about carene...and software

[Oldwarper]

There are some nice photos here:http://www.betasom.it/forum/lofiversion/index.php?t24151.htmlThey were beautiful but he thinks that a sea exit had the costs of a frigate... They were also very noisy. the crew had to wear suitable protective clothing.. I mean, they weren't a positive investment.

fascinating... and revolutionary!! !
with water in the wings... a pity that in the end were too expensive as management. really a very nice project!
Who knows what those pumps were like to shoot water at those speeds without cavitation. . .

 

[PaoloColombani]

... much cheaper versions of dipped wing hull, and perjoint without fuel costs:

 

[Exatem]

fascinating... and revolutionary!! !
with water in the wings... a pity that in the end were too expensive as management. really a very nice project!
Who knows what those pumps were like to shoot water at those speeds without cavitation. . .

As soon as I can (we are really taken lately), I see to deepen the topic. In fact on the purely technical side are (were) interesting. but we have in the forum an expert of propellers that perhaps could deepen the topic. Right, dragon? :wink::biggrin

 

[Drag]

As exatem kicked me out, let's go over this.

there are hydrofoils with "secrets" and hydrofoils with "dipped wings". the first are generlamente means of small displacement similar to motorboats equipped with alar surfaces that "secano" its marine merits. They behave well in calm waters and suffer from wave height. are driven by conventional diesel engines and propellers and are used in fast civil connections

we are talking about means that exceed 35/40 knots of speed, in addition to with inclinations of axes that can reach 30 °, the term conventional propellers, which for me means subcavious propellers is no longer appropriate, as it is necessary to pass to transcaviating propellers or for even greater speed to supercavious propellers.
this distinction is made on the basis of the type of profile used:
1) subcavious, classic wing profile normally series naca 16,66 and much more.(you try to contain the cavitation at most)
2) transcaviating, newton-rader type profiles, coming from the first through empirical modifications.(the cavitation extends along the whole back of the profile)
3) supercavious, profiles like tulin,hydronautics, to interderci a wedge.
(the cavitation is total and indispensable, extends far beyond the profile)
in the field of supercavious propellers there are then those ventilated, the profile pushes on the air entered, instead of on the water vapour.
then we have surface propellers, with supercavious profiles, which stand half in water and half in the air.
the case is wide and varied.
greetings to all

 

[Exatem]

As exatem kicked me out, let's go over this.

we are talking about means that exceed 35/40 knots of speed, in addition to with inclinations of axes that can reach 30 °, the term conventional propellers, which for me means subcavious propellers is no longer appropriate, as it is necessary to pass to transcaviating propellers or for even greater speed to supercavious propellers.
this distinction is made on the basis of the type of profile used:
1) subcavious, classic wing profile normally series naca 16,66 and much more.(you try to contain the cavitation at most)
2) transcaviating, newton-rader type profiles, coming from the first through empirical modifications.(the cavitation extends along the whole back of the profile)
3) supercavious, profiles like tulin,hydronautics, to interderci a wedge.
(the cavitation is total and indispensable, extends far beyond the profile)
in the field of supercavious propellers there are then those ventilated, the profile pushes on the air entered, instead of on the water vapour.
then we have surface propellers, with supercavious profiles, which stand half in water and half in the air.
the case is wide and varied.
greetings to all

Come on, come on.
You're telling me something more about "ventilates"?

 

[Oldwarper]

but for us terrestrial animals... that the only cavitation we know is to avoid as the plague in the pumps...
What exactly does that mean, how do they work and what do "cavious" and "supercavious" propellers imply?

 

[Drag]

What exactly does that mean, how do they work and what do "cavious" and "supercavious" propellers imply?

the cavitation can occur on the profile of the propeller for such phenomena:
1) the pressure on the profile drops below the pv steam press, frees water vapor that goes to fill the space left by the water.
2) release of gas dissolved in water, which are function of temperature and pressure, reached saturation a part of dissolved gas is free forming small bubbles.
3) a lowering of the level of the liquid caused by the depression on the back of the profile, resulting in air aspiration from the surface (you will have noticed the foamy skis left by ships).
an extreme case of this last case only surface propellers (half in water and half out), this is the typical case of propellers that aspire air and then we will say that they are naturally ventilated.
then there are special cases, where the propellers are immersed, and since the supercavitation is not easy to reach and maintain (unlike the surface propellers), we proceed to a forced ventilation, to understand you shoot air or exhaust gas motor directly on the back of the shovel.
now two words on the cavitation:
the phenomena listed give rise to an empty cavity in the liquid in contact with the profile, where inside they form bubbles that grow as long as the pressure remains below the pv, when the pressure starts to increase, becoming greater than pv then the bubble undergoes a contraction and then imploding releasing a high energy.
high local pressures arise in the implosion points, given the speed of the phenomenon and the very reduced surface against which the implosion takes place. Thus a real bombardment occurs to which the material hardly resists (personal experience, shovel cut at the root of attack with the hub in less than an hour of test).
all this makes us understand why oldwarper must avoid as the plague this phenomenon, the same applies to me in the case of subcavious propellers.
Now when some crazy decide to want to go with their boats at a speed greater than 40 knots, this phenomenon and uncontensible and would destroy the subcavious propeller in a short time, then can no longer avoid it try to exploit it by going to wedge profiles.
the face continues to push on the water, while the back is in complete cavitation, the cavity generated however extends well beyond the profile and therefore the implosion of the bubbles takes place away from the propeller, not damaging it anymore.
This is the phenomenon of supercavitation.
the portanza is remarkable, the performance also, since the resistance for friction on the back, practically disappears.
greetings to all:finger:

