You definitely want front foot pressure otherwise you'll have stability problems and gybing problems too. But too much is no good either and shimming for less stabilizer angle (but not neutral) will create more even pressure across different speed ranges.

Someone brought up mast angle relative to the board and this is important too with mismatched gear. Except I'd say you want to shim the mast for a more rearward angle in your case. That will make it easier to apply front foot pressure. The opposite is also true of course as I found when foiling on a board with the foil box set in a significant tail rocker which made be need my front knee bent and back locked out (VERY uncomfortable and unstable position). Shimming the mast to be just rearward of vertical relative to the top of the board completely changed the feel for the better.

Hey Tony another tip to play with - tilting the board to windward definitely helps pin the nose and control ride height as power & speed build - I think that is why so many dedicated foil boards, especially race designs, have such a square nose to maximise the pressure - even the moderate tilt I can achieve makes a real difference, lean out and push heels down to get wind effects across the board - and as usual it's harder to get it working consistently in gusty conditions

Thanks Pete, and thanks for the call today mate. Was good to catch up.

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Peter Hands said..
Hey Tony another tip to play with - tilting the board to windward definitely helps pin the nose and control ride height as power & speed build - I think that is why so many dedicated foil boards, especially race designs, have such a square nose to maximise the pressure - even the moderate tilt I can achieve makes a real difference, lean out and push heels down to get wind effects across the board - and as usual it's harder to get it working consistently in gusty conditions

That's because of the way the cosine graph sits at zero degrees. Lift is proportional to the cos of the lean. Aim to cruise with a bit of lean to windward and you get in the slopey part of the curve. Cranking a little more lean to windward can immediately knock off a useful amount of lift. If you start upright, at zero degrees, it takes quite a few degrees before anything happens.

wow it's official, my chances of an Engineering career are nil! thanks Ian I sort of sort of get it....

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Ian K said..That's because of the way the cosine graph sits at zero degrees. Lift is proportional to the cos of the lean. Aim to cruise with a bit of lean to windward and you get in the slopey part of the curve. Cranking a little more lean to windward can immediately knock off a useful amount of lift. If you start upright, at zero degrees, it takes quite a few degrees before anything happens.

Interesting point. Another way of looking at this is that the lift of the foil is constant for a given speed, and perpendicular to the foil. By tilting the foil to windward, the lift is split into a vertical (up) and horizontal (windward) direction.

That explains nicely why adjusting to gusts by increasing the foil angle works much better if the foil is already tilted. But it does not explain why placing the feet outside can create a more locked, stable feeling, even if the wind is steady. For this, Peter's theory about the wind effects makes more sense - with the board tilted windwards, the wind exerts a pretty constant force on the board. On the other hand, if the board is flat, then small changes in the board angle can cause a change from pressure on the board to the wind lifting the board (when the windward edge is up a bit). For this part, the cosine curve above does not apply directly, since the board acts as a wind foil.

To tilt the board to windward, you need to have the feet further outside, and/or have pressure on the heels instead of the entire foot, or the toes. That creates more distance between the "force attachment points" (mast attachments at the center line and feet). I wonder how much this helps with stability - think tricycle vs. unicycle, or the pole a rope walker uses.

Whilst I do not possess a conditioned mathematical mind, I do have a 90 wide board and patience that will hopefully see me get some tilt happening. Thanks to all of those who have commented. Cheers!

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Tony Wills said..
Whilst I do not possess a conditioned mathematical mind, I do have a 90 wide board and patience that will hopefully see me get some tilt happening. Thanks to all of those who have commented. Cheers!

I'd consider trying a foil dedicated board, Tony. (you have all the other pieces of the puzzle) In my experience, slalom boards are far from optimal for use with high aspect foils. You can get away with it when using the Naish but these foils are a different beast.

