Displacement software

[gonzo]

I am still drawing with a pencil, but the displacement calculations are just tedious work. Is there softwere where I can input the offsets and then the weight of building materials and will give me the waterline? Then I could change things like engines or tanks and it recalculates the waterline?
Thanks

[apex1]

I am still drawing with a pencil, but the displacement calculations are just tedious work. Is there softwere where I can input the offsets and then the weight of building materials and will give me the waterline? Then I could change things like engines or tanks and it recalculates the waterline?
Thanks

http://www.boatdesign.net/forums/design-software/step-step-design-your-boat-27900.html :rolleyes:

[gonzo]

I wonder if there is software where I can drag and click elements on the design and it will recalculate CG, waterline, etc.

[apex1]

Within some limits, Delftship and Freeship+ (basically the same) do that.
And they are quite easy to handle and have not a steep learning curve.

[gonzo]

Can you, for example, shift engines fore and aft?

[Rick Willoughby]

Can you, for example, shift engines fore and aft?

Yes. Use different layers to specify the envelope or as much detail as you like of any parts and move them around as you like.

Delftship has some limitations compared with Freeship. Delftship pro has a bit more functionality.

Rick W

[Ad Hoc]

gonzo
You need a set of hydrostatics to do this quickly and properly. Once you ahve a set of hydro's for your hull, you know where the KB and LCB etc are, then all you need to establish is the distance from the LCB to the LCG, you have a lever, then you ahve the displacement, then look at the hydro's for the MCT 1cm...and so on.

One doesn't need to play with layers, as suggested above, that just implies ignorance of how to design.

[gonzo]

Ad Hoc: That is how I do it by hand. It is tedious, slow work. I want to click and drag. Can you enlighten us out of our ignorance?

[Martijn_vE]

gonzo
One doesn't need to play with layers, as suggested above, that just implies ignorance of how to design.
Not neccessarily true at all. What Rick refers to is to represent weights in different layers of the model. By changing the geometry, the weight and corresponding center of gravity are updated by the software, very similar to using Excel only fully automatic.

Using Excel in different design stages is very common, no matter the size of the ship. Why would that imply "ignorance of how to design"?

[gonzo]

I suppose that my elementary knowledge of Excel is not enough. Back to the classroom

[Rick Willoughby]

I suppose that my elementary knowledge of Excel is not enough. Back to the classroom

Gonzo
Martijn is not saying you should use Excel he is simply pointing out that Delftship can be used to list the boat components as you would with a spreadsheet.

The benefit of using Delftship is that you can move things about as you like and not only automatically get updated CofG but can quickly see the result relative to the rest of the boat.

The simple example of my V11J pedal boat attached shows the result of using the layer control to remove the gearbox from the image or move it to a different location. This took all of 20 seconds. The boat CofG is automatically updated based on the weight data I have entered for the gearbox.

Layers are commonly used in CAD programs to reduce the complexity of what is being worked on at different times.

Delftship is the easiest drafting (or rendering) package I have used. Once you get familiar with "surfaces" it is very easy to use and quite fast. I have sent output files from Delftship to milling shops for machining metal parts and routing foam plugs.

Rick W

[Ad Hoc]

Gonzo
As i said, if you can get a set of hydrostatics for the hull, then i can help. But that doesn't help you, since you want the hydro's in the first place! A quick method, draw the body plan on a set of graph paper. For 10 stations, measure, roughly, using the graph paper, the area. Then Simpsonise them to get the basics hydro's.

Martijn
"..By changing the geometry, the weight and corresponding center of gravity are updated by the software,...Why would that imply "ignorance of how to design"?.."
This is because all one is doing, by this method, is trial and error, not design. One just "plays" about until the desired result is obtained. Anyone can do that with enough knowledge of using the software, but it ain't design.

With a set of hydrostatics, with the current GA and layout, the weights and centres will have been done. If the trim is wrong, after plugging through the hydro's, then all one is looking for, is the total tonne.metre moment.

