Wednesday, January 4, 2012

Simple plan

I've got an idea. Just an idea. I'm going to step by step mold the top of the monocoque in the ICEM Aero Expert workbench making everything as simple as possible (read: the fewest control points necessary). I don't know if this leads anywhere, just an idea.

So here is the starting point


A couple of points and a line


A couple of points and a line


A mirrored line.


There are our guide lines for the coming loft. Now we need a profile. I'm going to connect the dots in the front with a 3d curve using "near points"


Note this says N5. So there are 5 control points, or an order of 5. (I think). So if I click on control points, it create a new line and shows me the 5 weighted control points (circled).


Doing something similar on the straight lines shows 2 control points.


In order to make a loft we'll need a second profile. Otherwise I think it would be a sweep. Same theory as the first profile, N5.


Loft. Make sure to select the top profile first. This may be important later.


So, fiddling around with the Loft command, there is nothing I can do to get the loft to have the same structure as the profiles, in other words a surface with a v order of 5, and u order of 2. I can get it down to a minimum of 10 bezier surfaces.


Worse yet when you try to modify by control points you'll find that each of these Bezier surfaces has a v order of 5.


So I think bottom line with the lofts is this: if you have the greatest curves in the world and plan to make no edits to the surfaces go for it. It seems like the loft is not connecting the control points of the profiles, but projecting the control points from the first profile to the second, and then the control points from the second profile back to the first.

So what if this was a patch from curves instead of a loft?


The great part about this is that now we have a single bezier surface with a v order of 5 and a u order of 2.


We can even remove some control points and maintain the shape by left clicking on Nv:5 and selecting "3". Selecting and order of 2 sort of defeats the purpose of what we are doing because a degree 1, order 2 surface is by definition perfectly flat.


Now that I think of it, our profiles don't need to be N5, they could be as little as N3.

Double click on the front profile, right click on N:5 and change to N:3. In other words 3 control points.


Now the Bezier surface changes to a v order of 3.


Great. So how about we make this symmetrical across the zx plane.


I want to do a highlight analysis on this, to see if it's G3 continuous across the centerline


No surprises, looks good. How about a connection checker analysis?


Ok, it wasn't that bad. I've got two adjacent Bezier surfaces with a v order of 3, u order of 2 which are G3 continous. The simplier the shapes, I can see the easier it is to control them. But these shapes are so simple, they don't remotely resemble my intended object. Let's say that the sides of the monocoque are perfectly flat. I'll have to create a flat surface, and then make these curves G3 continuous with the sides of the monocoque.

I'm going to raise the mid guides


And I'll add a couple more points at y=0, and create a order of 2 line between the points


Combine them


Make a pair of N:2 profiles connecting these guides


Alright, so let's make a patch. We'll see that we have the desired structure, that is u:2 v:2