CDR_Ret

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

Not to beat a dead horse, I thought it would help to illustrate Phil's explanation to show that constant-camber deck construction actually works. Crothers et al claim that an upper edge of a cambered deck beam is a segment of a huge circle—too large to lay out on a lofting floor. So that is why the graphical approximations for a circle segment shown in earlier posts were developed. The following image shows a line of circles of equal diameter arranged along a vertical, rectangular plane. The edges of the circles adjacent to the rectangle represent the edge cambers of a series of deck beams arranged along a straight sheer centerline. This will be the basis for "constant camber." Now, please bear with me. All the following images were derived from a Sketchup model. If you connect the edges of the circles in such a way to create a surface on both sides of the reference centerline rectangle, this represents a cambered surface with no sheer. In Sketchup, you have to create a bunch of small rectangular faces to produce the surface, which I didn't illustrate at this point. However, taking a side view of the constructed cambered surface, it would look like this: The vertical edges within the surface are the included edges of the circles, or camber curves. The horizontal edges form the faces of the cambered surface. Note that these latter edges are all parallel with the straight centerline sheer—a geometrical certainty in a cylindrical surface. Let's remove the portions of the circles not included in the cambered surface to reduce clutter. This is a plan view showing the surface. (The deck/hull centerline is left-to-right in this view.) Again, the longitudinal lines that connect the individual deck beams (the horizontal lines) are parallel to the centerline of the vessel. Here is a perspective of the cylindrical cambered surface looking aft along the centerline. Obviously, the curvature of the camber is exaggerated for this discussion: Now, getting to an actual vessel deck, lets assume the centerline in the profile view is a generic curved sheer line. Then we reconstruct the same surface from that starting point. Again, the vertical rectangle with the curved edge represents the profile view of the centerline plane of the hull deck. Here, the cambered beam edges are arranged along the centerline sheer. Now, we create the cambered surface by connecting the nodes visible in the image with line segments (this is a process in Sketchup). This results in the "saddle" shape that Phil mentioned in his post. If we look at the profile view of this surface, we see that the longitudinal lines in the surface are all parallel to the centerline (sheer) curve. These lines could represent deck plank edges. They neither converge or diverge from the sheer profile in a constant-camber situation. So, how does this look in a real-world application where the deck beams are constrained by a hull? Let's take a hull-shaped "cookie cutter" and create a deck from this saddle shape that fits into a hull. I stretched out the cambered surface in the longitudinal direction to provide a more realistic proportion of length-to-beam. After cutting out the hull shape on one side, eliminating the parts of the surface outside the cookie cutter, and duplicating, reflecting and joining the two halves of the surface, this is what we have in perspective: Ignoring the facets, which are artifacts of the digital program, this surface represents a sweet and fair moulded deck. All deck beams have the same camber. Again, a profile view of this surface shows that all longitudinal lines on the surface are parallel to the centerline sheer. Note that the lower edge in this image is the outboard deck sheer line from which the rail line can be projected. However, to be perfectly honest, David (Druxey) reminded me that ship designers started with a sweet and fair rail sheer line, then established the positions of the outboard ends of the deck beams below that, and then from this information, developed the centerline sheer line as dictated by the widths of the deck beams and their camber. This is correct, but working the process in reverse of what was presented here still yields a fair curve without having to create separate cambers for each beam. I hope this illustrated explanation will help visualize what several of the contributors to this topic have been saying. Constant-camber geometry likely applied to vessels at least from the mid-1800s on, if not earlier, so modelers experienced with earlier vessels may be justified in having a different view of this issue. Cheers, Terry

