94 replies to this topic

[ita 16]

Hi hall , anyone knows if exist planing catamarans? Which?

[dumper]

sorry i dont know any details

[Doug Lord]

Yves Parlier experimented with planing cats building an rc version, a twin trapeze version and a 60' twin rig version. All these boats used a stepped hull without variable geometry. They used rudder t-foils to keep the back end clear. The drag of the 60 footer dropped to 20% of a "normal" cat above 20 knots but when the boat was slower it had high drag. Parlier had the 24hr. ocean record for a short while.
The most recent incarnation of a planing cat is "Hydroptere.ch" which uses a variable geometry planing hull, in addition to retractable surface piercing main foils and rudder t-foils. The whole front bottom of both hulls drops down to form stepped planing hulls. This boat has set several records in lake sailing.

Attached Files

•  Hydroptere.ch 2 6-3-11.jpg   211.83K   96 downloads
•  hydroptee.ch-hydros planing config.jpg   104.96K   126 downloads
•  Parlier%20test%20boat.jpg   41.79K   143 downloads
•  Parlier 60\' -aeroyacht.jpg   7.5K   117 downloads
•  Parlier rudder t-foils-stepped hull.jpg   21.69K   74 downloads

[ita 16]

Thanks Doug and Dumper,there is something more simple,12 to 20 foot ?

[eric e]

windsurfer?

seriously, the problem with planing hulls is the need to be always working

or they suck

this is not good for a craft powered by the variable wind

similar issues for foilers

the window is too narrow without power

[Presuming Ed]

Tri(pod/maran?), not a cat:

[Catnewbie]

ITA 16,

You should googlize : "Savistky", "Faltinsen", "semi-displacement hulls", " ........ for instance try the following:

"Procedure for hydrodynamic evaluation of planning hulls in smooth and rough water"

Daniel Savistky and P.Ward Brown Marine Technology Vol 13, No. 4 October 1976

It is a good startpoint, After this one and many others, I feel confident you will be able to achieve your own design soon

Sorry, The Acrobat file I wanted to attach is" too big to upload"

Good reading

[ita 16]

Thanks,all projects are interesting. Ihave created my prototype (12 feet),I want to compare this to existing designs.

[vmg]

http://www.ebay.co.u...=item3f192ffe23

As you can tell by the price.. it doesn't work!

[dumper]

Thanks,all projects are interesting. Ihave created my prototype (12 feet),I want to compare this to existing designs.

Any photos??

[Doug Lord]

Hi hall , anyone knows if exist planing catamarans? Which?

------------------------
Some people say the "Paper Tiger" is a planing cat:

[Doug Lord]

This definitely is a planing cat:

As is this:

Attached Files

•  Kona plus cb illus..jpg   96.68K   27 downloads

[k2mav]

Thanks,all projects are interesting. Ihave created my prototype (12 feet),I want to compare this to existing designs.

...it has channels a la RC 16? but rounded?

[ita 16]

Thanks,all projects are interesting. Ihave created my prototype (12 feet),I want to compare this to existing designs.

Any photos??

I prefer not to publish photos or data,to avoid polemics. I have photos and video description on my FB profile. Can you go to this?

[k2mav]

I think I have the render and the pics of the Proto. It looks good.
Saw the video, you need to make a 16 footer, there you will see how well it works.
For a better track you'll need square channels.

Will pm later.

[ita 16]

I think I have the render and the pics of the Proto. It looks good.
Saw the video, you need to make a 16 footer, there you will see how well it works.
For a better track you'll need square channels.

Will pm later.

The report detailed isnt on profile Bi...e ,is on my personal profile. The movie was made on the first day,I tested this cat only 3 hours, a few hours to make a movie good. I HOPE in future .

[ita 16]

This definitely is a planing cat:

As is this:

Yess , this is fun and fast .

[SUI1]

Ventilo http://www.ventilo.ch/ had a 16 feet catamaran with planing hulls called "zippo".

No more produced...

[ita 16]

Ventilo http://www.ventilo.ch/ had a 16 feet catamaran with planing hulls called "zippo".

No more produced...

I do not find on the website,you have a photo or data?

[k2mav]

Ventilo http://www.ventilo.ch/ had a 16 feet catamaran with planing hulls called "zippo".

No more produced...

I do not find on the website,you have a photo or data?

Ventilo.. Mattia also. But too flat, the best is an hybrid of current hull shapes and a super flat tail/transom + Channels/FW step btottom.

Below Ventilo, and Mattia

[PYC]

FYI,
Guillaume Verdier designed the Tomcat 18HT some years ago: http://www.guillaume...n-Voile-Legere/

[kinardly]

Not a cat but would the Hobie Trifoiler be considered a planing boat?

[eric e]

no

a foiling boat

as in the difference between a hydrofoil, gets up on foils

and a normal powerboat, gets up on the plane on the last few feet of hull

[Lost in Translation]

Randy Smyth's Scissors trimaran also has what look to be planing amas. The center hull is more traditional and is the only hull in the water when going slow. Very clever.

