Hi, I am trying to loft the blade of an aircraft winglet. The tip of the winglet has a curved leading edge, so the planform isn't a trapazoid. When I try to loft the shape, using the rib profile at the base of the winglet, the LE and TE as guides and then I place a point where the LE and TE meet, the shape basically looks good right at the base, then turns into a thin blade where it transitions to the point. I have tried tweaking all the loft parameters but no luck.
I have tried exporting as an IGES to Rhino, then using all the guide curve geometry I am able to get a satisfactory loft, but need to do this using Solidworks.
Because you have tried everything, I'm sure this suggestion won't help, but did you try to use the "tangent to profile" end condition option on the point profile? Is the point sketch on a plane roughly tangent to the end of the wing?
Thanks for the reply. Would you mind taking a look at the SW file and seeing if there is somthing I've missed? I tried your suggestion and can't seem to make it work either.
Good points from others about using end tangency at the point profile, but there is something more fundemental that is, I fear, being missed. It has been my experience after ten years of working with SWx that lofts/sweeps fail to deliver what you are trying to get out of them when you ask them to do too many radical changes in a single feature. My policy is to pay attention to how a loft 'wants' to work, and break the feature into sections that are consistent with how a loft 'wants' to operate. I did a propeller a few weeks ago, and here is how I did it: The main shaft, until it starts to converge to a rounded tip, I did as a single loft. Even better, let it start to converge at the end (but just a bit... do not completely converge), then use a trim or cut (depending on surfaces vs solids) to cut it back to the region that is mostly consistent in shape (there is lots of hard-won background behind this that you will figure out with a little experimentation if you don't look at any tutorials). Then, I built the portion that converges at the tip. I did it as a top convergence and a bottom convergence using surfaces (tangent to the root body) but that is not *necessarily* required. The variance between surface and solid techniques is a little too much to go into now - experience, education, and comfort level will inform that.
The topic of breaking things up into regions that look 'mostly' the same to develop the real shape you want was covered extensively in the middel protion of my presentation at SWx World 2006 - look at
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under tutorials (the middle of the left side fo the nav bar) and look at Curvy Stuff 6 tutorial. Be sure to get the sample files and the storyboard ppt to explore, step by step, the issues with getting greedy and doing it all in one feature and why breaking into individual faces gets past the prblems. I concentrated on it at SWx World because I have talked to folks who have spent as much as a week trying to tweak a single loft into doing too much drastic change (and failing), when, in half a day they would have nailed it if they had just broken it up into regions that have very similar characteristics. Concentrate on the hook and the volkswagon steering wheel in my presentation, ESPECAILLY the hub of the steering wheel - see how breaking into 'relaxed, similar' regions saves the day and improves quality. Look at the sample files and storyabaord ppt and judge for yourself.
Speaking of judging for yourself, its best not to go 100% with potential cranks on the web without independent varification. That's fair, and I encourage it. Just look through the ads in the design engineering magazines you probably get, and look at how the inevitable images with CAD 'face boundaries' lines (which look cool in ads) inform you. Though they are ads, you can actually see what the real Pro modellers do (because the ad agencies are just getting fed the raw CA data - I speak from some personal experience here) - when looking at airplane, car, and even human face images, you will notice increased face density in regions of radical change. relative to their more relaxed neighbors, when they break up models into multiple faces to isolate influence - which you are NOT doing if you are trying to pull off a complete propeller from root to tip in one feature (making one face, longitudinally). The root and shaft is really quite simalr, while the rounded or pointed tip does completely different stuff, screaming 'break 'em up!'. It's a message I've tried so amny different ways to share over the years - Let the product tell you how to model it! Think of faces, not features, and the product tells you how to model it. For real.
How are you controlling the twist of the wing profile (NACA?) as it goes up the wingtip? The wing profile needs to be restrained by means of a spine to keep it parallel to the aircraft centreline (x axis) or wing axis.
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I had the chance to look at the file. In the end, a better result was achieved using a construction surface at the edge and two Fill surfaces. The loft to a point is useful in some situations, but there is sometimes a better way to go about things.
The winglet has 1.5 degrees of twist from the root to the tip, it is actually a washin. The root airfoil and the tip airfoils are set at the 1.5 degree difference. The LE and TE were created on a plane, and then projected on a twisted surface, so I could use them as guides.
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