# Modeling Wingtip Geometry

I am modeling a RC plane as part of my hobby and I have run into a modeling problem in the wingtips. I have a airfoil and I have a profile that I want the wingtip taper into, but am having a hard time understanding how this can be done smoothly. In theory I’d like the taper to be consistent, or at least steep at the front and less at the back. But how do I determine the distance in from which to trim and taper the airfoil? The airfoil bulges to a maximum at about the front third, and that is really messing me up.

I am asking from a modeling standpoint, not from a aerodynamic standpoint. The plane would fly even with a squared-off wingtip.

170321 Temp.3dm (295.5 KB)

Hi Lawrence- I think I’d not have the edge surfaces in there necessarily, until the wing surfaces are clean and how you like them - that is, if I am reading what you have correctly, it sort of looks like the edge surfaces are driving the top wing surfaces. I think that is OK on the long edge, maybe, but the one that wraps around the corner, maybe not - I’d get that upper surface(s) looking good then build the corner or match the corner to it, if you see what I mean.

Make a clean surface here:

then trim the edges and make your transitions to the actual edge curves you want to hit…

-Pascal

Also Jim Carruthers did a webinar a couple years ago in which modeled a plane to demonstrate neon .might be some tips(no pun intended) there. Look on Mcneel’s website and past webinars. It may help.—Mark

I’ve seen Jim’s tutorial. His wingtip comes to a point, and I don’t think that is the correct way to do mine. I also want to have more control on my profile (in plan).

@pascal

I tried your suggestion last night. My model turned into a Frankenstein patchwork of surfaces. The problem I had was that I would trim front and back of the surface just short of the fillet, but then I would no longer be able to matchsrf with the vertical edge band. Is there a simpler way to model this?

The intention is to make the model into a solid, shell it and then get it printed. I was able to get the model to be a closed polysrf, but I could not get a closed shell. I then meshed the geometry and tried to offset the mesh, but that produced problems too (I am trying to offset .5mm solid). Is there an better way to thicken this geometry?

170322 Temp.3dm (6.3 MB)

Hi Lawrence - the wrap around layout in the second image looks like a reasonable one to me.

-Pascal

@pascal

I found someone with Magics 2.0 and was able to shell from there.

In the image you attached, the surface is going way past the edge of the wingtip. How did you imagine you would trim and make a transition? Like I mentioned before, since we can’t matchsrf with a trimmed surface, how then do we get that trimmed edge to align with the vertical edge band?

That bottom wrap around is not pretty if you look at it closely.

@pascal

I took another stab at it last night. With a clearer design intent, I was able to simplify the model.

Is there a better way to do those corners above the fillets? I’m doing a sweep2, matchsrf on the edges and then patch the top. One thing I figured out yesterday was that the refine match option in matchsrf causes the surface to be stiffer (by adding many control points) on subsequent matchsrf (for the other edges of the surface). So what I did was do a couple loose matchsrf to massage the surface into tangency, then I matchsrf all the edges again but with the refine match option on. Does anyone else use this workflow?

I do - if I refine, I generally do that as a last step. Refine is a little over zealous at times, so I also add knots ‘by hand’ here and there to make the match come closer without the zillion extra knots.

I don’t think you should need a Patch in this object though - it should be possible to get things nice and clean. Is this the patch?

Think about a layout like this:

Trimming back the main wing surface to the right to get that.

-Pascal

You are right, I probably should have done it like your second image. Is there any merit to keeping the seams aligned (as I have done with the fillet)?

170323 Temp.3dm (1.3 MB)

Hi Lawrence - I’d shoot for something like this -

170323 Temp_PG.3dm (146.9 KB)

I don’t think I got it perfect but along those lines…

-Pascal