View Full Version : fins for 2008 isonic 111 and 133

5th February 2008, 05:31 AM
Could you help me to choose right Deboichet fins for my 2008 isonic's
I will get soon the 111 that I intend to use with NP RSRacing 6,2; 7,2 and 8,4 and 133 for 8,4 and Gaastra Vapor 10,0
My weight is 88kg and I'm 185cm tall
I usually sail in choppy conditions and downwind slalom
could you recommend me the right model and length for each set

Ian Fox
5th February 2008, 05:43 PM
Hi Rafal,

In Deboichet, most iSonic riders prefer the overall efficiency of the classic SL2.
SL 3 has been working well in choppy downwind slalom for extra control.

For your size/sails/conditions, typical fin sizing would be :

iS111 / RS 6.2 SL2 34cm
iS111 / RS 7.2 SL2 36/38cm
iS111 / RS 8.4 SL2 42cm

iS133 / RS 8.4 SL2 44/46cm
iS133 / Vap 10.0 SL2 50-52cm

Sizing here assumes slight emphasis to speed/downwind slalom, and in all cases can be +/- 1-2cm depending on many variables -or simply building a most fin (cost) effective quiver.
Obviously if you're really well powered on the 10.0 you would be able to go smaller on that fin, but in most cases simply getting/staying planing is why a sail this big would be used on iS133, in which case the optimum fin needs to be bigger to offset the large sail.

Cheers ~ Ian

6th February 2008, 12:31 AM

Thanks for the info above. I have a new is111, weight 80kg and am a pretty good sailor. Better at formula than slalom.

My questions -

The standard fins that come with the is111 (44cm and 38cm) are a bit larger than your above recommendations. I understand that down wind slalom doesn't need large fins and my use of the is111 will likely be 95% free sailing and 5% slalom racing. I like the challenge of the race board.

My experience so far on 8 outings - I am very aware of how to avoid spin out, but the smaller 38cm fin seems quite prone to spinning out & is very sensative to rear foot pressure . Especially in the beginning half of a jibe in small chop. Spinning out in the middle of a jibe is not fun. I usually sail in a protected area where 20 knots of wind creates 12" chop, close together. Fin? Technique? Suggestions?

I have other similar sized boards with smaller fins than 38cm, but they are not nearly as sensative to spin out as the is111

I much prefer the 44cm fin up to 20 knots (6.5 or 7.5 sail).

Obviously, I am doing some upwind work as well as a little down wind so the only advantage of the smaller fin is increased speed and control if it is really windy.

Would the SL2's improve the spin out? I am not compelled to purchase custom fins for free sailing, but I might if the control and spin out can be improved.

Thanks for your advice.

6th February 2008, 02:38 AM
Thanks for your fast answer

In my home spot I get parity choppy conditions when I am on 6,2 that why I fought of taking the SL3 for IS111 and 6,2. Should I take the same size as your recommendation for SL2 or a larger due to a different shape of the fin?
And what do you think of the choice of ST3 in this case?
I read somewhere that SL4 fins are being prepared for the new season. Did you have a chance to try it and what do you think about it?

6th February 2008, 03:13 AM
Hi Rafal,

...for your size/sails/conditions, typical fin sizing (for 2008 iSonic) would be :

iS111 / RS 6.2 SL2 34cm
iS111 / RS 7.2 SL2 36/38cm
iS111 / RS 8.4 SL2 42cm

iS133 / RS 8.4 SL2 44/46cm
iS133 / Vap 10.0 SL2 50-52cm


Hi Ian,

thank you for your always analytic replies.

...but might you be so kind to refer above correspondence table to "old" 2007 iS111 and iS133 ?


6th February 2008, 04:14 AM
Ill chip in with two more fin question for iS 111 2007. I will use the board with 7.6 and 7.0 TR-3.
- In Deb case I guess SL2 38, would be right?
- How does Tectonics Goldwing work with 111 and which size would be right for above mentioned sails?

