Please help. I'm foiling a JP 135 with NP Al foil. As I'm quite crap at this stage I'm having trouble assessing how changes in mast base position are affecting trim and performance. Can anyone point me in the right direction. In case it matters, I'm 174 tall and 70kg. I almost always sail without the washer in the rear stabiliser

Generalization..back, you get up sooner..forward, keeps board in water longer. Of course, more or less wind has equal or bigger effect.

Hi Nelle, I'm very similar dimensions - 175 & 70kg. I've got a Naish hover 122. I take it your reference is in relation to the foil mast? I've found it sets best for me in the forward position to get the foil up and going earlier (but that's me - could be different for more advanced sailors). I've also found that when it's in the back position, gybing is almost impossible. The board doesn't feel as settled, and it feel like it wants to nose-dive a lot mid gybe. But that could be my poor technique too.
Ive got the rear foil wing set to flat or very slightly negative to help with control (when it's positive it will tend to get up and fly easier, but it's less predictable).
I tried foiling with the mast in the back position for a few sessions to get used to it (seems more manouverable). Then tried it in the forward setting to feel the difference (feel slightly less manouverable but a little more predictable). My preference is still forwards.

Hi Nelle, I have the same setup as you and still in early stages of learning. I set my mast base at the 125cm marking based largely on the NP foil thread on SB and haven't moved it from there. I find that as long as there's enough breeze I can get going and more focused on body/rig position once going. I do put the washer under front position for lift (again, have havent tried any other way).
In marginal conditions I've been trying to work on pumping technique, but not with a great deal of success (some people make it look easy).
Where I sail isn't ideal with swell and chop, but that's part of the fun .
A video from the other day...

I think Mort is on the money Nelle. I also have the JP 135 but it's modified and I run a different foil and big sails for racing so my settings don't really apply but I always run it between 124 and 126cm, that zone is the sweet spot. As an aside, the further back you put the mast base the twitchier the foil will seem.

As Mort does, I would run the washer under the front of the rear stab for more lift, this will actually make the foil more stable in pitch. Once you are used to dealing with the lift you won't want it any other way. It's counter intuitive at first because on a normal slalom setup you load up the rear leg hard, you don't do that on a foil, or at least you shouldn't once it's trimmed right. Having a more even weight distribution between feet enables easier fine control over the foil.

I reckon, mast base at 125, foil stab set for max lift, rear straps all the way back, send it.

I run the same settings! Washer between the front screw of the stabiliser (more lift), straps out and back (so they can go further back), and mastbase at 123 (the furthest back in the track i feel comfortable with)-125cm. With this trim it is still very back footed, but doable, and very jibable as long as you go downwind before the jibe and enter it with maximum speed (more speed shifts the power forward and stabilises the foil, making jibing easier).

Agreed I have same board with RSX foil, 85kg operator and run between 124 - 126cm depending on wind. Most of the time though have it at 125cm

Thank you all. More experiments to be done. Can't believe how much fun it is

I have also found that placing my rear foot in the strap prior to getting up to speed, then "launching" up on to the foil as front foot goes into strap has helped to stabilise and control the early stage of flight. At first I was trying to control with only front foot in strap, with less success. Good luck .

PS. 84kg and I'm using a 7m Cheetah in marginal winds.

Select to expand quote

Mort67 said..
I have also found that placing my rear foot in the strap prior to getting up to speed, then "launching" up on to the foil as front foot goes into strap has helped to stabilise and control the early stage of flight. At first I was trying to control with only front foot in strap, with less success. Good luck .

PS. 84kg and I'm using a 7m Cheetah in marginal winds.

My nastiest crash on my second go was when I did that. The foil reared up just as I was moving my front foot. It rolled over and I came down on the rail ... almost crushed nuts.

From Cluffy's other thread, some relevant info from WhiteofHeart who appears to know what he's talking about ....

"I have used the pryde foil quite a lot, nice foil, fast, but not optimal for lightwind. The front wing is small (about half my wing literally), and the power is pretty far back. The further your power is forward the earlier you fly. In light wind I'd put the base as far back as possible with this foil. I used it with a JP135 and the base was at around 123cm for light wind, with the straps all the way back and a washer under the stab for more lift."

Edit.. I just realised WoH hadreplied above Doh!