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 Post subject: Can a hydrofoil be shorter than current design?
PostPosted: Thu Sep 26, 2013 11:33 pm 
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It seems to me that foils are the light wind wepon of choice but i wonder what would be lost by loosing 20 cms of keel lenght. most foills are ridden in super flat wáter.
this question comes from seeing that most of the time foils are 30 cms in wáter and the other 60 cms on air.is this really needed?
torque wise the 90 cm length makes the keel more prone woble or breaking.
is this assumption correct?
Im want to build one from scrap and learn!
thanks for sharing.
Pedro


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 Post subject: Re: Can a hydrofoil be shorter than current design?
PostPosted: Thu Sep 26, 2013 11:48 pm 
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There are training foils that are only 50CM long.
The tried and truth length is around 90CM or three feet long.
There is also one that is like 10 or 12 foot tall, but that is more like an experimental unit for world record.


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 Post subject: Re: Can a hydrofoil be shorter than current design?
PostPosted: Fri Sep 27, 2013 4:13 am 
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...not sure but it might have something to do with the phenom of air getting sucked down along the leading edge. I've seen some video of it on moth hydrofoil sailboats I think. The vertical part of the setup sucks air down causing turbulence or reducing lift or both (?)

I've asked the same question and that is what someone pointed me to. I haven't yet been able to confirm it with a foil designer though...

Thanks,
Stafford

www.adventurekiteboarding.com


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 Post subject: Re: Can a hydrofoil be shorter than current design?
PostPosted: Fri Sep 27, 2013 6:59 am 
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droffats wrote:
...not sure but it might have something to do with the phenom of air getting sucked down along the leading edge. I've seen some video of it on moth hydrofoil sailboats I think. The vertical part of the setup sucks air down causing turbulence or reducing lift or both (?)

I've asked the same question and that is what someone pointed me to. I haven't yet been able to confirm it with a foil designer though...

Thanks,
Stafford

www.adventurekiteboarding.com

What you are referring to is called Ventilation. When air got sucked in through the strut to the fin.


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 Post subject: Re: Can a hydrofoil be shorter than current design?
PostPosted: Fri Sep 27, 2013 8:45 am 
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I will get back to this subject shortly. I do not think their is anyone more historically knowledgeable on this forum to provide the history and current production of hydrofoils in launching in shallow water OR short or longer shafts. However, a quick note on the subject of launching in shallow waters.

TO LAUNCH IN SHALLOW WATER DO IT VERY CAREFULLY SO AS NOT VOID THE WARRANTY BY HITTING THE BOTTOM!
:lol:
Attachment:
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file.jpg [ 203.81 KIB | Viewed 788 times ]


MANGO CARAFINO, PHOTO TAKEN 1999 MAUI, HYDROFOIL SURFING MODEL BALSA DICK BREWER OUTREEF WAVE CATCHER.


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 Post subject: Re: Can a hydrofoil be shorter than current design?
PostPosted: Fri Sep 27, 2013 9:27 am 
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windfreak74 wrote:
It seems to me that foils are the light wind wepon of choice but i wonder what would be lost by loosing 20 cms of keel lenght. most foills are ridden in super flat wáter.
this question comes from seeing that most of the time foils are 30 cms in wáter and the other 60 cms on air.is this really needed?
torque wise the 90 cm length makes the keel more prone woble or breaking.
is this assumption correct?
Im want to build one from scrap and learn!
thanks for sharing.
Pedro


Why do you say/think most foils are ridden in super flat water ???

I've never ridden in flat water (and never super flat), but only in a couple of feet chop as the most flat, but more often big chop or even 3-5 foot waves also, sometimes breaking too.

So the 100cm keel I have is perfect IMO :rollgrin:

I have seen Rush Randle, using super short keels on some test models a couple of years ago.

But as you DONT want the foil to reach the surface, as it will ventilate and you either crash or slow down, and you DONT want to touch the water with your board either - as this slows you down like hitting a brake - then it makes sense to have a keel of a certain length, in order to have some "room" for error and waves/chop :thumb:

This is just for going straight.

When turning and jibing/tacking, "height" is really really important, as you need some room when you trip around/change feet or jump around on your board - so it wont get down on the surface and make a full stop :-?

So lots of reasons why it has a certain lenght, typically between 85 and 100cm now.

8) Peter


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 Post subject: Re: Can a hydrofoil be shorter than current design?
PostPosted: Fri Sep 27, 2013 9:55 am 
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Have anyone experimented with increasing the distance between the foils for increased stability at (high) speed?


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 Post subject: Re: Can a hydrofoil be shorter than current design?
PostPosted: Fri Sep 27, 2013 10:10 am 
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KristianE86 wrote:
Have anyone experimented with increasing the distance between the foils for increased stability at (high) speed?


Definitely, mine is pretty "long".

I am sure it will be on cost of "turnability", so horses for courses !

As with kites, you can not get it all :naughty:

8) Peter


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 Post subject: Re: Can a hydrofoil be shorter than current design?
PostPosted: Fri Sep 27, 2013 2:22 pm 
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Heres the champ on a foil. Looks insane!!!!
https://www.youtube.com/watch?v=GXV3Wdu_Ms4


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 Post subject: Re: Can a hydrofoil be shorter than current design?
PostPosted: Fri Sep 27, 2013 5:48 pm 
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There seems to be a dimension used by some airlines for standard baggage size, of 158 cm, which is the upper limit for L+W+D.

So if you allow 102cm for the length and 44cm for the width, you are left with 12cm for the depth for example.
20 kg is a common limit for standard luggage.
This may be relevant in terms of travelling with a foil board.


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