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Comment by AmVess | Hacker News Reader

Run it through grass or weeds and then it won't seem so innovative. Also, $4300 more than a standard prop means that a single trip over an unseen gravel bar will be the first and last time anyone uses one of these.

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That price was for essentially CNC milled prototypes, I imagine if they cast them they would be a fraction of that price.

casting that shape would require some kind of sacrificial mold like a sand-casting process. cheaper than billet, but not by much unless you're talking big industry scale.

I wonder myself if it's small enough to use a laser-sintering print process to build.

If the two halves of a mold have some helicity, I suspect it is possible to cast such a shape. After all, the water also needs to flow through the prop, so too can the halves of a mold.

Even if the geometry doesn't quite work out, it's also possible you could cast a shape that can be "unscrewed" from the mould and then machine a relatively thin layer from the outside of the cast part (relative to how much you have to machine from a billet). It'll need some level of machining anyway.

Binder-jet printing of sand cores is pretty cool too.

Sacrificial sand moulding is done all the time and is pretty cheap:

https://youtu.be/lnHhP_kZ43k

Why would you cast it at all, when it's a perfect shape for forging the blades and then welding or brazing them (depending on the material) to a central hub?

They could offer very customized versions made in an Inconel 3d printer.. Wonder if that (economically & technologically - is inconel seawater safe??) really makes sense, though.

You can use direct metal laser sintering on most powered steels, no need to use Inconel. The reason it's often used with Inconel are the parts you want to make from Inconel are difficult shapes to cast and milling Inconel sucks, eats tools for breakfast.

4300 is within the sales price range of exotic propellers, anyway.

a feathering/folding prop for a 35 foot sail boat is about 3 grand already, and it's certainly not a single piece of billet. The real exotic race-y stuff for that size boat is ~6 grand.

Yes, it sucks to ruin a prop -- but it's almost certainly user error 90% of the time; either sucking in boat lines (which will lead to a stall and engine mount damage/ prop-shaft damage in a majority of cases, not prop damage.), or running aground.

Uh, plastic props for my harbour-pusher come in at lousy 45 bucks. Sometimes, i'm so happy to own a smol boat.

Hah. Jokes on you! I'll gladly try using a 3D printed version of this on my 600W angry-pixie-harbour-pusher - which they only sell overpriced plastic props for, anyway ;D

Btw.: Worst thing: ride backwards and you'll have to tighten the mounting screw or risk loss of prop. Best thing: Rudder survived hard prop contact with just a few scratches on the outer coat \o/

I look forward to seeing your HN post in a month's time about it.

How Hard Can It Be...?

I think it's a pretty cool design but repairability does seem like a concern -- Normally you'd take a stainless prop to a shop and they'd just weld + grind any small damage but that seems more difficult with the geometry of this propeller.

I don't see why it would be, unless you bent the blades really badly.

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