Just where do I start modelling this ?

Hi all,

Can anyone guide me in the direction of where to start modeling the wing of aircraft in pic attached .

My problem is the flicks at the tips of the wing (so called winglets). I am trying using Mechanical Desktop, and so far my skill only knows solid modeling, no surfaces, which I am guessing is what I need ?

Cam.

are you trying to make a solid model? or a surface. Basically you draw this like you would actually make the wing(sort of). you need to draw your cross sections of the wing and make a surface between them. I would draw the top and bottom guide of the wings and lines on the leading/trailing edges. the ends you will probably have to do as a separate piece. This would be easier with 07-09 because of the introduction of loft and sweep.

I dont have the time at the moment to draw anything but maybe later tonight or tomorrow i can if nobody chimes in.

Strangely enough this particular wing needs to end up as a solid for mass calculations, I have messed about a bit and can prob get it as a solid with various lofts between the ribs (I have loft and sweep in 05). However I am still interested to hear comments about skinning a traditional ribs and spars wing ?

if you create it as a mesh object, you can then run the command to convert it to a solid

noahma, i dont know that 05 has surface to solid, and the preloaded surface to solid doesnt work on mesh surfaces, only individual faces.

There is an autolisp routine that will allow you to convert a mesh surface to solid but it will not work for the internal area of a wing without multiple boolean operations.

cweeks, im curious as to why you need mass calculations of a solid wing? will you be using mass properties of foam?. Also do you need to exactly model that wing? do you have dimmensions you need to hit?

i just did this drawing quickly to show you the "skin" procedure.

Autocad isnt the best program out there for surface modeling freeform shapes so you have to really take your time setting up your splines.

You can see in the first pic i drew 4 horizontal reference lines, then a vertical line at their midpoint(varying heights), then another control point line the same height .25" in from the left side of each line(which are all at the same x coordinate. I used these lines as my control points for the spline to draw the upper camber of the wing.

I also drew the trailing edge of the wing as a spline, used the break command and broke it at each horizontal reference.

Next i mirrored the upper camber splines about the x axis and manually moved my control points(in plane) to get the lower camber of the wing. In Acad if you have certain numbers for your curvature i suggest you set them up using these control lines. With polar tracking it makes it really easy to modify the points this way after the spline is drawn.

Before i make a mesh surface i set my Surftab1 and surftab2 to adequate numbers. In this case i set them both to 20(number of cells you will have).

To make my surface i used Edgesurf. this will let you pick 4 lines(curves) that are intersecting at their endpoints to define a surface. I used the leading and trailing edge lines of each segment and then cross curves. You will only be able to do these 4 lines at a time. The reason i broke it up into so many segments was to show you . but really you could draw the leading/trailing edge of the wing and your cross section at the fusilage and at the tip. Drawing multiple cross sections will allow you to modify the shape at certain points of the wing(like you may have to)

so in total there are 6 separate surfaces there.

with other programs out there you have the ability to set constraints and do different style splines instead of the "through point" method. Also the ability to set the two (upper/lower camber) splines tangent at the leading edge of the wing would be nice.

In reality to do this right you would probably have to model the leading edge as one surface, the top and bottom separately and the trailing edge where your ailerons are.

Wow, a thousand thanks yous shift1313. I get the idea now, spot on tutorial. Certainly enough to start me down the road.

The reason for the mass calc's is I am using the wing from the aircraft I pictured on a fuz of my own design. It is indeed a foam wing. I am cading it so I can get the wooden bits laser cut and so I can mess about the component placement to get my CoG in the right place.

Just got a simple example to work, but your right I can't find a surface to solid command.

Cam.

in this forum i started a post called Mesh to solid. also if you check the autoLISP forum there is an autolisp you can download to convert a mesh to solid. The only problem is going to be in how you model the wing. It will take the surface and extrude it into the Z direction. so if you have any over/under hangs acad really flips out.

are you doing this for a project or just for fun? through my university i have access to unigraphics which is much easier to model the wing, make solid, and perform flow analysis on the body/wing to see high pressure areas, heat generated etc. just an idea.

glad it was helpful let me know if you need anything else.

http://www.cadtutor.net/forum/showthread.php?t=1408

thats the link to the autolisp.

Once again thanks for the help shift1313, I have found a very good application that will help no end with the modeling of the wing. I should be able to export DXF's from it and loft to give the required shape. It is profili2, sorry forum won't allow me to post the link.

I shall keep all your surface teachings in mind though.

Cam.

your not going to get the transitions necessary for manufacturing that kind of product if it were a real glider. modeling that for a video game is a different story and can be managed with AutoCAD. If your interested in shapes like that then look at Maya or Alias Studio both autodesk products. Or for manufacture a real glider... Pro/ENGINEER, Inventor or Solidworks.

Learning all the time here.

The drawing isn't going to be used for manufacture, it's just needs to be a look alike. However that's not stopping me in wanting to know if it can be done better.

So far the best I can manage doesn't really flow at the tips. 2nd pic below, it's enough for my actual needs but I wonder if it can be done better in autocad. I have had to do linear lofts between each of the sketches (1st Pic). If I try a cubic loft across all or even a few of the sketches autocad falls on it's arse. Have I reached the limits ? Also autocad refuses to fillet the arrowed edge, in fact it refuses to fillet just about every edge in the drawing now I mention it.

Cam.

don't you want a smooth transition? Or to look like the wing has tarp wrapped on? Your simply using the wrong software. The more rungs you add the better the transition. In Maya you can smooth the transition. In Alias Studio you would create the geometry with four part boundaries. In solidworks and Pro/ENGINEER you would model the form much like the Alias technique.

I was after a smooth transition in this case (hadn't even considered a draped on fabric look, kind of guessed that was way beyond AutoCAD). Anyway you have pretty much answered the question, I'm at the limits. It's not a problem for this design as the wing only has to look similar.

Thanks for the help guys.

the reason you cant fillet is because you are dealing with a surface and not a solid. By changing your surftab1 and 2 you will get a better resolution between your ribs. Standard is 6, i think max is 200 or so but i would start around 20 to 30. just type surftab1 and set it to 30, same for surftab2, then do your edgesurf again.

unigraphics is a really great program for modeling surfaces and gives you great control over everything. to create a solid you just need a closed surface and thats it. Even after the solid is created you can go back an edit your curves/splines and it will redo everything on the fly. I have also used it for flow modeling which may be a benefit to you.

acad 07 or newer has loft and sweep built in. these will give you a better surface to work with than the program you are using. It takes a lot more work to make something like this in cad(especially earlier versions).

Strangely enough I had drawn it as a solid, however I guess the answer will be the same, software in hand just aint up to the job.

Thanks again for all the help guys.

Cam.