[Catnewbie]

The VENTILO and MATTIA above-mentionned were designed by a french guy called Remy Laval-Jeantet, he is supposed to be Phd in Fluid Dynamics, he has worked with Parlier as well, at least for some time.

In the mid 90's he also designed a F18 with similar radical design, called the Cutter 18 but as for all his other designs the performance were questionnable, and during a test session including a wide range of beach cats (M20 HC Tiger A-cat ....)his F18 Cutter 18 arrived behind a Dart 15, in light wind, the crew on the boat were the guys who are the French F18 training coachs at ENV today.

Despite evidence that his concepts do not work, he is sure to be a genius, and he gained the nickname of "Laval Dejante", Dejante: in French means brain-freak, crazy, fool, stupid, sucker, mentally disable, don't remenber exactly the translation.

In the 90's he was travelling to see C-Cat, and during a trip to Australia, he managed to borrow an A-Cat to Barry Marmion, and as far as I know, he destroyed some part of the boat.

He pretended to be able to design boats but was hardly able to sail a HC16.

A pure ideologist with the same intellectual biais than the communists:( when you told them their system fail to deliver its promises, they answered you it is because the system is not enough communist). So if his designs failed to show performance, it is because the boat builder refuse the ultra-radical solutions or failed to make the boat the right way and so on, but never questions his own genius.

It could be a bit risky to invest on these ideas, just ask Enrico Contreas how many boats like that have been built, same question with Ventilo, it could be a good indicator.

Cheers Everybody

W

[hump101]

Just go back to basics. A hull that will plane will have very high form and frictional drag when not planing, and when planing will have very limited pitch stability combined with a variable centre of pressure - a poor combination for a vessel where the driving force is high up, and hence pitch moment is significant. One way around this is to use separate longitudinal planing surfaces, either with steps or with individual pods, but both have worse non-planing drag characteristics than a single planing surface, for a given displacement, hence only really effective on speedsailors which don't operate in sub-planing conditions. Better options include combining planing surfaces with alternative lifting surfaces that provide the required pitch stability as speed increase. This can be hydro or aerofoils, depending on application. The combination of planing surfaces and foils can be more efficient over a much broader speed and displacement range than either option on their own.

I felt it a real shame that Parlier's boat has been used as a reason to criticise biplane rigs, when the planing hulls probably held it back significantly more, in real terms.

[dumper]

i was talking to paul larson a while back and he said the hardest part of the record runs on sailrocket is accelerating to 30 knots, at that speed the hulls are planing

[SC65]

Yves Parlier experimented with planing cats building an rc version, a twin trapeze version and a 60' twin rig version. All these boats used a stepped hull without variable geometry. They used rudder t-foils to keep the back end clear. The drag of the 60 footer dropped to 20% of a "normal" cat above 20 knots but when the boat was slower it had high drag. Parlier had the 24hr. ocean record for a short while.
The most recent incarnation of a planing cat is "Hydroptere.ch" which uses a variable geometry planing hull, in addition to retractable surface piercing main foils and rudder t-foils. The whole front bottom of both hulls drops down to form stepped planing hulls. This boat has set several records in lake sailing.

There was also the infamous Hurricane 6.5, Randy Smith won the Worrel with at that time.

Attached Files

•  normal_Text 1.jpg   71.44K   233 downloads
•  normal_Text 2.jpg   25.81K   228 downloads

[Doug Lord]

Just go back to basics. A hull that will plane will have very high form and frictional drag when not planing, and when planing will have very limited pitch stability combined with a variable centre of pressure - a poor combination for a vessel where the driving force is high up, and hence pitch moment is significant. One way around this is to use separate longitudinal planing surfaces, either with steps or with individual pods, but both have worse non-planing drag characteristics than a single planing surface, for a given displacement, hence only really effective on speedsailors which don't operate in sub-planing conditions. Better options include combining planing surfaces with alternative lifting surfaces that provide the required pitch stability as speed increase. This can be hydro or aerofoils, depending on application. The combination of planing surfaces and foils can be more efficient over a much broader speed and displacement range than either option on their own.

I felt it a real shame that Parlier's boat has been used as a reason to criticise biplane rigs, when the planing hulls probably held it back significantly more, in real terms.

======================
I wouldn't write off advanced planing hull design if I were you: hydroptere.ch has been setting records with its combination of variable geometry stepped planing hull and retractable foils. http://www.boatdesig...ch-35033-4.html
This site has pictures of the variable geometry stepped planing hulls: http://www.sail-worl...ed-record/99629

[ita 16]

I decided about a board curves blend with planing hulls "without tunnel". the first day indicated speed 20 knots, wind 12-14.

[Doug Lord]

I decided about a board curves blend with planing hulls "without tunnel". the first day indicated speed 20 knots, wind 12-14.

==================
Any chance of seeing some pictures or more detail? Got a link?

