Hi guys,
after a discussion with a friend I made a bit of research on the net and found that :


available here : www.neilprydemaui.com/items.php?id=48

Did someone try one of those and is it worth the price ?

thiers a video of one of these on youtube .. chack it out .. 3 grand with the board and foil i think .. would the oard go anny good if u put a normal fin it it as well thou?

I've had the idea of building one bubbling away in the back of my mind for a while now. Even have a discarded old board which I could use.. and a CNC foil cutting machine

I would love to see one in waves.

So many ideas, so little time..

$3k.. I could use that for a lot of other things!

Yep, 3k is not budgetted for the moment.
I found a company called skyski which was selling foils. Unfortunately it appears that they don't have it in the catalog anymore !

The ones they are selling are around US$800. Maybe I will try one...

We have fantasised with the idea of building one too! We figured you could use any old board as long as it is fairly light. Probably plenty of thickness in the tail for extra strength. Saw an article on it once in the yank publication 'Wind Surfing' and the most memorable comment was that sailing on a foil is so quiet! Makes sense. If it was that good though they would have become more popular.

surfconnect here in qld had a couple at the beach a few years back.

you can buy the foil and stick it into your board.

a couple of things to note.

you need to beef up the fin box and then beef it up again.

you need to walk out into 1.2m deep water to launch which means water starting.

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Krisiz1 said...
If it was that good though they would have become more popular.

Not at $3k US.. That takes the shine right off for me.

I think it's an idea that needs further development - it could potentially open up lightwind sailing to more than just Formula sailors.

Have a look at the foiling moths - those guys are up on their foils from about 6 knots of wind. Waaay below planing conditions on a windsurfer. They carry a lot more lifting foil (and sail) than would be reasonable on a windsurfer though. I'd settle for 10-12 knots..

A 3-400mm deep foil on a wave board would be the go I reckon. Those days where the faces are chopped up and you struggle to hold a rail through the bottom turns would be transformed to gliding bliss if you were flying just above the chop on the face.

I kinda figured I should learn how to ride what I've got in a half decent fashion before modifying things and messing with off the wall ideas.

Have a look for vids of the foiling big wave surfers - it looks unreal.

Why is it so long?

I would assume it is because unlike a motorize hydrofoil the velocity is not constant so the board is rising and lowering a lot more.

If the pedistal (or what ever it is called) is to short then the board will contact the water regularly and with a higher drag factor would what to throw you over the bars a fair bit.

That's my theory on the length anyway

Please note
My theories may vary wildly from reality

May still need some fin in the water to oppose the forces from the sail as well

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elmo said...

I would assume it is because unlike a motorize hydrofoil the velocity is not constant so the board is rising and lowering a lot more.

If the pedistal (or what ever it is called) is to short then the board will contact the water regularly and with a higher drag factor would what to throw you over the bars a fair bit.

Also to do with ventilation.. the pressure is lower over the top of the foil, so it tries to 'suck' the foil up to equalise the pressure.. (hence you get lift) if you get too close to the surface, then you'll end up sucking air down to the foil instead which is VERY BAD!

There's a video of this stuff at:

Looks like he's about to get smoked by the other guy on the slalom board so it's evidently not very quick, though there could still be huge potential if the design is improved on.

That's shot in Ma'aleea Bay which has pretty flat water, so it would be interesting to see how it goes in chop. Seems to me that a smooth ride through chop could be the biggest advantage.

Love to try one.

Is it just me or does that thing look like the Biggest White pointer fishing lure you've ever seen??? I'd love to mod edit the video for a laugh!!!

why not try a bit of 'old style' windsurf hydrofoil ?!?

That last guy has got me inspired! 5-13 knots and he looked like he was having more fun than I've ever had in that wind. Does anyone know where there are any specs for the foil? It would save a lot of R&D if we could just copy one! So whose gonna be the first to make one?

I have made enquires about the Neil Pryde hydrofoils not so long ago. They do not use a standard fin box & the boards are well reinforced. I recon that you could use a deep tuttle box but would still need to make the board stronger. The ideal would be to design the fin so that you could remove the bottom foil - you could then easily modify the shape as needed. Use a stainless (or alloy) shaft with Deep Tuttle top and bolt on carbon foil. You just need to make a mould for the foil. Strengthening the board may be the hardest part!

Rush Randle (ex pro) and Kevin Ozee from NP Maui are the guys doing that particular brand in the first photo.
There was a decent article in a pommy Boards mag a few years ago.
Apparently you sail them very upright and use a lot smaller sail than usual.
Cammed sails are best it said. Cuts through chop obviously and is very quiet.
Nothing huge in the speed department but still early days..
Check out Neil Pryde Maui for more info.

Not so sure it is early days, I am pretty sure I saw something about Rush trailing foil windsurfers almost 10 years ago.

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AUS1111 said...

Looks like he's about to get smoked by the other guy on the slalom board so it's evidently not very quick, though there could still be huge potential if the design is improved on.

Foils don't seem to have slowed l'Hydroptere down too much. [}:)]

yeah but hyd is a boat.

so using foils massively reduces surface area drag.

with a windsurfer at speed the isn't much left in the water.

the moth foiler above was an australian invention i believe. the guys at KA Sails did that one.

I think a foil as they currently exist [windsurf] probably limits the wind range of a board more than a conventional fin.hydroptere,moths and other large hydrofoil craft have the ability to adjust the angle of there foils the same as a aeroplane with its wing flaps.

To me the advantages of a foil may be earlier planing and to make a smooth ride thru chop & rough water. To get planing in 8-10 kts means alot of extra time sailing

and there was this one

Foil design is a complex science especially on an unstable platform like a windsurfer.

The key to the whole thing is the depth of the foil below the surface as depth controls/limits cavitation and therefore lift. For a typical foils shape cavitation or ventilation means no lift. In the any of the videos it can be seen that that the rider continually battles to keep the board "flying" level i.e. controlling foil depth.

The other killer is that the faster you go the more lift generated hence you fly higher which means cavitation starts so lift is lost and you drop down again. It is for this reason that the pretty much any sailing craft using foils can trim the foil to control lift as speed increases or decreases. usually done by having a rotating part in the tiller handle that controls the angle of the foil. Solve this and you are on a winner. Some boats use a pointer sort of thing at the bow that tracks along the water surface. If the boat lifts too high the foil is adjusted. Simple idea that would be very affective.

Go to the local library and you will find heaps of books from the 60's when hydrofoil ferrys were all the rage. There was heaps of research done which is easy to understand and to put into practise.

Check this and scroll down to the bottom

www.seabreeze.com.au/forums/topic.asp?TOPIC_ID=55444&SearchTerms=foil

Well, I wouldn't like to crash at full speed with any of those under my board !

laird and his crew were ariginally desinging hydrofoil surfboards to reduce bump and jump when big wave surfing werent they

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windjunky said...

There's a video of this stuff at:

Wow! Can't say I understand how it works..Would it be hard to sail..? No more bashing over chop to wear you out..

Thr problem with the Randell design is that the front cavitating surface foil has to be adjusted rather laboriously with cords along the boom to let one lean out without painfull ankles.
Starboards Teisda said they are working on a foiling twinster with 4 foils that would just "jump out of the water". Where are our spies?