View Full Version : iSonic 105 Fin Suggestion for lightweight sailor

11th September 2006, 09:52 AM
Ian (or anyone in the know),

I have an iSonic 105, which I love. I am still figuring board tuning out. During the Spring, I found the board was pretty hard to control for a lightweight like me when using a 5.5 in choppy conditions. I was using the stock 34cm fin supplied with the board. When I used my 7.7 v8 with this board, I would put the 40cm fin on it. When overpowered, I found the board hard to control.

This summer, I tried the 34cm fin with the 7.7. It was a perfect match. What a difference!! I was totally in control even when overpowered.

So... with my smaller fins, what would you suggest I do for fins? I have a 5.5, 6.0 & 6.6 I use with this board. Should I look at getting a 31cm or would a 30 & 32cm quiver be better for these three sails? Should I go smaller for the 5.5?

Suggestions, please?


Ian Fox
11th September 2006, 01:34 PM
Hi o2bnme,

Definitely a lightweight sailor on overpowered 7.7V8 (pretty grunty sail as well) will be overfinned on iS105 with the 40cm option. Even at a svelte +/- 200lbs I'm already on 34cm in iS101 powered (or windier+) 7.6m conditions.

Basically, use the big (40cm) option for marginal to light 7.7m, or lighter wind/bigger sail(8+m) conditions, where it will work well, but once the action starts get onto the 34 asap for higher top speed ..and better control. (Note : if you're struggling with spinout on 34/7.7m V8) then it's likely the sail tune in those conditions (add more down/out haul and/or variable outhaul) and/or the chop is hindering your boardspeed, so go for a bit more speed bearing off or across the wind before you start to pinch up hard.

So to the fast stuff : yes , definitely a good fast 32cm is an asset in fast 6 or 5,5m conditions ; 32 will work well even in well powered 6.6 conditions and you can get away with 30 (lighter rider) in 5.5.
Going smaller than 30 is a bit marginal except in pure speed (flat water and high board speed) conditions as the iS105 needs a certain amount of fin to help maintain a flat trim across the tail.

Yes, a one fin "31" option will work well too, but with the usual provisos that not all fins size "performance" wise in proportion to their mechanical "cm" size,
(brand/model X 34 = performance size of brand/model Y 32 etc)
so when you're accurately selecting alternate fin/s, try and be sure to compare "performance" size rather than just mechanical size.

Selection of make/brand (etc) is usually influenced significantly by what is available at a practical level in your location (or accessible in practical way by phone/web/mail etc).

For a hi speed small fin to push the limits, it's good advice to make sure whatever you end up with, make sure it's a good one :)

Cheers ~ Ian

11th September 2006, 06:34 PM
Thanks Ian. Great detail. I'll try to find a 32cm fin to start with and if I still find I need something smaller for the 5.5 days, I'll go and get a 30cm.

Any suggestions on fin selection for me? I really like the 34cm fin that came with the board. Other than that, I don't think I have experience with small, fast fins.

Ian Fox
12th September 2006, 06:43 AM
Hi o2bnme,

The shorter versions of the Drake Pro (30, 32cm) should be available in USA via dealer order from Trident Sports without too much trouble.

Other options will be influenced by what is available (readily) locally at your location. GSport.com in HoodRiver have the SR6b, which is a good fast fin family ~ but it's a different nature to the DrakePro - and maybe not as ideal for lighter riders in your conditions once conditions start getting rough and the rider/board/fin start getting thrown around.

Sidebar : [it could be that a slightly more freeride fin- rather than pure race- could be an ideal compromise for a lighter guy struggling for fun/control in maxed out choppy iS conditions. There is serious technical merit for this, as super hi speed fins have fine foils, which don't develop real lift until they are moving really fast through the water, and usually in a narrow (controlled) angle of attack range. In rough, choppy and bouncy conditions, the actual board speed may feel fast but not be that quick, plus your fin's angle of attack will be all over the place (as the board is flying all over) - and the world's fastest fin won't be the best fin for those fast "4WD" conditions. Here something slightly "slower" (but with more "grip" earlier in the speed range, and a more relaxed foil [+angle of attack] will often be a better choice, and potentially even "faster" for sport riders in those control conditions. (eg; Drake FreerideFlow (new 2007) or GSPORT : Freeride) ]

I'd really recommend trying to borrow (or test) some smaller fins in your conditions before you buy; hopefully you can get hold of one or two options in the 30-32cm TT freeride/slalom size (not too rare !) - at least this gives you a real world benchmark ( for you, in your conditions) before you lay your $ down.

