Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Working Vessels => Topic started by: dillinger 04 on January 16, 2020, 04:45:52 am

Hello everyone
I have been playing around with the idea of drawing up my own set of basic plans or templets to build a small model steam boat.
Tool and materials I have to work from, a basic set of plastic french curve templets, and some graph paper. Progress I have made a sketch of the deck, and hull sides, however I find the basic set of french curve templets I have limited to work from with my drawings. Question has any one ever used  Alvin ship curves to draw a basic set of model boat plans if so are they worth buying as a tool to help in drawing model boats . Any help would be appreciated or other tools to work from Thanks David

I do alright with just the two basic french curves.
O0
.

David....a 12" flexible curve can be a good inexpensive investiment to compliment the set of plastic French Curves
Mind you, you still need end points, and the curve in your mind %) to set the bend
Derek
[PS.......these appear approx 1/2 in actual $ terms than 40 something years ago..... ]

Not sure what is in the core of current ones but it used to be lead and could break if misused.

%% .....obviously changed to suit Legislation of Lead poisoning .....[by some dogooder minority :X Group] ........sure my purchase [1963?] was packaged in a 3/4 diameter greyblue cardboard tube with a Green pressed steel screwed cap .......
I like the last sentence which acknowledges the new version is not as effective as the original
..................
courtesy of Google.
Staedtler Mars Flexible Curve  Discontinued Lead Core Version
24""  61cm Graduated Flexible Curve
No.971 6024
This flexible curve is the original heavy lead core version in original packaging. This item has been discontinued and replaced by a lighter metal core. This rare sought after lead core version is heavier and holds its shape better after initial setup.

I could never get on with those flexible strips. They always seemed to have a mind of their own and would retain a slight curve no matter how much I tried to rebend them to suit a new one. I'd have bought a set of Ship's Curves about 50 years ago if only I'd found out about them. These days it's all done in AutoCAD.
DM

Have you thought about going digital, I use autocad, basically i use the drawing technique learnt at school on the drawing board, but on the computer. I draw in 2d initially and then convert to 3d to check the parts fit correctly, its very old school but it suits me. Using a digital format means you can scale up and down and print or cnc cut component to any size.

I Concur, autocad, the spline function is excellent and you could still place a start point off the boat to start the curve off if the required shape in not forthcoming.
As for curves, a colleague used to use earthing wire (sheathed in yellow and green stripes) as a way of drawing curves on graphs, we had a bench vice that he used to straighten a piece of the wire in by clamping one end and using a set of pliers with wire gripped and rolled at the end, then pulled straight, then he cut the ends off and then bent the wire to suit the shape, it would do for several curves until it kinked and then he would re straighten again, until it got to short to reuse, he then replaced with a piece long enough, cheap and inexpensive (he used company wire so no expense to him), eventually tracing the shape with a pencil.

autocad, use a spline and set it to pass through the points command spline  method  fit  place points (just follow the prompts in the command line)

Hello everyone  who has responded to my post appreciated. I did try to utilize the free program on Trimble sketch up make
to try to make the shapes needed deck hull bottom , but I can not seem to get it to bend a straight line utilizing the program.
Auto cad sounds expensive ! and I am not that computer savvy when it come to these programs. That is way I though of asking about Alvin Ship curves as an aid to help with getting going again . I will try to send a pic of the deck I drew up it has been scale up via a copy machine. I need to re draw up the deck bigger as to get the appropriate width and length of the hull to fit the sides for a small model boat I just tried to re draw with the basis set of french curves but they are limited to shot to draw the appropriate curve bigger.

You can buy ship curves, see this topic on the Model Boats website.
https://www.modelboats.co.uk/forums/postings.asp?th=148181
Colin

see if this works image ?

image of deck

Hello David, the images are showing ok O0
Regards,
Ray.

