SardonicMeow

At a local Makerspace. I took a training class on how to use the laser cutter last year and did all the laser cutting this evening using the equipment belonging to the Makerspace. Just the thickness of the wood sheets. I used basswood because it's inexpensive and easy to get. (And because I really don't know much about the properties of other types of wood.) Maybe using a harder wood would have been better. I don't know. Yes, yes, YES! This is my Sultana build log, not a product development log. 😀 Completing the laser cutting is just the end of chapter one. I'm a long way from being done. I'm doing all this for fun. Like I said before, I'll share something once I have a complete, or nearly complete, model.

Sick of screenshots? Want to finally see some actual, physical pieces of wood? Well, I've been grinning ear to ear because I finally got my pieces laser cut! Here's one of the sheets after cutting. (I should have taken more pictures of the laser cutter in action, but I was too focused on getting the work done.) Here is a picture of the design, followed by the corresponding pieces dry fit. And various other pieces. Because someone requested it (hi, Patrick), the classic rudder is there as well as the modern rudder. This is my cradle for holding the ship while I work on it. And the laser cut pieces next to the original solid hull. Well, I kept the little bits that were cut out (see below), but probably won't use them. I have other ideas for the windows. Next time, a closer examination of the pieces and some lessons learned about laser cutting.

More design changes. First, I was concerned because there was no surface under the counter for the end of the hull planks to sit on. So, new shapes were added there. The new pieces are highlighted in blue in the picture. I was not happy with the transom windows, recess, etc. I spent some time redesigning the shapes and it now is closer to what's in my reference picture. Original attempt is on the left, new version is on the right. Originally I planned to glue the transom end piece above to simulated stern timbers, and also add some planking to cover the stern timbers on the inside. See the basic idea in the picture below. All those layers together is pretty thick, and trying to make the stern timbers thinner would only make then so thin that they would break easily. I realized that I don't need the stern timbers. There is already enough surface area for the pieces to be glued on, so the stern timbers were removed from those pieces. Instead, I will cut 3 transom pieces from 1/32" sheet: one with the recess pattern and two with the windows cut out. This stack will be glued directly on the back, very much as in the original Model Shipways plans.

I caught an error in my design. The bow former pieces end at a level that is too high. I corrected them and now they end flush with the forecastle deck level. I hope there are no other errors that I have overlooked. Ok, let's get ready for laser cutting. The laser cutter software is called RDWorks. It has some basic tools to create and modify shapes, but... Well, have a look at the message that appears at the bottom left of the RDWorks window. I think it says it all. I tried exporting one of the bulkhead shapes from Fusion 360 as a DXF and importing it into RDWorks. There is a problem. Notice how the edges of the shape aren't smooth and sometimes overlap. This is not a problem with RDWorks. I found lots of people complaining about issues with the DXF export function in Fusion 360. Apparently, it outputs splines in a format that many other programs can't handle. The solution I found is a Fusion 360 plug-in called "DXF Spline To Polyline". The plug-in adds a separate DXF export option to Fusion 360 that converts splines to many short line segments. Here is the same bulkhead piece exported using the plug-in then brought into RDWorks. Once I confirmed that the plug-in was working as expected, I exported every shape (bulkheads, fairing lines, keel, rudder, transom, etc.) as a separate DXF file. There were 51 in all. It was pretty clear that arranging the parts for cutting using RDWorks would be a pain. I found some strong recommendations for the popular open-source vector graphics software Inkscape. Learning the basic operations within Inkscape didn't take long. In Inkscape, I created a new document with a size equivalent to a 24" x 4" wood sheet. Then I imported a DXF and moved it into place. For items that will be scribed rather than cut, I set the color to red. Labels were adding to pieces using the text tool. However, in order to make sure they would be scribed by the laser cutter, I had to convert the text objects into paths using the Path -> Object to Path menu option. When the whole Inkscape document is saved as a DXF then imported into RDWorks, RDWorks will interpret each color as a layer, so the separation between the lines to scribe and lines to cut is preserved. Here's the first sheet of objects. I will end up with four total.

Since you mentioned it, I'll keep both rudder versions in the design. Anyway, while working on the layout for cutting, I realized that I'll have some extra space. So I designed a cradle for the model to sit in while I work on it.

In your second picture I can't help but notice the telltale orange wireframe of Blender. Was all this work done in Blender?

Thanks for all the responses. Lots of options to consider.

Interesting. I didn't know that not all plywood is created equal. Where would I get quality plywood and how would I know it's good? I should have mentioned in my original post that all the laser cut pieces will be planked over and/or painted over, so the appearance of the wood doesn't matter to me.

I'm working on a laser cut plank-on-bulkhead project and could use some advice from anyone who has done the same. My design is complete and I have been trained on the use of the laser cutter at my local Makerspace. So, I'm almost ready to proceed to the cutting. My first question is what wood to use. I know I don't want to use plywood, because I had issues with the plywood layers coming apart when I built the Virginia 1819 kit. Is basswood definitely out? My design has some delicate parts, so I guess basswood would be too easy to break? So what about cherry? Maple? Alaskan cedar from a certain someone? I really don't know how the different hardwoods compare. My design assumes sheets will be 1/8" thick. To what extent should I consider the grain direction when aligning parts? It seems obvious that long, skinny pieces should be aligned with the grain, but are there any other gotchas? How narrow can I safely cut parts? I have a few parts with sections that narrow to less than 2mm. Is that doable or will cuts that close together get burned through? Thanks in advance for your help.

