View Full Version : Isonic
31st May 2007, 08:40 PM
Hi Roger !
I am having a difficult time with my 115 and light wind stuff. Even though I am able to plane, I am only able to do it by going downwind. It feels like I am not getting enough resistance from my fin ( specially at low speeds ). But I am not sure if it has to do with the fin or technique.
Could you please give me some tips to plane earlier and going upwind in light winds on my I-115 ?
So far I found that lowering the boom ( few cm below the mid point of the cut; I am 173 cm ) helps to go upwind in marginal winds; although I am not sure if this is logical or not ( cause I am putting more weight on the board )
Where should I place the mast track ? ( now 3/4 forward )
And straps ? Now I am using them all the way back; is this ok ?
And finally, would a flatter sail profile help in this case ? or a deep profile is better to create more power ?
Thanks in advance !
31st May 2007, 10:02 PM
What size sail are you using?
What fin are you using in these conditions?
What is the wind speed?
Are you feeling fully powered up with that sail as you have it rigged? Does it feel heavy and sluggish or light and slippery?
With my 105, I find I am happiest when my sail is completely powered up. I find that if I pick a sail that's perfect for the wind conditions and can tune it such that it is light and slippery I have enough sail to power the fin and get up on a plane.
I start by bearing off the wind, pumping a couple of times to get on a plane and then I start to head upwind. If the fin is truly powered up, you should have no problem heading up.
When I don't have enough sail to power my fin, I experience what you are descrdibing.
As for mast track placement, on my 105, even with my 8.0, I always start with the track all the way back, and only move it forward if absolutely necessary. I would suggest starting with it back and shifting it forward 1 or 2 cm at a time to feel the difference. Be sure to test on the same direction/angle to wind in order to be sure you are comparing apples to apples. My guess is that the track position is affecting your decision on where to put your boom. Start with the boom comfortably higher ... I like it at my chin in lighter winds on my 105.
Good luck in your tuning. Once you have it set, you will plane sooner than others and float through lulls much better than your fellow sailors.
31st May 2007, 10:55 PM
thanks for your reply !
well, maybe I am pushing the limits of the board.
I normally use it with a V8 8.0 mts / 42 cm drake fin
And feel this lack of power when the wind is below a solid 13 knots.
Above that, no problem, but below that windspeed + currents, I am able to plane, but only downwind.
I dont know if it has to do with the supplied fin, since I read the curtis-drake needs to be at full speed to go upwind ( http://www.star-board.com/forum/viewthread.php?forum_id=6&thread_id=22615&pid=149868#post_149868 ).
Maybe with a different fin ( deboichet-drake ? ) or a bigger one ( 44 or 46 ) but everyone I asked told me that 46 is not the answer.
1st June 2007, 01:06 AM
Hi Daniel B.
Your 8.0 m2 V* should not be a problem.
The mast foot 3/4 forward could be a problem.
I always ran my mast foot on the Is 115 somewhere between the middle and the back.
What is your weight.
O2bnme weighs < 150 lbs. and I'm about 175 Lbs..
I sailed the Isonic 115 with an 8.5 m2 Retro and 8.5 NX4 alot, and I had no problems planing early or getting upwind once I got the board to plane.
Could be some technique issues here.
Can you describe what you are doing to get your board to head upwind (once you've dropped pretty far off the wind to get the board to lite up and plane)?
In marginal conditioons, less downhaul and outhaul (to give your sail as much draft as possible) wopuld seem better. An adjustable outhaul system is just made for this situation.
Fatten the foil to get going, then flatten it out to get better speed, less drag, and better upwiind angle.
To go upwind well, you need to really get the board lit up, then begin to lift with your front foot and push across the top of the board with your back foot.
Rail the board slightly lee rail down.
Hope this helps,
1st June 2007, 03:04 AM
To answer your questions:
I weigh 73 kgs, I dont know the convrsion into lbs, but I am the AVG guy in terms of weight.
I tried different things. Put weight on my back foot, to reduce the wetted surface; to move the weight forward, in a more classic technique, to close the gap and stay away form the rig, to stay more upright gettin more power frrom the sail, to give more outhaul to reduce the drag, to reduce outhaul in order to get more power, to rail the board ( in formula style ), etc.
I am using the sail with an outhaul kit.
Mast Track: I always feel more confortable with the mast base forward. Maybe this allows me to rise my boom. I normally feel that having a boom too high, doesnt allow me to go upwind well. I normally feel that the best place to put the boom is at the point I am able to maximize the distance between me and the boom ( this allows me to pump more efficiently ). If I put the boom higher, my arms are pointing upwards, and I am reduceing the distance.with the rig. If I move the base backwards, I experiment the same problems as lowering the boom.
Normally I need to go really fast to go upwind, and to go really fast I need to be power up to “free” the board.
That is my set up, although I now it differs with the “raise your boom” technique. Even with Formula equipment I found this set up to be the best one.
1st June 2007, 07:55 AM
Hi Daniel B.
Hmmmm... mixing "formula tuning" with Isonic slalom tuning may not be working.
73 Kg. is 160.9 lbs., so you are somewhere between O2bnme and my weight.
It sounds like you are trying to put weight on the back of your board through your back foot and a more upright stance.
Even if you have to pull the rig over a little upwind (so that it supports your weight better) you need to "push across the top of the board (i.e.
sideways, downwind, across the top of the water) rather than trying to "push down toward the surface of the water.
The rig, supporting your entire weight, frees up the back of the board.
As far as mast foot postion, formula boards are much wider and have a significantly different rockerline from the iS-115.
You need to head further off the wind to get the board to lite up and plane, then you can begin to pressure the fin.
Bigger fins will simply increase the drag and slow you down, preventing the board from planing freely.
As I suggested previously, perhaps some technique (or a better name would be "getting used to the board) may be causing your issues.
Hope this helps,
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