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On Jan 4, 2016, at 05:23, Hannu Venermo gcode.fi@gmail.com [electricboats] <electricboats@yahoogroups.com> wrote:
In one word, no.
Modelling is, in a word, crap.
Even the very expensive systems are practically useless, and most cannot
afford them (30k$).
At this time, we cannot effectively model even a small metal boat hull,
for strength calculations.
It fails due to the curvature/skin effects (the system becomes complex).
Seems incredible, but is true.
The same does not apply to commercial ships, for scaling-effects reasons.
Re: modelling confirmed by billion dollar corporations who does this for
machine tools ..
(I spoke to the guys who designed a famous major commercial lathe, and
they taught us about building machine tools)
and by an engineer who worked for me, and wrote his dissertation on FEA
systems.
We can make all sorts of pretty pictures that indicate area of more or
less stress (pretty easy and accurate), with even basic packages.
What we cannot currently do is use sw to make them "better".
The modelling is mostly just to show you what you manually modelled, and
somewhat confirm if it is likely to break under a given load.
Famous examples are several americas cup boats that spent millions on
modelling, and the boats promptly broke.
What we can do, easily, is use solid models to make bits and pieces.
But 3D printing is not the technology of choice, as its too slow,
expensive, and just the wrong tech for this.
Std 3d milling is much faster, cheaper, stronger, and more accurate.
Fwiw, "3d printing" a 14" prop with sintered metal would take about 20
hours run time, and cost a few thousand $$.
An amateur 3d printer toy might take 40-60 hours to do the same, at 1000
$ cost in plastic (ABS et al).
Milling, maybe 3 hours at 50-100$/hour at any jobshop near you.
Estimates based on current cost of industrial 3d printers, actual specs
and speeds of hobby printers, and std commercial small cnc mills in the
25 kW area, with 30x20" work areas.
Making "small" toy props in the 3" size would work well for "home" 3d
printers, but they wont scale up to larger ones.
Has to do with effects on scaling stuff up - just like why insects cant
be bigger than 30 cm (they cannot breathe).
Volume = dimension cubed, and the skin friction and vortex/efficiency
stuff does not scale up linearly.
On 27/12/2015 16:05, 'G. McWilliams' garrettmcw@yahoo.com
[electricboats] wrote:
> Although nuke prop design is classified photos do exist. I would think
> that modeling the basic characteristics in a tank would be trivial now
> that we have 3D printing to manufacture prototype shapes.
--
-hanermo (cnc designs)
Posted by: Dirk Harms-Merbitz <grasswood@icloud.com>
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