Ian Fox
6th February 2008, 04:29 AM
For Ken : Are you only experiencing the spinout mid jibe ? Obviously with a wider tailed board (like iS) there is more potential to spinout or slide the (wider) tail mid jibe at load/speed than say a similar sized freeride with narrower tail and/or even less fin. Generally the 2008 stock fins are quite OK, we use them a lot in testing and if they have too many vices it's pretty obvious :) Technique might also be a contributing factor, for the best results you really need to set up well on entry with back hand (and then rig) raked back but NOT opening the rig on entry and then keep a lot of drive(preessure) on thru the mast foot mid jibe. Even on the (wider) 122 it's possible to pull some rather insane jibes (for 120Lt pure slalom ) without having to "overfin" (for the conditions) the board to achieve it.
* Yes, the above recommendations are downwind slalom specific - which tends to run higher speed and less fin than typical, Fig 8 or upwind. In super light wind (and to some extent very high wind) you won't reduce the fin size too much for iS but in the critical mid range you would not want to be on too much fin for downwind.

For Rafal : Yes, for sure, the SL3 is definitely an option for increased control in the higher winds / choppy water (and so the small fin/s of your quiver). For SL3 you can use basically the same size as SL2 (SL3 is basically as SL2 with raked tip section and slightly more area but slightly less efficency ). SL4 is a promising new design with less lift (but more control in flighty conditions) than the SL2 or SL3, in general for iS you would use slightly more fin with SL4 than SL2/3. Most riders find the iSonics tune up best in pure performance with slightly more fin power than "average" - that's to say taking advantage of a little extra power/lift, but of course this makes for a more highly loaded ride; fast but maybe not so easy on the ride in rough/choppy conditions.

For Expander : for the older (slightly narrower) 2007 iS111/133 you would use similar fins but with a slight emphasis on the -1 to -2cm end of the tolerance. That's to say, the same or a little less will be ideal ; 2008 iS in these sizes can take just a little "more" fin for a given range than 2007 and still be OK/ideal. It's not normally a full size up, to keep it in perspective though (and the difference is les than say those caused by rider weight/style , water conditions and course upwind/downwind etc) .

Cheers ~ Ian

6th February 2008, 05:12 AM

Thanks for your quick responses. I am not looking for jibing lessons and I know my technique can be improved upon.

With the 38cm fin, the spin outs occur occasionally on the jibes and if I am heading up a bit into the chop.

I am working on my "lay down" jibes (sail raked back and sheeted in),keeping the pressure on boom/mast, knees bent adsorbing the bumps. When I spin out, it occurs just before the midpoint of the jibe, shortly after I sink the rail and begin carving. The fin spins out towards the center of the radius, which turns the board away from the direction I want to go.

Your point about the wider tails must be the issue, since I now recall a few spinouts on my formula boards mid jibe. Rare, but it has happened.

Practice makes perfect so I will stick with it.


Ian Fox
6th February 2008, 07:21 AM
For Lars : to be as accurate as possible for fin size recommendation/s needs some (even aprox) reference to rider weight, especially when considering highly "geared" or leveraged setups like iS at max performance. Assuming "typical" sport rider weight around 80 kg and good experience /race tuning etc, then TR-3 7.6m with SL2 38 would be dream, but a little on the large size for TR-3 7.0m unless underpowered 7.0m.
Think more in the range SL2 36cm or even 34cm if fully/over powered on 7.0m.

Tectonics Goldwing : A classic slalom fin if ever one existed, but not so ideal in new school short wide slaloms in "larger" slalom sizes. Goldwings (with a fine and narrow tip) also tend to (performance) size a little smaller than some other more powerful fins of the same mechanical (measured) size. I'm not sure what the absolute biggest GoldWing size is, but I wouldn't think much above 34cm as being all that effective. If you are thinking Tectonics in the 36+ size range for iS a more suitable model is their F8 Tomcat, but even that (as with most G10 based fins) starts to become a little soft for super hard (hi powered ) sailing on sizes above 42-44cm (where the structural properties of molded carbon fin starts to take over as a better design option to G10 which is reaching the limit of its strength [flex/twist] to thickness ratio).

For Ken - I wasn't ripping into your jibe technique, rather just drilling down into the factors that could be contributing to (what seemed like) a rather unusual scenario from your side. Certainly not what most guys would consider "spinout" in a typical sense. But wet is wet, and looking to avoid that, while not deflecting blame away from the fin, the specialised nature of getting the best from "wide tailed" slalom boards definitely benefits from a slight modification or tweak in technique away from the more conventional freeride carve jibe (which many have an advanced technique on, but sometimes find anomoly when they overlay that directly onto boards like HS/iS and similar wide tail/vertical fast foiled fin boards sailed with hi power to size ratio). Losing the fin/board to the INside of the turn mid jibe is certainly an unusual one, and almost certainly caused by major disturbance over the flow on the fin, which in most (not all) cases would be a setup/entry issue, which of course only shows itself when you weight into the turn to find the fin lift has gone.. I would definitely look at the way you are setting up your entry/rig depower, and also maybe moderately accentuate a rear bias in the jibe rather than setting up to carve forward along the fuller waterline length as you would on a more traditional or freeride design.