[ita 16]

on my FB profile or this simple video by a friend. http://www.youtube.c...XjGXQD3c&sns=fb

[ita 16]

facebook : https://www.facebook...=3&l=19a2bfd18a

[Doug Lord]

on my FB profile or this simple video by a friend. http://www.youtube.c...XjGXQD3c&sns=fb

=======================
Can't access your fb page. The boat in the video looks great-appears to have planing hulls? Are you using lifting foils as well? Got any numbers?

[MisterMoon]

Randy Smyth's Scissors trimaran also has what look to be planing amas.

Um, no.

[ita 16]

now is open , you can see on FB

[MountainCat]

There was also the infamous Hurricane 6.5, Randy Smith won the Worrel with at that time.

The performance of this boat as reported (close to 40 Knots?) appears to be much better than C-class, the Nacra F20C and the AC45s. The boat raises many questions.

Is the reported performance factual?

What happened to this boat?

How many 6.5's were built?

Why were more not built?

Where is more information about this boat?

[Börni]

A really cool concept! Looking forward to further reports on how the boat performs in different conditions and the development of the boat! Good work!

facebook : https://www.facebook...=3&l=19a2bfd18a

[Doug Lord]

now is open , you can see on FB

=========================
Looks great! Would you expect a penalty in light air performance and tacking? Good Luck-nice job!

[ita 16]

now is open , you can see on FB

=========================
Looks great! Would you expect a penalty in light air performance and tacking? Good Luck-nice job!

In tacking no problem, just penalized with a light wind,but over 10 knots you feel best accelerations of an A-class. It is not designed for racing but for emotions , like a windsurfer , seems to be very similar.

[bruno]

My understanding as a layman is that narrow hulls have smaller bow waves to push through.

[PYC]

Fantastic, ITA-16!
This is a perfect boat for a quick sailing session after work.
What is its weight?

[ita 16]

Fantastic, ITA-16!
This is a perfect boat for a quick sailing session after work.
What is its weight?

Thanks PYC , weight 55-65 kg .

[rob d]

If you have planing hulls is there a benefit of having a rudder gantry to move the rudders back another foot or so from the foils, 12 ft cat, planing hulls-12ft skiff ideas?

[hump101]

Just go back to basics. A hull that will plane will have very high form and frictional drag when not planing, and when planing will have very limited pitch stability combined with a variable centre of pressure - a poor combination for a vessel where the driving force is high up, and hence pitch moment is significant. One way around this is to use separate longitudinal planing surfaces, either with steps or with individual pods, but both have worse non-planing drag characteristics than a single planing surface, for a given displacement, hence only really effective on speedsailors which don't operate in sub-planing conditions. Better options include combining planing surfaces with alternative lifting surfaces that provide the required pitch stability as speed increase. This can be hydro or aerofoils, depending on application. The combination of planing surfaces and foils can be more efficient over a much broader speed and displacement range than either option on their own.

I felt it a real shame that Parlier's boat has been used as a reason to criticise biplane rigs, when the planing hulls probably held it back significantly more, in real terms.

======================
I wouldn't write off advanced planing hull design if I were you: hydroptere.ch has been setting records with its combination of variable geometry stepped planing hull and retractable foils. http://www.boatdesig...ch-35033-4.html
This site has pictures of the variable geometry stepped planing hulls: http://www.sail-worl...ed-record/99629

I'm not writing planing hulls off at all - the L/D ratio of a planing surface when running at optimum pitch in smooth water is higher than foils can achieve, once all the parasitic drag is taken into account. I'm just pointing out the limitations, particularly for long slender planing surfaces where the movement of the centre of pressure with speed is significant.

[dacarls]

Randy Smyth's Scissors trimaran also has what look to be planing amas.

Um, no.

Actually, Randy's new amas for Scissors are---VERY interesting.

[JimC]

anyone knows if exist planing catamarans?

Been tried lots of times, never much good. The reason isn't hard to find. A planing hull is a lifting surface, and much of the drag of lifting surfaces is controlled by the aspect ratio (yeah, just like wings and sails). All hulls have adreadful aspect ration, but the shorter and fatter the hull the better. Short fat catamaran hulls are dreadful of course, so what you get will either be a dreadful boat in sub planing conditions or a lousy boat in planing conditions, and probably both. So it may just be possible to build a craft that's a one trick pony, hence stepped hulls, but most likely not even that...

[Doug Lord]

anyone knows if exist planing catamarans?

Been tried lots of times, never much good. The reason isn't hard to find. A planing hull is a lifting surface, and much of the drag of lifting surfaces is controlled by the aspect ratio (yeah, just like wings and sails). All hulls have adreadful aspect ration, but the shorter and fatter the hull the better. Short fat catamaran hulls are dreadful of course, so what you get will either be a dreadful boat in sub planing conditions or a lousy boat in planing conditions, and probably both. So it may just be possible to build a craft that's a one trick pony, hence stepped hulls, but most likely not even that...

===================
Hydroptere.ch has proven ,without a doubt, that variable geometry stepped planing hulls can be made to work very well in conjunction with lifting foils. see the links in post 29.

