can someone help me with modeling my own design?

[Bart]

Hi there,

I’ve created a design which i want to build but de software is way above my skills and have no idea what to do.

I’m a graphic designer and i have no technical skills of boats.

So my question is can someone help me make my design into a floatable hull?

attached is a basic image of the design from above the waterline and top view….

thanks,
Bart

Attachments:

• boot2.png

[giorgio zuppin]

Well, it happens I have some spare time…so:
-Dimensions: Average lenght will fit.
-Desired cruising speed.
-Engines & Propulsion: (conventional, hybrid, electric etc. propellers (outboard feet or axle line ) or waterjets.
-Basic accomodation: n° of passengers/crew, internal bay for tender, rear platform etc.
Nice design to work on!
Bye, Jurgen.

[Bart]

Hi Jurgen,

length will be 45 meters and width will be 10. I’ve attached a new image with some dimensions in it and a quick sketch how it should look.

It’s becoming a model of 1 meter so engines and propulsion aren’t really important at first. No internal bay or rear platform.

Everything below the waterline can be made to your judgement…

Attachments:

• boot.jpg
• boot2-01.png

[giorgio zuppin]

O.K. Just a couple of days. ( hopefully )
Some details are not well suitable in a ship but let’s criticize at job ( both ) done…
See you later.
Jurgen.

[Silva]

Hi Rambler, Jurgen

Hi made an atempt at this model here is my result.

hope you enjoy.

Attachments:

• Newmodel-boot_Linesplan.jpg
• Newmodel-boot.jpg
• Newmodel-boot.fbm

[giorgio zuppin]

First, I must deeply apologize, Bart: some personal issues caused a huge delay in every involvement.
So my promise was gone…
Luckily, DS community has provided a good backup as I can see: My compliments, Mr. T: well done, a proper render of superstructures at all… for the hull I prefer other solutions:

In the last days I’ve got finally some spare time so kept drawing: ditched an “as is” version – yours is very good indeed, Mr.T – I’ve opted for a more conservative approach – away from Steve Job’s Yacht – a rounded dislocating hull ( at 40 meters LWL no choice ) bulbous bow and Azipod propellers.
It’s not finished yet as you can see but the core, the hull I mean, is well defined.
Comments and suggestions welcomed.
Jurgen.

[Robert Holme]

Hi Guys,

I’ve had a bit of a play with this as well, like Jurgen I opted for a bulbous bow but The stern shape suggested to me single screw.

Be that as it may my biggest concern with my own and the others is stability, ( G>M). Too much top hamper. Perhaps a tumble home may suffice? IMHO more beam is needed, probably best achieved by a less fine forepart i.e. the vessel needs to carry the 10m beam further forward, draft is an option but may be restricted by the ports the vessel needs to enter.

Just my 2 Bobs worth and worth exactly what you paid for them.

Best Regards
Bob

[giorgio zuppin]

My penny for your bobs:
At 690 Tons displacement I think this hull can manage the superstructure layout with enough seaworthiness, at 12 to 16 knots cruising speed.
Twin props arrangement for a leisure boat ensure handling and safe cruise.
Azipods because you do not need: axle lines, rudders, etc. Expensive and care needing yes, Rolls-Royce got some big trouble with their developement but You can fit a stand-alone electric motor in each and run on diesel generators, batteries, solar panels. Here’s a cool greenish boat!

Bye, Jurgen.

[Robert Holme]

Hi Jurgen,

If KG>KM I don’t see displacement having relevance but then again I’m no naval architect. My understanding is a vessel is unstable in the aforementioned condition and once it starts to roll it keeps on going until G is lower than M i.e. it has capsized.

Best Regards
Bob

[giorgio zuppin]

Please, Bob don’t let me mess with theory.
Since I am no more than a well informed ignorant, ( kind of nautical moron, to be clear…)
Displacement IS relevant changing it means to change coefficients and ratios, keep in mind that “G” must be calculated and is a direct result of weight distribution: more moulded volume gives more options.
Pfeew! Hard job and sure not correct at all.
Sorry, Jurgen.

[Bart]

Hi guys,

Thanks all for giving this a shot.

