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  1. #22
    Quote Originally Posted by boards_ronnie View Post
    A video on the North foil.
    Interesting bit is the bit about the two tuttle boxes. The forward one for the usual kite foils and the North high performance foil and the rear box for the North foil he is using in the video.

    https://www.youtube.com/watch?v=BoWClt-2WIg
    It is actually funny to see 5 windsurfers out slogging in those conditions. Is it part of the problem with windsurfing? I have tons of beach friends that simply refuse to use anything bigger than 5.0. As if we were still in the 90s and sails did not have a huge upper end. Result is the embarrassment you see in the video: there is no reason on earth why those windsurfers should be slogging. Still they are, no wonder that the mythology about kites being more efficient took old.

    As far as hydrofoils faster than slalom, I do not think they are. Talking with the racer guys top speed is similar to formula, below 30 by a good chunk. And I know that I am in the upper 20s at most with my 85L when I pass or keep up with them. Manufacturers are pretty honest about it actually, as the north video shows. Probably the only way to go around it would be with an adjustable hydrofoil, but that, as again the North video shows (with the planned alternative "speed" hydrofoil), is probably far into the future.
    Last edited by duzzi; 25th April 2015 at 07:35 PM.

  2. #23
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    When you see a slalom board at full tilt most of the time it is only the fin in the water and a small planing flat at the rear of the board kisses the water when there is some disturbance to that lift pushing the board up onto the fin again. Slalom board design with low wide noses and deck concaves etc are designed to work as part of the aero- dynamics at those speeds. So if you consider the overall shape involved it is essentially the opposite of a foil...or a foil upside down and has less wetted surface than a foil.

    So apart from enabling a situation where enough lift can be created at very low speed to reduce wetted area to just the wing of the foil I see no real benefit in these designs. It all suggests a low wind performance tool as opposed to a high wind speed performance weapon to me.

  3. #24
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    Miker
    Explain how hydroptere works then. Foils are way more efficient than planing surface, trouble is as I explained in earlier post inverted T foil has to be large enough to get board out of water ( to reduce its drag!) meaning it is too large at high speeds. Hydrofoils/ foiling cats/ hudroptere utilise constant lift/ reducing area foils. ( fins angled at 45 degrees which as they rise out of water obviuosly present less wetted area.At any given speed the produce equal lift to load. T foils give more and more lift with rising speed...but there are inherent and as yet unsolved issues utilising constant lift foils on boards. ( google Hydroptere and Bruce foils for a much more concise explanation)

  4. #25
    Senior Member Navegante's Avatar
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    Attachment 11930Attachment 11931Attachment 11932

    A bit of foiling practice today. On trial a kite foil, the foiling plane of this unit is too far back and lifting/getting airborned did not prove easy.

    If the mast was tilted/angled forward it may work better.

    Never the less a great afternoon on and off foil.

  5. #26
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    Alpinefoil have a forward curving mast and have the XLP wing designed for lift-off in very light wind.
    Don't know if it would work on a windsurfer (the box looks too far forward on their board) but it does show you can make a forward-curving mast.

    If that was my windmeter, I'd be getting it checked. Let's just say it works in very light wind.

    https://www.youtube.com/watch?v=sKKyFiDb7GM

  6. #27
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    Quote Originally Posted by Alphie View Post
    Miker
    Explain how hydroptere works then. Foils are way more efficient than planing surface, trouble is as I explained in earlier post inverted T foil has to be large enough to get board out of water ( to reduce its drag!) meaning it is too large at high speeds. Hydrofoils/ foiling cats/ hudroptere utilise constant lift/ reducing area foils. ( fins angled at 45 degrees which as they rise out of water obviuosly present less wetted area.At any given speed the produce equal lift to load. T foils give more and more lift with rising speed...but there are inherent and as yet unsolved issues utilising constant lift foils on boards. ( google Hydroptere and Bruce foils for a much more concise explanation)
    I do not see many similarities between a foiling tri-marine and a windsurf board personally

  7. #28
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    That's perfectly true miker, there is very little at moment . The system used on foiling cats etc has a much bigger speed range and probably represents the highest efficiency on wind powered water craft.( Hydroptere set its max speed of around 55 kts in 25 kts wind) At some stage we will see boards using constant lift foils ,when we do we will see a massive jump in max speeds. Besides there are similarities with regards to fact nearly all systems use an inverted T somewhere , provides pitch stability on hydroptere, which as anyone who,s tried any foiling craft knows this is a critical and sensitive issue. ( it led to many injuries on air chairs ( sort of foiling kneeboard) in 90,s ,so much so I believe foiling tow craft were banned at UK ski clubs)

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