lighter winds with a 6m or 6.5 rig.
For single fin use with a 4.7 rig, you should maybe use a 25cms fin.


The Dyno 95 is my favourite board!






Haha, I'm just quoting myself now, so that the shorter quote people are challenging, above, is put back with the important context.

I stand by what I explained in great detail, and there's plenty of stuff to try there.

The point of writing all that was to question what a lot of people will tell you, namely that when you spin out, the fin is to blame.

I do accept that there are good and bad fins, and there are fatter fins which will take greater sideways load before they spin out. A fatter fin tends to give better lift at low speeds but can be slow at full planing speed.

You can also have the single fin fitted in an unhelpful place in the board and, as was pointed out after I wrote the above, you can have the trailing edge of a fin set too close to the tail of your board.
Water conditions can also make a difference, with choppy conditions often inviting a fin to spin out sooner or more readily than when you use the same fin on flat water.

But spinout is usually caused by you overloading the fin in relation to the lift it's producing, and your first remedy for this is to reduce load on the back foot, via the stance adjustments I've listed.
Many people learning make the mistake of trying to solve their spinout problems by fitting a bigger fin - which can spoil other performance issues for your board.
It's also good to learn how rig load is transferred to the front or back foot and, over time, this is as important as learning to gybe well.
Bad stance is the number one cause of spinout, and one definition of a 'bad' stance is where the rig power is overloading the sideways load on the board tail via the back foot.

The other thing to mention here is ventilation - often wrongly described as cavitation. This is where the lift from the fin breaks down because air has been sucked in to the deflected flow of water over the fin.
That can be caused by the board bouncing over chop, or by a bit of seaweed. In this case the cause of the spinout is not your board stance, because it's the fin lift that broke down, but good stance and good rig settings will help you to immediately correct it.



The specific issue here is that the Severne Dyno comes supplied as a tri fin, but can be used as a single fin which changes the style of board remarkably from a wave board to a freeride or blasting one. The single fin is not supplied so you need to take time to find one that works in this setting with the sail size you want to use.
In removing the thruster fins you inevitably shift the fin area backwards and, with the centre fin fitted via a powerbox, you can't move this fin forwards to rebalance the board for single fin use.
The chopper tail of the Dyno makes the box relatively close to the tail and, after several conversations with others who have tried using the board as a single fin, it does seem that an upright single fin is the way to go, rather than a swept-back freeride fin. The problem with any board where the tailing edge of the fin can be sit too near the tail is that invites the ventilation issues described above.



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"Dyno 95 fin options" started by Sea Lotus