Those damn’ chines

[Guillaume Barjou]

Hello all,

I have a small project, I want to build a dory, like the Gloucester Light Dory, made of 3 shits of plywood plus some pieces of wood, really simple.

I am using FreeShip 2.6 so I can access to “Tools/Develop plates” function.

But I’ve not succeeded, for the moment, to model my hull as I would want.

The shape is ok, but I can’t develop plates, as there is allways some corners that don’t behave like I would like them to.

Please find in the attachments my 2 last tries.

Doris 3 is built with a hull containing 3 vertical points and 8 horizontal, then shaped to the dory shape using background images. Then I select the control line along the bottom of the hull, I turn it into a chine and the hull change into a chined one, except a small part under the bow, that I cannot manage to make developable.

For Doris 4, I tried to build a hull with 1 vertical point, in fact I draw the bottom of the hull, then I extrude the side line, and I move the extruded point to match the top line of the hull. But there also, some area do not develop.

Thanks for your hints/help.

Lomic

Attachments:

• Doris-Lomic3.zip
• Dory4.fbm
• Dory-Lomic4.jpg

[Jesus Cruz]

The first thing you have to do is split the hull in more than one layer, that will give you better results with the developing of the plates,

That may help you, and get better results

cheers and good luck

[Guillaume Barjou]

ok I will try this way, thanks!

[Jesus Cruz]

The most layers that you use the better the results

[Guillaume Barjou]

I believe you’re right, but in my case, the hull is just made of 3 shits of plywood, very very simple, the max layers I can do is 2, one for the bottom of the hull (which is flat with front and rear with a little scoop) and one for the border, and that’s it. I could make another one for various pieces of wood that come inside the hull but I don’t need them to obtain my developed plates.

And for the border plate, I have no real idea how to build it from nothing in an independant layer.

For the bottom it is ok, I did it on one of my tries, I started the project with a boat of 2 vertical points (which is the minimum accepted by Freeship)

[Icare]

Theory:
If you wish to cut plywood planks based on your design, you have to keep in mind that planks can be bent in only one direction (they aren’t rubber made!). That is you can make a cylinder (a pipe), but you can’t bent the cylinder and make a torus (a donut) or close its edges (and form a sphere) or bend a square in two opposite directions (and form saddle shape). You can experiment this for cheap, just using paper 😉 It the paper makes a crease instead of a smooth bend, the plank will break.

In Delftship/Freeship, each plank (of wood) must be drawn on a different layer (of virtual tracing paper). Thus, if your design is correct, DS/FS will unfold each plank without stretching it.

Practice:
So, once the bottom is drawn, rename its layer “Bottom”.
Create a new layer and rename this new layer “Border”, and change its color, too (this makes easier to see which layer you’re working with).

Now, select the Border’s layer, then select the bottom plank’s outter edges, and extrude them upwards and slightly outwards. This wild create the border’s ***base*** in the Boarder’s layer (i.e. in an other layer than the bottom’s), and they will be knitted together (this will avoid the leak points).

Now, select each point on the border’s top (one after other) and move it to its final coordinates. Check for the «developability» of the planks using the convenient button (in FreeShip v.5.x, the red hull in the right of the Home menu). Note: The Gaussian Curvature can be used, too (the green and orange hull, besides the Developability button)… if you can understand the colors meanning. Think of setting the precision rendering as high as possible with the «Low/Medium/High/Very High» button (on the left of the Home Menu).

Then, you can check for the unfolded design using the Unfold button (Tools menu).

I quickly made a five-planks model to show you the operations and the buttons (using FS 5, but these buttons exists in older versions, too). You can find bellow the different stages of the operations on the screenshots below, and I added the model’s file (for FS 5).

Attachments:

• 1.Bottom.jpg
• 2.Board-base.jpg
• 3.Board.jpg
• 4.Bow-and-stern.jpg
• 5.Fake-Deck.jpg
• 6.Unfolded.jpg
• Five-Planks.fbm

[Guillaume Barjou]

If you wish to cut plywood planks based on your design, you have to keep in mind that planks can be bent in only one direction

thanks, I do understand this, and I am using an already existing design, which is build with 3 sheets of plywood, so it works fine in reality but not in Freeship, the ways I have tried until now.

So, once the bottom is drawn, Create a new layer and rename this new layer “Border”,select the Border’s layer, then select the bottom plank’s outter edges, and extrude them upwards and slightly outwards. This wild create the border’s ***base*** in the Boarder’s layer , and they will be knitted together. Now, select each point on the border’s top and move it to its final coordinates

Except for the layer trick, it is exactly one of the ways I’ve tried, I have to try again with layers, but I did have extruded the border from outter edge of the bottom.

