I think most foil boards now have cutouts in the tail, and they are advertised as helping get the boards flying even before they are planing. I'm wondering how important these cutouts are for non-racing foiling?

Cutouts allow a slightly higher speed on the same width wide tails.
Also allow an extra bit of looseness to pump up onto foil.

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shmish said..
I think most foil boards now have cutouts in the tail, and they are advertised as helping get the boards flying even before they are planing. I'm wondering how important these cutouts are for non-racing foiling?

Cutouts help unstick the board if the board is large enough. If the board is not yet planing, hard rails are not efficient to unstick anyhow. Look at the wingboards made for high lift foils, they all have huge tailkick to help unstick the board before planing speed / facilitate less drag when pumping without speed. For the boards which are designed to use with faster foils (next years production boards) we're getting sharper and sharper rails, flat(ish) tails & cutouts for some brands. Im not convinced on the efficacy of cutouts for smaller boards (sub 65cm in the tail / 75cm at the widest), but on the other hand dont think it hurts either.

I suspect they are more of a fashion accessory.

They seem to help. The widest board I've got, the IQFoil is 95cm wide. When you get borderline board planing without flying on the foil, like after a touchdown or when you're picking up speed without giving the foil a hard kick, it makes noise.

It surprised me at first, because it sounded like a very loud bathtub drain going SLURRRP right behind me. The first time it happened I freaked out a bit and looked behind me to make sure something big wasn't chasing me, but then I realized it was the cutouts making noise.

I just made a foil board with (what i thought) was over sized cut outs.

As the board accelerates, you can feel when the water lets go of this area. The reduced drag make it a lot faster to get onto the foil.

On wide tailed boards the cutouts are a necessity as they reduce the surface area so you can sink the tail to increase the angle of attack of the foil to get out of the water. Without tail cut outs you get to much lift right at the tail of the board and this actually starts to pitch the nose down as you accelerate.
The same effect can be achieved with rocker or tail bevels as per surf/ sup foils. The problem with this is at higher speeds on touch downs it can suck the board down, slowing you and changing pitch. A cutout with sharp edges gives much better release with speed touches. On a slapper cutouts are a way to reduce drag and increase speed.
On a foil cutouts are a way to introduce tail rocker.

Niall, that is one beautiful board. Looking forward to seeing the silver surfer on the track.

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regal1 said..
Niall, that is one beautiful board. Looking forward to seeing the silver surfer on the track.

You were the one that convinced me to reduce the surface area in the tail. And you were right.

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AUS299 said..

regal1 said..
Niall, that is one beautiful board. Looking forward to seeing the silver surfer on the track.

You were the one that convinced me to reduce the surface area in the tail. And you were right.

Are those cutouts difficult to make? I've done a reasonable amount of work with epoxy and cloth but have never vacuum bagged.

So what are the chances of the ideal hull width matching the ideal deck width? About zero. Dinghy's have the same problem. They solve it a little more elegantly maybe, but it's all the same, nothing new. Little outriggers for feet and footstraps have done the same job but they are even more ugly than cutouts.

What about the Starboard Foil Slalom!
Anyone ridden one?
Looks clean narrower bottom plan shape without the cut outs on the bottom.

Elix is doing interesting things:
www.facebook.com/WindfoilWorld/posts/are-these-the-next-foil-boards-prototypes-by-funboard-elix-and-starboard-windsur/2193036374317961/

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Grantmac said..
Elix is doing interesting things:
www.facebook.com/WindfoilWorld/posts/are-these-the-next-foil-boards-prototypes-by-funboard-elix-and-starboard-windsur/2193036374317961/

The AC75 bustle. Progressive take-off maybe ? Gentle touchdown?

Doesn't maximise the number of blanks you can cut out of a block of foam or the number you can get in a shipping container though.

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shmish said..

AUS299 said..

regal1 said..
Niall, that is one beautiful board. Looking forward to seeing the silver surfer on the track.

You were the one that convinced me to reduce the surface area in the tail. And you were right.

Are those cutouts difficult to make? I've done a reasonable amount of work with epoxy and cloth but have never vacuum bagged.

Vacuum Bagging was part of the build that I enjoyed the most. You just need to make sure you have all the layers prepared before you start. Laminate, Peel Ply, Release film and breather blanket. And a reliable bag which did cause me some stress.

On the hard corners, especially around the cut outs, I inserted timber to make sure the cloth etc. was forced into the shapes that I wanted.

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AUS299 said..
I just made a foil board with (what i thought) was over sized cut outs.

As the board accelerates, you can feel when the water lets go of this area. The reduced drag make it a lot faster to get onto the foil.

Your description of the 'action' is exactly how I remember it on my father's new course board design shaped in the early 2000's. The boards just became wider, fins deeper & seemingly uncontrollable in chop off the wind. The cutouts also helped in that respect.