State of the art 3D printed RC yachts

[Joules]

https://3dprintedradioyachts.com/why-3d-printing/

Very interesting and informative link.   I have done some shell printing over the years for micro gliders etc  Just started on my own design model yacht and the above turned up during a search.

[Joules]

My design is more a keel boat pond yacht.  The actual model will be about 670mm long, but after reading the above website I decided to give spiral printing a go with the new 0.3mm nozzle.  That limited me to a 200mm test print, I was not disappointed.  The model design was started a couple of days ago as just a doodle idea, got more serious yesterday and prepared for 3D printing today.  The print took 6.5hrs at 0.1mm layers.  Once the print was done and the hull started cooling I had to puncture the deck before the shell imploded.  It was a little funky at the bow as the print spirals out and you need tons of cooling to stop it just being a melted blob.  With hind site, don't print a closed bow and do a plug for it.  The hull came in at 10grams, that is just crazy light, even compared to a 2 part styrene vac moulded hull.  The flat deck is a bit floppy, I should have designed it with some camber to make it more rigid, but not an issue as I need to open it up for ballast and test floating.  Rhino gives me some handy hydrodynamic analysis, this can be scaled up for the larger hull, to see how much weight I can have above the deck without it falling over in the water !!!   My cheap cnc craft cutter rounds out the equipment for model yacht making as it can cut multi panel sails in minutes and vinyl patches for hatch covers.  I can't ever remember building a hull in less than a month and this thing doesn't need paint.

With the deck cut out, the hull now weighs in at 7grams.

[Joules]

That didn't take long, the ballast was 7 UK pence.  The translucent hull was very useful for seeing the waterline.

7 pence weighs 18 grams.

And, the hull is watertight.

[slowcoach]

Very interesting Joules, I might have a go at that myself 

Rob

[Joules]

Progress being made Rob as further designs are tested before I commit to something bigger.

[awemawson]

Those look pretty slick Joules 

What the maximum footprint you can print on these swish machines of yours?

[Joules]

That would be the grey keel boat at 225mm long.  I am working on printing two halves and welding them together, but then the 150mm x150mm bed becomes the limit on beam, or angle the boat is printed at.   This was the precarious print for the Whitehall 14 rowing boats, the second one I increased the size of the transom for more support.  You can see the shake got progressivly worse on this print as it got taller, but being printed in a spiral you can't have support unless you are going to cut it away afterwards and repair the damage.

[Joules]

Oh !!!

Well, that was just about the worst bit of design and printing I have done.  I cocked up on the hull thickness, lack of support from the start.   The outside is pretty bad, it did use the full height of the printer, but I could hear the hot end clicking as it passed from one edge to another, the print had worked a little loose. The inside looks much better as the hotend wasn't flicking the print before doing its outside run.  Then the weight.....

My chosen Whitehall craft weighs in, full-size at 93kg ready to float off the trailer.   My calculated weight after I saw the first few layers print comes in at a scale 137kg !!!  hmmm, over built it.   I have a very thin double skin spiral print in reserve that will print the same size hull as this but come in at a scale 68kg.  When you think the full size craft has teak wood work and bronze fittings, buoyancy tanks, the bare fibreglass shell is probably lighter than that.   I'm not even sure I want to print the other half of this and just go straight for the skinny hull.  The risk is the hull will be floppy till it has wood work added to firm it up, or I will bugger up the prints, welding the parts together.

You can get an idea of the size it will be, based on comparison to the small one piece models. Their scale weight is 144kg, as thin as the skin looks in scale size it's way too thick.  By the way, 1:10th scale is good, as 1kg=1gm.

[Joules]

And on we go....  Cut my losses on the lard craft, and went onto the lean mean, rowing machine

I started with the bow and made sure it was well supported by adding a frame that got printed to support it.  This was a 10hr print over night, happy with the weight at 31gm, not so happy with the poor finish on the front.  Some Titebond glue makes good filler for PLA and it stays put when you add it, patched a couple of other places too.

Next came the stern, and worrying thin transom (0.5mm)  It had to be this thin as other issues pop up if it is much thicker than the shell.  As it turned out I had issues with it and had to fillet weld it before removal from the print bed.  Whilst the iron was hot I also welded some layer gaps that had appeared during printing.  After that get it weighed...  35gm for a total weight of...  errrr 67gm, guess it rounded them up.

[Joules]

From here two halves become ONE

Sorry no pictures of it wrapped in masking tape to keep it all in line as it was a three handed job at that point.  Come to your own conclusions for the third hand.

Tack welds are added outside and in, once these are done the hull is strong enough to be handled as one, ready for the filler weld to be added internally.   The technique here is to be swift, have your finger behind the weld, if your finger gets uncomfortably hot you are in trouble as the whole lot can go.  So move on when your finger gets warm and stagger the fills.  Work around till you have the lot done, taking care near the edge as it is more heat sensitive, just like tig welding only in plastic, and without gas, or plasma...  Ok it's not much like tig welding.

When the filler weld is done you can start on the outside.  If you have done it right, those external tack welds are now raised a bit.  Carefully glide the welder over the surface blending the tack welds back in and filling the gaps.  Don't get depressions in the plastic, you want it to be proud but welded.   Take a razor blade and scrape the welds externally to blend them back into the hull, if you open a weld up just add a little filler and keep it above the hull lines so you can work it back.

At this stage, with some patience and luck you should have a very light and pretty strong (it's 2100 wraps of PLA) hull that should be watertight as you welded all the pin holes ?   The welding tool is my old waxing tool from lost wax days, carving and welding pretty much the same with PLA or wax.  A temperature controlled iron would also work with a fine point tip.  You have to control the heat going into the PLA.    Little and large together, happily this exercise has mostly been a success, though the printing was fraught as I was on the limit with the printer.   A 3 part hull is quite feasible with good planning.  A larger printer with a more rigid construction would be heaven, watch this space.

The overall weight of the hull is 68gm, so just over a gram of filler weld added as the external weld was shaved back.

[Joules]

Another day, another test piece.  This time a small section of clinker hull to gauge the practicality of printing and welding a larger model.  I haven't found any examples of model 3D printed clinker style craft.   Designing it is a little more tricky, and the method I use for printing these hulls doesn't allow for the planks to really overlap as you would end up with voids between planks.

[slowcoach]

I like the look of that Joules.

Rob