design motorboat

[Onda]

Hi.

I recommend a book first of all.
It is in my opinion a bible, a little dated by now, but really great.
It's written for sailing boats, but in the newest editions there's a chapter for the engine.
covers the design of a boat, from start to finish. from the hull, to the structures to the motorization.

this link where you can find it:
http://www.libreriauniversitaria.it/principles-yacht-design-lars-larsson/book/9780071487696.

then as for the design you usually walk a spiral:
a hull is drawn, the lamination plan is determined. the structures are drawn based on a regulation.
design the interior,
a motorization, position and size of the tanks.
you create an excel sheet with the weight and center of each component.
so you get the weight and the total center of the boat.
at this point it occurs that the calculated centerpiece corresponds with that of the hull. Because it's not, it's recomincent. And here's the spiral.
Of course, with weight and baricentre, you can make maximum speed forecasts. if the boat was unable to plan, or lightens or increases the motorization.
Starting from such a reduced motorization, like 40 cv, it is worth trying to make the boat very light, otherwise risk not to plan at all.
greetings
wave

 

[sail]

Hi.

I recommend a book first of all.
It is in my opinion a bible, a little dated by now, but really great.
It's written for sailing boats, but in the newest editions there's a chapter for the engine.
covers the design of a boat, from start to finish. from the hull, to the structures to the motorization.

this link where you can find it:
http://www.libreriauniversitaria.it/principles-yacht-design-lars-larsson/book/9780071487696.

then as for the design you usually walk a spiral:
a hull is drawn, the lamination plan is determined. the structures are drawn based on a regulation.
design the interior,
a motorization, position and size of the tanks.
you create an excel sheet with the weight and center of each component.
so you get the weight and the total center of the boat.
at this point it occurs that the calculated centerpiece corresponds with that of the hull. Because it's not, it's recomincent. And here's the spiral.
Of course, with weight and baricentre, you can make maximum speed forecasts. if the boat was unable to plan, or lightens or increases the motorization.
Starting from such a reduced motorization, like 40 cv, it is worth trying to make the boat very light, otherwise risk not to plan at all.
greetings
wave

exact: the bible.

If English were ostico I would also recommend the book of sergio crepaz, but I do not remember if it also deals with motor boats.

for structural dimensioning, if you do not want to go to the eyemeter, the abs norms are easy to understand and give good results in terms of lightness, more than the rena that tends to be more conservative.

 

[Onda]

at the regulatory level I consider the aps a little dated, in any case a reference.
The majority of Italian motorboats are designed with the rhine, a regulation that I don't love because it looks more like a set of witchcraft formulas than an engineering verification.
you can use ISO in 12215 standards from .1 to .6 which have the defect of not being free.
otherwise you can use the norms of other regulations, such as the gl, which are excellent and free:http://www.gl-group.com/infoservices/rules/pdfs/english/schiffst/teil-3/kap-3/englisch/inhalt.pdfon this link you will find a valid list of requirements for designing a boat, and the regulations to follow.http://www.3sconsulting.it/doc/lgg-002.pdfwave

 

[Onda]

Otherwise there is the bv regulation with a really well-made composite legislation. also this free.http://erules.veristar.com/dy/app/bootstrap.htmlif you are looking on the site also have a free software for sizing composite material structures.

I personally use, unfortunately, the rena, sometimes the aps, sometimes the gl and iso.
depending on the product, market and flag.
for such a small boat, I think that a good choice is the island at the cost of subscribing the standards.
greetings
wave

 

[nicola1985]

not to burden the forum unnecessarily, please use the appropriate attachment management function to add images.
Thank you.

Sorry I didn't understand how to use it, so I bypassed.
next time I will try to succeed. . .

 

[nicola1985]

therefore infusion. I have the impression that nicola intends to be serious.
but then once you create the 3d model you will have to create a mold, with which system do you intend to proceed?

I have a polystyrene cutting machine. . .
if I commit myself I can also find a milling machine and a rapid prototyping machine.. .

 

[nicola1985]

Hi.

I recommend a book first of all.
It is in my opinion a bible, a little dated by now, but really great.
It's written for sailing boats, but in the newest editions there's a chapter for the engine.
covers the design of a boat, from start to finish. from the hull, to the structures to the motorization.

this link where you can find it:
http://www.libreriauniversitaria.it/principles-yacht-design-lars-larsson/book/9780071487696.

then as for the design you usually walk a spiral:
a hull is drawn, the lamination plan is determined. the structures are drawn based on a regulation.
design the interior,
a motorization, position and size of the tanks.
you create an excel sheet with the weight and center of each component.
so you get the weight and the total center of the boat.
at this point it occurs that the calculated centerpiece corresponds with that of the hull. Because it's not, it's recomincent. And here's the spiral.
Of course, with weight and baricentre, you can make maximum speed forecasts. if the boat was unable to plan, or lightens or increases the motorization.
Starting from such a reduced motorization, like 40 cv, it is worth trying to make the boat very light, otherwise risk not to plan at all.
greetings
wave

All right... now I'll read a little here and I'll get a little culture to start drawing something.

exact: the bible.