Oh, right. I'm modeling the Sultana replica, which has a diesel engine. So I need a cutout in the rudder. After looking at some reference pictures, I tried creating the cutout, which is roughly elliptical. It didn't look quite right. Here is a screencap, cropped and flipped horizontally, from the YouTube video "Sultana Haul Out". I see what's wrong now. On the replica, the rudder has been extended back to make up for area lost to the cutout. As a result, the back edge is nearly vertical. Also, another detail is that the bottom edge of the rudder is higher than the bottom of the keel. And a little bite will need to be taken out of the sternpost. (Also interesting is that, in 2013 when this was recorded, the Sultana's hull was painted red below the water line. It was all white when launched. I don't know when the red color was added and whether or not it's still like that. I have noticed other changes in the paint job as well.) Here is the revised rudder. The Schooner Sultana book says that the prop is 32 inches in diameter. At 1:64 scale, that's 12.7mm. I checked and the cutout is large enough.

I think I have things set up properly for the rabbet. Have a look at the picture below, which is a view directly from the side. There is a thin gap between the keel and false keel. My plan is to put a thin rabbet strip there. The idea is taken from Chuck's Syren practicum. Have a look at the diagram on the bottom left of page 4 to see how it's supposed to turn out. Also, I plan to cut the keel from thicker sheet than the false keel.

Thanks for your comments. But I don't think I'll be quitting my day job just yet. Working on the cap rail at the bow. First, a fit point spline to match the correct curve. Cap rails will be 1/8" / 3.2mm wide. I use Sketch -> Offset with an offset of 1.6mm to create the inner edge. The offset is repeated to create an edge 1.6mm in the opposite direction. The original line is removed and the shape is closed. And mirrored. Here is the piece roughly in place. The actual piece will not be flat; it will slope down as it follows the top the bulwarks. And here's a big picture of everything. There is one notable change. I decided not to include the gun stocks as part of the aft bulkhead pieces. I realized that I would have to plank around them, which seems like too much trouble. And with that, I think I have designed all the pieces that I want. Now I need to arrange them for the laser cutter. I'm still debating basswood vs. some other wood to use in the laser cutter.

Reference marks were added to the scribe lines for each bulkheads (in the same sketches where the fairing lines are drawn). These reference marks indicate the location of the wales and the bottom of the bulwarks on each bulkhead. Next I turned to the end piece for the transom. After some careful measurement, I determined that the transom outline on the Model Shipways plans seemed to be properly sized. I scanned the image and brought it into Fusion 360. So far so good. In this image the Model Shipways transom is on the left, and the Chapelle transom on the right. The general shapes are similar, but the MS transom windows are larger and spaced further apart. Also, on the MS transom the lines for the recessed portion of the transom are higher. (There are also some symmetry issues with the MS drawing.) So what's correct? As I mentioned at the start of this build log, I will be using the Sultana replica as the standard. Fortunately, I found a good picture of the Sultana's transom at the website "829 Southdrive". Picture by the website author "Baydog". From this picture, the windows should be fairly small, and the recess line is fairly low. That makes the Chapelle drawing the closer match. Following the Chapelle transom and the reference photo, I came up with these two sketches for the two pieces. Solid parts were created in the 3D environment to see how they will look. (The real parts will be curved.)

I've decided to go with the bulkheads at the bow that are perpendicular to the false keel. I have added some extra pieces at the bow. Blue lines are fairing lines that will be scribed onto the pieces Shapes of the stem, keel, sternpost, and rudder were traced from the inboard profile image. Bulkheads at the points where the deck level changes were doubled up so that there will be good surfaces where deck planks start and end. There is also a cutout now, partially obscured in this picture, for the hatchway ladder that goes down into the hull. And so here is what everything looks like at this point. Still to be done: design the transom end piece it might be nice to laser cut the cap rail at the bow add guide marks for the wales and any other useful reference marks Then it's a matter of exporting each element as a DXF and arranging them for the laser cutter. I need to decide soon whether I want to use basswood sheets or some harder wood. Because there are limitations on the width of hardwood sheets, that will affect how I can arrange the pieces for cutting.

Yeah, on some of the build logs for Master Korabel kits I noticed that they use a big lateral piece to hold the other pieces, including some angled pieces. It seemed like a great idea to steal. But on this ship, it doesn't seem to gain me much. It would be more appropriate for a ship where the timberheads form stanchions for tall bulwarks with gun ports. On the Sultana, the bulwarks are really short. So I think in the end I'll be going with conventional bulkheads all perpendicular to the false keel.

I've been trying different ideas for how to deal with the bow. The first option is fairly straightforward. There are holes in the bulkheads for the bowsprit. Blue lines are fairing lines that will be scribed on the parts. Option two is a bit more radical. There are pieces at an angle somewhat analogous to cant frames. Horizontal pieces matching the curve of the bow will hold them in place. It looks cool, but I don't know if there is any advantage to it.

