HMS Hood

So my first build has started.... Just.

I have a lot of work to do before I even touch any materials. I have found a CAD file I can use to begin with. It has a lot of the components I need in a raw form 



I have to scale all the parts to 1:150 from the current scale of around 1:385. Also this model is meant to be a static display model, and so I will have to add all the motor mounts and servo mounts, and the holes for prop tubes etc. I will also be adding structural members along with mountings and compartments for batteries, the receiver and the Arduino along with the mounts for ancillary items for lighting, smoke and other effects.

Once these changes are implemented in the CAD Files, I can then start the printing. The Hull will be printed in 12 sections, as shown below




Once printed, I will then clad the hull with carbon fibre to provide both stiffness and also waterproofing.... I guess this is the start of a long project 

So, although many may think I am jumping the gun by considering motors this early in the build, but I want to include the motor mount in the hull CAD File. I also want to be able to include the battery compartments as well, and also check the shaft alignments as well.

I think I am looking at mounting four MFA 919D 540 motors driving four 30mm props. The prop size was chosen for their closeness to the scale size of the actual props and think I should be running them at speeds of less than 400 RPM. it is strange to be talking low RPM, as I am coming from an RC Plane background and so it would be nice if anyone would kindly point me in the right direction. 

The overall length of the model will be around 1748mm, and as yet, I have no idea of what the final weight will be, as I have not yet created the final assembly file of the 3d printed components. I also have no idea of what the ballast weight will need to be to get the vessel to sit right in the water.... So I am kind of estimating what I will need, but the estimate is based on virtually zero knowledge of what I am doing. Any help will be appreciated 

First build?

Ambitious.... but should be good.


Just a thought, with something that size made from those materials and with all the ancillaries, you might find that you don't actually need ballast and if you do then it's probably going to be a case of trial and error with shot or similar.

Good luck.

Yes, it is my first boat build, but not my first model. Some differences between this and the last builds...
This is a ship, and my experience up to now has been making planes.

My planes were built using shop bought kits, this one is a bit of a hybrid. I am 3d printing the model to create formers which will then be clad in fibre glass or with timber or other conventional modelling materials....

I guess I do not have to worry about weight as much as in the past, a few grammes here and there will not cause it to plunge out of the sky....... Unless I have made a serious error in building 

So, the cloud today was that I blocked an extruder (again) on my printer. Fortunately I had a spare hotend, but that has caused a significant delay at work. There were two silver linings as a result, one is that I have ordered a direct drive print head, so hopefully that kind of blockage is a thing of the past, and I can also print faster.

The big silver lining is that I have been able to do some more work on my battleship. The first steps are to convert the cad model I have into useable and printable components. This is a bit of a challenge, as it would appear that the original files was created as a solid object and then just hollowed out. I have been able to spend the day converting the hull sections into useable part drawings. an example are the prop shafts. In this image, you can see the result of the hollowing process:-

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so the next step is to add some material to give strength to the prop shafts, and then hollowing them out. I also used this process to build up some flat surfaces in order to be able to mount the servo for the rudder. 

The motors and the prop shafts are just 'placeholders' based on the descriptions of the components from various model shops. The motor mounts will be made by printing the basic shape, then overlaying it with carbon fibre. This should ensure accuracy of positioning as well as strength. The assembly drawing of this is as shown here:-

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I have also made a decent boss for the rudder assembly, and had to play a bit with the props. the overall stern areas of both hull sections will look like this when assembled:-
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I think I will be using a larger rudder than is drawn here, that will make no difference to the construction of the hull, as the mounting pillar is the same between the two rudder assemblies I have seen. I know the props are show here as all being the same hand.... That was just simplicity for a placeholder, I think I will actually make my own set of props when the time comes. I will use my 3d printer to make a right and left hand print of the larger and smaller prop, and then use the 3d prints to try my hand at lost wax casting. I have a small induction furnace I built as a little project a while ago, and this seems an ideal time to try it out, and now that the printer is back up and running, I have to go and do.... work 

When I built my model of the titanic year before last, it was recommended I put in lead shot as ballast and cemented them in with a wax layer. I used just shy of 5kg and that model is approx 1.4m long. The shot was evenly distributed through the hull and then fine tuned with extra small bags once the running gear, radio, and super structure etc were installed