Phil, Your perspective diagram is just what is needed to explain the concept of "constant camber" as it applies to deck form. I was considering using the term "saddle" in an earlier post in order to explain the essential shape of a ship deck where all beams had identical cambers along a curved sheer, but I was concerned that would just add to the confusion. Well done! Since some of the issue seems to center on the historical use of the term "camber," it's always helpful to go to the etymology of a word to understand where it came from. The etymologyonline.com source provides the following entry for camber: camber (n.) "convexity on an upper surface," 1610s, nautical term, from Old French cambre, chambre "bent," from Latin camurum (nominative camur) "crooked, arched;" related to camera. As a verb, "become slightly arched," from 1620s. Related: Cambered; cambering. I consider this website to be fairly authoritative. They provide a link to their list of principle sources, which is quite extensive. It is possible and even likely during the past 400 years that writers and draftspersons could have misappropriated the word, not fully understanding its origin, and applied it to situations not intended by its initial usage. We even see the same thing happening in more modern times. A cambered road surface is crowned to facilitate water runoff (✔️). But the word also now applies to banked race tracks (❓) as well as the design feature of vehicle steering mechanisms that facilitates restoring turned wheels to the straight-ahead orientation (⁉️). Tom, I must respectfully disagree with your conclusions. If you create a deck beam template with a particular round up or camber at the deadflat, then use that pattern for every beam forward and aft of deadflat arranged along the moulded centerline deck sheer, you will obtain a fair, curved surface. (See Post #15 in this topic, which illustrates this approach I used.) This is a mathematical necessity, as Phil noted. The length of the beams is determined by where they intersect the ceiling timbers (at least that's the way it worked for 19th century ships) but this in no way affects the moulded deck surface. It is true that the beams appear flatter near the ends of the hull, but their surfaces are still parallel to adjacent beams with the same camber, so the surface they form will be a fair one. I will defer to those who have studied ship construction in earlier periods where builders may have reduced the camber toward the ends of the ship, since the camber was less effective to shed water on shorter beams. But this wasn't a geometrical necessity, and eventually was superseded by the more standard practice of constant camber as stated in the references I have cited above. Terry

Hey Dean. My customer is this guy named CDR_Ret. He's neither rich nor values form over substance. He is really particular about substance. Not having ever built an actual model ship from scratch, I'm probably overthinking many of these details that would never see the light of day in a finished model. Since my nuclear engineering background was founded in following rules and specifications, I find it natural to review the basis for every detail that I don't have personal knowledge of. And since it is more than likely that I will never actually build a model of the ship I am researching, I hope to at least create the most accurate set of plans possible based on all available resources, so someone else can have that privilege. Sorry to have hijacked your thread. Did you find the answers you were looking for? Best wishes. Terry

David, Yes, that likely is the actual way the deck sheer line is created. The method I described reflects the process I had to resort to because Galilee's original plan's rail sheer wasn't fair to begin with. I suspect that a draftsman before the advent of 3D software may have had to resort to an iterative method to arrive at both a fair rail sheer and a fair deck sheer. Thanks for injecting a bit of reality into my comments. 😬 Terry