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boardsurfr said..
That explains nicely why adjusting to gusts by increasing the foil angle works much better if the foil is already tilted. But it does not explain why placing the feet outside can create a more locked, stable feeling, even if the wind is steady. For this, Peter's theory about the wind effects makes more sense - with the board tilted windwards, the wind exerts a pretty constant force on the board. On the other hand, if the board is flat, then small changes in the board angle can cause a change from pressure on the board to the wind lifting the board (when the windward edge is up a bit). For this part, the cosine curve above does not apply directly, since the board acts as a wind foil.

except the board is moving forward.
in ten knots of wind the board is doing 20+ knots forward so the wind is on the nose and not so much blowing across the deck ; because of scoop it is more under the nose than over the deck.

i drew a picture that i think illustrates Ian's post...

First outing today using GTR in approx iQFoil config - 95+, 900 front, 255 rear at -1.5, FGO 8.0 - pushing for a bit more speed, but very gusty today ...
REALLY nice, more balanced and slippery than 330 stab, why on earth hadn't I tried it earlier ....

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Peter Hands said..
First outing today using GTR in approx iQFoil config - 95+, 900 front, 255 rear at -1.5, FGO 8.0 - pushing for a bit more speed, but very gusty today ...
REALLY nice, more balanced and slippery than 330 stab, why on earth hadn't I tried it earlier ....

Yes, now just imagine switching to the 115+ fuse

^ Actually if you get the chance to try a 115+ I'd make sure the mast is right for it. I can't find the page but it may start becoming a stiffness issue.

Have been using the 115+ for ages, with 110 mast, fantastic, just prefer the 95+ when conditions better suited to beam reaching

I have a SB 100 Fueslage for sail if anyone is keen!

105 ?

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seanhogan said..
105 ?

yeah sure that one. Sorry been a long time since i used it the half dozen or so tries I had before switching to F4. Also have an 800 front wing, but they are fairly common...

So I took the mast base for the rig all the way forward, have a rubber washer between the fuselage and the centre stab screw location. I also removed the rear footstraps and voila, I am enjoying nice stabilised flights with some decent up and down wind angles. Must say that tilting the board to windward when tracking upwind helps too! Can't say I'm missing the rear footstraps as it's allowing me to make very small back foot movements which in turn helps control the flight. Breezes are generally always gusty down here so I'm happy that it's finally working.

Many thanks for the words of advice along this short journey.

I have just bought one as I'm getting old and need to slow down ?? chasing a 900 front wing as I'm only 75kg and think the 1000 might be too big. So if anyone out there has one they will sell please let me know. Cheers

You got the 1000 wing with your GTR? That's odd, I think the standard wing is the 800. The 800 is a great all arounder and may be preferable for your weight. For me at 90 KGS the 800 is great for about 14 knots upward.

Be advised, the SB fuse is changing this upcoming season. The front wing mount is changing and thus all front wings will get a revision. Stabs remain the same. Not sure what availability will be of the older design parts. I am guessing there will be some level of support given that its the IQ design for 2024.

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tswei99 said..
You got the 1000 wing with your GTR? That's odd, I think the standard wing is the 800. The 800 is a great all arounder and may be preferable for your weight. For me at 90 KGS the 800 is great for about 14 knots upward.

Be advised, the SB fuse is changing this upcoming season. The front wing mount is changing and thus all front wings will get a revision. Stabs remain the same. Not sure what availability will be of the older design parts. I am guessing there will be some level of support given that its the IQ design for 2024.

Cheers, no I didn't get the 1000, I want to foil in 6-8

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Tinlyds said..

tswei99 said..
You got the 1000 wing with your GTR? That's odd, I think the standard wing is the 800. The 800 is a great all arounder and may be preferable for your weight. For me at 90 KGS the 800 is great for about 14 knots upward.

Be advised, the SB fuse is changing this upcoming season. The front wing mount is changing and thus all front wings will get a revision. Stabs remain the same. Not sure what availability will be of the older design parts. I am guessing there will be some level of support given that its the IQ design for 2024.

