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Old Mar 22, 2013, 01:47 PM
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ak79's Avatar
United States, CA, Torrance
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Help!
Solidworks lofts not so hot

I keep getting some annoying problems in Solidworks that don't happen in inventor. I'm pretty set on learning more about solidworks.

Problem is my Trailing edges devlop a centerline that migrates away from center and ends up on the face of the surface towards the tip. All my constraints seem to be good, the TE's are perp to the planform and centered. Any help would be great.

I attached some pics.

Also, my lofts always seem to have "flat" spots in them like the airfoil sections are made up of small lines and not curves. I can't see these flat spots in the actual foil cross sections but they show up in the lofts. Very hard to see, until you do a zebra or actually machine the parts. I import my foils like everyone else using xy points.

Any help would be great

Ali
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Old Mar 23, 2013, 07:41 AM
not bad for one eye
atlantic canada
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If you post the solidworks and airfoil text files I'll see if I can help.

Paul.
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Old Mar 23, 2013, 10:45 PM
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Some programs do that when one foil has a different number of segments than the other. I don't know how to fix that in Solidworks.
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Old Mar 24, 2013, 12:00 AM
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The general CAD rule for a loft is that it uses 90 degree points.This is why the flats are there. try a skin or ruled surface: a ruled surface to a differential foil will show you how many data points to adjust for a clean sweep.
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Old Mar 24, 2013, 03:18 PM
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Hmmmm, I was just thinking today that maybe there was something up with the number of points, maybe not enough. When I get back to the office Monday I'll check it out and upload a file here if anyone wants to look at it.
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Old Mar 24, 2013, 05:54 PM
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In the mean time take a look @ this:
Beginnings at complexities (9 min 30 sec)
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Old Mar 25, 2013, 07:14 AM
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I can take a look and see what is up. It is non-trivial lofting in solidworks with DLG foils. I've had to work some magic.

-Sam
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Old Mar 25, 2013, 07:52 AM
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under Tools>Options youl'll find settings for how accurately SW draws curves and, presumably surfaces. Have you played with this to address the faceting?

when I am lofting aerofoils I always use truncated TE's like you show, but I drive my lofts with guide curves at both upper and lower edges as well as several strategic places around the foil, connecting equivalent foil points between each foil section. works like a charm!
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Old Mar 25, 2013, 06:02 PM
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Ok here is a sample file, plus the airfoil txt's if anyone wants to look at it for me.

Ooops, I guess solidworks file are to large for RC groups, can't attach it.
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Old Mar 25, 2013, 06:08 PM
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Quote:
Originally Posted by Andy_RR View Post
under Tools>Options youl'll find settings for how accurately SW draws curves and, presumably surfaces. Have you played with this to address the faceting?

when I am lofting aerofoils I always use truncated TE's like you show, but I drive my lofts with guide curves at both upper and lower edges as well as several strategic places around the foil, connecting equivalent foil points between each foil section. works like a charm!
I looked a few times, didn't see that option in the menu?
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Old Mar 27, 2013, 05:14 PM
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What program/programs do you use to generate your airfoils before importing to SW.
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Old Mar 29, 2013, 12:58 AM
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Quote:
Originally Posted by dlpaul View Post
What program/programs do you use to generate your airfoils before importing to SW.
I've just been grabbing foils from drela so far. From charlesriverrc
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Old Mar 29, 2013, 05:04 PM
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an answer

OK Gang: I knew there was sumthin' different about Dr D's foils- here it is:
They are control point splines: so go to edit/ show points- or whatever tool to show:
> drawing is referenced from 100%y+ through to x0 % and the bottom returning to100% X and y zero. Great for running lofts, but this is the root of the Gap reason.
The way I run them is a poly line connected as lines, from x 100% to x 0 %, bottom as one, top as another. I know it's tedious, but it is very accurate. final export to laser files would be to convert to arcs for final product.
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Old Mar 29, 2013, 07:33 PM
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atlantic canada
Joined Jun 2008
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Ali I was able to reproduce your problem by deleting a few points from one of the profiles and adding washout. I doubt you're using washout by your choice of foil. If so, you may have to "Project" your guide curves onto a surface. Without the washout things look good, so you my want to check you're not accidentally adding some when you're defining the profiles.

Paul.
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