Exatem
Guest
a failure. . .
Exaggerated costs, terrifying vibrations, we didn't sell one. and they were all dismissed.
but let's talk about it in "over and under... "
In a while... first I finish my submarines.
Exaggerated costs, terrifying vibrations, we didn't sell one. and they were all dismissed.
but let's talk about it in "over and under... "
In a while... first I finish my submarines.
Exatem
Guest
What would you have in mind?
I'm intrigued. . .
Er Presidente
Guest
mannaggia, broken dream!
Okay, wait.
speaking of "planant" and displaced and "variable" shortcomings in function of speed, I had come to mind, sin that as often happens technology too much thrust does not marry with usability.
cigars
Exatem
Guest
But you know... a hydrofoil is a hybrid. a middle way.. No meat or fish...
while sailing quietly is a small ship with huge appendages. When it accelerates it becomes a hydroplane that cannot take off. . It is not that in the military field they have had a great development. the Russians, something but when they could spend. . .
Today we prefer other close defence solutions and Americans are studying (also thanks to us), something very interesting.
I will talk more about it (I have already done the drafts, I have to correct and then publish).
Have faith. :wink:
sampom
Guest
Exatem
Guest
And your idea?
What would you have in mind?
Er Presidente
Guest
I once saw them "live" (when they were still in fashion) were impressive, the greatest demonstration of power I've ever seen, even more impressive than dragonsters.
a dragster takes you to the stomach, seeing an offshore at full speed at sea is like seeing a dream of superhuman power, a more mental than physical.
I happened in the middle by mistake, but I'll never forget.
:smile:
sampom
Guest
nothing special, more than anything else would interest me now the technical development of the project for professional curiosity. understand what you leave and how you work. pull down two lines of carene with cognition of cause until reaching a complete set-up.
then I dreamed of something around 50'
biggrin, but returning with my feet on the ground you could start from a comfortable day cruiser or at most fall into the dimensional limits of the parent (it was only 7.5 mt now you can get a little bit more).In short, see what can be drawn out with our cads and knowledge (of whom has :biggrin:, I address myself to you and this section).
in the end a nice render to "impsor" and keep in the room of the daughters.
greetings
Marco:smile:
Special-one
Guest
It is also interesting to see the implications of the wave motion on the size of the hull, the pressure to impact with the wave and the pressure generated, but as our friend Ugo costaguta says, "foundations of hydronautica" there is nothing better than the test in the naval tank.
Exatem
Guest
there is not only "water foundations" of u. f. costaguta but also:
“marine structural design” of bay, “ship construction” of eyres, “principles of naval architecture” vol. 1 and 2 of lewis, “pratical ship hydrodynamics” of bertram, “basic ship theory” of rawson-t upper, “ship hydrostatics and stability” of brian, “introduction to naval architecture” of tupper... some of these were used by the same steuraguta in addition to the numerous texts of the advocacy, the texts used to the naval academy of livorno, etc. etc.
This is because it is evident that, in citing theories about hulls and their behaviour in water, we refer to experiences of others. I do not unfortunately have the possibility to make a naval tank in the garden (in fact, to think well I do not even have the garden) and even if I had, I would probably not be able to use it. one thing is expressing considerations, personal ideas that can do without reconnaissance and practical applications. another is to speak of rules, which they are for all. when we talk about resistance of materials, we rely on experiences made by someone else and become “verb”. I do not think that a “mechanical” puts itself to do traction tests to the material samples in the house cellar. takes for good what someone else has experienced and translated into rules
Exatem
Guest
Always simple questions, huh?
the factors in play are: weight, speed, dynamic and static thrust, trim angle, wet surface and motion resistance and are dependent on each other. the right angle depends on the position of the center of gravity and the dynamic pressure center. In addition to complicating things, the setup changes in the race so knowing how to determine the weight and the center becomes fundamental. in a planing hull the weight of the boat is supported for a quota that varies from 1/3 to 1/13 from the static thrust. everything else is supported by dynamic thrust. an increase in weight of a displaced ship, will immerse it a little more, will make it go a little slower, but its geometric forms of famine remain substantially unchanged. the same increase on a planing hull, can prevent the same from planing substantially changing its characteristics. therefore the study of a planant hull is more difficult than a displacement.
but the displacement famines have obvious limits to overcome certain speeds so to push beyond, it is necessary to pass to the planant famines. a planing hull finds its main support in the dynamic reaction of water. a hull is in planata when the water is in contact with the bottom only inside the edges, at that point the boat rises on its wave of prora, decreases the angle of order and increases the speed without increasing the power. the speed of planata is not the maximum speed reached. Indeed, the greater the difference between speed of planata and maximum speed, the better the boat will be.
today also large hulls are used for fast transport using semiplanting hulls. it was in the 1960s that the design of planing hulls had its impulse beginning the creation of what is called " deep." were the offshore competition boats to demonstrate the superiority of this kind of hull, especially in sea conditions formed though, for lengths greater than 20 meters tried to stay on more “traditional” hulls. some tests carried out in tanks dating back to the war, had shown that the resistance increased with the increase of the angle of the dihedron therefore the design with variable dihedron and flat stern, was still considered the best. but boats that did not have the opportunity to reach high speeds, could not benefit from this solution. in fact the first race hulls were born for hulls of about ten meters and for speed of 40-50 knots. in such size it was also important the distribution of weights and the better stern diedro was between 20 and 30 degrees. the planata occurs when the hull is fast enough to generate a force due to the pressure of the water under the hull that depends on the speed itself, the incidence and the affected surface. the effect of this pressure is to produce a f force perpendicular to the bottom and that consists of two components a vertical and a horizontal that is resistant to advancement.
