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Loft problem
geoff_josey
Member Posts: 65 ✭✭
in General
After early posts and help with lofting I have made some progress - albeit slowly.
I am now trying to understand the cause of the strange loft between 2 aerofoil sections.
I have spent some time playing around with the settings without success. I think the outlines are not duplicated as per previous problem.
See Rudder061220
Thanks
I am now trying to understand the cause of the strange loft between 2 aerofoil sections.
I have spent some time playing around with the settings without success. I think the outlines are not duplicated as per previous problem.
See Rudder061220
Thanks
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Comments
https://cad.onshape.com/documents/34b0333610049129d5b130a8/w/bff5cfe806b893bcd0e6c20c/e/e9ef25d85861e4ee1989bf33
When select loft and then the 2 outlines via the features menu it works fine. When I try it selecting from each sketch it takes a long while and then comes up with an error. Not sure why.
One issue that I found was that the imported airfoil profiles actually had multiple lines on top of each other in many areas but not all the lines were duplicated. This meant that for some users, it was very difficult to make the correct selection - sometimes they'd select the entire profile (accidentally) by selecting the face, and other times (trying to select the edges of the sketch) they's select part of the open profile.
I can't tell if that's an issue with this specific post, but for general "lofting airfoil profiles" issues this has come up more than once on the forum.
good points on duplicate lines.
What tricks/methods help find duplicates?
I think I found it by trying to figure out why the selections didn't work as expected in those sketches...and then some trial and error select, delete etc.
Using box-select (using both "to the right" and "to the left" selection), as well as Create selection > Edges > Loop / chain connected also helped to investigate.
Once you're aware there may be duplicate lines, it's not too hard to find them...it's when you don't know they're there that things are super-hard to figure out. The sketch & selections just don't behave right. For new Onshape users particularly, this is a really difficult thing to troubleshoot.
It's interesting, the waves of problem types that come through the forum. Often they're related to excercise sets used in education (remember the many boolean problem posts of that multi-cube puzzle part people were trying to make, back in the darkest days of 2020?), and feature very similar problems - either with the excercise, the instructions, or the challenges of learning a new CAD system remotely.
Please see the post thread below describing using dividing lines to find open geometry. This is a little late to your OP but may help diagnose issues in future. I am sorry, I do not remember who first posted this method that some call 'binary search'. It is surprisingly efficient.
https://forum.onshape.com/discussion/comment/59027#Comment_59027
good tips on finding duplicates. I think 'select other' helps discover and deal with them too. You are right - these are the esoteric kinds of issues that can stymie newer users (and older ones speaking from recent experience).
It is good to know how to find problems and then it is OK to delete overly complex or duplicate geometry. Especially working with imports.
I have noticed the 'waves' of common parts/issues too! It has been fun to see the holiday theme surging lately. Glad we have new people discovering this pretty awesome package.