Reviewing the responses here, I am having some difficulty reconciling these views with what I have read in resources contemporary with the age of sail. Granted, I am not an expert on this topic, so please bear with me. First, dealing with camber. My understanding is that "camber" refers to the round up of the beam athwartships, not longitudinally. Camber is visible in the body plan, not the profile view. The curve of the moulded deck in profile is the centerline deck sheer. This definition of camber is confirmed in both Crothers' books and in various dictionaries. The term "camber" itself is not used in the Record of American and Foreign Shipping 1890, but the context of the word "crowned" referring to the shape of the deck beams is unambiguous. My understanding is that the American Shipmasters' Association (ASA, and its successor, the American Board of Shipping, ABS) were essentially American construction standards setters for underwriters similar to Lloyds of London. I'm not sure what Mr. Davis's point was in the Woodenboat article, but if the deck beams with a "constant camber" (meaning to me that all beams use the same camber template created at the deadflat body plan) are installed in the ship to create a fair sheer curve along the ship's centerline, then all deck planks laid parallel to the centerline will also have the same deck sheer. It seems to me that the sheer of the outboard rail is contingent on the intersection of the deck beams with the moulded hull surface, assuming a constant rail height above the deck is to be established. A sweet and fair rail sheer in profile depends on the deck camber, the moulded beam of the ship, and the shape of the hull. If each beam had its own round up based on its length, then the deck planks would not provide a uniformly fair surface. Perhaps I have misunderstood what was intended in the above comments. In attempting to reconstruct my grandfather's ship's main deck using the principles Crothers stated and the ASA's construction standards, the following image shows how the moulded deck's surface lies true and fair. All beams have the same camber. The gaps resulted from variations in beam spacing. The deeper beams are in way of hatches and masts per the ASA Record...-1890. Brigantine Galilee's reconstructed main deck beams, constant camber (2-1/2 inch roundup). Model in DELFTship. Dean's concerns about introducing the "spring" in deck beams in a model are correct—up to a point. There is no reason to include this feature in a model because the stresses relating to an actual ship aren't present. In any case, the forces involved springing a beam compared to the other stresses in the hull were minimal. A 40-foot beam would be sprung only 4 inches (0.83%), and that would be included in the total design camber for that beam. Beams near the ends of the ship would have little or no spring. Recall that the purpose of the beam spring and stanchions is to reduce the weight of beams on the sides of the ship by transferring that weight to the keel. Regarding the shape of the beam bottom surface, it is pretty clear from both Crothers and the ASA Record... that the bottom of the beams (at least merchant ship beams) in the latter 1800s were not curved. From the Record of American and Foreign Shipping-1890, it states "The beams may be reduced in moulding one-fourth at their ends; the underside straight, and upper side crowned." (p. 38, emphasis added). The bottom surface of the beams being flat seems to be evident in a photo taken of the Galilee's hold in the 1960s, 70 years after she was built. I'm not sure that any "spring" in the beams would be evident from this vantage point. Also, considering that the keel is basically gone at this time in the vessel's history, eaten by ship worms, the spring, if present, would have been released. Derelict Galilee's hold, showing main deck beams, hold ceiling, beam clamp, and knees (c. 1965). A question I have is this: Though the beam bottom surfaces were straight (not crowned), were they horizontal? Or were the bottoms angled fore and aft to follow the deck sheer? This would be significant only at the ends of the ship. Reconstructed forward main deck beam in Galilee with a horizontal bottom surface (perspective looking starboard toward centerline). Only the port half of the beam is visible in this image. Same deck beam but with the bottom surface following the local moulded deck sheer line. Based on the quotation from Crothers in my previous post, I would say the intent would be that the lower surfaces of deck beams were horizontal. This would also reduce the work in fabricating beams and simplify installing the beam stanchions to bear against a perpendicular surface. Thoughts? Terry

Please permit me to put my oar in, since this topic has recently been of some concern for my research project. I have finally found some contemporary and near-contemporary wooden ship construction rules for my late-19th century brigantine merchant. William Crothers, in his book American-Built Freighters and Packets of the 1850s, makes the following statements: "The true form of the camber curve is the arc of a circle of great radius, which is difficult to draw due to the space required." (p. 55) "Three methods of developing a proper curve for deck camber—one mathematical, one geometrical, and one natural—are illustrated [in Figure 3.6]. In all cases, the maximum moulded breadth of the deck is the database." (pp 55, 57) [Frankly, the first two methods he shows appear to be two different geometrical methods. The third is springing a long uniform wooden batten between marks at the ends of the reference beam on the lofting floor and marking the curve at the required roundup.] Brackets are my additions. "This [the deck camber] was arbitrary and was commonly 6 to 8 inches in forty feet." (p. 57) "The established camber curve, or round up, is constant throughout the length of the vessel." (p. 57) The following passage was completely new to me when I first read it. It refers to "springing" the deck beams. "An attempt to spring a [straight] beam, which might be moulded eight to ten inches, to the maximum height of camber curve, would exceed the elastic limit of the substance of the beam. The maximum allowable spring in a beam is about one-eighth of an inch per foot of length, but this figure is reduced to one-tenth of an inch in actual practice. The solution was to cut a portion of the camber into the beam itself on the upper side and, if necessary, on the under side. In any case, the required moulded depth of the beam had to be retained. (p. 57) [Farther on, he explains that the beam is placed in the ship and fastened to the clamps, then jacked up in the middle to attain the required camber. A permanent stanchion under the beam is then installed, which transfers some of the weight of the beam to the keel below, relieving the load in the ship's sides.] I discovered in the Record of American and Foreign Shipping-1890 that deck beam scantlings were determined by vessel tonnage. Beams adjacent to hatches or mast partners were 10 percent larger than standard beams. The underside was to be straight, and cambered only on the upper surface. All beams in the vessel (for a given deck) were to be maintained throughout the vessel. An exception was made that beams toward the ends of the vessel could be reduced by one-eighth throughout the length of the beam. A later standard identified the "ends" of the ship to be one-fifth the length from the stem and stern post. One question I haven't quite answered yet is whether the bottom surface of a beam is parallel to the moulded sheer of the deck as the top surface would be, or is it parallel to the waterline? Crothers suggests that the latter is the case. He writes, "At the beam ends, in way of the clamp, the lower surface of the beam was snaped to rest flat, or horizontal, on the clamp. If necessary, the clamp itself was trimmed to accommodate the end of the beam." (p. 207) This makes sense only if the lower surface of the beam was parallel to the waterline. Any thoughts on this information. None of the foregoing applies to wooden warships, sadly. Terry

