My procrastination was correct. The rudder hub has taken hours of design work and I still don’t have it done. Two things, so far, are complicating things. The weld flanges are not square with the part. Instead they are slanted according to the lay of the ship mold lines. I had to chop the top off the upper section to a slight angle corresponding to the floor angle of the machine room. The lower plate is slanted even more with the line of the hull at the bottom. I drew them square, removed them and then rotated them to the correct angle. The second problem was worse. How to skin the sides of this complex part? My first attempt took a few hours, but it was a bust. It wouldn’t/couldn’t print. The skin had no depth. That breaks rule number 2 of the three rules about designing for 3D printing. To add depth to the walls was an exercise in futility. I’m going back to old school. I’m going to skin the contours with 0.040" styrene sheet glued into gluing lands I’m designing in the part.
Here’s the upper part showing the angularity of the upper surface and weld flanges. The walls on this part are thick and will print. Note: This part has no taper making it easy to just extrude the walls to the desired height.
Here’s the comparison of the first attempt and the second. When the first attempt is exported as a printable STL file, the side walls, without thickness, disappear. Something that has no depth can’t exist in our 3 dimensional world. Everything that can exist has thickness unless we’re talking about an electromagnetic wave. All those zig-zag faces has to be hand woven and it took a lot of patience and care.
This part is not yet complete. It has a center section with more taper and it has a fairwater leading edge that has to be drawn and printed OR made model RC Plane style by carving a block of balsa or carving foam. I can even make the shape out of clay and cast a resin shape to do it. I can also skin the shape with balsa. I have experience with balsa and styrene. I do whatever is least expensive. This part supports the rudder, but the rudder itself will be skinned with balsa and be very light weight.
On another tack…
I got all the materials for the machinery either in hand or ordered. The stainless steel rod stock arrived from Amazon and I picked up the KS Metals brass tubing that will serve as the sleeve bearings. The fit is, by design, perfect.
All I have to do is cut the shafts to length. There will be no polishing or finishing needed, and being stainless, I won’t have to worry about corrosion occuring over the years the model will be on display.
I’ve got the bearings in hand and will design and run a test article to find the right diameters for the various sleeve and bearing mounting holes. Just telling the printer I want a hole of X size doesn’t guarantee that it will be that. Most likely it will not. The resin expands and changes during printing and post curing. For most applications this usually does’t matter. But here I’m trying to print holes that are going to be tight fits on bearings and machined pins. For the pins that I’m machining, I adjust the size based on the actual hole, but in the case of finished bearing and sleeves, I have to print the holes the right size. For through holes, I can open them up if they’re too small. Not so for blind holes like the cups that will hold the tiny bearings at the ends of the ram rods. These will have to be right.
So I’m creating a test article with a series of holes representing those needed in the model. I have converted all the key dimensions to full-size 1:1 to draw them in SketchUp and will reduce to the 1:32 scale. I will start with the actual recorded size of the bearing/sleeve o.d.s and then enlarge by small increments. I will note their sizes on the print itself. After printing, the sizes that work best will be incorporated into the model’s design. It will be much easier (and cheaper) to print on piece with a bunch of holes than to print the real complex parts of the model only to find that the bearings don’t fit.