In higher winds, my favorite board, a Tillo 125 Freefoil, is an absolute delight. At 195x75, I can uphaul it (two feet behind the mast is easier) and it's small enough to be nimble and not misbehave even in gusts approaching 30. If it has one fault, it's the beveled tail common to multi-use boards designed about 12-18 months ago. The lack of a square back edge meant that water would wrap around and make the board very sticky on take off. Since I'm using an 1100cm2 wing with it, it takes going about planing speed to get off the water and in anything less than a full powered gust not even pumping like a maniac would get it to break free.

I attributed some of the stickiness to a bottom handle and the additional US tracks but ultimately the tail was proved to be the issue.

Since in my neighborhood, summer means little or no wind most of the time, I've had enough days between sessions to risk having the board out of commission and it seemed like a good time to tackle the project. I must give credit to utcminusfour for the suggestion to build a vacuum setup which is helpful and invaluable on another project I'm working on. He's done a similar mod on a Naish, iirc. Also on wing forums, a lot of discussion has been going on about the new school shapes which emphasize a clean release as wingers are using smaller foil wings and depending more on board speed to get off the water.

There's not much to the mod other than a nice clean vertical edge to allow the water to release. The results are difficult to describe without it sounding like I'm selling snake oil. I think I've knocked about 5kts off the wind speed needed to get off the water. Instead of needing full power, I can pump off the water in wind barely enough to foil in. Yesterday I was foiling along with other foilers with 1-1.5 meters bigger sails and much bigger wings and a fin running 4m2 bigger than me (9.5 to 5.4).

Photos below - paint and blems will be cleaned up this week. I was in a rush to get it "dry" as I wanted to try it over the weekend.

Original tail



XPS glued down a bit of pour foam to get everything nice



Quicky rattle can job to get on the water by the weekend

Interesting, think there two ways to lift off, one is what I think you're doing,using board speed, in this case cut outs create less drag, higher speed, faster lift... The other way, pumping with sail/foil with very little forward speed and more vertical lift, close to wingers do

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miamiwindsurfe said..
Interesting, think there two ways to lift off, one is what I think you're doing,using board speed, in this case cut outs create less drag, higher speed, faster lift... The other way, pumping with sail/foil with very little forward speed and more vertical lift, close to wingers do

Paducah, wow, that was a tail job!, glad it is working for you.

I can do the sail/foil pumping to get up, but if the wind is too low can not foil and return to the water. Forward speed is essential for windfoiling IMO. So normally, I start with the sail pumping to get forward speed and as that increases can pump the foil too if needed. Can also just pump the foil, but that takes more wind to get up.

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miamiwindsurfe said..
Interesting, think there two ways to lift off, one is what I think you're doing,using board speed, in this case cut outs create less drag, higher speed, faster lift... The other way, pumping with sail/foil with very little forward speed and more vertical lift, close to wingers do

I agree. When I used a bigger, more lifty wing with this board (NP HA13), the tail was nowhere as much an issue as I could more or less bounce the board free but the smaller, quicker and much less draggy AFS wing is my preference to use on this board. So, optimizing for that became my priority.

More and more wingers are using smaller wings and the need for a board that approaches planing speed is becoming more important to them and bottom shapes seem to be changing pretty quickly in that world. A lot of the motivation for this mod came from that part of the world - although my conversations with utcminusfour predate this thread: www.standupzone.com/forum/index.php/topic,38048.0.html

Incidentally, I shared my work with Alex and he's definitely in approval. He's tried to optimize the release on his v.2 Freefoil boards with refined cutouts and side rails in the tail.

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Paducah said.. I think I've knocked about 5kts off the wind speed needed to get off the water. Instead of needing full power, I can pump off the water in wind barely enough to foil in. Yesterday I was foiling along with other foilers with 1-1.5 meters bigger sails and much bigger wings and a fin running 4m2 bigger than me (9.5 to 5.4).

^^^Super-interesting.

In light of your recent testing - what do you think to optimise for 10-12 knots lift-off with 1050 cm2 foil (sweetspot) and 5.9m sail?
Long and narrow (say 56cm) to glide up to speed e.g. Kalama Barracuda (displacement hull) or current W114 width (66cm) but more volume in tail and sharper rails for best planing performance?
Is it necessary to hit planing speed to get a 1050 foil to lift a 80kg rider ??
If not the Kalama board is going to work better in marginal winds - as long as it's stable enough to uphaul.