Mike, as others have said, laser cutting in conventional use applies only to cutting essentially 2D objects from 2D patterns. The 3D model is constructed from these parts. If 3D laser ablation is actually a thing, it is a very specialized process. Computerized 3D manufacturing involves either additive (i.e., 3D printing) or subtractive (i.e., multi-axis milling) processes. Shapeways offers photoactive additive manufacturing methods involving lasers, but I suspect that isn't what you are looking for. Terry

Working on the escape trunks, now that the grandfather journals have been delivered to all the cousins and siblings... The Sturgeons had two escape trunks. These acted like airlocks in spacecraft to allow emergency egress in case the boat was bottomed for some reason. The only difference is that there is high-pressure sea water outside instead of a vacuum. Basically all US submarines following WW II had the capability to mate with the McCann rescue chamber. This required a flat surface surrounding the upper escape hatch fairing, which was equipped with a haul-down bale, external hatch operating gear, and, later, anchor points for the Deep Submergence Rescue Vehicle (DSRV) snubbers. The flat landing surface on the albacore/cylindrical hulls had to be faired into the hull shape. So, I tried to illustrate all of these features in this model. The haul-down bale was actually attached to the emergency buoy cable, which was manually released from inside the ship. The buoy carried a cable to the surface of the ocean, to which the rescue device was attached by divers. The DSRVs used the cable to visually guide the vehicle to the stricken sub. The DSRV would mate to the hull above the hatch, then attach snubbers to the four rings to steady the vessel before blowing the skirt dry and entering the sub. In truth, this is a lot of surmising, since none of my boats ever went through a DSRV drill or deployment exercise. Location of the fore and aft escape trunks. The forward trunk was in the bow compartment and the aft trunk was in the engineroom. This is the forward escape trunk landing area. I had difficulty modeling these because I don't recall them being so prominent. But there were other things surrounding them like safety tracks, so perhaps they were. The aft escape trunk. Since the upper parts of the escape trunks and hatches were located within free-flooding areas and/or ballast tanks, there were a lot of other pieces of gear associated with them that couldn't be installed in way of the pressure hull. These included line lockers, the emergency buoy, retractable cleats, towing fairleads, hydraulic capstans, and so on. Given time, I may actually get to those. Terry

Tony, that looks simply ... agonizing. I can appreciate how much labor went into those lines. Terry

Keith, are you a lawyer by any chance?

Just don't call a ship a boat, unless it's a submarine! I don't know how many articles I read over the past several weeks about the "boat" stuck in the Suez Canal! 🤨

Continuing to work from aft to forward, today is the towed sonar array tube and faring. The Sturgeons were already being constructed when the US submarine force received their towed arrays. These sonars were towed a long distance behind the ships to remove the receivers from the vicinity of the largest sound source in the area—the towing submarine itself. So the early towed array systems were add-ons for the Permit-, Sturgeon-, and the Los Angeles-classes. (The towed array systems for the Sea Wolfs and Virginias are totally internal.) The handling gear for the array cable was installed in a forward ballast tank and the sonar array itself was stowed in a long tube that led to the stern planes. The "flushing tube" laid against the hull and was covered by a low fairing topside. The aft end of the tube had to extend far enough aft so that when the ship executed a sharp turn, the array wouldn't be cut off by the prop. (The Soviets solved this problem by putting their array and handling gear in a pod on top of the vertical stabilizer of the rudder.) The sonar tube was called the "flushing tube" because the array was deployed and retracted by pumping water through it to "flush" the array out and lubricate its retraction. The most difficult part of modeling this component was the topside flushing tube fairing, which twists in three dimensions as it lies along the hull. Sturgeon Class Towed Array Flushing Tube and Support Aft view of the Towed Array Flushing Tube Towed Array Fairing Modeled in DELFTship Terry

