Mar 2, 2016 | By Alec

When looking at new filaments to use for a particularly challenging 3D printing project, you’ll often read about certain qualities, such as durability, high strength and so on. But the truth is that those are only guidelines and real results depend completely on what you use it for and what geometric shapes you’ve designed. To illustrate that point and show that there are genuine differences between various materials, two makers decided to set up a challenging test: can you 3D print boat propellers? And if so, what material works best? The results might surprise you.

This interesting, if slightly unscientific test was carried about by veteran 3D printers Bruce, from 3D Printing Systems, a major 3D printer reseller in Australia and New Zealand, and Hayden from 3D printing service provider Clone3D. Drawing on past experiences and contacts in the marine industry, they set out to look at the strength of various materials when used for boat propellers: very thin, technical components exposed to the motor’s great power and the ocean’s harsh, salty environment.

As they explain to 3ders.org, they were trying to get to terms with the misconceptions that surround the wide variety of 3D printable filaments currently available. “The huge array of materials and myths that float around them is definitely a minefield, not to mention the environment some materials require to printed in, heated bed, heated chamber and separate support materials are in some cases a necessity for a successful print,” they say. Carefully mimicking the hobbyist environment, they ignored the industrial strength 3D printers they have available, and instead turned to the well regarded UP BOX desktop FDM 3D printer. Though this did limit their material choices, it still proves that you can achieve a lot on a regular machine.

On that machine, they 3D printed four well-regarded filaments: ABS, Wood/PLA, Polycarbonate and Carbon Fiber PLA. The Wood/PLA composite was added for a laugh, and both didn’t expect it would add anything. “Com'on really, a wooden boat propeller!” they said. Before 3D printing, they first made a 3D scan of a 15HP Yamaha outboard motor using the EinScan-S 3D scanner (also known as the ScanMaster Plus). Though this caught a perfect image of the outside of the propeller, the insides had to be CAD engineered by Sarah of Idea Beans.

The results were excellent: a perfectly compatible propeller. Four versions of the prop were 3D printed with a solid fill at 0.25mm layers by Hayden, who has extensively worked with the marine industry in the past. The results were first strapped to an engine on dry land, as you can see in the clip, with the survivors actually being launched in the harbor.

So how did they do? Rather surprisingly, the Carbon fiber PLA didn’t make it past the first hurdle. Though carbon fiber is known for being harder than many metals, it actually showed significant damage during the dry land test. “It’s not bad though. If you were stuck at sea, and needed a prop to get you home, you’d get home,” Hayden said of the failure. The ABS propeller, however, did just fine. “It looks as good as when we put it on,” the makers remarked. The same was the case for the Polycarbonate part, as you can see. More remarkably, the Wood/PLA (coated with lacquer) was also a perfect fit, and performed much better than expected.

They then moved over to the real test: attached to an actual boat at sea, and giving them so actual horsepower. This really separated the men from the boys. The ABS propeller, to begin with, cracked slightly during the second test. The Wood/PLA composite, unfortunately, did not make it. After a good start, Hayden was forced to paddle back to shore with a broken propeller spine. Aside from that, the fins performed quite well and they believe that a slightly reengineered propeller can definitely be made from 3D printed Wood/PLA composites.

The real test was saved for last: can Polycarbonate, always presented as a proper engineering plastic, survive the harsh conditions of a propeller? Yes, it can. “It was incredible, full throttle,” they say. The 15hp motor was no trouble at all for the very powerful propeller. It’s an interesting test that really emphasizes how much variation you can find in 3D printable materials and geometries. And to answer our initial question, yes you can 3D print a wooden boat propeller. But a Polycarbonate part definitely has our preference.

 

 

Posted in 3D Printing Application

 

 

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Glenn Holland wrote at 3/2/2016 7:29:01 PM:

Just watched your 3D prop. demo. You have done exactly what I need done. I have a prototype prop that I need scanned and then flipped. Need a mirrow image/a left hand prop from a right hand original. They are for twin electric outboards on a launch I have built (Redwing 18). I am using two right hand props now and she does not like to turn left at all. I have been told by those who have experience that I need counter-rotating props. If you will send me an email address I would like to send you enough specs. so you can price the job, if you are willing? Yes there are companies who can do it around close but the prices I've been quoted for one or two are quite high. thanks in advance for your reply, Glenn Holland/NC/US gholland1@nc.rr.com



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