 

[Exatem]

Thank you dragon!
but now begins the "bombarding" :biggrin:
pump-jet...
is one of the "emergent" solutions for underwater propulsion. I had to take care of it myself, but, not knowing an acca on the propellers, I did only the "bozza" of a stator-rotor while I performed the development of the hull of the "mystery object". then everything went to a university and to people with fluid dynamics who made the necessary corrections. However I was doubtful whether a pump-jet solution is valid only for diving or if it can be used even in surface ships (we could apply a couple to the sampon yacht...). :wink:
Bye.

 

[Exatem]

...we could apply a couple to the sampon yacht.. .

I wanted to add that in January we start throwing something down. enrolled at the moment result:
sampon: contractor and part of the design staff. (voluntary)
dragon: expert in propellers and means of propulsion. (forced)
er president: motorist (forced but without exaggerating! )
Come on, people. Anyone who wants to try to create the new poster for the sampon room is welcome. :biggrin: registrations are open. . .

 

[Exatem]

@drag.
I don't remember if we've already talked to you but I'd like your opinion on these:http://www.vdvelden.com/rudders.cfm?pk=497〈=enThank you. . .

 

[maxopus]

I don't understand an hour of this sector, the only hand I could give you is that of good modeler 3d.
So if you were to serve... take a whistle.

 

[Er Presidente]

I wanted to add that in January we start throwing something down. enrolled at the moment result:
sampon: contractor and part of the design staff. (voluntary)
dragon: expert in propellers and means of propulsion. (forced)
er president: motorist (forced but without exaggerating! )
Come on, people. Anyone who wants to try to create the new poster for the sampon room is welcome. :biggrin: registrations are open. . .

Engineer!
Dude!
But now that I do, do I clean the candles?
Can we use a diesel 6 times, slow handsome?

 

[Er Presidente]

But if we make it hybrid, I'm in and I'm in.

 

[sampom]

... to the yacht of adopted...

..adopted: (voluntary). . .
...the bedroom adopted ...

..nothing to do, now the alzeimer is unstoppable:biggrin:

You seem to have met me this morning, but remember how my nick is written.

Hello exatengreetings
Marco:smile:

 

[Exatem]

I don't understand an hour of this sector, the only hand I could give you is that of good modeler 3d.
So if you were to serve... take a whistle.

I'm sure if you're gonna whistle...
like a mist siren.. .
enlisted (see how easy it is? ).

But if we make it hybrid, I'm in and I'm in.

Hybrid? solar-diesel-electroeloic to rhymes?
I like it.. .

..nothing to do, now the alzeimer is unstoppable:biggrin:

You seem to have met me this morning, but remember how my nick is written.

Hello exatengreetings
Marco:smile:

I'm not sorry. .
I always call you Sam. It's that the n and m put them too close on the keyboard... But these caxxates have been writing too many... Do I have to start worrying?

 

[Onda]

If I can be useful, I take care of composite hull structures. usually sailing, even if some motorboat passes me underhand. .

wave

 

[Exatem]

If I can be useful, I take care of composite hull structures. usually sailing, even if some motorboat passes me underhand. .

wave

but of course you can be useful.. .
skillful enlisted! :biggrin:

 

[maxopus]

Kill that battalion we set up

 

[sampom]

If I can be useful, I take care of composite hull structures. usually sailing, even if some motorboat passes me underhand. .

wave

but of course you can be useful.. .
skillful enlisted! :biggrin:

I would say yes! enlisted and signed..:biggrin:
that then the sail has always fascinated me (headed, that è the sea) and I would not even mind an elegant sloop or, why not, an important ketch (referencing comparison to the convenient motor shuttle).

Come on, let's discuss it. I don't know which side to start but I look forward to your input.

greetings
Marco:smile:

 

[sampom]

He's dead battalion that we have set up

..maybe better "crew?: Jiggrin:

salti
marco