Took a few hours this weekend to build the submarine rudders and the stern light. The Sturgeon balanced rudders acted together on a single shaft. The lower rudder worked as a standard rudder when the ship was surfaced. Submerged, the upper rudder added twice the turning leverage. Let's just say that these SSNs were pretty nimble when submerged. At a flank bell, you had to hang on during the turn! Sturgeons had a single, combination stern light housing. The lower enclosure provided the screening needed for the 135-degree stern light used underway. The upper lamp was the 360-degree aft anchor light. Both lamps were in pressure-proof globes rated to the ship's maximum operating depth. The light to be illuminated was selectable from inside the ship. Terry

Yeah, I've heard these stories even back when I was still in the Navy. The circumstances change every time I hear it. The one that was popular back then was that President Clinton had authorized the sale of a poly-axis propeller milling machine to the Chinese even though it was on the strategic items restricted list (or whatever it was called).

Rather than continuing to clog up a thread on the features and foils of the DELFTship modeling software with my personal project, I decided to move the relevant posts regarding the project to a separate thread. If Admins can move the original posts and responses to this thread, that would be appreciated. Otherwise, not a biggie. The original posts can be found at the following links: Hull against background plans. Seven-bladed screw. Stern Planes and Control Surfaces. Follow-on progress will appear here. Does this qualify for a "build log?" 🤔 Terry

Taking a break from editing the final drafts of the transcriptions of my grandfather's diaries. Added the Sturgeon's stern planes and control surfaces. Started using some of DELFTship's useful tools, like the Mirror tool. This way, you only have to create one-fourth of the complicated curvy surfaces, such as the vertical stabilizers. Then you can mirror the part across the vertical longitudinal plane and the horizontal plane. Only a quarter of the work! Those vertical slabs really weren't stabilizers. They were originally intended to house the aftermost set of PUFFS (Passive Underwater Fire Control Feasibility System) sonar arrays. That idea fell through for this class, only to be resurrected in a more sophisticated form with later classes of submarines. I think an engineer finally figured out that having a passive sonar array so close to the propeller probably wasn't going to work. Every ship of the class had these housings, though. Here is a view showing the control surfaces. Several popular hull plans of this submarine class floating around on the Web show the hinge of the planes at an angle to the centerline of the hull. [Edit: 8/6/22 That simply wouldn't work. The planes have to hinge on a line perpendicular to the hull centerline. Rethinking this, since the planes taper from inboard to outboard, the seam between plane and the stabilizer would show a taper. Some day, I might actually take the time to fix this.] There was only a single huge hydraulic bellcrank to rotate them. They acted together, not like aircraft ailerons. Next will be the upper and lower rudders—when the opportunity presents itself. Terry

Hi Rubkvi. Nice looking vessel! Actually, getting the vertical scale for waterlines is pretty straight forward if you have a good set of plans and 2D software. First, you take the profile plan and find the dimensions of either its overall length (93.40 m) or its LPP (82.20 m) using the drawing software. This will be a certain number of inches/centimeters. (I noted that the numbers along the keel appear to be frame numbers, not length, nor are they station lines.) Then you divide the drawing length by the hull length to find the scale inches per meter. Then build a ruler using this scale. Make it long enough to reach at least to the weather deck. Rotate it to the perpendicular and place it on the vessel's baseline. (Again, the horizontal lines in the body plan are decks, not waterlines.) The vertical ruler is in meters. This should get you to the point where you can create your waterlines for planning. The station lines will be more difficult. There are 12 station lines visible in the forward view (counting the body plan outline). Figuring that the lower hull's maximum beam (at the tank tops) is about 49 m from the bow, that works out to about 4 m between stations (with maybe 1 m of the bow bulb sticking beyond the forwardmost station line there). A big problem you will have with these plans is that you have little idea what the hull shape is for the stern aft of maximum beam (and there is no aft view of the body plan). Unless you have additional plans and/or photos of the stern area in drydock, this will be difficult to replicate. Hope this helps. Terry

Great stuff, Kiyoo! DELFTship exports curves in the DXF format and, as you said, the curves become polylines. The number of line segments depends on the precision level used in the program. I use CorelDraw for the 2D part. It has a feature to convert the corner nodes to smooth nodes, like Bezier curves. The downside is that there are a gazillion nodes, which interferes with creating smooth, fair curves. So far, I'm with you! Terry

