Build log 2014-11-20 : First print

Hull was printed in ABS from Ultimaker.

I like Ultimaker's ABS as it melts quite well with Acetone, muchlike ABS from model kits. I previously tried ABS and SmartABS filament from FormFutura but their ABS didn't react well to Acetone.

Print settings in Cura were as follows:

Layer height
0.15mm
Shell thickness
0.8mm
Bottom/Top thickness
0.6mm
Fill density
100%
Print speed
80mm/s
Support type
Touching build plate
Platform adhesion type
Brim
Retraction
On

I could probably print faster than 80mm/s but I'm usually not in a hurry on don't have to print multiple parts.

It took me over an hour to remove all the support material. Let's say Cura is quite generous with support structures.

That hull is pretty small. When designing it on SketchUp, even though I gave all the dimensions I thought it looked "big" (plus you always tend to zoom in and out on your computer). And I was somewhat disappointed I had to build around a 20mm propeller.

But now that I had it in my hand, size feels about right.

I've designed it like a tank with 3.3mm walls. It is HEAVY. And ABS is heavier than water (plywood on the other hand is lighter, giving extra buoyancy).

There are a few things I have to fix / improve

Holes in the motor mount were a little too small. They're 2mm in the model (for 2mm bolts). I'll enlarge them to 2.20 or even 2.50mm (giving me some play to line up the motor and prop shaft).

Same with the stuffing box channel. I will probable increase it to 3.20mm (from 3.00mm). I've actually hammered the brass tube in the channel. It's not as bad as it sounds and I could even forego glue. Just brush the keel/skeg with acetone to seal the brass tube in place.

I fitted the prop shaft with a thrust collar. Collar fit right but the grub screw to secure it to the shaft would not clear the hull. Oops. Will need to trim some excess plastic in the 3D model.

Hull was brushed with acetone so that the surface would melt and seal (3D prints aren't always watertight).

Hull spent one night in my kitchen sink and there were no leaks. I'll have to weight the hull before/after to make sure there was no water "soaked in" but I think the acetone did a good job. Plus hull will be painted anyway.