[ita 16]

anyone knows if exist planing catamarans?

Been tried lots of times, never much good. The reason isn't hard to find. A planing hull is a lifting surface, and much of the drag of lifting surfaces is controlled by the aspect ratio (yeah, just like wings and sails). All hulls have adreadful aspect ration, but the shorter and fatter the hull the better. Short fat catamaran hulls are dreadful of ecourse, so what you get will either be a dreadful boat in sub planing conditions or a lousy boat in planing conditions, and probably both. So it may just be possible to build a craft that's a one trick pony, hence stepped hulls, but most likely not even that...

Yesterday the fourth day of testing,wind 10 to 18 knots,terrible steeply wave,my speed was the same as windsurfing and kytesurf. I believe that the mix of boards curves and flat surfaces to be ok for catamarans. are so many 18 knots speed with a 12 feet. This is probably the future. Objective fun is reached,next goal is to fly.

[eric e]

videos would be good

will this be a bimare product?

[PYC]

Objective fun is reached,next goal is to fly.

The two best boats I ever sailed are Bimare X16F and international moth. Cannot wait seeing it fly.

[ita 16]

Objective fun is reached,next goal is to fly.

The two best boats I ever sailed are Bimare X16F and international moth. Cannot wait seeing it fly.

yea , good . I should have results in about 1 month !!

[ita 16]

I have not enough time to build the foils for flying, I hope next season. but, I believe that the hulls are well behaved, the only problem is the difficult wave in Cesenatico, it is very difficult to create a 12-foot for all conditions of wind and wave. it was still great fun.

http://www.youtube.c...U&feature=share

[ita 16]

videos would be good

will this be a bimare product?

not bimare , is personal project.

[ita 16]

videos would be good

will this be a bimare product?

not bimare , is personal project.

http://www.facebook.com/catamaran.stunt

[Amati]

Chris White did one.

http://www.wingo.com...te/tiltrig.html

Bootiful? Now known as unlimited speed sailer.

Scroll down the page, also Sea Spider,

http://www.windjet.c...id=21&Itemid=56

Many others, Portsmouth speed week history should hold some gems, as well as AYRS...

2 hulls.....?

http://www.alibi-architecture.eu/prao/dossiers/seb's%20toy.pdf

[ita 16]

Chris White did one.

http://www.wingo.com...te/tiltrig.html

Bootiful? Now known as unlimited speed sailer.

Scroll down the page, also Sea Spider,

http://www.windjet.c...id=21&Itemid=56

Many others, Portsmouth speed week history should hold some gems, as well as AYRS...

2 hulls.....?

http://www.alibi-arc...s/seb's toy.pdf

thanks, all interesting projects. are very useful to my research. I look for the right balance between planning hull, fly boat, and standard old style, to get a cat excellent in all situations, and for different crews. I think I have succeeded, for the most part, the hulls of the stunt 13.9 are perfect, now I must develop good Appendices "rudders, boards." in the movie you see the prototype "stunt 1.2, 12 ft" with wind 10-12 knots. how do you feel?

http://www.facebook.com/photo.php?v=10151214786932909

[Amati]

Can't get the Facebook link to fire, but saw the other one- if you're already helming at the back of the hull, have you tried raking the sail back and sailing off the rudder? Kind of like sailing on a windsurfer skeg? Maybe use the daggerboards only for light airs. Be easy to try-

Watching your cat trying to achieve liftoff was, um, like watching chop jumping down at the Gorge, so maybe the windsurfer metaphor isn't that off?

It's hard to tell if you have hard chines or not, but if you do, and usually planing cats don't go very high upwind anyway, maybe footing upwind in higher wind without the drag of the daggerboard might give you better VMG? Use the chine(s) for some dynamic lateral lift?

At the very least, you could then concentrate on rudder design ideas.

[ita 16]

Can't get the Facebook link to fire, but saw the other one- if you're already helming at the back of the hull, have you tried raking the sail back and sailing off the rudder? Kind of like sailing on a windsurfer skeg? Maybe use the daggerboards only for light airs. Be easy to try-

Watching your cat trying to achieve liftoff was, um, like watching chop jumping down at the Gorge, so maybe the windsurfer metaphor isn't that off?

It's hard to tell if you have hard chines or not, but if you do, and usually planing cats don't go very high upwind anyway, maybe footing upwind in higher wind without the drag of the daggerboard might give you better VMG? Use the chine(s) for some dynamic lateral lift?

At the very least, you could then concentrate on rudder design ideas.

excellent observations. my big problem is the curved boards are not good on a planing boat, only by applying large foil rudders are managed to stabilize the jump effect "caused by the curved boards." All this system works well just for fun, is not good for the race. in the new boat I will use only straight boards, the effects planing is already very good and even more constant speed without the boards curves. the boat seems very fast upwind, I compared at sea with class A, with 10-14 knots of wind we had the same speed but I go 5 degrees less. I modified the hull, from 3.6 m to 4.15 m , because I had no bow sufficient length to correctly use the system wave piercing. from 2 months to know if I did good work. my goal is also to fly the boat for fun, I will prepare rudders with foil straight boards with foil, but I doubt that the position of the boards is correct. you think these changes will be good?