SUP paddlers are not planing to paddle up in flat water but they're using big foils and not fighting 8kg rig weight.


Confused - thoughts?

If you wanted to go a step further make some blanking plates for whichever fin boxes you are not using or just put some thin sticky back over them.

Thanks for this Paducah - so interesting and beautiful craftsmanship.

I've been looking hard at the Freefoil as a smaller option compared with my custom 91/232cm Convertible which is a couple of years old. I'm wondering whether on the narrower/ lighter board I couldn't perhaps pump a 7.0 or even a 5.7 up in winds where the big board likes an 8.5. It looks like Alex is now making two "Freefoil" style boards in basically the same sizes but one has the hard release and cutouts for windfoil and the other the kick-tail for winging. He also has a discounted demo board which looks like a hard release with no cutouts. Sounds like the cutouts are really helpful - not surprising given he's about the only guy not always using them.

Do you think the 125 is a poor choice for my 100kg? I love the idea of the 190cm length and 75cm seems wide enough but maybe the 156 (80/230) is more sensible. getting closer in size to what I already have though. It does sound like you're able to use a smaller sail on your modified setup than you might on a bigger board.

azymuth - those very interesting questions are honestly above my pay grade. I've never been keen on the idea of more narrow boards getting up faster because of my windsurfing heritage, the notion that wide boards planed sooner. Yet, yesterday's experience was revelatory and far exceeded my expectations. I think someone with a better understanding of hydrodynamics would be able to tell us which hull - narrow, canoe-type displacement or wider "Simmons" style planing board with a good release is more easily driven to the 8 kts or so at which point my foil can start to lift my relatively light weight. Or maybe it's not an easy question to answer and depends on sea state, etc. I'm basing my speed estimate on my GPS call out speeds at lift off/min speed from my other foils (about 8 kts on a Starboard 1000 and 9 kts on an IQFoil 900).

I'll try to wear a GPS tomorrow and get a better idea of what the take off speed is. I will say that before the mod, I could sometimes bounce a NP HA13 off the water before the board felt like it was sliding. I never could do that with the smaller AFS F800 as it felt like molasses until there was enough pressure from a gust to break free. Once sliding, it would easily and quickly get up in the air. That sticky feeling has disappeared.

Someone on the French forums has shaped a narrower canoe-like board and seemed happy with it. It's been a while so I don't have the link handy. Looking back, it's not as goofy as I thought when first seeing it. If necessary, I could probably do some digging and find it.

mr. love - I've thought about tape but that seems like such a kludge and don't know if that would leave a residue for that odd time I actually inflate a wing and use it with this board. I've tried some things laying around the garage but it was pretty obvious that I was coming up with dead ends. I recently learned about these which will probably save me a day of cutting and sanding: www.k4fins.com/product/k4fin-blankers/ The other thing about tape is the chance that they start to peel. Maybe some temporary adhesive vinyl like crafters use? I've got a roll or two I used for sail numbers - tomorrow looks breezy and I may try it and report back. The carry handle will stay exposed because it is - no pun intended - very handy.

Awalkspoiled - thanks but don't look too closely. Not yet anyway until I've cleaned it up. Alex M. has the v2 156 now and a 136 coming out in January. The 125 (honestly feels a touch less) is going to be a really small under you at 100 kg. I felt like I was on the edge with it at my once 72 kg. I'd contact him for further details. The video of the new 156 is on his web site. I'll admit I don't know what effect cutouts have and how the shape of them affects their efficiency ie how much more efficient having the release perpendicular to the water flow is vs an angle. I'm not really sure what I did would be considered cutouts, anyway, but rather just cleaning up the trailing edge and reducing form drag.

There probably is considerable overlap between the boards but I suffer from living in a really light wind locale so the extra 3 or so kts on the low end doesn't sound like much but means a lot of extra sessions for me. Also, the rides can be very different - one really likes to go straight and fast, the other turning and playing.

I'm 95kg, 125L would be lots if you don't use sails bigger than 7m

With short boards, you got a boat speed of about 4 knots. With a small wing, the stall speed is somewhere between 8 and 10 knots. So how do you get from 4 to 8 knots? Board length helps, but boat speed goes up with the square root of board length, so it's not the complete answer. SUP race boards are 14+ ft long, but even they don't reach 8 knots. Displacement hulls are not the answer for foiling.