If the total tm is say 100, then this means moving, for example 10tonne 10m, can this be done in the design?...if the total displacement is say 25tonne and the boat is say 20m with an engine say 5tonne, then clearly no, since this would mean moving the engine 20m. As a crude example. One doesn't need to "play" to design, one needs to understand what 'design' is!

[peterAustralia]

HULLFORM works exactly the way you describe

You enter a table of offsets and away you go.
Actually it is not quite that simple, but is fairly close.

You start by making a new design, you have to enter the number of lines.
Example a V hulled ama would be the most simple and have 2 lines.
A flat bottomed sharpy would have 3 lines.
You enter draught, stem height, transom height, overall width and overall beam and then go

It will make a shape that looks weird, do not panic, add some more sections and then slowly but surely you add data points. As to displacement calcs, what you do is enter a figure along with the center of gravity and it shows draught, freeboard and trim angle. You can keep on increasing displacement until gunnel touches the waterline if you really want to.

There are a couple little tricks, if you have a kink in the lines, it is smart to have 2 sections say 10mm apart, the line between these 2 sections has a very high intersection flexibiity. This separates the line into 2 parts, very useful if you want to change something after you have added the offsets.

IF You are going the method of offsets, HULLFORM is excellent.

Example, say I had the dory book by John Gardener (I do in fact), and wanted to put a dory design into the computer. First I would convert all to metric (take a while, but I only use metric) and then enter the numbers into the computer. For a complicated thing like a swampscott dory I could do the entire process in an hour, and have it perfect.

If you have problems and cant get it to do something, ask,,,,, if you ask you can get help..

you can ask me if you like peterevans_33 at yahoo dot com dot au

HULLFORM is free.

If you have something simple, show me and maybe I can make a start for you. I have a little spare time until I start my new fulltime job in a few days.

Once again,, if you are going down the offset path, Hullform is excellent. If you are drawing freehand, and want to bend curves etc, maybe another software package is superior. I am sure freeship, hulls and delfship and superior products, but for just doing offset work, hullform is excellent.

If you have a diagram, and a smallish table of offsets, email them to me, and I can email back a hullform file, from that starting point you can modify this line, modify that line, move this station etc etc , and see what happens.

kind regards
N Peter Evans

peterevans_33 at yahoo dot com dot au

[Martijn_vE]

With a set of hydrostatics, with the current GA and layout, the weights and centres will have been done. If the trim is wrong, after plugging through the hydro's, then all one is looking for, is the total tonne.metre moment.

Really?
You seem to keep missing the point here.
Rick is referring to a method where the software calculates the cog of a set of weights while adjusting the location of individual weights graphically.
Yes, that's design.

On the other hand, how to calculate the trim angle from the calculated cog and cob is not design. That's hydrostatics.

But I think we're getting off topic here.

[Ad Hoc]

Martijn

Clearly your definition of design is totally different to mine.

I'm referring to something that is real, and has real attributes and can be verified by other independent sources and can be built. Something that has been created from nothing from many sources to arrive at a solution.
You're referring to how a software can be used to move things quickly and having all the 'numbers' crunched for you. But of course without any verification, since the computer doesn't know what is right or wrong.

..and never the twain shall meet.

[Martijn_vE]

And again you're missing the point.
Too bad.

[fcfc]

Any decent mechanical CAD package will give you the mass and CoG of the parts you have entered, be it a boat or a full plant. Recomputing the waterline should be easy for any marine design software or add on.

The very big main problem is that you have to enter ALL the part in the system without missing one. You do it with a pencil, a spreadsheet, or with the CAD program is equally painfull I fear ...

[Ad Hoc]

Martijn

Ditto...and never the twain shall meet. :P

[apex1]

Any decent mechanical CAD package will give you the mass and CoG of the parts you have entered, be it a boat or a full plant. Recomputing the waterline should be easy for any marine design software or add on.

I fear thats only true to some extend, and not worth trying for a pro!



Gonzo

try Freeship+ to play around a bit. It is extremely easy to learn, and you will soon find out if it fits your needs.
You then can purchase the delftship programme which has some advantage over the free Freeship+ and does´nt cost the world.
You are professional enough to know what such a program can do for you and what it can´t.
Proper design of course has nothing to do with any software, but you are not the one who must learn that. (and some others will never)

Regards
Richard

[Rick Willoughby]

Gonzo
Delftship is available as a free download usually available from here:
http://www.delftship.net/

HOWEVER THE SITE IS STILL DEAD (Martijn are you aware of this?)