I like both designs made. The decks on the first design looks more to my design but i like jurgens last hull very much.

I’m not at home for a few days so not easy to view the designs very well or give comments.

Still working on a radar boat at the moment so i have plenty of time. no need to apologize

regards Bart

[Robert Holme]

Hi Jurgen,

Sorry but I think we must agree to disagree.

My understanding is that this is a real world project so I believe it must fit real world parameters.
I don’t believe that Delftship’s calculation algorithms are suspect therefore I accept what it is telling me.

In my own fbm the VCG is above the transverse metacentre which is unacceptable.

In Tubarao’s design the VCG is raised to some 16 m with the addition of the superstructure and his transverse metacentre is some 7.6 m……………..highly unstable. The centre of buoyancy in both cases is around 3.2 m although Tubarao’s displacement is less than yours and mine by an average 200 tonnes.

Displacement is only relevant in as much as it affects the size of the couple either righting or causing the vessel to loll/capsize.

Attached is my fbm which consists of hull and deck, I saw little point in going further with an inherently unstable design. This was re-enforced by Tubarao’s result.

I also attach a PDF which shows a negative righting moment of 27.475 tonne metres at 5 degrees of heel from my fbm.

Best Regards
Bob

Attachments:

• Boot.fbm
• BootMCH.pdf

[giorgio zuppin]

“Not Guilty, Your Honor!”
And I try to explain why.
Conditions of the project are to provide a suitable hullform to a brilliant exercise of styling.
It mens keep dimensions and general layout in Plan wiew, superstructure design and weights – at the moment – are irrelevant.
My attempt was aimed to ensure a good buoyancy in such a skinny plan and achieve a decent displacement to obtain a good metacentre and room to lower weights of all technical equipments and plants.
I deliberatly ditched the original superstructure design, sketching instead a more conventional layout – to be completed with cabin roof plus a flyng bridge atop – because aesthetically I have the taste of a Dinosaur …
By the way the result is:

Or:

As you can see the mission IS possible – b.t.w. how you estimate VCG? –
Jurgen – still a nautical moron –

[Robert Holme]

Hi Jurgen,

I like your concept.

I don’t estimate VCG but Delftship does a wonderful job of calculating it in the layers dialog. For reasons I don’t understand it fails to provide a calculated result in the design hydrostatics page.

Attached is a jpg to show what I mean. As you add or remove layers from the hydrostatics in the layers dialog, the VCG is updated in real time.

Best Regards
Bob

Attachments:

• VCG.jpg

[giorgio zuppin]

Thanks to the Jury for the verdict, I’m obliged.
Anyway, I truly earned the title of “Nautical Moron Of The Year”, believe it or not I NEVER noticed these annoyng Acronyms on top of the layer’s property sheet…
Shame on me indeed, in a way to regain some self respect I went through the manual – i.e. ‘?’ button – and I realize we are on a slippery path.
VCG is proper of any single layer, in any way it’s calculated – help, please DS’s lords – and it’s obvious why it’s not displayed on Hydros page.
I must take for granted that datas are only a useful help to arrange designed volumes, because the “real” VCG is a cumbersome function depending by materials adopted, placement of tanks and technical services, layout and weight of superstructures, etc…
Better if we talk about linesplan and drawing issues.
Ahem… Bye, Jurgen.

[Robert Holme]

Hi again Jurgen,

Before I discovered Delftship I had occasion to lift an historic iron auxiliary schooner from the water as she was in danger of sinking due to the poor condition of the hull. There were no drawings or lines plans or any relevant information.

It all had to be developed from measurements and photographs.

Attached is a PDF of the way I did it using Simpsons rule and 1st and 2nd moments of inertia. COG was of particular importance in as much as it had to be BELOW the line of lift otherwise the vessel became unstable when it exited the water. Next came displacement because this determined the size of the cranes required for the lift. The lifting lugs and the bulkheads to which they were welded also had to be measured and tested to ensure they could handle the loads.

A very interesting exercise……………. my calculations were within 2 tons of the actual lift weights recorded by the cranes.

Also a couple of jpgs of the vessel up and away.

