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Kris Avonts

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About Kris Avonts

  • Birthday 05/30/1956

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    Geel, Belgium

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  1. As I further explore FreeCAD, I want to share the next simplification to my proposed method in post #10. The polylines of 2 segments can be dropped completely, just constrain the three control points of the spline with symmetry. That will bring them all three in line and then you can make the middle one coincident with the target (offset) point. Done! The more I explore FreeCAD, the more I start liking it. Its GUI with the different workbenches is a bit awkword and not as coherent as a commercial product but it's free software and all files stay yours. I hope this helps some more FreeCAD users. best regards, Kris
  2. You go really fast TonyM. But you should when I read about all your plans. Especially the idea of use 3D-printing to make jigs or plug is appealing to me. My intentions on the other hand are a little different. I want to reconstruct the hull in 3D based on an existing ship plan by using as much as possible the same construction techniques that the original artists uses. For instance if I know that the bottom of a frame consists of 3 sweeps (arcs), I will draw 3 sweeps and no spline. I'm sure it will my 3D work harder but I will give it a try. best regards, Kris
  3. In addition to my sketcher B-spline workaround I have to warn that the curvature of the resulting spline is much less fluent then the one that is drawn with the multiple-point B-spline tool from the draft workbench. See the next screenshot (magenta is draft spline curvature, blue is sketcher spline curvature). The explanation is simple. The points from the sketcher spline that I made coincident with the offset points all have zero curvature in that point. In a fluent curve zero curvature should only be present in inflection points where curvature switches its sign. The general curvature trend along the spline is however almost identical. So if you don't seek the utmost curvature smoothness, the sketcher spline will do fine because it maps very close to the station line. all the best, Kris
  4. Hi TonyM, I think I can show you a way to get the splines for the stations to pass through your offset points. I also do it as an exercise for myself to get more confident with the sketcher and/or draft workbenches and their capabilities. First I extracted station 5 from one of your screenshots, removed most of the background and inverted your resulting white B-spline to black. That image was then imported in FreeCAD with the image workbench, scaled and moved. I scaled to some arbitrary size so I could use your numbers for the position of the offset points in mm units. Then I started sketch000 to define your offset points. The vertical line is a polyline with its lower point at the origin (coincident constraint) and then vertical distance constraints for every other point are added. Next are the horizontal lines added to reach your offset points. To make the desired B-spline, I started a new sketch, sketch001, and imported the horizontal lines from sketch000 as external geometry. Now the actual work can begin. First I tried the work around form the FreeCAD forum I mentioned in the topic ‘Need CAD type program’ (https://forum.freecadweb.org/viewtopic.php?t=30180#p249022).That was a disappointment because it resulted in lots of errors being reported and even complete crashes (stop reacting) of the FreeCAD program. Then I invented my own work around that I will describe next. Draw a B-spline along the profile of the station. Start with a point at the top about the same height as your highest offset point, then 2 intermediate points are placed on the way to the next lower offset point. Then 1 point next to the offset point. Again 2 intermediate points on the way to the next offset point where again 1 point is placed and so on until you reach your lowest offset point. This results in 22 control points in this example. Then I switch to construction mode and draw polylines of 2 tangent (press 2x M key between 1st and 2nd line) segments along the spline at each offset point except the highest and lowest. Now I constrain each polyline with symmetry. Next I constrain all polyline points to be coincident with the corresponding spline control points. Now we can put the spline over the station line by a coincident constraint for the endpoints and the points that correspond to offsets. That looks awful but we can touch up the spline by moving the intermediate points into position until our spline pleases the eye. The result looks like this. Now you have a sketched station line that passes through your offset points. Just to compare, I also used the draft workbench to draw a B-spline through points with the end-line snap active. You see the draft B-spline in magenta colour and the sketcher B-spline in light blue. They are almost identical. For me this was a pleasant exercise and I hope you can use some hints from this example to refine your model. Best regards, Kris
  5. I want to share the current state of my FreeCAD work. It is for an English third rate ship (74-gun) from the second half of the 18th century. I must admit that it is a far too complex ship to start with, but my desire to bring such ship to live won from logical reasoning. Here we go: It is just a bunch of points. I used both draft points and part vertices. The exact difference between the two kinds is unclear to me. They are arranged horizontally along the waterlines, half-breadth lines, top-timber line and topside. Vertically they follow the location of the stations. The next picture shows this more clearly. I made curves through these points both with draft splines and the tools from the curves workbench. I wanted to use the Gordon-surface tool from the curves workbench to skin the network of curves. That was a disappointment and only resulted in errors. My network of curves, that looks quite OK visually, is far from a real network because intersection points of horizontal and vertical curves are actually not coincident. I think you can only get that by using sketches that import these intersection points from external geometry (sorry if this sounds very FreeCAD slang). My tree-view of this model also lacks structure and that makes it difficult to keep track of more then 300 points already. Conclusion: I will try to start over the effort and use sketches from the start. best regards, Kris
  6. Yes, that is a traditional start with DELFTship. I guess the tricky parts to map the model to the lines of an existing (ancient) ship plan will follow. Anyway thank you for starting this effort. best regards, Kris
  7. That is fantastic news, Ab. I can hardly wait to walk around in that virtual ship. And the fact that it took 3 years for that model makes me realize that I have to spend some more effort. thanks and regards, Kris
  8. Hello Ab, If what you show is made with DELFTship, I call that a masterpiece. I also have used DELFTship but never realized the lines I wanted. Maybe I miss the point with DELFTship because I believe that every point that you make is a control point. So it is not a point on the hull. From the control points, lines for a hull are made by subdivision and you can adjust these lines by moving around with the control points. Every movement of a control point will affect several hull lines. For me that resulted in overly adjustments and a lot of frustration. Maybe I should give it a second chance as you prove that DELFTship can be mastered. best regards, Kris
  9. Hi TonyM, I also have tried out FreeCAD to model a hull. But until now that was not very successful. I even have problems of making points from the waterlines in the half-breadth plan to coincide with the same points viewed in the station lines of the body plan. About the splines in the sketcher, it is a fact that you can only make constrains for the control points and not the points of the spline itself. There is however a workaround for this and it is explained in this video: https://forum.freecadweb.org/viewtopic.php?f=10&t=9364&start=420 It seems a lot of extra work to me. So if you start a topic showing some hints on how to construct coincident points, I'm interested. best regards, Kris
  10. Hello j (Hardwoodhorder), I bought some boxwood about 2 years ago from Dictum, a German company that sells tools for the woodworker. They also offer a range of materials where you can find 2 offerings for boxwood. See here: https://www.dictum.com/en/european-wood-caa?p=5&followSearch=9700&o=1&n=12 The 2 last items in the European woods section are boxwood: The boxwood I ordered is no longer on display on the Dictum website. It was called ' Buchsbaum-Kantelsortiment, 4,5 kg '. Its cost was 55 euro and this is what I received: The largest pieces are 50 mm square and the longest is about 270 mm. The smallest are 20 mm square and the shortest is about 120 mm. You can see that some edges show some remains of bark (I turned all such edges up for the picture). Also take into account that there are shipping costs as weight is 4,5 or 10 kg, and it depends where you live. I paid 16,80 euro for shipping to Belgium. I hope this information is useful for anyone looking for boxwood in Europe. Best regards, Kris

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