[Amati]

Are you planing upwind?

[ita 16]

at the moment I do not think I can call planing, but the boat has a good speed, the bow is almost always out of the water, when accelerates the tendency to bear away.

[Amati]

Have you tried sailing with just the rudders, no daggerboards? I suppose you'd have to plug the daggerboard slots to lessen drag-

And rake the rig back to balance things....

[Amati]

And as long as it's just for fun, have you considered a shallow v foil that would span between the the hulls?

Something like this? ( sorry for the crudeness of the cartoon, you'll have to connect the dots).

. .
.

Nice thing about not being bound by class rules. A little like the Russian river hydrofoil approach. You could try attaching it through your present daggerboard holes. They might be a bit far back though? Maybe not. At least they would offer you the opportunity to experiment with the depth of the thing. Less distance to fall back to the water, no tip loss, 2 water piercing struts though. Would be a logical transition from your mast building, maybe? Dihedral!

And how much more wetted surface would it be than your daggerboards now?

[Amati]

I guesses it could shaped like this to give you some vertical lateral resistance, and fit inside of the existing daggerboard wells:

| |
| |
.

Or

| |
.___.

Or as a dolphin striker that acts as structure as well as lift and lateral resistance:

| | |
|
.

You'll have to imagine that the middle vertical foil is joined at the middle of the v foil. There's got to be an iPad app out there for this kind of graphics....

[Amati]

A picture!

http://www.foils.org...ery/hydsg01.JPG

Might be wider on a cat though, still, looks like fun...

A bit more technical

http://www.tspeer.co...ils/generic.pdf

[ita 16]

A picture!

http://www.foils.org...ery/hydsg01.JPG

Might be wider on a cat though, still, looks like fun...

A bit more technical

http://www.tspeer.co...ils/generic.pdf

I believe that with the straight boards increase performance very much, I've never tried without boards , is a test that I will soon. I think the rig is already very backward toward the stern. topic foil: in the first test I wanted to use simple but effective system with straight boards and L foil, after this test also will appraise V foil as you suggested. I do not remember how the immersed surface of the boards, are also used on Class A 15cm x110cm.

[Amati]

This is a very cool project- keep us in the loop?

[ita 16]

This is a very cool project- keep us in the loop?

I'm also curious to see the results of the first test. we will race pasqua March to vele di pasqua Cesenatico, with 2/3 boats. I'm not sure to be fast because we do not have time to test before the race. I will keep you updated. thanks for the compliment "cool".
greetings

[ita 16]

This is a very cool project- keep us in the loop?

I'm also curious to see the results of the first test. we will race pasqua March to vele di pasqua Cesenatico, with 2/3 boats. I'm not sure to be fast because we do not have time to test before the race. I will keep you updated. thanks for the compliment "cool".
greetings

This is a very cool project- keep us in the loop?

I'm also curious to see the results of the first test. we will race pasqua March to vele di pasqua Cesenatico, with 2/3 boats. I'm not sure to be fast because we do not have time to test before the race. I will keep you updated. thanks for the compliment "cool".
greetings

We have completed the first test in the race with the Stunt 13.9 (S.9) in the race "Vele di Pasqua Cesenatico.." condition variable wind from 6 knots to 18 knots, flat water and waves 1.5 m. Stunt it has proven to be fast and fun more than what we thought. I was impressed by the speed and acceleration when I passed a Tornado in upwind. with wind at 16 knots upwind and big wave has proved to be as fast as a class A, why?: I made 5 years of testing with boards curves, T foil, etc., and I think that fly on small catamarans is not easy and involves many problems of various kinds, for this reason I have decided about the "DO NOT FOLLOW tHE FASHION" and I are dedicated to planing or semi-planing hull , and I think I did an excellent job, the stunt is really fast, I adopted the straight boards that I allow to have a more constant speed, especially in upwind with great wave, when all boats equipped with foil jumping on the crest of the wave and so slow down, the Stunt does not lose speed and accelerates immediately after the wave, getting an average speed very high. the only problem with this little cat seems to be only the great speed he has, maybe a little dangerous for inexperienced crews.

[Chris O]

How about some video shot from another boat showing relative speed and hull shape effectiveness?

[ita 16]

How about some video shot from another boat showing relative speed and hull shape effectiveness?

I destroyed my gopro in the first race, as soon as possible I make a movie.

[pcraig]

When I got Clive Everest to draw up the lines for the C-class Invictus, we used the Hurricane 6.5 as inspiration along with Clives experiences with his A-class and mine in various dinghies and multi's. As a result Invictus has a rather flat U section along most of the hull as opposed to the more oval sections preffered elsewhere.
Part of the rationale was that C-class generally isn't short of horsepower and therefore speeds necessary for semi-planing should be easy to achieve even in relatively light winds when more conventional cats would be bogged down. The initial rig for the boat caused us lots of grief and masked the performance pros or cons from the platform. I've not spoken to Paul or Gordon for a while and never got a chance to find out how they felt the platform stacked up with a decent wing on her. Interestingly they plan to use the existing platform later this year, so there is some potential still there.