The flexible (rubber?) curves might do for model building purposes.But they are not properly fairing according to mathematical models of ship hulls used in ship theory, because they don't posses the same properties like real splines used in traditional manual lofting practice on ship yards, or today implemented in the algorithms of lofting software used for hull design.
A spline bends according to Bernoulli's beam bending theory (which still is linearized, and thus cannot be applied in e.g. pipeline laying because of too great deflections).If I remember correctly, according to Bernoulli the 2nd derivative of the deflection is proportional to the imposed (negative) bending moment
(I'm too lazy to check with Wikipedia, if what I write is rubbish).The mathematical model of a spline is constructed by piecewise low degree polynomials (degree 3 or cubic) whose endpoints are the interpolated offsets of the hull's shell surface (in the YZPlane i.e. the curves of the body sections or hull frames).This interpolation property of the offsets is called C0 continuity and gives the first set of boundary conditions to determine the unknown coefficients of the spline polynomials.The second set of boundary conditions is the the required equality of the inclinations (or gradients I guess is the proper mathematical term) of adjoining spline polynomials.This means, unless you have a knuckle or crease line at an offset, the tangent or 1st derivative of say left and right polynomial must be the same.This is called C1 continuity.The final set of required boundary conditions for determining the polynomials' coefficients is the equality of curvatures, which in mathematical notion is the 2nd derivatives, or tagged as C2 continuity.
Putting all this together leads to a set of linear equations for determination of the coefficients, which in case of cubic splines can very easily be solved by use of the Gaussian elimination scheme.Since the coefficient matrix is sparsely populated (of so called tridiagonal guise) the procedure is even computationally rather inexpensive.I hope this little digression into the underlying "theory" of splines used in the mathematical representation of ship hulls wasn't too offputting.

Forget all the rubbish I wrote in my last post.
I would suggest you download the free version of the hull lofting software DELFTship (look here (https://www.delftship.net/DELFTwp/downloads/)),
or its fully free predecessor FreeShip (look here (https://sourceforge.net/projects/freeship/))
and install it on your computer.
It even runs within the WINE wrapper on Linux (that's the way I use it since I lack a Windows system on my private hardware).
Then play with it. It comes with a few sample hulls of all types of ships and boats.
I admit, it takes a little while to get accustomed to it.
But once you got the knack, you can produce fully fairing hulls in a few hours.
I attach a few sample screen shots from a hull that I drew a while ago only after a tiny general arrangements plan of a well known British Emergency Tow Vessel which discovered by chance somewhere in the Pinterest realm.

I would really like to get to know and understand CAD but I've never used it before. Is it possible to get a program that runs on a MAC? I don't mind paying for a program as long as its not too expensive. I looked at coreldraw but wow its costs a lot of money  much more than I would be willing to pay. If possible I would like a program thats installed on my MAC rather than a web based system. So is there such a thing? And how hard is it to learn?

Mark,
After a lot of web searching I found it is possible to get Coreldraw free. It is not the latest version but I found Corel 11 about 3 years ago and use it all the time.
Don't ask where I downloaded it from, I can't remember, but keep looking and good luck.
Martin

I've used CorelDraw 12 on my Windows PC's for years, in combination with AutoCAD R14 (now 2013). While CorelDraw is a vector drawing program I wouldn't consider it as a true CAD package c/w AutoCAD, although it handles colouring and shading more like a proper graphics program than AutoCAD does.
I recently bought a copy of AutoCAD 2013 from an Internet supplier for twenty quid, although I don't know if there's a MAC version. If there is then, knowing Autodesk, it won't be free! However you can get a free download of Turbocad 10 for a Mac, which might be a better bet than CorelDraw.
Dave M

I don't know anything about MAC OS, and software that can be used thereon.
But I know that the underpinnings of MAC OS are a derived version of the FreeBSD kernel, the Unix.
Since Linux was modeled after Unix and the core of its operating system is based on the GNU tools,I could imagine that WINE or a similar approach might also work on MAC OS.
As for free CAD software, have you had a look at FreeCAD (also available for Windows and MAC), QCAD, Blender, or InkScape?
The latter is similar to CorelDraw I suppose, but totally free and OpenSource.

Thanks for all of the advice lads  I'm going to look at a few tutorials on line and try and get into this :))

Hello Deadwood
Thank you for the information appreciated I will look into this, DELFT or free Ship I like to be very careful when downloading off the internet, is this as safe as Trimble SketchUp to download . Thanks