Working on the transom this time. My goals include creating a strong surface that the end transom piece can be attached to. Also, I wanted to ensure that there is some open space behind the transom windows. Here is in innermost piece. And the next two pieces. And some pictures of how the transom pieces fit together with the aft bulkhead pieces. Blue lines are the fairing lines that will be scribed on the pieces. Next, as I have been gently reminded, I have to figure out how to deal with the bow of the ship.

Ha. No, let me see if I can make something usable first. At the end of all of this, if there's interest, maybe I'll post the DXF files for others to use.

You're correct, Lou. I think you overlooked the part near the end of my last update where I mentioned that bulkheads near the bow still need to be done. My last picture is just showing the current state of the design, not the final one.

Several bulkheads were added at the center of the ship. Because little to no fairing will be required, no fairing lines were identified for these bulkheads. And here's another bulkhead in the aft part of the ship. But maybe there is an opportunity here. If the bulkhead is positioned appropriately, then I can do this... And that takes care of making the swivel gun stocks. The same is done for the other locations with swivel gun stocks. And just to get an idea of what the final product will look like, I thickened the bulkhead templates to the appropriate thickness. This is what it looks like so far. I still need to work on the transom and bulkheads near the bow.

Before I add any more bulkheads, I think it's a good time to cut out the notches for the masts and bowsprit. The kit-supplied dowels are 6.4mm in diameter for the masts and 5.15mm in diameter for the bowsprit. Tapering will be required above the deck, but I'm happy to leave them at full diameter within the hull. I edit the sketch for the false keel. Rectangles are added with a width equal to the diameter of the dowel, then rotated and moved in position to line up with the masts on the inboard profile image. A similar procedure is followed for the foremast and bowsprit. Finally, the Sketch -> Trim tool is used to get rid of the lines that aren't needed. I hope that little pointy bit at the front won't break.

Yes, that's something I hope to do. Probably not. The bulwarks are very short -- just a few inches above the deck level in some places. I think I'll do things like in the practicum: end the hull planking just below the level of the deck, then fit a strip for the bulwarks above it, with another strip on the inside.

Finally I will start to find the shapes for some bulkheads. I know that I will want bulkheads at the three points where the deck level changes, so those seem like good ones to start with. I start by making the inboard profile image visible, since it shows the internal structure. Via the construction menu, I create an offset plane at the point where the forecastle deck drops down to the main deck. It's 52.7 mm back from the forward perpendicular. Next I make the hull and deck surfaces visible. I select the offset plane and go to Sketch -> Project/Include -> Intersect. As I move my mouse pointer over the surfaces, anywhere the offset plane intersects with a surface, the intersection curve displays as a red line. I'll click to select the first intersection curve. And the one across the deck. And finally the one on the other side of the hull. When I click Ok the three curves are saved as a new sketch. There is some overlap where the deck and hull lines meet. To edit the sketch any further, I have to break the link between the intersection curves and the surfaces. I select a curve, then right click and select Break Link. This is repeated for each curve. The curves change from purple to blue. Now I go to Sketch -> Trim. When trim is active, segments of lines in a sketch that can be trimmed will turn red when the mouse pointer is over them. I trim off all the overhangs. And I add a notch 25mm above the baseline. The first bulkhead is complete. I can right click on the sketch, choose Export to DXF, and import the shape into laser cutter software. Of course, I need to add a matching notch to the false keel. I would also like to add fairing lines to each piece. The procedure is the same, but I don't need to include the intersection with the deck surface, and there is no notch. For the other bulkheads at places where the deck level changes, I follow the same procedure. For the second bulkhead, the hull lines don't quite reach the deck curve. In this case, I first use Sketch -> Extend to extend the lines, then use Trim to trim any overhang. I edit the false keel sketch and add notches at the appropriate locations for the three bulkheads I've created so far. And here's a view of all the sketches defined in this session. All of these will be exported for use on the laser cutter.

My goal is to produce templates for laser cutting. Hopefully it will be more clear in my next update.

The next thing I need to figure out is the exact placement of the decks and the deck camber. I bring up the inboard profile image. Starting a sketch in the centerline plane, I trace the lines along the underside of the planking on each deck. The lines for the two innermost decks (main deck? and quarter deck?) are very slightly curved. The other two are just straight lines. The sketch continues alone the rabbet and back to the start. I'll be using this sketch for the false keel. Notches for bulkheads will be added to it later. The deck camber isn't obvious from the Chapelle plans. On the Model Shipways plans, there is a diagram showing an arc over a span of 72mm with the highest point of the arc at 2.5mm. I assume this is the camber at the widest part of the deck, but can be applied overall. Applying those measurements, I create arcs on the 3D model passing through the start and end points of each deck. Surfaces are lofted across the arcs. For the two larger deck sections, the line of the deck along the centerline is used as a rail, because it's curved. That gives those deck sections a very slight saddle shape. (This picture makes it look like I'm creating a solar-powered ship. 🙂) Here are all the surfaces to this point.