Cheers, no I didn't get the 1000, I want to foil in 6-8

Ahh...sorry I think I misinterpreted your post. So you are looking to get a 900 to add to your 800?? I would go all the way to 1000 and glad I did. The 1000 is amazing. Very pumpable but retains a good high end. I would think the 900 and 800 are too close.

I also have the 650 having skipped the 725 in between. Very glad I went with this spacing.

If you really want to go in 6-8, definitely the 1000. You might want to add one of the longer (+) fuses with the shims. I once used the 1000 wing on the 115+ with a 0 deg shim and it lifted ridiculously early. So early that I had to go back and change to -2.0

Hi all. Just acquired a Starboard 105 plus fuselage. Intend to use a 800 / 725 front wing with 255-2 tail. Been using the old 95 fuselage as I can run windsurf angles up to now. The 115 forces me more up and down wind. Anyone used the 105 with thse wings. What angle on the tail wing works best? Do like a bit more back foot pressure than front but expect more front foot with the 105

For all the longer fuses (115, 115+ and 105+) I like the -2.0 rear angle for the 800 wing. Just seems to have the broadest wind range.

On the 95+ (GTR setup with the larger 330 tail wing) I like -1.0. I use this with softer freeride sails that need the extra stability and forgiveness of the bigger tail wing and more lift in back.

Tony, I am a bit late into this discussion, but I had the same issue of too much lift. With the 800 wing and 330 stab on the standard 95 fuse. I ended up making my own shim, which is about -1.7 degrees (lifts up the leading edge of the stab).

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tbwonder said..
Tony, I am a bit late into this discussion, but I had the same issue of too much lift. With the 800 wing and 330 stab on the standard 95 fuse. I ended up making my own shim, which is about -1.7 degrees (lifts up the leading edge of the stab).

Very interesting Andrew. If you could flick me a photo of how you shaped the shim and its thickness, it would be really appreciated mate. My foiling buddy only said after following me around on Sunday that I'm still porpoising badly...

To make the shims I use the fuse as a mould. First put a length of sticky tape over the 3 screw holes where the stab would fit. Then with two more pieces of tape form up a trough. Then clamp the fuse in a vice at just the right angle. Then pour epoxy in to the trough. To get a shim similar to mine you will need it to be about 4.5mm thick at the front stab hole and 1.5mm thick at the rear stab hole. You may need to make a couple until you get this right. Once the epoxy sets, peel off the tape and pop it out of the fuse. clean up all the edges with wet and dry. Then drill the three holes. You will need to use longer bolts to secure the fuse when using shims.

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tbwonder said..
To make the shims I use the fuse as a mould. First put a length of sticky tape over the 3 screw holes where the stab would fit. Then with two more pieces of tape form up a trough. Then clamp the fuse in a vice at just the right angle. Then pour epoxy in to the trough. To get a shim similar to mine you will need it to be about 4.5mm thick at the front stab hole and 1.5mm thick at the rear stab hole. You may need to make a couple until you get this right. Once the epoxy sets, peel off the tape and pop it out of the fuse. clean up all the edges with wet and dry. Then drill the three holes. You will need to use longer bolts to secure the fuse when using shims.

Excellent - thanks!

You can do a similar thing with knead it available at bunnings . Put tape on your wing and fuse where they connect. Poke a hole on the tape where the screws go. Mix up the knead it putty and put it on the fuse enough so it will squish out the sides when you tighten it down. Surround the holes with it, don't put it over the holes. Put the wing on, tighten down to the required angle and leave to set for a little while. Just before it is fully set trim off the excess with a very sharp knife. Quick and easy way to make a few different angle shims. Aqua knead it dries slightly flexible so less likely to snap. It should release from the tape OK but you can use some Vaseline or car wax on it to help before you apply putty.

I just cut up one of these to make shims:



Buy a few different sizes to get more or less angle, bit of sanding to fine tune it. Unless you want to add silly amounts of angle, they work quite well.