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  #46  
Old 12-23-2013, 10:08 AM
Baltic Bandit Baltic Bandit is offline
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Doug that's not true. regardless of where the crew sat the very weight of the boat's amas would themselves contribute to righting moment, and the fact that the crew sits to windward of the leeward hull means crew weight contributes to RM. The fact that you have wand driven foils doesn't change this

In fact while its true that theoretically you could have negative lift on a foil if the weather hull rose too far out of the water, in practice what you had was that as the weather hull rose, the feeler sent the foil to neutral and the WEIGHT of the crew and the weather ama (and rig) would generate the RM necessary

The Hobie/Rave system sucked going to weather - it was ok on a close reach, and a hoot from a bean to a broad reach. because of the rig power limits, it was useless much deeper than a broad reach.

But fundamentally screaming back and forth on a reach gets boring after a while
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  #47  
Old 12-23-2013, 10:13 AM
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Doug Lord Doug Lord is offline
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The feelers and wands cause the windward foil to develop downforce when required-proven time and again on both the Trifoiler, Rave, Osprey and Skat.
And described by Greg Ketterman here:

HYDROFOIL SAILBOATS IN GENERAL
"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."

------
* 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.dl
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  #48  
Old 12-23-2013, 10:18 AM
Baltic Bandit Baltic Bandit is offline
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"when required" - that in no way refutes the point I was making... unless magically the foils never go through less lift and then neutral lift on the way to negative lift Because if they go through neutral lift, then at the point of neutral lift - which is well before you will have negative lift due to the feelers, you will have the weight of the weather ama and the crew to weather of the leeward foil - all generating a downwards force vector due to gravity.

and that downwards vector, combined and offset from the lift vector of the leeward foil - creates a force couple that sailors call - Righting Moment.

Do you understand how this works even? Because from your comments it seems that perhaps you do not.
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  #49  
Old 12-23-2013, 10:19 AM
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Doug Lord Doug Lord is offline
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Flying Phantom

This is the Flying Phantom thread-lets get back to that boat...... we can continue a discussion of different foiling systems in another thread if anyone would like to.
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  #50  
Old 12-23-2013, 10:30 AM
Baltic Bandit Baltic Bandit is offline
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Quote:
Originally Posted by Doug Lord View Post
This is the Flying Phantom thread-lets get back to that boat...... we can continue a discussion of different foiling systems in another thread if anyone would like to.
Ok - but then Doug you ought not have cheered the digression. If you digress the thread, odds are some of us will respond. Shall we ask the moderator to delete all the posts from #45 onwards?
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  #51  
Old 01-13-2014, 06:38 AM
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From Phantom International, 1/13/13:

new website: http://www.phantom-international.com/

Flashback on these last weeks with Gurvan Bontemps – Flying Phantom Test Pilot
“I’m very happy with the new boat, the one we presented during the Paris Boat Show and that is the first production unit. The last two weeks were dedicated to sailing sessions with the new One Design Flying Phantom. The 4 sailing sessions were very instructive in order to discover the boat: we have new mast, new foils, new sails and the boat is much lighter than the prototype boat.
We continuously optimized the settings and L-shaped foils and T-shaped rudders were validated. We experienced different conditions with a range of wind speeds from 6 to 20 kts including flat water and moderate sea.
The new boat exhibits more stability, as compared to our prototype without any impact on performance, furthermore as the One Design boat is lighter the take-off is earlier than what we used to have in 2013 with the prototype and the boat is also foiling very well upwind.

We had a session with my crew Benjamin Amiot between Saint Lunaire and Saint Malo in areas with high current and significant waves and by changing slightly the foils’ incidence, we moved the boat in mix flying-skimming mode that allowed us to sail at a level of performance that is not achievable with F18 Catamarans. The boat was exhibiting a lot of power and stability leading to a smooth ride in full control even in difficult sea conditions.

We sailed also with Louis Viat (Franck Cammas crew on Groupama C) and François Gabart (winner of the 2013 Vendée Globe). Louis was really surprised by the performances and the simplicity of the Flying Phantom as compared to his experience with the C-Class Catamaran. François is an experienced F18 sailor and is used to multihulls and he was able to safely fly within the first 10 minutes. After 30 minutes he was pushing the boat in full flying mode with a big smile on his face. For him the biggest surprise was the ability of the Flying Phantom to go between 5 and 10 knots faster than a conventional F18 catamaran, even in moderate conditions.

We think we really moved a big step forward in beach catamaran sailing and we will race the boat the coming season in dedicated Flying Phantom events but as well in fleet races and long distance race.

We would like also to thank early adopters and top multihull sailors that ordered the first units of the Flying Phantom OD and We are looking forward to the first customers’ deliveries in April.”
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  #52  
Old 01-13-2014, 06:43 AM
Baltic Bandit Baltic Bandit is offline
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Quote:
Originally Posted by Doug Lord View Post
From Phantom International, 1/13/13:

new website: http://www.phantom-international.com/

Flashback on these last weeks with Gurvan Bontemps – Flying Phantom Test Pilot
“I’m very happy with the new boat, the one we presented during the Paris Boat Show and that is the first production unit. The last two weeks were dedicated to sailing sessions with the new One Design Flying Phantom. The 4 sailing sessions were very instructive in order to discover the boat: we have new mast, new foils, new sails and the boat is much lighter than the prototype boat.
We continuously optimized the settings and L-shaped foils and T-shaped rudders were validated. We experienced different conditions with a range of wind speeds from 6 to 20 kts including flat water and moderate sea.
The new boat exhibits more stability, as compared to our prototype without any impact on performance, furthermore as the One Design boat is lighter the take-off is earlier than what we used to have in 2013 with the prototype and the boat is also foiling very well upwind.

