A friend of mine has asked me to make him a Hopper type barge to tow behind his tug. He already has a scratch built shoe box, but it does not tow well and doesn't look the part. I will be 3D printing it and I have designed it in FreeCAD. Attached is my first attempt. I should mention that it has to fit in his transport box. It is, length-542 x beam-150 x depth-120 mm. The sections are glued together and use the 1.75mm filament as location pins. The bow section can be used as a stern.

Having just put the barge design into the slicer and looked at the printing times which were very long (30 odd hours) I had a thought 😀. Why not print the hull in Spiralised Vase Mode. This gives one wall (0.8mm thick) on the inner and outer. It has no change of level steps as it prints a continues line and gives a very smooth surface. So the experiment goes on. The infill is only suitable for the long lengths of the hull. The stern and bow will still be normal plastic prints with infill. The infill can be 3mm ply or Balsa. Maybe ply as it will give it some weight. The hull will of course be sealed and painted.

While looking into hull design to reduce print time I have come up with another idea. So Fig 1. is the original idea where the ply/balsa was sandwiched between the hull walls and Fig 2. has the ply/balsa as cladding on the outside of the hull. They both take about the same amount of time to print: 2.5 hours per 50mm height. This is better than the solid plastic hull at 7.25 Hours per 50mm. It is just a case of which one would be nicer to work with.

Having not done a build blog before I didn't realise I could have just updated this blog. However I ended up creating a new blog "Update to Hybrid Hull" so this continues there..🤔

Having been successful with my 3D printed hull concept I have decided to make the the next project a self propelled Hopper Barge. I have just started the design work which is loosely based on the attached pictures. It works out at about 1/54 scale which is a bit odd but suites my printer. Although the pictured barge uses a 360° Schottle drive and bow thruster I will be going with a conventional inline 480 brushed motor.

Well after Chum444 suggestion I thought I would venture into Kort type nozzles. Little did I know I would be getting into such an interesting subject. So I have learned that it is not just "stick a pipe over the propeller and that will do" As always I try not to buy parts when I can use CAD and 3D. So now I have got into hydrodynamics, or at least bit of an understanding. I am used to looking at NACA (National Advisory Committee for Aeronautics) aerofoil sections as I have been designing a 3D printed sail wing. I hadn't realised they use NACA sections in Kort design (Makes sense I suppose). The pictures show where I am at. (1) is my own idea before I found out about NACA. (2) is NACA 4421 profile from a professional design, but I got the cord alignment wrong. (3) is the same with the cord aligned in the correct manner. (4) Is what I think will be the best as it is based on the diagram in picture HE-Kort (3rd from left). All will be tested.

Here I was just testing the motor and ESC (Brushed) on the bench. All was going well, until I switched the ESC off. Then, poof it went, a cloud of white smoke coming from it and a spray of hot solder. See picture. Now the house stinks of burnt electronics (Wife not impressed). It was an Mtroniks Viper Marine 40A ESC which I have had for a number of years and has never been stressed. I don't think it ever had more than 8 Amps through it. It was also a replacement, as the first one blew up. I have never bought another. They are now £53 so it was not going to be replaced. Luckily the slow blow 10 Amp inline fuse blew otherwise I might have had a bigger problem. This was going in the Kort Nozzle test rig. So back to the drawing board. 😁 Before anyone asks. Yes it was running within spec. IE.. correct input voltage etc.....😁