The original board has a bunch of characteristics typical for displacement hull, including angled rails and and angled tail kick. Both end up sucking water upwards, and in turn suck the board down into the water. That basically counters the effect of the foil, which starts to contribute lift in the 4-8 knot transition region. Most of the water flow is off the back, not the side rails, so the tail kick does most of the slowing down. Sharp edges, like those from Paducah's modifications, let the water go straight off the back, and eliminate the "suck down" effect. His reports confirm that the effect is quite large.

I think this is a perfect example of how a "2-in-1" board can add "compromises" that negatively affect performance. The kick tail idea is from wing boards, but the positive effect is mostly optical (signalling potential buyers "made for winging, too"). It does, however, have a clear negative effect by making takeoff harder. With very large front wings, that effect is less pronounced, since the lift produced at lower speeds is higher, and the gap between board speed and foil stall speed is much lower.

Hey JJ.
On the skinny and long board thoughts. One thing to remember is those SUP boards only work when pointing straight downwind. You even have to start paddling on your knees before you can even get to your feet. Putting this kalama design into a windfoil board might be tricky as you very rarely point dead downwind when windfoiling except when gybing. Never say never. Time to shape some foam and start the R&D. I'll happily come test it with you.

Modern wing boards are going with a hard release edge or even a pin tail, they are also getting narrower.

I agree with Miamiwindsurf and boardsurf

I have used a board pretty similar to yours with the tail cutout and chimed rails and its very sticky for wind foiling although the extra length really had no advantage to lighter wind performance.

The slingshot wizards generally pop up on the foil from a near standstill much like the wing boards (with some athletic pumping of course)
they have somewhat harder rails and no angled tail cut out so you have an option of board speed if you don't want to pump or by bearing off a little you can engage the foil really quickly.

From experimenting with many different board brands, if the foot traps are more out on the rails you adopt a board speed approach to popping the foil up, if the front (and particularly) the back strap are in more inboard and directly over the foil you can literally stand right over the foil to get the bugger up and flying!

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azymuth said..

Paducah said.. I think I've knocked about 5kts off the wind speed needed to get off the water. Instead of needing full power, I can pump off the water in wind barely enough to foil in. Yesterday I was foiling along with other foilers with 1-1.5 meters bigger sails and much bigger wings and a fin running 4m2 bigger than me (9.5 to 5.4).

^^^Super-interesting.

In light of your recent testing - what do you think to optimise for 10-12 knots lift-off with 1050 cm2 foil (sweetspot) and 5.9m sail?
Long and narrow (say 56cm) to glide up to speed e.g. Kalama Barracuda (displacement hull) or current W114 width (66cm) but more volume in tail and sharper rails for best planing performance?
Is it necessary to hit planing speed to get a 1050 foil to lift a 80kg rider ??
If not the Kalama board is going to work better in marginal winds - as long as it's stable enough to uphaul.

SUP paddlers are not planing to paddle up in flat water but they're using big foils and not fighting 8kg rig weight.


Confused - thoughts?

JJ I have winged a kalama board with similar tail shape, to say its "tippy" is an understatement it probably helps to be lighter weight rider of course but once you get a couple of quick pump it fly's up on the foil.

Pretty Work Paducah!

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Paducah said..
Someone on the French forums has shaped a narrower canoe-like board and seemed happy with it. It's been a while so I don't have the link handy.

Probably FranckG31 : here's the link to built log :

www.windsurfing33.com/forum/viewtopic.php?f=42&t=121365&hilit=planche+ronde

a video :



Franck is definitely going down the size regarding front wing. I've seen him ride wing that looked the size of a stab. Quite fast even with light wind.

He once let me try his set up. The round hull glides effortlessly and take off is smooth. He rides quite 'back footed', at least compared to my shortstyle board.

But his design is still a planning hull with square tail for release. He designed a hull for minimal drag during preplanning.
Now his design really requires accurate rake setting (he adjust rake precisely depending on wind, sail and wing size). With correct setting, the foils gives lift as soon as there's some forward speed, so even if it doesn't lift the entire gear and rider, the wet volume required is reduced, so it gets narrower, and drag is reduced, thus permitting easier acceleration so more lift generated by the foil, and so on.

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6u1d0 said..
...the wet volume required is reduced, so it gets narrower, and drag is reduced, thus permitting easier acceleration so more lift generated by the foil, and so on.