If English were ostico I would also recommend the book of sergio crepaz, but I do not remember if it also deals with motor boats.

for structural dimensioning, if you do not want to go to the eyemeter, the abs norms are easy to understand and give good results in terms of lightness, more than the rena that tends to be more conservative.

no English is not too ostic for me...
for the rules I thank you was what I was looking for.

Otherwise there is the bv regulation with a really well-made composite legislation. also this free.http://erules.veristar.com/dy/app/bootstrap.htmlif you are looking on the site also have a free software for sizing composite material structures.

I personally use, unfortunately, the rena, sometimes the aps, sometimes the gl and iso.
depending on the product, market and flag.
for such a small boat, I think that a good choice is the island at the cost of subscribing the standards.
greetings
wave

thanks to you for the rules...
at university have the rules iso which I can freely consult.
for the sizing I will rely on the fem method I have available the hyperworks software in student version and md nastran at the university.


I would say that to start I mortgage a famine with delftship (which I downloaded after being registered) I do the calculations and then I try to export the model created in solidworks or caia.
I then proceed to some structural analysis with the fem.

 

[nicola1985]

is not addressed to you but to the many, too many, that blah blah blah blah, but never post an explanation for the neophytes or a proven, reliable method, that I know.. to dimensional a cabbage of iron.
But since you have "colto", I speak to you to speak to everyone (as I speak to nuora because mother-in-law means).
since there are undisputed skills, it would be educational and perhaps rewarding, to post occasionally one own method to solve even simple problems (simple for those who have the solution). I don't ask to unveil industrial secrets, but how do you size a deck? if you cannot and want to reveal such secrets, at least indicate the method adopted.
I'm sorry if I yelled at you somehow.
Bye.

You're right. . .
Well if you want I can post small tutorials to use hyperworks, but the problem remains that this software is not free, yet...
for the sizing of a complex structure in my way of proceeding it is useless to proceed by hand, but just use the fem method with critical eye.

 

[Onda]

for the sizing of a complex structure in my way of proceeding it is useless to proceed by hand, but just use the fem method with critical eye.

I don't think that's the right procedure.
a boat dimensionalizes with a regulation, for example the iso, and it occurs (wanting) with the fea.
For a six-metre motorboat, I think it's useless, maybe it's good to check the stresses on the stern mirror caused by the engine, but for the rest I think it's useless. When you do the sizing by keeping your speedboat in the register.
then it is built well to be robust, and on this point many yards come down to compromises to break the costs.
A finite element analysis can be a good exercise, but for practical purposes, unless you put 300 horses to the motorboat and don't make him 60 knots, I don't see a big need.
wave

 

[sail]

I agree with wave: the fem is not the answer.

also because, as you will know, in this type of gigo analysis (garbage in = garbage out) it does it as the master and evaluate exactly the carchi to which is subjected such a small bark is almost impossible (slamming, dynamic loads, etc.).

much better a practical excel sheet based on years of regulatory experience.

also because modeling a sandwich structure with dynamic loads is not trivial.

It's okay if it's a test to hang with the student sw, but...


As for the definition of the hull, savitsky formulas can give you a first point from which to start.

 

[PaoloColombani]

I have a polystyrene cutting machine. . .
if I commit myself I can also find a milling machine and a rapid prototyping machine.. .

with polystyrene you can get the bulk of the model or the mold, you leave the thickness useful to cover with spatula resin to resume then with control milling. you can decide to make in this way the model on which to go to obtain the mold by means of glass layers and a minimum of frame, or even to make the mold directly.
a milling machine is located quite easily up to 12,000 mm of work plane but the cost hours-machine can be caruccio. Have you talked about rapid prototyping, know someone who has a prototyping machine for such size?

 

[nicola1985]

with polystyrene you can get the bulk of the model or the mold, you leave the thickness useful to cover with spatula resin to resume then with control milling. you can decide to make in this way the model on which to go to obtain the mold by means of glass layers and a minimum of frame, or even to make the mold directly.
a milling machine is located quite easily up to 12,000 mm of work plane but the cost hours-machine can be caruccio. Have you talked about rapid prototyping, know someone who has a prototyping machine for such size?

no such a great prototyping machine there is only multimillionaire companies.
I was referring to a small prototyping machine for details.

for the moment I want to dedicate myself to the design, then I will see a little thing to do with the possible production.
It could be just an exercise.

for the moment I looked at some typologies of hull. I would have opted for a v planant hull, what do you say?