We had a session with my crew Benjamin Amiot between Saint Lunaire and Saint Malo in areas with high current and significant waves and by changing slightly the foils’ incidence, we moved the boat in mix flying-skimming mode that allowed us to sail at a level of performance that is not achievable with F18 Catamarans. The boat was exhibiting a lot of power and stability leading to a smooth ride in full control even in difficult sea conditions.

We sailed also with Louis Viat (Franck Cammas crew on Groupama C) and François Gabart (winner of the 2013 Vendée Globe). Louis was really surprised by the performances and the simplicity of the Flying Phantom as compared to his experience with the C-Class Catamaran. François is an experienced F18 sailor and is used to multihulls and he was able to safely fly within the first 10 minutes. After 30 minutes he was pushing the boat in full flying mode with a big smile on his face. For him the biggest surprise was the ability of the Flying Phantom to go between 5 and 10 knots faster than a conventional F18 catamaran, even in moderate conditions.

We think we really moved a big step forward in beach catamaran sailing and we will race the boat the coming season in dedicated Flying Phantom events but as well in fleet races and long distance race.

We would like also to thank early adopters and top multihull sailors that ordered the first units of the Flying Phantom OD and We are looking forward to the first customers’ deliveries in April.”
IOW
a) having experience with cats and foiling cats is mandatory for "safe flight"

b) even then it takes time to actually sort out flying.


Hardly an easy boat to fly steady then
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  #53  
Old 01-13-2014, 07:18 AM
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From Phantom International:
http://vimeo.com/83829320#at=0
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  #54  
Old 01-16-2014, 08:04 AM
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Flying Phantom

Great Flying Phantom Picture. Note inboard lee foil tip:

click for best view-( pix by Pierrick Contin.fr)
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Flying Phantom F 18 Catamaran-flyingphantomod_09012014_sailingsession_-1.jpg  
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  #55  
Old 01-20-2014, 11:46 AM
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The most significant one design foiler in years-video from SA frontpage. Interesting that the inboard lee foil tip is out most of the time. Be interesting to see if boats flown with the tip always immersed will be faster:
http://vimeo.com/84585161#at=0
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  #56  
Old 01-21-2014, 05:49 AM
idkfa idkfa is offline
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Not impressed, in the SA video what's the wave height, 1' max? Have a look from 1.50-2 what's all the pitching about? This is not a stable boat, post a video in normal conditions versus a late afternoon light air sail.
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  #57  
Old 01-21-2014, 06:53 AM
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not
Quote:
Originally Posted by idkfa View Post
Not impressed, in the SA video what's the wave height, 1' max? Have a look from 1.50-2 what's all the pitching about? This is not a stable boat, post a video in normal conditions versus a late afternoon light air sail.
==============
Any sailboat will pitch in the right combination of waves-she was rock steady before and after that episode.
I disagree-this is a very stable foiler compared with almost any other foiler ever.
I'm not sure how "light" the wind was in that video but one of the attributes of this boat is it's ability to foil in light air-(7kts)-previous incarnations of multihull production foilers needed 12-15 knots before they'd fly.
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  #58  
Old 01-21-2014, 06:55 AM
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schakel schakel is offline
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Quote:
Originally Posted by idkfa View Post
Not impressed, in the SA video what's the wave height, 1' max? Have a look from 1.50-2 what's all the pitching about? This is not a stable boat, post a video in normal conditions versus a late afternoon light air sail.
It's for flat water ok but to say I am not impressed is somewhat different.
What about this?

Impressed?
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Flying Phantom F 18 Catamaran-jaws_-_david_pu_u.767.jpg  
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  #59  
Old 01-21-2014, 09:55 AM
Baltic Bandit Baltic Bandit is offline
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Quote:
Originally Posted by Doug Lord View Post
==============
Any sailboat will pitch in the right combination of waves-she was rock steady before and after that episode. I disagree-this is a very stable foiler compared with almost any other foiler ever.
I'm not sure how "light" the wind was in that video but one of the attributes of this boat is it's ability to foil in light air-(7kts)-previous incarnations of multihull production foils need 12-15 knots before they'd fly.
Doug you've never sailed it
in fact you have never sailed a foiler other than a Rave so you really don't have much to compare it to, much less make outright assertions about the F18 stability or its actual One Design pedigree.

<removed jab at other member>

Last edited by Boat Design Net Moderator : 01-21-2014 at 05:17 PM. Reason: Reported post: Removed jab at other member; he has been asked not to jab at you, so the same must apply to you about him.
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  #60  
Old 01-21-2014, 12:38 PM
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Tom.151 Tom.151 is offline
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Quote:
Originally Posted by Doug Lord View Post
Interesting that the inboard lee foil tip is out most of the time.
Just a lovely boat -- interesting observations by Gabart about how easy the boat was to sail.

Is not the tip being out of the water just a reflection of the amount of (excess) lift that would be available if the foil were fully immersed (for the current conditions)? (Once the boat got flying anyway.)

Seems like that's the 'balance of forces' condition. Or am I missing something on your reasoning?

Wouldn't that also be expected for a boat designed to fly in light air?
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