Delftship Pro gives a bit more functionality. The cost is really no more than a small donation when you consider the power of the package.

It can be a little frustrating getting to understand how to work with surfaces but typically after 40 hours of reasonable effort it can be mastered to great satisfaction.

Rick W

[gonzo]

I don't need a computer to have common sense for me. Ad Hoc is being rather snooty. I will give some of those programs a try and then start the questions on how to make them work ;)
Thanks,

[apex1]

I don't need a computer to have common sense for me. Ad Hoc is being rather snooty. I will give some of those programs a try and then start the questions on how to make them work ;)
Thanks,

Use the link I provided, go straight to the last side and DL the two .pdf files, the rest is a piece of cake for you, believe me.
Ad Hoc has some reason to be a bit hmm, ja, snotty. There are members around here still believing, that their Playstation can replace the knowledge earned by a proper education. That battle will continue, I´m sure.

Regards
Richard

[gonzo]

I am asking for a specific solution to an aspect of design. He seems to think that calculating what happens when you change a heavy part is not designing. That would rule out all the major Naval design firms that use tank testing and shuflle stuff around to see what happens.

[marshmat]

Wow. Things really took a nasty turn here.

I suspect we can probably all agree that, unless you're a software engineer, the computer program is not the design- it is just a tool. A tool that, in good hands and with its outputs properly interpreted, can speed up some otherwise tedious parts of the design process.

And, just as you would end up with an expensive disaster if you put a young teenager at the controls of a hydraulic excavator, you'll end up with a heap of worthless data if you put someone at a CAD workstation without first making sure that they know what they're doing.

CAD automates some of the tedious parts of manual drafting. It does not, and cannot, replace knowledge, understanding and sound engineering judgement.

And Gonzo, since you've made it quite clear over the last few years that you do seem to know what you're doing, you will likely have few difficulties automating some of your calculations with a basic marine CAD system like Delftship/Freeship. There's a bit of a learning curve to get used to working directly in 3D, but it all becomes second nature quite quickly if you already know what you're trying to end up with. Being able to see your CB, curve of areas, curvature plots, etc. update in real-time is quite a nice change after drawing by hand for a while.

Rick- Just wondering, have the prices for Delftship Pro come down? Because it was a loooong way from affordable the last time I checked.

[apex1]

Matt
it is about 150$ or so, when I recall well. Thats next to nothing.

Gonzo
the reason I was recommending Freeship+ to start with, is simply that it has more features than the free version of Delftship.
And due to the fact that it basically is the same programme you have no problem to switch to Delftship Pro when you decide to purchase th full version later. The Pro has some features Freeship has´nt.
Sure there are others like Maxsurf Rhino and so on. All are way too expensive and much steeper a learn curve than Freeship / Delftship to test just a bit.

A last word to John (Ad hoc), I assume he does´nt know Gonzo is not a novice.

Regards
Richard

[Rick Willoughby]

...

Rick- Just wondering, have the prices for Delftship Pro come down? Because it was a loooong way from affordable the last time I checked.

Mat
When I made my donation the basic Pro was EUR120.

It looks like Martijn is fixing the site now so still cannot confirm if this is the case. Some of the add ons I consider quite expensive but I only have the basic Pro primarily so I could export the different formats. It was also a means of showing appreciation for a great little program.

Rick

[Ad Hoc]

gonzo
"..He seems to think that calculating what happens when you change a heavy part is not designing.."

Where do I say that??

You first asked:
"..Is there softwere where I can input the offsets and then the weight of building materials and will give me the waterline? Then I could change things like engines or tanks and it recalculates the waterline.."

my reply:
"..Once you have a set of hydro's for your hull, you know where the KB and LCB etc are, then all you need to establish is the distance from the LCB to the LCG, you have a lever, then you ahve the displacement, then look at the hydro's for the MCT 1cm...and so on..."

