Is this the future of RC boat props?

[Meniscus]

I'm sure that many have already seen this, but check out the laser cut props from H&M:

H&MProp.jpg H&M_Prop_2.JPG

I guess we won't have to deal with cast props in the future as technology moves forward.

[txboatpilot]

How do I check them out?? No link or info?

[Meniscus]

I can't direct link due to the site.

http://www.hydromarine.de/ look under "NEU" which translates to "New", then down towards the bottom.

Translated link

[cyberhoops]

Interesting. The prop was created with Stereo Lithography. There are a couple types SLA, but in the classic form there is a liquid goo that gets hit by a laser. The goo hardens where the laser hits it. The tray holding the part is lowered to get another layer of goo and the process repeats.

It basically builds up a plastic part with in layers. Sometimes it is done with a powder instead of a liquid, but I guess someone found a plastic that has decent properties for a propeller. The plastic we have used for various test parts would never have been strong enough to be a race prop.

[marker]

They use metal powders

http://www.3dsystems.com/products/datafiles/datasheets-1007/SLS/DS-Sinterstation_HiQ_US_0407.pdf

Mark

[cyberhoops]

I stand corrected since the page does mention Chromium Cobalt as the material for the part.

So, they are doing DMLS - (Direct Metal Laser Sintering) from metal powder which does take a pretty high powered laser. I had the impression they were doing plastic since they had the web structure behind a blade as support. You normally don't see that with sintering (or at least not with the parts we did that way). But hey - you learn something new everyday.

[NorthernBoater]

Link that is translated.

http://translate.google.com/translate?hl=en&sl=de&u=http://www.hydromarine.de/&ei=0ZOsSdz5LoSTngfo_OW9Bg&sa=X&oi=translate&resnum=1&ct=result&prev=/search%3Fq%3Dhydro%2Band%2Bmarine%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26hs%3D5Bf

[Diegoboy]

Translated Direct link

[icelert]

Having worked with SL and sintered metal parts in my occupation as a windtunnel modelmaker, let me say that props might not be best objects for this technology. In my line of work, SL is a great tool for prototyping and creating complex shapes at a favorable cost. However, it has been my experience that knife edges are very weak because of the absence of a grain structure in the powdered metals. These parts are also especially hard and we use diamond grinding discs to shape and smooth the material. Too much heat in the grinding process will also case the edges to break free. As was mentioned, the laser moves through the part from top to bottom creating miniature grain patterns that would not be desirable in a props finish. Balancing and polishing would still be a necessary and more difficult process that with BeCu props. Modifying or cupping props like these is a definite no no. Plus sintered bronze contains tungsten which contributes to the hardness and also is a health hazard when grinding.
Given the advances in SL, it is only a matter of time before newer and better materials will become available that in my opinion will be better suited for use in high strength knife-edged applications.

[Ub Hauled]

It looks very brittle to me even on the pictures... it kinda looks like rock.

[icelert]

I have seen a few SL resin Allison and Merlin dummy engines for use in scale hydros and they are a work of art! Not cheap but beautiful.

[Meniscus]

This thread took a different route than I anticipated, but I like it.

I have the following questions:

1. So we're saying that this technology, as currently implemented, has the result of a brittle edge. Is that correct?

2. Is there another technology that someone is aware of that would be more suited for prop production?

3. Why don't we use polymer props? Do they still flex too much under load? Even Polyethylene?

Oh well, I guess I'll keep printing my secret props on my 3D printer => Z-Corp, but I guess if I had one of those, then I'd be making molds of all kinds of stuff, LOL!

.....looking forward to feedback on the questions above.....

[icelert]

Question #1- Yes, that has been my experience with sintered metal edges.

Question #2- 5 axis CNC's like the Mazak Integrex can produce some great props! A big investment though.

Question#3- I am no expert in polymers, but flexing under load(upsetting dynamic balancing+performance) in addition to the small thickness requirements for prop design is certainly a challenge.