This weekend, I had a chance to use my new 2014 Is90 in sustained winds of 35kts+ gusting to 45kts. I was using a 2014 North WARP 5.2, and tried 3 fins: Vector Rockit carbon 32cm, Select Caspar Speed 29cm and Drake R2R 32cm DW slalom. Water conditions initially were pretty flat, as the wind changed direction became choppy with short 30 to 45cm chop

The Is90 is like no board I have ever sailed, the impression it gives is that there is no top speed…. Unfortunately there is also no way to stop it accelerating either, which makes it extremely scary and creates control issues. Most of the time, this unlimited speed is great, however in very high winds or choppy water the lack of adjustability is an issue. The second feature is the directional stability – I have rarely sailed a board less responsive to foot pressure (Think Fanatic Jag or f2 Sputnik 270) – the tiny wetted area and narrow tail are to blame, so it is important to select a fin with lots of rake to give back a little more control – however, that locked in feeling is awesome once you get used to it. This is a board for experts who sail at 100% all of the time, it is an absolute no compromise racing machine which requires a lot of time to tune and to learn how to sail well.

From my original outing on this board, I knew that it was really fin sensitive. Sailing in pretty extreme conditions, the need to have the correct fin became even more apparent. I started on the Vector 32cm – this is an old favourite and suited the Is87 perfectly, however, on the Is90 it was pretty much unsailable! My first 2 runs, on a beam reach on flat water both resulted in embarrassing catapults, I was well powered up, but certainly not overpowered. The issue seems to be the speed of the board and narrow tail, which makes it difficult to control the fin, this causes tail walking, and also makes the board turn downwind and accelerate even more; I found it really hard to bring the board back upwind. Sheeting out results in even more tail walking and causes the nose to lift always resulting in a catapult.

Next out I tried the Caspar Speed 29cm, this is a very upright rigid fin with a very narrow cord. This was certainly a massive improvement on the Vector, and I didn’t feel that the board was trying to kill me. The tail walking issue went away and you could push the board to very high speeds, unfortunately the wind had shifted and there was no flat water, so I didn’t manage to set a representative speed, but a vmax of 33kts seemed good in the conditions. The problem with this fin was the lack of upwind performance, and spin out on a beam reach, also gybing was unpleasant, as the board would spin out trying to enter the gybe.

Next I borrowed a Drake R2R DW slalom 32cm. This fin was significantly more raked back than the Vector (the tip of the fin around 4cm further back when laid side by side) it is also thinner in the top 30% of the fin and has a narrower cord at the base. This was the best of the 3 fins, although I felt that it was still a touch big in the choppy conditions – I would love to have tried a 30cm as well. The Drake didn’t cause much problem with tail walking, and caused no problem in the gybes, but I did find that it was really working my ankles to keep the board under control, I feel that a smaller fin may also help to make the board more maneuverable and select a more adjustable line in the chop

An interesting comparison between my old 2012 Is87 and new Is90. The old Isonic 87 was a wonderful board when conditions got tricky; it seemed to float above the chop and was so adjustable that you could steer your way through. The 87 was also a board that you could manage your speed if required. The downside was that it was not particularly quick, it was also difficult to carry speed through the gybe unless well powered up. The Is90 is undoubtedly the quicker board, in the right hands much faster, able to carry a bigger sail, better speed through the gybe, however this comes at the expense of sailability

I know that a few people here have been using the Is90 for the past season. Has anyone tried with a 30cm fin? would a 28cm work? Remi is advising to use smaller fins than I used on my Is87 (due to very narrow tail), however, specs printed on the board suggest about 2cm bigger fin for a given sail (I always felt the the Is87 specs advised too small a fin)

Is the Is90 OK as a smallest board? what size sail do you use as the smallest sail?

The iS90 as you have mentioned is an incredible board and rides quite differently to earlier models and even its peers in bigger sizes. Its off the wind performance is incredible but pushing it hard upwind takes some time to get used to say in comparison to the more paralleled railed earlier models. I sail mine in the ocean and use a 33cm Lockwood slalom2 carbon which gives me ample drive upwind but is slippery going broad.
Recently I got to use it at Burrum heads in flat water and threw an older KA Lockwood 30cm g10 in it with a 7.0m (I didn't use my Cl sl2 because I've ruined too many fins here before and am somewhat precious of it). I was probably a bit ambitious using the smaller fin as I didn't have much drive pushing it hard upwind although it felt fine going broad.
The following day the wind was a bit lighter and I tried a 31select Casper speed which felt okay but again had no joy pointing. I ended up changing up to the iS107 and 7.8 making life easier.
I was chatting to Vando who has an iS90 whilst we were both sanding our damaged fins on the bank and he mentioned he uses a 32 Vector g10 (not sure of model) with most sail combos.

Sorry I am typing this on my phone and just lost a heap of text. Short of the long is rreally powered up I reckon a 30 will work but 32/33 in marginal conditions would be better

I haven't tried one yet but knowing how good a fin designer cChris Lockwood is maybe a tribal 32 slalom could be a suitable choice or even the more raked slalom weeds I saw a few guys using at burrum.

Smallest sail used with the iS90 was a 5.5 in pretty ballistic ocean conditions and it felt great although IMO its sweet spot is a fully powered up 6.3. The 7.0 is pretty perfect too. Never thrown the 7.8 on it yet but might give it a go one day.

Btw I'm around 1.8m & about 90kgs.