for each dihedron angle, corresponds to an optimal angle of incidence and the purpose is to maintain this angle within the speed range that can be used by the hull. then in practice it occurs that at low speed the angle of incidence is exceeded generating a great pressure resistance while a too flat trim increases the resistance of the wet surface. the optimal hull should therefore have the center of gravity as backward as possible to make better at high speeds and a wide stern surface to prevent the boat from sticking to the low. that’s why flaps and power trim are used. they have a corrective effect by moving the pressure center to the stern and lowering the bow.
the hull can be concave (hook), convex (cocker) or straight, the dihedron angle can take a n° “n” of values for which, the position of the pressure center is subject to a huge number of variables. from the structural point of view the convex shape is more rigid and allows weight savings. the hull often has longitudinal skates, increase dynamic sustenance and reduce the wet surface, moreover as the flows under the hull to v are diagonal, they also have the task to straighten and channel such flow. skates also increase directional stability as water pressure increases on vertical walls.
in the early days of the hoff-shore race, the boats had the center of gravity very aft, in case of rough sea, they were filled with the zavorra chests in the bow to lower the same. more recently much attention has been devoted to submerged appendixes to reduce its friction. the power trim allowed to vary the thrust and trim the hulls. Counter-rotating propellers and surface propellers have further increased performance. and it was an important innovation as the resistors reduced by increasing the speed reached by 20%. In fact, at high speeds, the resistance of the appendix could exceed half of the total resistance. even more recently there has been a demonstration of the superiority of multihulls compared to motorboats. this thanks to the aerodynamic support generated by the tunnel between the hulls. the problems were mainly structural because of the stresses to which the area is subjected, destined to hold together the two hulls that are manifested above all in moving waters.
but here should intervene our friend dragon who knows more than I do.
then my ships are all displaced (when they are not submarines) so... satisfied. :wink::biggrin
Exatem
Guest
Let us pretend that there is a shipowner and a builder (we).nothing special, more than anything else would interest me now the technical development of the project for professional curiosity. understand what you leave and how you work. pull down two lines of carene with cognition of cause until reaching a complete set-up.
then I dreamed of something around 50'
In short, see what can be drawn out with our cads and knowledge (of whom has :biggrin:, I address myself to you and this section).
in the end a nice render to "impsor" and keep in the room of the daughters.
greetings
Marco:smile:
the shipowner will ask: flow, speed, stazza.
the builder will need to know: type of boat, type of motor apparatus, diving, special accommodations, crew and any passengers, class and type of construction, etc. etc.
So we have a first problem. What does the shipowner want?
we define the input data and then start with the "project vacuum". . .
for the constitution of the working team, registrations are open! :biggrin:
I would prefer a convenient displacement shuttle. . .
pp.s. I'm going to see u561. an American with a serious false historian (the English officially asked American explanations), but he speaks of submarines, I cannot exempt myself.
then there is an important Italian appearance. . .
sampom
Guest
sampom
Guest
Er Presidente
Guest
Give me a link!
:smile:
Exatem
Guest
Er Presidente
Guest
Exatem
Guest
Dear President.
I found a drawing of the external views of the sparrower and this gave me the cue to return to the subject.
we begin by classification of naval means on the basis of their livelihood in water.
will therefore exist:
- aerostatic sustenance (air cushion or bubble cushion imprisoned "cab captured air bubble")
- hydrodynamic sustenance means (aliscafi ad ali secanti or immersed, planant discharges)
- hydrostatic sustenance (displaced means are monohull or multihull, submersible...etc.)
while for the second it is worth the law of bernoulli (let's for now stand the speech on hovercraft and cabs), for third parties the principle of archimede applies.
Let's talk about hydrodynamic sustenance. These are means whose support, at project speed, is guaranteed by the portance generated by alar profiles. Now I'm not going to discuss this as I speak to the author of the "real history of aviation", but let's see how these profiles can be.
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. are those used for example in the connections with the islands.
hydrofoils with dipped wings. keep at high speeds, the wings completely immersed. Contrary to "shorts", they do not have their own stability as if they tilt,the surface of the wing profile does not vary. therefore they are equipped with "alettoni" as the planes controlled by an automatic set-up control system. are platforms capable of "cutting" the waves therefore are suitable for military uses. the Italian navy made 7 sparviero class whose characteristics were:
length 24.6 meters (22.8 with extended wings), larg. 12.3 (10.7). the dive was 4,4 meters displacement with the extended wings, 1,8 with the retracted wings and 1,6 "in flight". the displacement was 60,5 tons. the motor apparatus was hydrojet tag (see fig. 3) with the water sockets on the supports of the wings.
ad ali secanti
View attachment 12345679 ad ali immerse
motor apparatusAttachments
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Er Presidente
Guest
Come on!
they were really beautiful.
:smile:
they were really beautiful.
:smile:
Exatem
Guest
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.