Best Regards
Bob

Attachments:

• Nellydisp2.pdf
• NelAftLiftingBrackets02.jpg
• NelComingAshore01.jpg
• NelConnectforeward01.jpg

[Robert Holme]

Hi Guys,

Well I had a bit more of a play with Tubarao’s design in as much as I added materials to the layers just to keep it simple and to prove my idea I only allocated the same material to everything, (5mm Aluminium).

Woo Hoo………… now we have a proper output in design hydrostatics for VCG :laugh:

Attached is a jpg of the result

Best Regards
Bob

Attachments:

• TbootMCH.jpg

[Silva]

Hi Maryak .
Tanks for your comments on my design,
i can only say that the tittle”Nautical Moron Of The Year” is indeed mine for it took me 2 days to discover the meaning off VCG “Vertical Center Gravity” . so all your technical discussion is slowly making some sense to me for this is the first time i tried to start a new hull without a lines plan or some photos for guidance.
now that being said y only have to add please consider that i am a amateur CG modeler with a passion for boats, so if you could please explain what is happening in the attachment it would be great. thanks.

Best Regards
Tubarao

[Robert Holme]

Hi Tubarao,

Let me try and explain

1. We are in this instance referring to the transverse settings, (port to stbd).

2. There are basically 3 states of equilibium for a ship.

Stable………. this is when viewed fore to aft from the keel up lowest is centre of buoyancy, next is centre of gravity and last is the metacentre.

Neutral………. this is when the metacentre and the centre of gravity are at the same height above the keel. The centre of buoyancy is still below both the others.

Unstable………. this is when the centre of gravity is above the metacentre.

OK, now when the vessel moves from upright to some angle of heel a moment of force is created between the metacentre and the centre of gravity.

When the metacentre is above the centre of gravity this moment of force acts to try and push the vessel back upright.

When the metacentre is below the centre of gravity this moment of force acts in the opposite direction and causes the vessel to either loll, (take on a permanent list) or if it is big enough the vessel will capsize attempting to put the metacentre above the centre of gravity. This is the case with our designs and is what my diagram is showing.

All of the above also applies longtitudinally in the hull but it is more relevant to damage control and such things as floodable lengths so in this embryonic stage of development the transverse ones are the ones that say if we are viable or not

Attached are a couple of jpgs which show stable and unstable equilibrium.

Hope this helps

Best Regards
Bob

Attachments:

• fig3-11.jpg
• stabil7.jpg

[Silva]

Hi Maryak.

Yes this helps a lot, Thanks.

Now i’m beginning to understand how to see the stability off the model during the modeling process. this is really helpful
for achieving good stable hulls.

Another question is raising now , i’m not really familiar with the density to put in the layers, can you give me some guidance about this issue!(for example what is the average density for various types off hull like wood, iron, aluminium, fiberglass and so on, also various materials like bronze or stainless steel use in the apparel and calculate the over all tonnage)
or where to find this information.

Thanks again and sorry for being such a annoying “fresh water sailor” :S

Best Regards

Tubarao

[Robert Holme]

Hi,

Very Happy to help a fellow learner. I find some of the things in yours and Jurgens models beyond me. e.g. I don’t understand how you get things like bilge keels rails and other odds and ends into your models without any control edges or faces, just a series of points connected by “ordinary” edges.

Here is a site which provides what you need, in DS they are input as Tonnes per cubic metre.

http://www.engineeringtoolbox.com/metal-alloys-densities-d_50.html

Best Regards
Bob

[Robert Holme]

It’s me again,

Seeing as how you guys did all the hard work modeling the hull, the least I could do was try and stabilise it!

Now the only complete model I have access too is Tubarao’s so that was the basis of my stabilisation.

I believe that if we add 23.5 tonnes of ballast to the keel with an LCG of 30.6m and a VCG of 2.8m we should be somewhere around the mark of a GM of 0.6m, which is pretty good for an old imperialist who thinks a GM of 2 ft is at the low end of typical for passenger vessels.

Best Regards
Bob

[Silva]

hi Maryak

Thanks for the link. very useful stuff.

Best Regards

Tubarao

[Author]

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