[ita 16]

When I got Clive Everest to draw up the lines for the C-class Invictus, we used the Hurricane 6.5 as inspiration along with Clives experiences with his A-class and mine in various dinghies and multi's. As a result Invictus has a rather flat U section along most of the hull as opposed to the more oval sections preffered elsewhere.
Part of the rationale was that C-class generally isn't short of horsepower and therefore speeds necessary for semi-planing should be easy to achieve even in relatively light winds when more conventional cats would be bogged down. The initial rig for the boat caused us lots of grief and masked the performance pros or cons from the platform. I've not spoken to Paul or Gordon for a while and never got a chance to find out how they felt the platform stacked up with a decent wing on her. Interestingly they plan to use the existing platform later this year, so there is some potential still there.

I do not think it is right to abandon a good project boat for follow the trends imposed by other designers, I think you again need to test your boat with new rig. good job.
Regards Michele

[Amati]

When I got Clive Everest to draw up the lines for the C-class Invictus, we used the Hurricane 6.5 as inspiration along with Clives experiences with his A-class and mine in various dinghies and multi's. As a result Invictus has a rather flat U section along most of the hull as opposed to the more oval sections preffered elsewhere.
Part of the rationale was that C-class generally isn't short of horsepower and therefore speeds necessary for semi-planing should be easy to achieve even in relatively light winds when more conventional cats would be bogged down. The initial rig for the boat caused us lots of grief and masked the performance pros or cons from the platform. I've not spoken to Paul or Gordon for a while and never got a chance to find out how they felt the platform stacked up with a decent wing on her. Interestingly they plan to use the existing platform later this year, so there is some potential still there.

 

 

When I got Clive Everest to draw up the lines for the C-class Invictus, we used the Hurricane 6.5 as inspiration along with Clives experiences with his A-class and mine in various dinghies and multi's. As a result Invictus has a rather flat U section along most of the hull as opposed to the more oval sections preffered elsewhere.
Part of the rationale was that C-class generally isn't short of horsepower and therefore speeds necessary for semi-planing should be easy to achieve even in relatively light winds when more conventional cats would be bogged down. The initial rig for the boat caused us lots of grief and masked the performance pros or cons from the platform. I've not spoken to Paul or Gordon for a while and never got a chance to find out how they felt the platform stacked up with a decent wing on her. Interestingly they plan to use the existing platform later this year, so there is some potential still there.

 

 

When I got Clive Everest to draw up the lines for the C-class Invictus, we used the Hurricane 6.5 as inspiration along with Clives experiences with his A-class and mine in various dinghies and multi's. As a result Invictus has a rather flat U section along most of the hull as opposed to the more oval sections preffered elsewhere.
Part of the rationale was that C-class generally isn't short of horsepower and therefore speeds necessary for semi-planing should be easy to achieve even in relatively light winds when more conventional cats would be bogged down. The initial rig for the boat caused us lots of grief and masked the performance pros or cons from the platform. I've not spoken to Paul or Gordon for a while and never got a chance to find out how they felt the platform stacked up with a decent wing on her. Interestingly they plan to use the existing platform later this year, so there is some potential still there.

I suppose with the hulls angled out a bit that in light wind you would have a decent narrow beam low cp hull riding on the corners that would fatten up as you flew a hull and it in essence rotate out onto the then flat bottom?

 

Where did you distribute the rocker?

 

If this was proprietary, please check here:  (    )

 

edit:  department of redundancy department above above above.....

[ita 16]

to facilitate my work, I decided about making a mold that goes well for hull left and right, but I'm already working on a model of class A prototype for research, on which I will be working with two asymmetrical hulls mirror.

 

[pcraig]

Amati, no proprietry stuff.
 
Cant remember the exact rocker distribution, but anyone who knows Clive, knows that he likes using fairly basic maths functions in ms excel in order to define his curves. He normally outputs this into a CAD file and builds the models up from there.
 
The meeting we had to establish the general underwater shape was way back in 2002/3 so I really struggle to remember too many of the details, but your general points are correct. Rocker distribution was possibly more than typical at the time as we were worried that even with the boards, that tacking would be a pig unless she had reasonable rocker, so perhaps we went a bit overboard. Max rocker was just aft of the boards. You can get a rough idea from the pics below, which I hope Norman doesnt mind me sharing. I must admit the large bows were my fault. I was overly worried about the prospect of pitchpoling which was stupid given the volume of the hulls and the buoyancy up at the bow and only having the wing pushing the bows down when sailing in light airs downwind before any apparent wind kicked in. With hindsight I would have reduced the stem height by at least 1/2.
 
