Sweep with guide curve fails to make wing

I'm trying to create a wing with quater-ellipsoid taper.

I have two paths on the front plane for leading and trailing edge of the wind, and a profile on the top plane for the root profile.

Lofting to a smaller profile at the wing tip doesn't work because the Loft profile is not maintained exactly between profile sketches.

A sweep with path and 1st guidecurve ought to do it, but it comes out weird.

(I know about creating the profile after the path and guid, so it's not that...)

See

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SolidWorks 2007SP5

Any thoughts? /gh

Reply to
gustaf.heland
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I would use the surface loft with guide curves. If you draw your profiles centered on 2 parallel planes with guide curves the profile taper is pretty consistent. See image

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weevoe

Reply to
weevoe

Well, that sort of works, except that "pretty consistent" is not really what you want when you spent all that effort in developing the profile.

Seems this is not a task for SW.

I had it done in Rhino3D using "Sweep along two rails". Doesn't need all the intermediate profiles, and is fully consistent rather than just "pretty".

/g

Reply to
gustaf.heland

What intermediate profiles? There are two, the others you see are generated by the two with the guide curves. I don't know what you mean by "fully consistent" so I used the term "pretty". Your term "fully consistent" is ambiguous at best. It would depend on how you measure/evaluate the surface profile, where, how many places & to how many decimal places. I am not going to take the time to do surface profile analysis...that would be on you. I was just showing you how it could be done since obviously you do not know SolidWorks.

Reply to
weevoe

My gosh! It's so funny with people who use anonymous forums to vent their frustration...

Using you method SW generates a surface which is a "pretty" good approximation of a sweep.

It is not 100% correct. If you make a cut of the resulting body the profile is NOT an exact scaling of the original profile. It is slightly different. A swept wing should have each section be exactly the same profile, that's what I mean by fully consistent. Not some ambiguos at all I would say...

Make your guides curve a bit more and you will start to see significant deviation in intermediate wind sections.

And I have many years of SW experience go> What intermediate profiles? There are =A0two, the others you see are gene= rated

Reply to
gustaf.heland

e:

Sorry, typo: "Wind sections" should read "wing sections".

The scale is different, yes. Of course. But any section of the wing at any location along the should still be an ortogonally scaled copy of the original profile. This is what I mean with "fully consistent". A consistent (scaled) profile as you move along the sweep.

What happens in SW when you use a Loft here, is that some kind of surface approximation math comes in to play which creates a surface that looks sort of OK, but makes no effort to keep the wing profile consistent. If you section the wing in the middle the profile will be (from an aerodynamic point of view) very different from the root and tip profile.

I made an image to show the problem:

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(If the guide curves are straight lines the profile is correct all the way, though, but that's not a very good wing...)

Reply to
gustaf.heland

Rhino does, assuming an inappropriate option isn't used, scale a swept section as a function of the distance between two sweep trajectories. For the indicated example that would be equivalent to scaling as a function of chord so probably appropriate. It does NOT, however, give the user explicit control of section plane orientation so if it is assumed the section remains parallel to the input section as it is swept there will be unexpected errors with the example trajectories.

Doubting is good.

Reply to
noBadCAD

You're as safe flying as ever. The VW engine passing overhead may be cause for concern.

Reply to
noBadCAD

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