Other than obvious fin issues, check the fin is firm in the box and/or no structural issue between the actual blade and basing material..

Cheers ~ Ian

6th February 2008, 05:13 PM

I sail a HS111 with 6.7 RS racing in say 15-25 knots quite regularly (although lately, now that my new F93 has arrived, not a puff!) with a 34cm drake slalom fin. A wee while ago I managed to spin it out mid gybe, trying to do fast alpha's. Alpha's here in OZ land are GPS timed runs including a gybe, lots of fun. Infact, as I found out, very challenging when trying to push a wide arsed board around traveling at 30 knts. So having spun it out once, I tried it again on purpose, actually isnt bad fun, when you know its coming.

In 20+ knots of wind, in chop, to sucessfully gybe a small slalom board we lean our weight as far forward as possible and really bury the whol rail of the board. The board then slices through it all and we emerge out the other side.

Now try doing that with a wide arse board, sure the rail will bury, with even more foot pressure and commitment, but due to the width, the fin will be high and dry. Once you achieve this level, then you have a spinout mid gybe.

So, I discovered 2 options:

1. Bank the board only a little bit. This works well, however the arc will most likely just fit inside a small football stadium. This is ok if you like going back upwind.

2. Contrary to small board gybing technique, bury the rail of the back half of the board and keep the nose up. This will keep the fin in the water.

Heres some footage of me gybing, slow it down throughout, and you will see even at the very beginning of the gybe, just how much board comes out of the water.


Hope this helps

7th February 2008, 01:45 AM
Thanks Ian,
Im 1,87, about 90 kg and doing some national comps. I did suspect that two fins would be the way to go. If I go for 38 and 34, at least I would be able to use 34 on my iS87 for 7.0 as well I guess. You mean F8-Tomcat, right?

7th February 2008, 03:33 AM
Maximus & Ian,

Thanks again for the help. I think a good part of my problem is the short choppy waves at my favorite sailing spot. As I metioned before, in 20 knots of wind we have 20 to 30 cm chop, spaced about a meter to a meter and a half apart. Air gets under the board quite easily with the bouncing, which increases the chances for cavitation and spin out.

Placing more weight to the tail of the board makes some sense, which should help keep the fin in the water. It doesn't seem like it, but I may be carving too tight in the middle of my jibe.

Thanks again,

7th February 2008, 03:58 PM
If you are thinking Tectonics in the 36+ size range for iS a more suitable model is their F8 Falcon
Not really...................

Tomcat in 38+ size between SL1 & SL2, you can take 48 without any problem
Falcon from 22 to 36, it work's like SL3 => Forget for iSonic
GW from 26 to 38, between SL2 & SL3 => Good on Sonic, increase downwind capacity for iSonic but big lost upwind

Ian Fox
7th February 2008, 05:24 PM
Hi Lars,

Yes, F8-Tomcat was definitely what was intended, "F8-Falcon" was a typo and obviously refers to the smaller small raked/slalom speed fin in sizes below 36cm.
Thank you Papounet for the graphic presentation.

Sure you can buy a Tomcat in 48cm, but most powerful riders in power mode on wide tail boards will find a G10 pretty soft at 48cm, and maybe not as ideal as a good carbon molded fin in that size..

Cheers ~ Ian

7th February 2008, 05:50 PM
I've used my new Tomcat 42 and 40 on my '07 111 with respectively 7,8 and 6,8in wind 12-13 and 16-26 and I'm pretty stocked.I was scared that in marginal wind I wouldn't be competitive but I've found that it worked.Please note that I can't comment how it would have been with sl2.When stronger and rough the soft touch of G10 could help to push better the board.
Still waiting to test some new Falcon on smaller board (not Starboard).

7th February 2008, 08:42 PM
G, i don't think you need as Big Fin's on iSonic for thoose sails....
For my 9X Kg, on my "Old" iSonic 125 :
8.4 => Tomcat 42 ( 44 should be better in marginal winds )
7.4 => Fin's Tracer 37, work's anyway