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Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
BTW, about those ducts ... can't you turn a shape from styrofoam on a CNC or Lathe (not exactly sure how, but that's what you have MEs for) and add some glass fiber on the inside surface for rigidity and use those?
The ducts you have will have non ideal airflow, no diffusion at the intake/outlet and the corners are still going to generate tip vortexes. The inside surface should have an axisymmetric shape like this :
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
yes my ducts are primative, but the Hexagons were needed becuase i couldnt get a thin circle to be ridgid. Im sure your rocket throat like duct would increase the effecincy... but they'ed break for sure.
And i think you menat "divergence". I think im losing 18% of my battery power to vortex and copper heating, so the spiroid design prop may not yield a result worth the effort. i think i can lose 200 grams by changing from CF to monokote. each battery whieghs 176 grams, so i could then double the capacity and keep the mass the same.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
wrote ...
yes my ducts are primative, but the Hexagons were needed becuase i couldnt get a thin circle to be ridgid.
Poor shape for rigidity, the flaring alone would help a lot even if you made the shape out of just glass/carbon fibre ... with the styrofoam core would it really be a problem?
Why do you need monokote? Isn't your craft open frame?
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
That thesis I linked earlier just used a partial donut above the throat and a straight flared cylinder below it. For a more optimal shape of the outlet for hover lift I'd sooner look at rocket engine designs than aerofoils.
Hover lift seems far more important to energy efficiency than drag in forward flight ... and I don't think an aerofoil shape would particularly help much with the latter either, it's not like the shape is designed to be wrapped into a cylinder.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
first duct has been made, simple cylinder, 2 inche tall, polystyrene housing insulation, 21 grams. Fairly ridgid. HexTronic motor (DT750) and APC 10x3.8 prop seen above. Im thinking of putting 2 balsa cross ribs in at 120 degrees to the main shaft.
Spray paint is not compatible with PS, and i need a way to colorize these components, i wonder if latex spray paint will work?
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The Physics Of Propellers (And Electrical Motors).