 

[Exatem]

sergio crepaz in his book -theory and design of sailboats - writes that "...the design represents the conclusive moment in which they converge technical knowledge, personal convictions and creative elements".
This means that when you take the white sheet in your hand, in our mind the project is already defined, you know what you will want to achieve.
a good method is undoubtedly to document itself by collecting as many elements as possible on vessels similar to that in mind.
the design at the end must be the graphic expression of dynamic and static calculations with particular regard to dynamic elements calculated through hydrodynamic theory and experiences.
to achieve the final goal, you will have to go several times along the so-called “project vacuum”, already appointed by wave, changing to every passage the solutions that did not have to be satisfactory.
Geometric elements, dimensions, appendices, onboard accommodation, motorization, costs must be examined, and so on until the final result is reached.
coming to the design, the first to be realized will be the building plan.
it is the most important of the drawings and from it all the necessary elements are obtained to the proseguo of the project.
the volumes and centers of famine, the center of float, moments of inertia, the metacentres, the coefficients of famine necessary for the calculation of resistance and stability.

It is also necessary to define the correct terminology to be adopted. I don't know what your level of knowledge in the naval field is. I therefore allow myself to list some to allow you both to use the correct terms, and to understand its meaning.
if you already know these definitions, better.

when we talk about boats made of wood or fiberglass, the building plan is called "out of the bands" while for metal hulls it is represented "in the middle" (then if you want, we will see how the plan is made).
when talking about length of a ship, you mean length of the hull structure excluding each protrusion.
important is the length between the perpendicular lpp (or lbp in English) with which the length measured by the perpendicular passing through the axis of the rudder, to the perpendicular that intersects the prora straight with the full load water line (lwl).
the floating line is indicated with dwl and generally, it is made to coincide with that of the full load displacement.
the master section corresponds to the cross section that has the maximum width.
the corner that forms with respect to the base plane, is called the madman's rise (deadrise).
the width referred to the deck is indicated with b and is called beam.
with the term construction height indicates the straight between the base line and the beam and is indicated with d.
the base line (or construction line), is the horizontal line tangent the lower face of the keel in correspondence of the main section. is indicated with bl, lb or lc.
with the letter t indicates the dive of the hull.
the area of the floating plane corresponding to the lwl is indicated with awp while the area indicated with ax is the area of the submerged section of the float.

to finish this introduction we mention the hull coefficients that are: cw the coefficient of the floating plan given by the ratio between the area of the floating plane and the area of the rectangle circumscribed.
the coefficient of finesse cb is given by the ratio between the volume of famine and the parallelepiped enclosed by lwl, bwl and t, (the volume of famine is the product of lwl x bwl x t x cb).
the prismatic or longitudinal coefficient cp is obtained by dividing the volume of famine by the volume obtained by multiplying ax by the length to the corresponding float.
the coefficient of section cx is the ratio between the immersed area and the area of the rectangle circumscribed.

to conclude then there are relations between the various coefficients that allow to obtain them alternately knowing one of them and the coefficient of the sez. teacher: cb = cp x cx; cp = cb / cx.

 

[Onda]

provided that I am not an expert on hulls, especially those of motorboats.
the choice of a carena depends on the type of use, in a motorboat, a flat carena from the least resistance and the greater facilitate' to plan. as the door is directed perpendicularly to the hull and therefore lifts the boat from the water.
a v hull instead creates two carriers (one for each side of the v) that oppose each other and make the hull very stable. Obviously the vertical component that lifts the boat from the water is less and the hull needs more power to plan at the same speed.
But it's a hull that keeps the sea well and has good road stability.

normal mind modern famines have a pronounced V input and a flater stern and are called to variable geometry.
then can be present skates and redan. the first are now used on almost all the hulls while the second only appear on the race boats.

However, on larsson's book, you find more precise directions.
wave

 

[sail]

a v planante is fine. now you have to give a maximum definition of length, glare, immersion, displacement, weighed, think about what angle to give to the deadrise, whether it is constatnte along the length or deeper to the bow and more flat to the stern, etc...

edit: wave is always faster.... ^_^_^

 

[nicola1985]

I thank you for the precious notions you are giving me. . .

At this point I have to study a little the book you have suggested to me and when I have the clearest ideas I will begin to pull down some lines.

 

[paolo.valente]

Good evening, I need help ... I would like to build a remotely controlled motorboat that is able to pull me by letting me plan with my weakboard table, (water ski type) . Can you help me? I would need a project already made. I had thought to adapt a motor outboard from 15/20 cv to burst .. thanks in advance ...

 

[Exatem]

Good evening, I need help ... I would like to build a remotely controlled motorboat that is able to pull me by letting me plan with my weakboard table, (water ski type) . Can you help me? I would need a project already made. I had thought to adapt a motor outboard from 15/20 cv to burst .. thanks in advance ...

I'm not suggesting that you pursue such an idea.
even assuming you can get as much as you want (even if 20 cv seems a little bit short), explain where the motorboat ends when the skier falls into the water? and even if it doesn't fall, would you be able to keep on the skis while driving the vehicle?
too dangerous... Did you see the video of that motorboat without control that a few days ago it risked to end up on people in the sun?