View Full Version : F-type 138 VS Isonic133

27th October 2006, 06:43 PM

I own a F-type 138 2005 for the moment.

Sail it most of the time with 8.5 and 9.5. with the 52 Stock fin.
I am 67kg and 180cm.

It is very early planing board ,very simple to ride upwind+++

But when I want to go downwind it is like there is a break on the board when I reach the 48Km/h.

I own also a Isonic 105 and sailed it also with the 8.5 but it is hard to get it upwind.

Would a Isonic133 be faster than the FT138?
What about fast planning and upwind?

The Isonic145 is the almost the same as the Ftype138 I think?

I like to replace my FT138 but I have my doubts.


27th October 2006, 11:50 PM
Hi Danny L,
Where do you have your mast foot positioned on the FT138?
48 Km/h is 26 knots, and that's not really very fast for off the wind on the FT 138.If you get the mast foot back until the board is almost "tailwaking" I think your speeds (on all points of sail) will improve significantly.
At 80 cm wide, the Isonic 133 would be faster for sure, but again, you must tune the board for the best speed and this usually means having the mast foot a little further back than the middle of the track for a light weight sailor such as yourself.
As far as getting upwind on the Isonic 105, again mast foot tuning, fin size (are you using the smaller or the larger fin?) and technique are all factors.
I'm now sailing the Isonic 101 and find it goes upwind very well "on the fin", but I'm not trying to sail it with anything as big as an 8.5 m2 rig. That's a little "too big" in my opinion. I've sailed it with a 7.5 m2 Retro and 6.6 m2/5.6 m2/and 4.8m2 Huckers, and with these sails it's a little rocket ship, getting upwind (once you get the board up to a speed where the fin starts to work) is no problem at all.
When you are planing fast, on the Isonic 105, check to see where the spray is coming out from under the board.
Most of the white spray should be coming out from under the upwind front footstrap or behind. You should see not appreciable "spray" to leeward and the lee rail should be in pretty much "green" water.
If you don't get the Isonic 105 "up on the fin" it won't be very fast, and you won't get the good lift (upwind) from your fin.
At your weight, if going fast is what you like to do, and giving up a little bit of early planing isn't a problem, upgrading your FT-138 to the Isonic 133 would seem a step in the right direction.
Hope this helps,

28th October 2006, 02:12 AM
Thanks Roger for the advice,
I read a lots of exlanations from you and I am in the right direction.
I have expearenced with the mast foot position on the FT and the Is
I surfed the Isonic only with a 8.5 and yes it fiels a little big,it works but not ideal ,this is not my intention for the board,but when you get a new board you want to sail it,most of the time it was 12 to max 15 knots and I bought it for +15 knots.

It is just the downwind speed on my FT,when I push it the same way than the Isonics suddenly it is wanting to fly, it just comes out of the water,loosing control,when I try to run it flat (Mast position middle)there is a break that comes on,I was thinking that the fin was to big.

But my board is 2 years know and is ready to be sold.

Is there a big difference between the Ftype138 and the Is133 ?

Do I loose much in planning treshold?
Would I win in Max speed?
The surfing style on the Isonic133 ,can it compare to same turbo foot on the FT138?

For me it is the Is133 or the 145.

Can the Is133 handle Severne C2 9.5 without problems or do I need a bigger fin?

thanks alot,
Ps:Starboard support is the best.

28th October 2006, 06:03 AM
Hi Danny,
I don't havean Isonic 133 in my demo fleet, so I can't answer your question on the 9.5 m2 rig, but it would seem like it would be alot better than the 8.5 m2 on the Isonic 105.
Yes, I think you will loose a little on the early planing end if you move from 88 cm wide to 80 cm wide, but you are fairly light so unless you sail on freshwater all the time, I think you could probably overcome this with technique.
But I'm puzzled.
Maybe you rig quite differently than I do, but a 7.5 works pretty well for me in a sloid 12 knots, and I weigh about 10 kg.more than you do.
Do you have another sail in the 7.0-8.0 m2 range that you could try on the Isonic 105? Maybe rig it pretty "fat" and use an adjustable outhaul to "slim it out" once you get planing.
In a solid 15 knots, I'm normally on the 6.6 m2 Hucker on the Isonic 101 or the Isonic 115 I had last year.
As far as getting more top speed from the FT-138, yes, I've used fins down in the 50 cm range (Deboichet Concept 50) with a 6.5 m2 rig and the board simply flew. It does sound like you are tailwalking on too much fin here. Also, when I got max. speed on the FT-138 I had the mast foot all the way back and the 50 cm fin on very flat water in around 18-20 knots on a 6.6 m2 race sail.
Yes, the Isonic 133 should be definitely faster than the FT-138.
Hope this helps,