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CDR_Ret

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About CDR_Ret

  • Birthday 02/01/1950

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  • Gender
    Male
  • Location
    Colorado Springs, Colorado, USA
  • Interests
    The physical sciences; Worldview, science, and education; Technical and educational writing; Reading: Accurate historical fiction, classical science fiction, biographies; Wood carving and ship models; research projects relating to landform origins, especially the US East Coast Carolina Bays.

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  1. Roger, the CO of my first submarine described the nuclear propulsion plant as "just a sophisticated way of boiling water." 🙄
  2. Mustafa, Thinking that you might not be able to run DELFTship, I created the nine stations you would need to hand draft the plywood planks in my 2D program. This is what I came up with: A couple of issues are evident. The main problem is that the body plan is not consistent with the profile and plan views. So you will be able to use that view only for general reference. I think you can get all the important details from the other views. Also, the image is slightly tilted (less than half a degree), but that can be enough to throw off some dimensions. I corrected the tilt in this image. Even with a lower-resolution background image, you should be able to adjust the the chines to create fair edges for your plywood planks. If you view the surfaces using the Developable tool——you should be able to adjust the crease edges to create a completely fair surface. What you are looking for is a solid green color indicating the surface curves in only one direction or is perfectly flat. This means you can cut the plank out of a flat piece of plywood stock. Usually the program will show red shading near the edges, especially if the edges themselves curve in more than one direction. This is how my brigantine's cylindrical transom looks because of this effect: As far as sizing the background images and other considerations for starting a DELFTship project, see my tutorial available at this page here in this forum. Again, contact me if you need some assistance getting started. Cheers! Terry
  3. Mustafa, I think DELFTship is a Windows-only platform, sadly. But like Roger said, you can create stations along the length of the hull in both profile and top views. Then pick off heights and breadths of the "chine" lines at each station and plot them in the body plan view. When you connect the dots with with straight lines at each station, you have your third view. The harder part will be generating the true shapes of the plywood planks. I think this can be done by drawing diagonals in the body plan view for each plank, then picking off the distances from the associated diagonal of the top and bottom edges (chines) at each station. This sounds more complicated than it actually is. [Edit: If there is a twist to the plank, I'm not sure this will actually work.] Terry
  4. Hello Mustafa, I think it may be doable. The interrupted lines in the plan and profile views represent edges of developable sheets of plywood. The body plan view can provide the true widths of the sheets at the dead flat point. So your software should be able to create the necessary pieces in 3D. Does your software "unwrap" surfaces to create the plywood templates? If not, I recommend DELFTship Free. This program also allows you to create truly developable parts using visual cues such as solid colors. Let me know if I can be of further help. Terry
  5. I've noticed that browsing presence is often absent, too, in the mobile version of the site (Android phone using Chrome). Terry
  6. B.E.'s solution works and that's a plus. However, the fact that the image folder's name is an active link was totally unknown to me and, obviously, to other members. I still think it would be more useful and intuitive if the scroll arrows were active as soon as you enlarge a gallery image. Why not move this feature up one layer so the casual viewer can scroll through all the images that are in the Gallery ribbon? Alternatively, include some kind of label or tool tip that alerts (new) users that you can scroll a particular album. Or do both. Reserve the large, really high-resolution images for the folder view. Terry
  7. Heh. Now if I could actually get to building the model, that would be an accomplishment! Looking forward to seeing how this comes together, Mike. Terry
  8. It would be a convenience to have right- and left-scroll buttons added to the individual photos in the Gallery at the top of the MSW forum page. This way, one doesn't have to exit the photo currently being viewed to look at the next one in the series. Terry
  9. My experience is somewhat dated, but even fairly recent marine steam turbine power plants included steam-powered devices called "air ejectors" (basically a Venturi suction tube) whose main purpose was to reduce the turbine condenser pressure very close to an absolute vacuum in order to maximize turbine efficiency. But they also removed noncondensible gases, mainly nitrogen and oxygen, from the steam. The discharge of the air ejectors went into another condenser that removed the the residual condensed steam, returning that water to the steam cycle, while venting the noncondensible gases to the atmosphere.