The big thing that hurt was that the hulls were designed assuming the rig weight was the same or slightly less than Cogito. The first rig wasnt even close to Cogito weight so the immersed hull was significantly more than had been intended and didnt really allow to hull to unstick, although there were moments of glory! as you can see in the photo. This was only the second day the boat had ever been on the water and before the wing issues really kicked in.

Attached Files

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•  Pauls Pictures 119.jpg   118.11K   84 downloads
•  Pauls Pictures 147.jpg   78.69K   59 downloads

[ita 16]

I managed to make a movie, we had little wind of 7-8 knots, just enough to trapeze but still fun.

 

[Amati]

like the way the bow meets the water.  very nice....

[ita 16]

like the way the bow meets the water.  very nice....

Thank you. seems to work very well, I hope to do a movie with more wind to help evaluate the functioning of the semi planing hull. you soon

[pcraig]

ita 16, What length is your boat (sorry if you have already given the figures earlier!) It looks short. Ok its not big winds, but it looks like you're digging a deep trough with the leeward hull, partially because you're trapezing so far aft and partially because it looks like the fwd hull shape doesnt have sufficient curvature to allow you to get forward and trim the bow  sensibly.

It does look like a fun little boat though.

[ita 16]

ita 16, What length is your boat (sorry if you have already given the figures earlier!) It looks short. Ok its not big winds, but it looks like you're digging a deep trough with the leeward hull, partially because you're trapezing so far aft and partially because it looks like the fwd hull shape doesnt have sufficient curvature to allow you to get forward and trim the bow  sensibly.

It does look like a fun little boat though.

yes, the boat is short, 4.15m, 7 m mast, sail+ mast 10 m2, width 2.35m, weight 70 kg. the stern seems to be somewhat submerged but depends on the speed and position of the crew, is designed to immerse of about 5 cm. was born as a fun boat but we have seen that not much else difference from Class A in  race.

[ita 16]

like the way the bow meets the water.  very nice....

Thank you. seems to work very well, I hope to do a movie with more wind to help evaluate the functioning of the semi planing hull. you soon

finally a bit of wind, about 12-14 knots, the wave of Cesenatico is varied and bastard, the S .9 is short but behaves like a boat of greater length. I put pictures in the video where you can see the behavior of the hull and sterns, maybe I was a little backward, but I needed to improve the framing of the video.

 

[Doug Lord]

 

Can't get the Facebook link to fire, but saw the other one- if you're already helming at the back of the hull, have you tried raking the sail back and sailing off the rudder? Kind of like sailing on a windsurfer skeg? Maybe use the daggerboards only for light airs. Be easy to try-

Watching your cat trying to achieve liftoff was, um, like watching chop jumping down at the Gorge, so maybe the windsurfer metaphor isn't that off?

It's hard to tell if you have hard chines or not, but if you do, and usually planing cats don't go very high upwind anyway, maybe footing upwind in higher wind without the drag of the daggerboard might give you better VMG? Use the chine(s) for some dynamic lateral lift?

At the very least, you could then concentrate on rudder design ideas.

excellent observations. my big problem is the curved boards are not good on a planing boat, only by applying large foil rudders are managed to stabilize the jump effect "caused by the curved boards." All this system works well just for fun, is not good for the race. in the new boat I will use only straight boards, the effects planing is already very good and even more constant speed without the boards curves. the boat seems very fast upwind, I compared at sea with class A, with 10-14 knots of wind we had the same speed but I go 5 degrees less. I modified the hull, from 3.6 m to 4.15 m , because I had no bow sufficient length to correctly use the system wave piercing. from 2 months to know if I did good work. my goal is also to fly the boat for fun, I will prepare rudders with foil straight boards with foil, but I doubt that the position of the boards is correct. you think these changes will be good?

=====================
You've done a great job-the new video looks real good. Why do you say, above, that curved boards are not good on a planing boat?

[ita 16]

 

Can't get the Facebook link to fire, but saw the other one- if you're already helming at the back of the hull, have you tried raking the sail back and sailing off the rudder? Kind of like sailing on a windsurfer skeg? Maybe use the daggerboards only for light airs. Be easy to try-

Watching your cat trying to achieve liftoff was, um, like watching chop jumping down at the Gorge, so maybe the windsurfer metaphor isn't that off?

It's hard to tell if you have hard chines or not, but if you do, and usually planing cats don't go very high upwind anyway, maybe footing upwind in higher wind without the drag of the daggerboard might give you better VMG? Use the chine(s) for some dynamic lateral lift?

At the very least, you could then concentrate on rudder design ideas.

excellent observations. my big problem is the curved boards are not good on a planing boat, only by applying large foil rudders are managed to stabilize the jump effect "caused by the curved boards." All this system works well just for fun, is not good for the race. in the new boat I will use only straight boards, the effects planing is already very good and even more constant speed without the boards curves. the boat seems very fast upwind, I compared at sea with class A, with 10-14 knots of wind we had the same speed but I go 5 degrees less. I modified the hull, from 3.6 m to 4.15 m , because I had no bow sufficient length to correctly use the system wave piercing. from 2 months to know if I did good work. my goal is also to fly the boat for fun, I will prepare rudders with foil straight boards with foil, but I doubt that the position of the boards is correct. you think these changes will be good?