Kiyoo, As others have said, DELFTship's usefulness to the ship modeler (besides being free) is visualizing the 3D hull, then converting that shape to 2D patterns in a 2D software similar to the process you have described above. I don't want to highjack your interesting topic with the details of that process here. What I would like to understand, from simple curiosity, is the process of converting a 2D vector drawing to a laser-cutting pattern. Is that conversion done in the laser control software, or do you have to make the cutting beam allowance in the 2D pattern beforehand? Looking forward to seeing how one does that. Terry

There are many here who have a much more detailed understanding if this concept from a historical perspective. But it simply means the combined width of a frame (room) and the distance between frames (space). So room and space (R + S) is the total distance from, say, the forward surface of a frame to the forward surface of the next frame. The way I understand it, the concept is meaningful only if the frames are set square, have the same sided dimensions, and are equally spaced. But I could be mistaken.... Terry

May I suggest that the best way to avoid cumulative errors is to measure each frame's position from the same reference point? I had the very same issue with my Galilee plans. 16-inch double-frame room, and 12-inch space. 58 frames. I used a spreadsheet (Excel) and created a formula to calculate the positions of the aft, middle and forward faces of each double frame referenced from the aft-most frame. Each of these positions are 28 inches farther forward along the hull in relation to the previous frame's. The results can be accurately calculated to whatever precision you choose, and in whatever units you need (including fractions, if desired). After the spreadsheet is filled in. You can use a long precision ruler to accurately mark your frame positions. Hope this helps. Terry

I have attempted 3D hull modeling in Trimble's Sketchup. Several members have attempted using the open-source Blender as well as Fusion 360. You can read about their projects here in this CAD and 3D Modelling/Drafting Plans with Software forum. My preference has been DELFTship Free, a for-the-purpose naval architecture program that offers a free version for modelers and backyard boat builders. The company offers a manual that would be good to go through before getting too far into using the program. While the user interface is improving, the actual work in the program can be difficult to pick up until you get to know it or have some guidance. However, that is even more true for the other programs I mentioned. Only DELFTship is configured for ship modeling. It also has the ability of exporting files to an STL format, which you will need for 3D printing. As far as tutorials go, there are some videos available on the Web. Several of our members, including myself, have posted limited tutorials here on MSW. Just search for "DELFTship" in the Search Field and check them out. I highly recommend downloading my Background Images Guide that I posted in the New Version of DELFTship thread here. The company just released a major version update that makes using background images for modeling a lot easier than in previous versions. DELFTship Free and its manual can be downloaded here. Please feel free to contact me by PM if you have any questions on getting started. Terry

Hello, Rubkvi, and welcome to MSW! The short answer to your question is No, there is no shortcut, automatic way accessible to the average ship modeller to convert scanned 2D drawings to a 3D digital model. Essentially, one must import a good-quality set of plans into a 3D CAD program such as FreeCAD, DELFTship, Blender, or one of the others mentioned in the posts in this CAD forum. Then you build the model in the program. You should read through the topics in this forum to understand why this is the case. Just accurately digitizing scanned prints can be a laborious process, even with the best CAD software. Feel free to ask about the pros and cons of the various methods. This is a very helpful and knowledgeable community! Terry

Anaxamander49: The short answer to your question is, the reference length is whatever works best for the plans you are using. If your plans show the perpendiculars, those would be best, since that is what the program references in its viewports ("AP" and "FP"). The numerical hull length is critical mainly for hydrostatics and hydrodynamics calculations the program can perform, which generally aren't of concern for modelers of historical vessels. The program works best for creating building plans if you are using the moulded surface of the hull, not the outer planked surface. For this reason you wouldn't want to use the overall length of the hull for the model's length. I found that anchoring your plans to the underside of the rail, and the inner rabbet lines along the stem, keel, and sternpost works best for starting the hull form. All the other details can be added later, if desired. I would recommend you download the free manual (Manual_13_mc0.pdf) from the DELFTship website, if you haven't already done so, and read through the the first three sections (Interface, Settings and Preferences, and Hull Modeling) to become oriented to the software. The manual is adequate for getting started but isn't comprehensive. It describes more what the program does rather than how or why. And it is definitely lacking in processes and pitfalls. Please feel free to PM me or the others here who have worked with DELFTship if you have any questions. Terry