In fact I believe that it doesn’t run well in the bow, and in your nice and detailled example, you’ve done cutted bow :cheer:

I am building a model of the ship right now (scale nearly 3/10), and I used my Freeship plan, without using the developped plates, I’ve copied some significant sections and I’ve made some female templates, inside which I will bend my sheets of plywood. The tricky part will be to ajust the sheets to the desired shape, but I have a few tricks in mind to avoid complications 😉

But it would be easier to print the developped plates 😆

Thanks for your help. I will try again this method but with the layer hint also 🙂

[Guillaume Barjou]

I am trying Icare’s method but I do not succeed.

I create the bottom, OK.

I add a new layer “border”, I select the outter edge of the hull in the “bottom” layer, and I extrude it in the “border” layer (on Y and Z).

Then I change the perspective view to “Check developpability”, and it is already wrong… :blink: :S :pinch:

Attachments:

• developpability.png

[Icare]

I select the outter edge of the hull in the “bottom” layer

I ain’t sure I was neat enough: Take care to understand the layers’ thing. When you extrude a polygon’s edge, the new polygon you’ll create will pertain to the layer whose name you can read at the Layers dialogue box’ bottom. In your case, you must read “Boarder” as layer name, thus any new polygon you’ll create will pertain to the Boarder layer, even if it was created by the extrusion of a polygon from an other layer (Bottom layer). If you miss this point, the developability is impossible, and I’m affraid there’s no way to move a polygon from a layer to an other layer, except to delete and re-draw it… and when you understand this, you may have a whole net of meshes to re-draw. That’s why I suggest to use different colors for each layer (layers’ dialogue box). You can also check for the layer mistakes by displaying them only one at once, but it takes much more time. 😉

So, are your planks on different layers?

If they are so and if the developability is still faulty, it can be because of an useless complexity of the design. Look at the following examples:

– In the first example, the median lines (I circled their center) are of no use, but they make the bottom to be considered as non-developable… however it is developable.

– In the second example, I deleted these lines. But two simple and unused points lost on the middle of their lines (not corner points) can be considered as harmless… but they spoil the whole boarders’ developability computation.

– In the third example, I finally deleted the points, too, the design is as simple as possible, and it looks finally developable.

Remember: the simpler, the better!

Attachments:

• bad-lines.jpg
• bad-points.jpg
• better.jpg

[Guillaume Barjou]

So, are your planks on different layers?

YES!

I add a new layer “border”, I select the outter edge of the hull in the “bottom” layer, and I extrude it in the “border” layer

I do extrude the new part IN the “border” layer

Look at the following examples

Thanks for you complete and detailed examples, they are very clear 🙂

Remember: the simpler, the better!

well, I agree with that, but I am not currently creating a boat out of my mind, but re-creating an existing one, with its shapes/curves… and it is made of developped plates, I use some old images of its plans to try to build it inside Freeship. I am a bit confused, or I am missusing freeship, or it cannot hold those curves to develop them.

I’ve joined the two pictures that I am using for making the plans, maybe the shape is not developpable with freeship?

But I tried even one time without curving the bottom of the hull before extruding the border and it was already not developpable, I must miss something :dry:

Attachments:

• Doris-Dessus.jpg
• Doris-Laterale.jpg

[Jesus Cruz]

Try to split the “border layer” into two layers Aft border and Fwd Border, eliminated any point that is just connected to two edges, that usually “messes” with the developability.

To be honest i have use delftship for ship a lot more complex than yours and I haven´t had problem.

Regards

[Peter Edmonds]

Lomic

I hope Icare’s example/solution is of value. I haven’t looked at it yet, and I am a very new user of DS.

I believe it is important to understand something of the developable plate process to manipulate your surfaces effectively. Have a look at the first half of my recent response to the “Developable Surfaces” topic.

The dory shape you provide looks readily developable. Dory design, with its relatively simple hull surfaces, should lend itself to generating the developable surfaces. The shapes will be largely from cylindrical elements, with minimal use of conic surfaces. The simple test is that it should be quite easy to plank up many a dory hull shape in sheet ply, with negligible alteration to vessel shape.

Once you have an understanding of the developable surfaces, and are working accordingly, it becomes an issue of dealing with it within the techniques and vocabulary of DS. (This latter is part of what I am trying to address.)

[Edoardo Benedetti]

So, are your planks on different layers?

YES!

Have you checked “Developable” in Layer Properties?

[Author]

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