=====================
You've done a great job-the new video looks real good. Why do you say, above, that curved boards are not good on a planing boat?

thanks Doug. I have made many good test in the past 6 years, always test at sea with wave and not flat water (too easy without waves), curved boards, boards J, T rudders, all these generate vertical thrust in the position where they are, but all the other thrusts present on a beach cat are discontinuous movement and intensity "crew position, thrust the sail, etc." these variables must also apply the pitch, the wave, acceleration etc.. , All of this changes the boat trim and the incidence of the foil which rarely work in the right position. I happened to Vele di Pasqua in Cesenatico with 18 knots wind and wave 1-1.5 m to have a medium speed greater or equal to the new clsse A, they were jumping on the crest of a wave and then fall and lose a little speed, I accelerate very immediately after the crest. foil system is almost impossible to manage on beach cat, are too small, they have a gait too inconstant to be able to balance the system of foil, just big and wide cat can get good results, "" "" is easier to see a fly AC72 who AC 45 or worse still 18 feet "" "" "". I believe that the future of beach cat is semi-planing hulls, easier, more fun, very fast, low cost, less dangerous. I like to follow trends, but only if these are really good , For this reason I decided about a different road which is not imposed by others. I do not exclude, however, to make further tests with foil, for the S .9 I still want to try to create a foil kit for my clients who want to experience the thrill of flying or nearly so, it will be difficult and it will take a long time but I think I know already how to do.

 

Regards, Michele

[Doug Lord]

Michele, thanks for the thoughts on foils + planing. I like your approach and it's important not to discard any technology-like you said. Lifting foils-properly designed and implemented-should be an asset to a planing hull-particularly one with a very low aspect ratio like a cat hull. As you probably know, Parlier used lifting foils(daggerboard+rudder T) on Mediatis Region Aquitaine with it's stepped planing hulls and a famous powerboat designer(Eugene Clements) uses a rudder "V" foil in concert with his very small step(.75"/19mm) on a 40 footer!). You have an excellent approach-it's all a question of testing.I think you could find a net gain from the right type of lifting foil. Good Luck and keep us informed!

[pcraig]

Michele, vid is good, but doesn't look much different to the previous vid. It looks like both you and your tune up buddy are permanently  2ft to far aft. get your weight forward and I think the boat will trim out nicely. I would say trap by the daggerboards on reaches, not the back beam. And when sitting in get forward.

 

Boat looks good and would be a great intro class for the A.

[ita 16]

yes, 2 feet forward is better, but I could not rotate the camera. when I have time available begin testing on foil, but also some tests to evaluate a prototype of a class A, maybe in September I will have a new model to be tested for the future, I will not change the current Class A ZERO, it goes very fast and is always in the top positions, but "as a researcher" I would go on and on.

thank you very much for the positive comments, I'm not used here in SA.

see you soon, Regards, Michele

[Amati]

Old school, but perhaps the Russian practice of ladder foils barely lifting the hull out of the water?

Crashes become less of or no event, since you have better anti dive redundancy with foils and planing surfaces- kind of like racing offshore powerboats do with deep V hulls- they are expected to land after launch at speed

Speaking of which (catamaran speedboats/ hydroplanes) why not try a WIG design approach with a solid flat deck that gives some lift- your design is small anyway, how much weight would it add? Honeycomb, bolt on to test?? I can suggest a design handbook if you're interested- I think you're going fast enough for some lift. I suppose some Formula Windsurfing hull ideas might rub off here too? They are little airboats, after all. Imagine a Formula Board type deck with your cat hulls on the sides. Retract daggerboards and move back at speed.....

Resistance goes down a lot with each inch hull is raised out of the water, especially at higher speed/length ratios, so even a bit of lift helps, if you can keep drag under control, which WIG might do.

With wave piercing hulls, ladder foils (flying low) become stabilizers, (WIG too?), might make for a more controlled ride

[Amati]

Vortex on steroids.

[Amati]

An example of a small WIG hull in big waves- crash? What crash...

Check out this video on YouTube:




Sent from my iPad

[Amati]

the book is 'secrets of tunnel boat design' by James Russell

[Amati]

http://eprints.soton...083/1/51083.pdf

 

good article on low reynolds number airfoils in ground effect-  given that the deck of your cat has a chord measured in feet, re would be even higher than 80,000, which looks like it might be excellent?

[ita 16]

An example of a small WIG hull in big waves- crash? What crash...

Check out this video on YouTube:




Sent from my iPad

incredible small powerboat, trim and stability after the jump is perfect, even the hulls work very well.

[Amati]

And what would the wing loading be in WIG be for your cat?

[ita 16]

And what would the wing loading be in WIG be for your cat?

based on the very backward of my boards, I think the max load is about 210 kg, and is distributed only on the boards, but I think I also use foil rudders. the max load (210) is very approximate because I want to reduce the load that comes from sail.