With the NP Pinkie I definitely had to be planing before it would foil. But with 1000 sq cm wing I'm not so sure. Seems to get up before the board is properly planing. In which case why are we stuck on planing hulls? The AC75s don't have planing hulls but at 70 feet long the displacement speed is 1.5 times sqrt 70 = 12 knots. Plenty to foil on maybe without worrying about planing. Foiling moths bypass the planing mode altogether, they use canoe-bottomed hulls, and they aren't much longer than a windfoiler.

Bigger foils start to lift well before planing hull, BUT....the foil lifts the hull into planing mode before the foil lifts the hull out of the water..so foil, hull, then foil again.

Foiling.. If you are planing and not on the foil something's wrong.

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Ian K said..
With the NP Pinkie I definitely had to be planing before it would foil. But with 1000 sq cm wing I'm not so sure. Seems to get up before the board is properly planing. In which case why are we stuck on planing hulls? The AC75s don't have planing hulls but at 70 feet long the displacement speed is 1.5 times sqrt 70 = 12 knots. Plenty to foil on maybe without worrying about planing. Foiling moths bypass the planing mode altogether, they use canoe-bottomed hulls, and they aren't much longer than a windfoiler.

Yes for most foils, we can foil at a speed that is less than planing speed, which to your question "why are we stuck on planing hulls"?

Isn't there a speed threshold where a board goes from displacement to planing? I guess if we have enough power any board could plane, but a planing hull allows us to plane earlier (maybe allowing us to reach speed threshold with less power). If that isn't complete bull****, then the principle applies to foiling. We want a board shape to allow the foil to reach lifting speed with the least amount of effort.

The w114 foils up more quickly than the freestyle 115, mostly because of the square shape of the tail and the more parallel rails?

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thedoor said..

The w114 foils up more quickly than the freestyle 115, mostly because of the square shape of the tail and the more parallel rails?

Who knows? Maybe moths went to a canoe hull for maximum volume for minimum wetted area. As soon as the foil starts lifting wetted area reduces and away you go?


Or maybe as a compromise foil boards will soon be equipped with "bustles"
www.sail-world.com/news/233558/Americas-Cup-Two-designers-AC75-hull-shapes

You don't need a flat hull to get up to foiling speed. Below are some pictures of a mod from a few years ago

Ian K,
I am convinced there are better shapes to use than the barn door if you want to ride smaller sails and big wings. We just need to figure out what they are. To my eye 2020 freeride boards are just scaled down versions of the race boards. I personally want something that SAILS in displacement not slogs because to catch a 12 knot puff you see a lot of 6-8.

I copied the race boards (full width at transom and flat bottom) for my first board build and I found it better in light air ONLY if I rigged my 7.5m. Then I found I could carry that big sail way further up into the wind range. This is a great solution for racing where they are always going to rig big and be uber physical. Unfortunately in yacht design most cruising boats copy the race boats, windsurfing is no different.

Take a look at the boards for winging, SUP foil, Surf foil. Most of them break every rule of thumb we have for slapper windsurfing.
I just picked up a Slingshot Shred Sled to explore this line of thought. I am not saying this board is the end all be all (I have not ridden it yet) but I am excited about the potential for my venue and style. I know I am going to learn things that the marketing has not told us. If it sucks at least I can sell it locally unlike my old windfoiling gear.

DarrylG,
What brand are you? How was that mod received? I can see how that shape would launch easy, is it sticky in touch downs?

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Ian K said..

thedoor said..

The w114 foils up more quickly than the freestyle 115, mostly because of the square shape of the tail and the more parallel rails?

Who knows? Maybe moths went to a canoe hull for maximum volume for minimum wetted area. As soon as the foil starts lifting wetted area reduces and away you go?

Or maybe as a compromise foil boards will soon be equipped with "bustles"
www.sail-world.com/news/233558/Americas-Cup-Two-designers-AC75-hull-shapes

The moths being the shape they are is just a consequence of them being that shape before they started sticking foils on them (believe it or not). But the wings they had provided good leverage over the foil. I guess thats part of the reason why we still have wide race foil boards, you need the width to allow leverage over the equally wide foil wings.

There are plenty of good reasons why the theoretically very earliest foiling design is not popular, chiefly how cumbersome it would be in the air, but for the very earliest liftoff, a long narrow, lightweight displacement hull is going to be quicker to lift than a wide short one. A 220cm barn door reaches hull speed long before a shape like the Slingshot Flyer 280 or something really extreme like the Serenity would. So, with a big, lifty wing set up not where a fin would be but pretty far forward underfoot, we'd be up in the air crazy early but couldn't do much once we were there. The Serenity never really planes at all, but can hit 8-9 mph - plenty for foiling - as soon as the sail will fill with wind. There's no place to put a foil on a stock Serenity but I've foiled on a Kona. It's about the equivalent of driving an Eldorado while sitting in the back seat, but even though the foil is too far back it does lift early.

I always try to shim/trim my foils so that the board planes first, then foils (so do a couple of pros I know). If it foils first, then it is probably trimmed too "high" and I am always chasing lift to keep it under control as the speed changes when up foiling. Up and down, up and down. Pogo sticking. I don't like that.

If it is trimmed/shimmed more "down" I can get the board planing then quietly press the foil up into flight, and it retains its trim when the speed increases. No bucking bronco. This makes things nicer if I get into a panic or have to bail out without crashing. Since I don't have a good full-foiling jibe yet, I can come down off the foil without slowing down and do a planing jibe without any drama. Exit into the new direction and quietly press it up into flight again.

This works well for my freeride foils, but I am still adjusting things with my racing foil.

Yes, even at subplaning speeds, the foil is already lifting. This helps the board get planing more easily. This is important for those boards (such as formula) that have a lot of nose rocker.

One thing that is different about windfoiling and sailing is our ability to pump. Perhaps the shapes we use are more a function of maximizing the effect of pumping so that we get to planing/foiling earlier

Didn't moths have wide flatish hulls in the 70s/80s?

Look at wing and hybrid boards - many have gone away from planing shapes already. In some of them, you'll have to look hard to find a large totally flat area. Rails are more kayak-like, flattish area in the center has lots of concave, tail is a step tail. Windfoiling, you can get reach planing speed with many setups, or at least get close. With winging, that's usually impossible, especially on the small, very short boards. Their shapes are already (partially) optimized to reduce "stickiness".

I think it's a bit comical to see slalom-like tails with assorted cutouts on freeride foil boards, especially those shorter than 6 or 7 feet.

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utcminusfour said..
DarrylG,
What brand are you? How was that mod received? I can see how that shape would launch easy, is it sticky in touch downs?

Utc, they are just homemade back yard creations. FTY ( faster than you). A few photos on my Instagram page ( Darryl.griffiths)
I was just trying a few things on that old board. Cut the rails off and moved front straps to square up stance, and then cut a heap of vee in.
Actually worked pretty well, touch downs are where it was best. Super smooth if hitting waves etc, no sticking or grabbing. Fun experiment

Winging is a bit of a different animal, so I wouldn't assume that what works well for wingding will be optimal for windfoil, but I am sure there are features that are mutually beneficial.

I do know that my levitator (150L) had an easier/quicker release to foil than my shredsled (142L) when it was marginal. Could be width, but I also think proper rails make pumping much easier, or at least I could pump much more aggressively on the levi. But if I have enough power in the sail all I need to do on the shredsled is weight the tail.