Log 2014-05-31 : Wheelhouse ...

As I shifted from PLA to ABS for 3D printing, I learned the hard way ABS is much more tedious to print right.

ABS is printed at a significantly higher temperature: around 260°C vs around 200°C for PLA.

ABS also tends to retract/warp when cooling down. The base of the print must hence really stick to the printer's glass plate if you even remotely hope to prevent warping.

Glass plate was covered with Kapton tape and them covered with ABS slurry: ABS is dissolved in acetone to get a watery substance that has to be brushed on the print plate.

Even that way my first prints in ABS showed significant retraction/warping.

Worse: one of the doorposts broke (ie: two layers of ABS "got loose").

And it only went downhill from there. Nozzle got clogged (I suspect that at 260°C any dirt or even leftover/unextruded plastic will just burn). While trying to get the nozzle off to scrub it good (and burn any residue on the kitchen stove) I only managed to snap the wires off of the temperature sensor.

My printer is essentially useless for the time being until I get replacement parts from Ultimaker - which is going to be a problem as they struggle to meet demand. Yay !

Anyway this was Tuesday. And the next weekend was Bateaux en FĂȘtes in Massy (20km south of Paris) a nice event where I was to sail with other tuggers.

I decided to reuse one of the "semi-failed" prints to make a temporary wheelhouse, put the lights on and give it a quick coat of paint to have it look somewhat decent.

Primer and paint were of course at 500km away at my parents'. Had to get spray cans here in Paris. There's a home improvement shop a couple paces from my office that usually stocks the same brand and colors as I used on my Odin. I try to stick with the same paint in order to reuse paint across boats.

Of course, they didn't have exactly what I needed (satin-mat RAL9010 pure white). Only had some water-based kid-proof version.

Wheelhouse was printed in "natural" ABS which is whiteish and somewhat translucent. All areas around lights were first painted black with Tamiya Acrylic paint (with a brush) to make them somewhat opaque. Took like five coats of black and then three coats of white.

After some quick sanding (3D printing is not good at making smooth "walls") wheelhouse was primed with plastic primer. A couple hour later universal primer was applied.

Again some wet-sanding at #600 grit. Not enough obviously as the "finished" product still shows the typical surface of 3D printed parts. It probably needed two extra rounds of priming+sanding I guess. But at four o'clock Friday morning (with your alarm clock going off three hours and a half later to get to work) you tend to lower your standards drastically.

A new wheelhouse will be printed as soon as I get the printer back up and running. And this time I'll spend the required amount of time to really prep the parts before painting to get a nice finish.

I didn't use the supplied window panes on this interim wheelhouse. I instead cut panes from a 0.40mm clear styrene sheet (from Evergreen). Glued them with CA glue and as expected they got somewhat cloudy. I'll need to get some "canopy glue".

I also had to put a new hatch with a GoPro mount together. Threw a few plywood parts together to make a replacement hatch I would use instead of the "scale wheelhouse". Also added lights to the "filming hatch" so that I'd be able to film at night. A glass of epoxy and a glass of G4 sealer/primer later and it was done. Ugly as hell but it worked and proved watertight. Function over form ...

Interim wheelhouse

Interim wheelhouse

From a distance and with some overexposure it doesn't look too bad



Bending and painting the railings was also some kind of mess ...

Lights on

Lights on

Very decent brightness

Propeller was changed/upgraded as there was some heavy towing planned at Bateaux en FĂȘte. I got a 4-blade #174 45mm Raboesch prop to replace the 4-blade #147 40mm propeller I usually sail with.

Type 147 4-blade prop

Type 147 4-blade prop

40mm dia, pitch ratio 1.03, final pitch 41mm

Type 174 4-blade prop

Type 174 4-blade prop

45mm dia, pitch ratio 0.89, final pitch 40mm

Type 174 props obviously have much more blade area. Combined with the increased diameter it gave a significant increase in thrust. The minor loss of pitch was negligible (if not a welcome side effect).

It proved a wise move considering the massive tow we got to play with at the meeting ...

Obviously current draw increased but event with some heavy towing (ie: constant full throttle) I was able to get a solid hour and a half out of the 7.2Ah battery. Could probably have gone up to 2 hours. Motor was barely above air temperature and ESC was cool (rated at 60 amps ....).