Yes, exactly the one I was remembering but too lazy to chase down. Thanks! I think the chimes on my board work the same so not so sure they are too much a negative to the objective.

Yesterday was a nice 8.0 foiling day so, for "science", felt compelled to rig the 5.4 on this board again with the GPS to get some numbers. For context, it was about 30 degrees, the lake is at 350 m altitude and I weigh about 63kg. For the truly curious and scientific, the density altitude* was about 1200 m.

Winds reported by the local airport were generally 10-15 /11-16 kts but the first hour was definitely lighter around 8-9kts and a lack of gusts. I would have easily flown with an HGO 8.0/Starboard race foil even in the lighter conditions. Generally, at what seemed like around 10-11 kts, I could pump off the water with energetic pumping. GPS seemed to indicate that around 6-7 kts the board would release from the water and begin to slide/plane and take off speed was generally around 9 kts. From observations, if the 8s were getting off the water without or just barely pumping, there was enough wind for me to get off the water. The 8.0s were ridden by intermediate 75-85 kg riders with Moses wings from 1500 (950)-2000cm(W1100). I was riding an 1100 AFS mid aspect wing with a North freeride 5.4.

I tried taping the US box slots but the tape began to peel. I tried the vinyl at home but it was clearly too flexible. Probably, the k4 slot fillers are the easiest solution. The difference between tape and no tape was not noticeable.

My take from all this is that paying attention to board drag and how it releases from the water is worth the effort. Sometimes, some very small and easy changes can transform a board's behaviour. I haven't changed the foiling performance ,which was always good, but I have made it easier to get in the air by a noticeable amount which encourages use over a wider range of conditions. I'm not claiming that this board is better than anything else - only that it is much better at taking off than before.

Edit - buddy on an 8.0 when the wind was a bit lighter.

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baldy123 said..
Hey JJ.
On the skinny and long board thoughts. One thing to remember is those SUP boards only work when pointing straight downwind. You even have to start paddling on your knees before you can even get to your feet. Putting this kalama design into a windfoil board might be tricky as you very rarely point dead downwind when windfoiling except when gybing. Never say never. Time to shape some foam and start the R&D. I'll happily come test it with you.

Cheers Pete, I'm sure you're right (and Dean confirms) - the super-narrow Kalama type boards will lack stability to confidently uphaul in swell in light winds - which kind of negates the point for me.

Look forward to seeing more of you back on windfoil after your recent reacquaintance

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Paducah said..
Yes, exactly the one I was remembering but too lazy to chase down. Thanks! I think the chimes on my board work the same so not so sure they are too much a negative to the objective.

Yesterday was a nice 8.0 foiling day so, for "science", felt compelled to rig the 5.4 on this board again with the GPS to get some numbers. For context, it was about 30 degrees, the lake is at 350 m altitude and I weigh about 63kg. For the truly curious and scientific, the density altitude* was about 1200 m.

Winds reported by the local airport were generally 10-15 /11-16 kts but the first hour was definitely lighter around 8-9kts and a lack of gusts. I would have easily flown with an HGO 8.0/Starboard race foil even in the lighter conditions. Generally, at what seemed like around 10-11 kts, I could pump off the water with energetic pumping. GPS seemed to indicate that around 6-7 kts the board would release from the water and begin to slide/plane and take off speed was generally around 9 kts. From observations, if the 8s were getting off the water without or just barely pumping, there was enough wind for me to get off the water. The 8.0s were ridden by intermediate 75-85 kg riders with Moses wings from 1500 (950)-2000cm(W1100). I was riding an 1100 AFS mid aspect wing with a North freeride 5.4.

I tried taping the US box slots but the tape began to peel. I tried the vinyl at home but it was clearly too flexible. Probably, the k4 slot fillers are the easiest solution. The difference between tape and no tape was not noticeable.

My take from all this is that paying attention to board drag and how it releases from the water is worth the effort. Sometimes, some very small and easy changes can transform a board's behaviour. I haven't changed the foiling performance ,which was always good, but I have made it easier to get in the air by a noticeable amount which encourages use over a wider range of conditions. I'm not claiming that this board is better than anything else - only that it is much better at taking off than before.

Edit - buddy on an 8.0 when the wind was a bit lighter.

Thanks for following up with more data
I suspect your light 63kgs makes your board improvements more noticeable.

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azymuth said..
Thanks for following up with more data
I suspect your light 63kgs makes your board improvements more noticeable.