Thanks for the really quick response Sausage. I hear some really good things about the CL fins - In the UK James Dinsmore (British Slalom Champion) uses them in his Is90.

I bought a set 36, 34 and 32cm Drake R2R DW fins - they were second hand and cheap, initial impressions are good, they certainly suit the character of the board - I may swap them out for Sonntag fins (which I use in bigger sizes) or CL fins at a later point, but will test a few first

I was out sailing with Ross Williams (PWA sailor), he was able to point better on his Taboo.... although this may have something to do with the relative level of skill. However, I felt that it sailed pretty well upwind with a 32cm, I don't remember any spin out issues. but with the 29cm Caspar Speed it would not point at all

When sailing broad, I found it really difficult to bring the board back up wind without sheeting out. I recon I was really pushing the comfort zone of this board (at least I know that it will handle a powered up 5.2m). The very narrow tail certainly makes it handle very differently to Isonics of the past

Yesterday I collected my 2015 Is107 - conditions are looking good on Friday (public holiday in UK), Looking like 7.0 or 7.8 day, so will spend time on both Is90 and Is107

the r2r dw stick to recommended sizes, other fins go a size smaller & probably a size smaller than that again with cl fin. I personally use select s09's... 33cm/7m, 31cm/6.3m, 29cm/5.6m, they probably arent ideal fins for it as if i go bigger & run straps all way back it can induce a little bit of a speedboard roll until it settles on main part of rail, but the above sizes have more than enough grip. Im also used to using quite stiff fins & a little bit more shrek dimensions than I would like.

5.2 pretty small for that board, I wouldnt consider using below 5.6, 6.3 I find to be sweet spot which ive used in 30 knots messy chop. I do think the '14 90 takes a little longer to dial but you can get it to happy skim just on tail & float board over the chop, feels awesome when it does. To do what you asking probably run straps right to front, I dont like putting mast foot too much forward of recommended as it put a little too much rocker in the water.

It's not an upwind board, it's kinda like those old 265/270 pure downwind shapes. It'll point fine but washes off chunks of speed doing so, but it trades that upwind for all the offwind speed & acceleration you'd ever want. If you want a med wind figure 8 board go the iso97, if highwind fig 8, downwind & speed then the 90 is great. The 90 is very thoroughbred shape, the 80/87 is more user friendly & straps more inboard.

The 107 is another awesome board ('14, I imagine the '15 is more of the same), if you want to match guys closer to the wind that board will do it, ive noticed little speed difference between broad to beam reach, if that is way chop lining up to go fast dont worry bout bare off just let it do it's thing.

If you are having control issues with the 2015 i90 in strong winds try out a very soft raked fin like a Techtronics Falcon or Vector EX.

The fin twists off hugely dumping the lift. They do feel a bit different to sail though.

On my 2011 90 litre Sonic the 36 EX fin worked fantastic in strong winds.

I did not need to sail upwind in the gusts.

You do need to use a bigger size due to their softness,rake and low area.

My 36 EX is very,very soft but the 34 EX is much stiffer and I had more control with the bigger size in strong winds. Less feel of spin out too with the bigger size.

This proves a really soft fin has its advantages if the conditions are strong.

I once tried the 36EX in my i87 but it felt too big but in the 2011 i90 it was perfect.

If you are a using Lockwood fins--- perhaps try a 30 or 31 size.

The 38 Lockwood fin in the 107 felt very draggy but the 36 felt the opposite,quite slippery.

Going a little smaller in size with these fins can make a big difference!

Thanks for all the excellent advice. I think that it will be very rare to use the Is90 with a 5.2 very often - I will mainly use it with 6.3 and 7.0m and occasionally with 5.7 and 5.2.

For my Is107, I will be using Sonntag SL-P, I have a 40cm and 43cm that I used in the my Is110 - the 43 will be too big for the Is107, but I will probably invest in a 37cm or 38cm. The SL-P has a very soft tip, I find that it is powerful, but the flex means that it remains very controllable

For the Is90, I will continue with the Drake DW R2R fins. I makes sense to use same model of fins in different sizes for one board because a 32cm from one brand will be like a 34 from another brand

I like the idea that the CL fins can be used in smaller sizes than comparable fins - to me this makes a lot of sense, also more convenient as the longer the fin, the more likely to hit something

Hi Matt, I used the 34cm Drake DW fin a lot with 6.2/ Isonic 2014 90 last year. This fin worked very well with this combo, upwind, across and downwind. 7.0 you will go with the 36cm DW. With the 5.2 the 32cm DW is the smallest you want to go in those fins. Anything smaller you wont get the drive you need from the fin. The 6.2 is definitely the best size for the 90.

I had the 2014 iSonic 90 last year and mainly used it with my Reflex 6.2 and 34cm Venom. Awesome combination, very fast and controllable.

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AUS02 said..
I had the 2014 iSonic 90 last year and mainly used it with my Reflex 6.2 and 34cm Venom. Awesome combination, very fast and controllable.

That is great to know, I think that the Drake R2R DW fins are very similar to the Venom. I have a 34cm to use with my 6.3, which I think will be the best sail, board, fin combination.

I have been in contact with Remi Vila from Starboard; he recommends using quite small fins in the Is90 - 28-30cm for 5.2, 30-32cm for 5.7, 34cm for 6.3 and 36cm for 7.0. I have now found a 30cm which I will use for high winds with my 5.2