  10. Hi, anaxamander49. I have attempted creating ship plans in Sketchup, Blender, Fusion 360, and DELFTship Free. All of these are open source, have free licenses for hobbyists, or are offered as a free version of the professional software. Sketchup creates surfaces in polygons and there is no utility for creating useful hull plans that provides the information a ship model builder needs (e.g., stations, waterlines, and buttock lines). Also, if you attempt to scale down a full-sized digital model to model size, you risk losing precision in fine details due to the way Sketchup works (points, lines, and polygons simply disappear!). Blender and Fusion 360 have (very) steep learning curves and, again, they don't really lend themselves to creating 2D building plans useful to ship modelers without a lot of fiddling around. While Blender is an amazing program, its developers are continually revising the features and interface, so a casual user never gets up to speed in the program. DELFTship Free, in my opinion, is your best bet for creating useful working ship model plans. The program's 2D plan output shows the hull and expected details in standard profile, body, and plan/halfbreadth views. These views can also be customized to show specific objects and omit others, if desired. The program can export 2D DXF images in polyline format that can be imported into 2D vector graphics software for editing and formatting. In addition, the model surface is a true subsurface object that can be precisely shaped with a customizable control net to match existing 2D plans, if required. Like you, I used the program to reconcile incompatibilities among the three views of an existing set of hull drawings that I have come to believe was an unknown mixture of conjecture and actual measurements. The result was a fair hull that seems to reflect contemporary photos of the ship. If you haven't already, I recommend reading through the many topics within this CAD and 3D Modelling/Drafting Plans with Software forum pertaining to the various 3D software others have attempted to use when creating ship plans, and then draw your own conclusions. If you are having difficulties getting started with DELFTship (the manual isn't very good on work flow or process, just feature capabilities), please contact me or the other members who have used the program. Having a guide can help you past many of the frustrating aspects of this program. Best regards. Terry
  11. My two cents, which basically corroborates what has been stated previously ... The following information is abstracted from pages 316 and 317 of The American-built Packets and Freighters of the 1850s: An Illustrated Study of Their Characteristics and Construction by William L. Crothers. In the mid-19th century, the spacing of ladder rungs and stair treads was dictated by the natural step of the average 5-foot, 8-inch man (according to Crothers—a value he never provided!). Vertical ladders for accessing deckhouse roofs had equally-spaced rungs. The distance between the upper rung and the roof surface was the same as between the lower rungs, to avoid creating a surprise and misstep when accessing the roof. The lowest rung was at a variable distance above the deck, but could be a larger step than the space between the other rungs. Stringers were at least 4 inches deep to provide toe room at each rung. If the upper end of a ladder ended at a coaming, the upper rung (or tread) was at the same height as the deck outside the coaming, again to avoid tripping or other surprises due to height differences. Inclined ladders (stairs) had treads that were closer together than vertical ladders. However, all treads were equally spaced—from each other, from the lower deck, and from the upper threshold. This is so the user experienced the same drop and rise whether descending or ascending. The number of treads was determined by the height between decks and the inclination of the stair. As the stair angle from the horizontal decreased (became less steep), the vertical distance between treads decreased, and the width of the treads increased. Again, the reference for these dimensions is the length of an average person’s step or pace, but no absolute value was given. Stairs and ladders were made for the specific location where they served and were not interchangeable. Often the lower ends of the stringers of inclined ladders/stairs were cut plumb with the deck (“dubbed off”) below the lowest tread to eliminate a tripping hazard. While the era Crothers discusses is several centuries after the OP’s interest, I imagine these principles were more or less followed from the earliest times simply due to their practicality. Terry
  12. Thanks David. I think everything has been said that can be said. I appreciate everyone's contribution from multiple points of view and I learned a lot, personally. Terry