Cheers ~ Ian.

12th September 2006, 08:24 AM
Thanks Ian. I can't even find the Drake website anymore. Did it go away? Also, what is the Trident link? I found one that has a 2002 Starboard image on it and doesn't list anything about Drake.

The 34 Slalom Pro is a great fin for me. I really like how it sticks to the water. I think I'll go on a limb and order the 32. But for anything smaller, I think I'll take you up on the idea of going more freeride.

Ian Fox
12th September 2006, 11:21 AM
Hi o2bnme


Trident Performance Sports USA LTD.
Ph : 604 929 9626
Fax : 604 929 4955
Email : info@tridentsports.com
(but they will supply via retailer)

Cheers ~ Ian

Erik Loots
16th September 2006, 11:40 PM

I use on isonic 105:

7.5 with 40-34
6.9 with 34
6.3 with 32-28

the 28 is a bit smal and only works in really hard wind. All fins are drake slalom pro. I weight 80kg.

18th September 2006, 06:47 PM
Thanks Erik. If you are 80kg, I must be a feather weight. ;-) I'll keep those numbers in mind. I would love to find a friend with a full quiver of fins for me to try out. But I know that won't happen.

Erik Loots
20th September 2006, 12:47 AM
you know if you are really overpowerd and do not have control. Than the easiest solution is take a smaller fin. Maybe some more leech in your sails.

So you do not have 1 fin @ 1 sail option.

I have now 1 board and use it fom 12-35 knots I can hold it because I can tune my board down with the fins.
I have drake sl pro 28,30,32,34,38,40
The drake fins are not very popular in holland so cheap thats why I use them. I am just waiting for a cheap 36 fin...

I have few examples:

Is105 + 6.3 in 18kn wind vs 25kn wind is drake slalom pro 32 vs 28
Choppy versus flat water with 20kn is 32 vs 30

I can not tell what fin will be the best, it just depends on circumstances, weight, etc. The standard fins do their job good if you want more... than you need more fins to ride your board as high as possible in any circumstance.

If you want the fastest& best fin for SB.. I would go for Deboichet SL2 & Deb upwind.

21st September 2006, 09:45 AM
Well, I ordered a fin... I contacted Trident Sports and they said they didn't have many fins left. They didn't have any of the size I was after. So, I went looking for the Deb S2/S1 fins... Sailworks sells them. In talking to them, they directed me to the Techtonics. So, I took their recommendation. I ordered a Goldwing 30cm. Hopefully I'll get a chance to use it soon... now I just need some 5.5 or 6.0 conditions.

21st September 2006, 11:56 PM
Hi o2bnme,

I have a number of Tectonics Goldwing fins (34,36 and 38) and I find that they are awesome performers. In my opinion, they are really first class slalom fins, and their price is still within reason. The Sailworks folks gave you a great recommendation. I doubt the you will be disappointed. Please let us know what you think once you get some good days under your belt.

21st September 2006, 11:56 PM
Hi o2bnme,

I have a number of Tectonics Goldwing fins (34,36 and 38) and I find that they are awesome performers. In my opinion, they are really first class slalom fins, and their price is still within reason. The Sailworks folks gave you a great recommendation. I doubt the you will be disappointed. Please let us know what you think once you get some good days under your belt.

22nd September 2006, 01:03 AM
SteveC. You bet. I got the fin today. This was my first experience with a fin that does NOT have the brass inserts. I called Sailworks to tell them I received a fin that never finished production. ;-) Jim explained to me how they work. Ha

Anyway. The fin looks top notch. I'll share more after I get on the water.

26th September 2006, 12:53 AM
Well, there were too many weeds at Hatters for me to use the new 30cm fin. So, I went out with my weed fin. It worked very well for the conditions. I'll report back when the wind picks up this Fall for lake sailing with a 30cm fin. ;)