Appreciate that. No doubt that my weight is a factor in using a small sail in light conditions. (It also makes me slow as *** in windy conditions.) What will be fun to see is using a bigger wing and see what is gained and lost in terms of lift vs. drag. Comparatively to the heavier riders, I had a higher kg/cm2 ratio but the foil is a lot lower drag. When powered up, the speed difference was significant.

Well, I got lucky. Our resident photographer was actually snapping pics on this day and got some of me flying. Mind that they were taken about a km away (yes, a really nice lens).

Finally got the cosmetics done and ordered some slot fillers (blankers) from K4 which were inexpensive and arrived quickly. As impressed as ever with results. Noticed the other day that not only is take off much quicker, but it's easier to bounce off the water when underpowered and get going again.

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Paducah said..
In higher winds, my favorite board, a Tillo 125 Freefoil, is an absolute delight. At 195x75, I can uphaul it (two feet behind the mast is easier) and it's small enough to be nimble and not misbehave even in gusts approaching 30. If it has one fault, it's the beveled tail common to multi-use boards designed about 12-18 months ago. The lack of a square back edge meant that water would wrap around and make the board very sticky on take off. Since I'm using an 1100cm2 wing with it, it takes going about planing speed to get off the water and in anything less than a full powered gust not even pumping like a maniac would get it to break free.

I attributed some of the stickiness to a bottom handle and the additional US tracks but ultimately the tail was proved to be the issue.

Since in my neighborhood, summer means little or no wind most of the time, I've had enough days between sessions to risk having the board out of commission and it seemed like a good time to tackle the project. I must give credit to utcminusfour for the suggestion to build a vacuum setup which is helpful and invaluable on another project I'm working on. He's done a similar mod on a Naish, iirc. Also on wing forums, a lot of discussion has been going on about the new school shapes which emphasize a clean release as wingers are using smaller foil wings and depending more on board speed to get off the water.

There's not much to the mod other than a nice clean vertical edge to allow the water to release. The results are difficult to describe without it sounding like I'm selling snake oil. I think I've knocked about 5kts off the wind speed needed to get off the water. Instead of needing full power, I can pump off the water in wind barely enough to foil in. Yesterday I was foiling along with other foilers with 1-1.5 meters bigger sails and much bigger wings and a fin running 4m2 bigger than me (9.5 to 5.4).

Photos below - paint and blems will be cleaned up this week. I was in a rush to get it "dry" as I wanted to try it over the weekend.

Original tail



XPS glued down a bit of pour foam to get everything nice



Quicky rattle can job to get on the water by the weekend

It seems really a good job Paducah.
I wonder what would have been the performance if getting totally rid of the tail section...meaning no cutouts and vertical tail for clean sharp edge release. I am not a fan of cut-outs, They add drag instead of reducing it at low speeds which are the ones interesting us, for the flow to release cleanly some water speed is needed, before that is all drag. Personally my next board will be without cutouts, somehow like the new wingfoil boards from fanatic, totally flat and square tail section. Nonetheless, testing is the ultimate verdict..if it has worked and you had an improvement, well done!

Ciao Edoardo

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dimacced said..
It seems really a good job Paducah.
I wonder what would have been the performance if getting totally rid of the tail section...meaning no cutouts and vertical tail for clean sharp edge release. I am not a fan of cut-outs, They add drag instead of reducing it at low speeds which are the ones interesting us, for the flow to release cleanly some water speed is needed, before that is all drag. Personally my next board will be without cutouts, somehow like the new wingfoil boards from fanatic, totally flat and square tail section. Nonetheless, testing is the ultimate verdict..if it has worked and you had an improvement, well done!

Ciao Edoardo

Thanks! Functionally, I don't think it makes much difference one way or the other. I really didn't add cut outs since the shelf is pretty far back and water flows off the edge cleanly. The center part of the tail I added is traced off a 78cm slalom board so you how far back things are vs a conventional board. Cutting that part off would have had two negatives, imho. 1) Lose a bit of volume in the tail which is helpful for getting back in light air and starting off, and 2) it would have been functionally irreversible - if I screwed it up, it would have been much harder to get back to zero. If this had gone sideways, all I had to do is grind it off and paint.

I think cutouts have a function but it's more complicated than "cutouts = earlier flight" etc. I'd agree with you that a good, flat release promotes earlier flight.