  13. "Once again into the breach" (Henry V-Shakespeare) Because of the persistent view that a constant-camber deck couldn't produce a fair deck, but one with unfair areas in its surface, and because my last attempt to demonstrate that this was not the case was apparently derived from a non-standard approach to ship design and construction, I decided to experiment and see what the outboard-sheer-line-in approach would produce. I had no preconceived notions on this approach, but it seemed that if the outboard sheer line was fair, then it makes geometrical sense that using constant cambers in attached deck beams would also be fair, since corresponding points on the adjacent beams would fall into a curve parallel to the outboard sheer. Many mentions have been made how constant-cambered decks weren't the case in 16th, 17th, and early-to-mid 18th century ships, and I can understand how that is likely due to the relatively low length-to-beam ratios and quite pronounced sheer lines in those eras. But ships became stretched out in the latter 1700s and through the 19th century, so there was less imperative to hand-tool the deck camber, I would think. So, here goes. Using Sketchup again, I created a generic, non-circular curve in three-space and attached it to a vertical plane that corresponds to the centerline of a fictitious hull. The curve represents the outboard deck sheer of the vessel. Outboard sheer line in perspective. Plan view of the outboard sheer line. Profile view of the outboard sheer line with the centerline plane behind (looking to port). As before, I created a deck camber edge from a segment of a large circle, then placed its center point on the centerline plane. I also added horizontal and vertical guidelines to ensure each camber template was correctly placed longitudinally and on center. These identify deck beam "stations." Cambered deck beam template and positioning guides. Next, I dragged the camber template down until its edge intersected the outboard deck edge. This was repeated using duplicate copies of camber templates at each beam station line. Duplicating camber templates and positioning them at the outboard deck sheer line. Completed deck skeleton. As in the previous example in Post #32 of this topic, I "connected the dots" to create the faces forming the cambered surface. (I deleted the curves on the far side of the plane so I didn't have to create 2 million facets, only 1 million...) Cambered surface created from the camber templates. You may see where this is leading. Again, to create the deck surface as confined by the outboard sheer line, I created a "cookie cutter" from the outboard sheer line to intersect with the cambered surface. Sketchup allows you to create cutouts of 3D objects using other objects that intersect the one of interest. The cookie cutter's surface is parallel to the z-or vertical-axis of the model. Outboard sheer line turned into a cookie cutter. After creating the intersection with the cambered surface, I deleted everything but the surface of interest. Intersection that represents the outboard sheer line in the cambered surface. Deleting the surface outside the outboard sheer line, duplicating the half-surface, mirroring it, and rejoining the two half-surfaces yields a fair, cambered deck. All cambers are the same. Completed cambered deck surface. Finally, taking a look at the orthogonal profile view of the deck, we can see that, while the centerline sheer is smooth, there is a distinct flattening there in the middle, which probably would not be considered "fair" overall. The longitudinal lines in the deck that could represent deck plank edges are no longer parallel to the centerline sheer. This doesn't indicate a problem in form or function, however. Profile view of a constant-camber deck created by referencing the outboard deck sheer line. So, while this method of constructing a deck might introduce some unfairness in a deck, it doesn't seem to be a significant problem. Recall that the camber round up was exaggerated in this example. With a camber of only 6 or 8 inches, viewing the flattening evident in the above diagram over a length of several hundred feet would be indiscernible, I think. Snide comments about resorting to digital programs to support one's point aside, I don't see any other way to easily and economically illustrate the concepts we are discussing without otherwise resorting to actual plans of actual ships that were built in a particular way. Then what does that prove, except that it worked in that instance? I can't speak about cambers in the forward areas of a ship departing from a fair sheer because I haven't researched those. If anything, those exceptions probably prove the rule. If someone could present an example of such a case, I would appreciate it so I can visualize that situation. I can't conceive of shipwrights having to create numerous deck beams, all with different cambers in order to provide a fair deck in "ye olde days," but perhaps that was the case. It certainly doesn't make geometrical sense to me. Terry
  14. Charles, My reference to a "cookie cutter" is literally what I meant. Think of a quasi-cylindrical tube with a cross-section in the shape of the plan view of a hull, which is the white, boat shape in the image. The cutter intersected the camber surface along the z- or vertical-axis, so the result is a true, three-dimensional shape in all dimensions. Crothers claimed that mid-1800s ship decks were constant camber. My post was intended to simply refute the claim that a constant cambered surface could not produce a fair deck surface. As with many areas of creative human endeavor, making absolute claims about how something can be done simply doesn't hold true because someone always comes up with an effective alternative. Terry
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