Which I further elaborated:
"..With a set of hydrostatics, with the current GA and layout, the weights and centres will have been done. If the trim is wrong, after plugging through the hydro's, then all one is looking for, is the total tonne.metre moment...If the total tm is say 100, then this means moving, for example 10tonne 10m, can this be done in the design?...if the total displacement is say 25tonne and the boat is say 20m with an engine say 5tonne, then clearly no, since this would mean moving the engine 20m. As a crude example. One doesn't need to "play" to design, one needs to understand what 'design' is!.."

How does moving "items" about in a program to find the waterline and having several new positions (after trial and error) automatically update the final data constitute design?..this is iterative and just indicates one is not designing, one is being reactive. Because ones does not understand what is required to find the solution to the problem.

It seems, if as Richard says, your not a novice, then you're missing the point.

Matt didn't, he understood perfectly:
"..I suspect we can probably all agree that, unless you're a software engineer, the computer program is not the design- it is just a tool..."

A computer just makes the process quicker. It doesn't design for you...if you start with a mess and don't know what to do, you'll just end up with a mess a whole lot quicker!

[gonzo]

If I manage to not understand like Herreshoff, Stephens and Frers don't understand, I can live with it. Also, if you don't have answerd to my question, please stay out of my thread. Whether what I do is design or not in your opinion is of little importance to me. Your harrassment and interfering I can do without.

[Rick Willoughby]

Gonzo
The Delftship site is up and running again. This link gives some details on the free version:
http://www.delftship.net/delftship/index.php?option=com_content&view=article&id=31&Itemid=4
You need to create a log in to download. There is no obligation associated with logging in. It allows you to participate on the site board.

Rick W

[marshmat]

Delftship Pro core looks to be 178.50 euro now (about $250-$300 CDN), small change to a company or a pro designer, but quite a hit for those of us who are students or don't use the software in a professional capacity. Add a few of the extensions and it can really add up. I know Martijn has a great piece of code here- I use the older, open source version myself- but he's apparently aiming it at the professional market now, which makes it hard to justify for those of us who don't get paid for our designs. (A student licence of Rhino is only $200, by comparison; add rhinomarine/orca3d and you're up to $400 as a student- for what is overall a much more versatile program. Commercial licences are obviously much more pricey, so for a design house that only does boats, Delftship Pro might make a lot of sense.)

AH - yes, I do get what you're saying, but I also get what Gonzo's saying- and I don't see why the two of you are in such a huff over this. All that Gonzo's asking for is a tool that can automate the hydrostatics and weights/moments calculations for him, so he doesn't have to slave away with calculator and planimeter every time he wants to change something. And all AH is saying is that you can't just drag stuff around and expect it to eventually work, you have to look at your calculations and interpret them correctly in order to figure out what needs to be done to achieve the desired result. I know both of you know all of this....

[gonzo]

Yes, that's it. Also, the dividing designs in ten makes for bastard divisions on the stations. As a builder, that is a source of great frustration. Try spacing things 29" 11/16 or 783.2 mm. The other option is to divide in ten, do the calculations and then redraw the lines to a logical spacing. A planimeter or the Herreshoff squaring method end up being more efficient.

[Ad Hoc]

Ahh..i see the sado's are out again hitting with negative points because they don't like to be questioned or being told that playing with a computer is not design...gesss..when are you lot going to grow up and get a back bone!!!

And for the spineless, not leaving their name with comments like: "Nasty"...pathetic, QED!

hey, just got another:
"Try being less arrogant"

How about having a spine to post your name and issues on the website in public, rather than hide behind the anonymity of anonymous hits because you don't like what someone has written, nor the courage to say so, and probably not the intelligence too, judging from your comment. Simply weak and pathetic!!

It doesn't take much to rattle the cage of those weak individuals who do not like views other than their own.

[Ad Hoc]

Matt
"..AH - yes, I do get what you're saying, but I also get what Gonzo's saying- and I don't see why the two of you are in such a huff over this..."

Im not in any huff...just stating the methodology that's required to get the job done, that's all. Any "huffing" is a personal interpretation, i can't control that!