New Catamaran Foilers

Cat Foiler Links

Links to threads about other cat foilers:
1) http://www.boatdesign.net/forums/multihulls/vampire-cat-canted-t-foils-51329-2.html#post740664
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2) http://www.boatdesign.net/forums/multihulls/gc-32-super-cat-45062-12.html
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3) http://www.boatdesign.net/forums/multihulls/whisper-foiling-catamaran-51411.html
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4) http://www.boatdesign.net/forums/mu...ip-foils-no-wands-major-innovation-53096.html
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5) http://www.boatdesign.net/forums/multihulls/foiling-nacra-f20-revolution-continues-49161-2.html
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6) http://www.boatdesign.net/forums/multihulls/flying-phantom-f-18-catamaran-43898-7.html
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7) http://www.boatdesign.net/forums/multihulls/gunboat-g4-uptip-foils-50397-11.html

 

A Class Catamaran

A Class cat on foils and the story behind the video: http://www.catsailingnews.com/2015/06/q-with-bob-fischer-retrofitting-1998.html#more
http://www.catsailingnews.com/2015/06/q-with-bob-fischer-retrofitting-1998.html#more

 

Stiletto XF

The Stiletto is(probably) back in both a foiling and non-foiling version:

https://sailstiletto.com/own-a-stiletto-catamaran/

 

Modified Nacra 20 FCS

This is a heavily modified NACRA FCS-wider and different foils. Done by Phillipe Kahn:
https://www.youtube.com/watch?v=kQkIHdOgsMs

 

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From The Foiling Week, 1/23/16 :
https://www.youtube.com/watch?v=5m4aZEWSaUI

 

S6 Foiler

In the post that is quoted above I somehow got the length wrong-the boat is 14'
not 12'. Website including S9 specs: http://www.s9team.eu/
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UPDATE: Michele Petrucci is developing a larger version of the S9-the S6-about 16' LOA--render below:

 

S9 in Texas

Two S9's have arrived in Texas in the last two weeks:

 

S9

S9 video: https://www.youtube.com/watch?v=zyifEzJ37wQ&feature=youtu.be

 

Nice video.
What would happen if you just sit on the trampoline ? I'd imagine that would give more of a "magic carpet ride to the sunset feeling" than hanging in the trapeze.
Just curious if it would be possible.

Cheers, Hans

 

S9

The boat uses main foils with dual,independent wands(surface sensors) so if the crew just sat on the tramp the boat would pretty much stay at the same angle of heel as it was when he/she was on the trap. The only difference is the proportion of lift on the foils changes a bit. The dual wands automatically correct any excessive heel. The boat would sail by itself if the crew wasn't on board.
Personally, I think I'd like the trap better than sitting on the tramp which has always been uncomfortable to me.....

 

Stiletto

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More on the Stiletto from The Foiling Week: http://www.foilingweek.com/blog/2016/03/stiletto-manufacturing-nominates-schickler-tagliapietra/

 

I disagree. The individual T foils and wands provide dynamic stability but when the crew moves inward from the trap and the foils go from both lifting to fighting each other the induced drag increases proportionally. Upwind the drag increase would be enough to force the boat to head off to stay foiling. Downwind it would make sense to sit on the tramp and it would still foil with sufficient wind.

About the boat sailing without the crew -the upwind performance is improved significantly with the addition of the crew weight shifting side to side. A boat optimized for sailing without the crew weight shift would be extremely wide beamed.

The boat does look very well behaved and stable -and fast in what looks to be light wind. I would like to see how it behaves in high wind and waves because that is a limitation of the cheaper waszp.

 

Is it realistic to believe the Stiletto will easily foil? I thought the boats had to be very light in order for the boat to take off in anything but heavy air. I was under the impression that even the GC32 can't foil upwind in moderate conditions.

 

Wands

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The foils don't fight each other-regardless of weight the dual independent wands stabilize the boat.
An S9 crew fell overboard at The Foiling Week last year and the boat continued to foil for 3 kilometers with no crew.
The dual independent wands allow the same righting moment regardless of crew weight. Because of the way the wands work the crew is able to sit in the center of a Rave and on an Osprey the crew can sit anywhere and the wands keep it level. The Hobie Trifoiler has dual independent "feelers" that move each foil to provide all the RM for the boat-that's why the crew sits in the center on that boat.
The Whisper cat also has dual independent wands and that boat can be sailed singlehanded or doublehanded in almost any breeze because the wands automatically compensate for the lack of a second crewperson.
I think you're right that the wand controlled boat that allows the crew to move probably has reduced drag.


Heres what Greg Ketterman has to say about how the "feelers" work on the Trifoiler. The way the wand works is very similar:

"Hydrofoil boats can be categorized into two categories; 1) Incidence controlled hydrofoils* and 2) surface piercing hydrofoils. The difference lies in the way the boat maintains the proper altitude above the water surface. A surface piercing hydrofoil boat maintains proper height by varying the amount of foil submerged. The boat raises up as the speed increases and reduces the amount of foil submerged and therefore the lift. The boat finds equilibrium at the proper altitude. An incidence controlled hydrofoil sailboat has a mechanism that controls the angle of attack of the foil to maintain the proper altitude. It is generally believed that surface piercing is simpler, but incidence control is more efficient. In reality, it is the method that works with fewer problems that is simpler.
From the beginning it was felt that incidence control was better suited for a sailboat even though most of the existing hydrofoil sailboats were of the surface piercing type. There are many advantages of the incidence controlled foils; however, the most important is what I call the DLA (dynamic leveling affect). This is the increase in righting moment or stability due to the ability of the windward foil to pull down. The DLA has little affect on the low wind performance, but it essentially makes the top speed of the boat limited to the strength of the boat. Conventional boats with a finite amount of righting moment can only extract so much power from the wind, but with the DLA, the righting moment is virtually unlimited.
Intuitively many people think that the added drag of the windward foil plus the increased induced drag of the leeward foil would offset the gain in righting moment, but calculations show and practice proves otherwise. The dynamic leveling affect not only produces a dramatic increase in top speed, but is also responsible for all the other key features that this stability provides.
The other major advantage of the incidence controlled foils is they are less affected by the waves and other surface affects. Drag and losses associated with the surface are the major reason incidence controlled foils are more efficient.
All hydrofoil sailboats have problems with ventilation; however, surface piercing foils have larger problems, because the foils are piercing the surface at a smaller dihedral angle which makes it easier to ventilate."
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* On the Trifoiler the entire foil was moved to control RM, lift and negative lift hence the term "incidence controlled foils". On the Rave the incidence was generally fixed at +2.5 degrees for the main foils though some owners found a way to decrease the incidence on the windward foil. Lift and negative lift on a Rave foiler is generated by the wand (designed by Dr. Sam Bradfield), a surface sensor(dragging in the water) and attached directly via linkage to a flap on each main foil. The wands are independent just like the trifoiler "incidence controlled" foil sensors.

 

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That's a hard question to answer without any facts about weight, foil area etc.
But one clue is the involvement of Doug Shickler and his partner-they were instrumental in engineering the G4.