Giles G-200 Progress – Intersection Fairings

Moving along nicely now with the Giles G-200.  I realized that before I put any more time into the cowling, I needed to have all the rest of the intersection fairings finished up.  Really, the most complicated part, topologically speaking, is the intersection fairings.  Since the topology of the fairings must flow into the cowl, it’s really more about figuring out the topology of all the blends than it’s about getting the shape 100% nailed down.  I’m going to do a post later this week on the new tsBevel command, which was included in the 3.3 release of T-Splines for Rhino, but I will tell you now this is my absolute favorite new tool.  It’s a super powerful way to create very nice orderly blends between surfaces.  I used tsBevel on both the wing to fuselage and gear leg fairing to fuselage fairings.  It gets blends like this about 90% there in just a few minutes, and then I just do a bit of point editing to sculpt them to a final shape.  Here’s some screen shots:





I’ve stopped using tsCrease to make my crease fades on blends like this – there’s just too many restrictions on the fade out and the proximity to star points.  Instead, I just bunch up the points, and then spread them out as I want it to fade.  Takes a bit more point editing, but the control is much greater.  I’m going to do a final sculpt and fitting of this surface in the coming week, and then extrude it out into the final cowling model.  Getting closer….



2 Responses to “Giles G-200 Progress – Intersection Fairings”
  1. Karl says:

    Interesting stuff. I need to design a mortise and tenon type joint in a hydrofoil; perhaps I should look at T-splines.

    From a theoretical standpoint, how do you establish what the desired shape of the fairing should be, aerodynamics-wise? There have to be better and worse shapes. Pretty is one thing; efficient is often quite another. I recall Mike Arnold going to some impressive lengths to get all these details correct on his AR-5, using basic principles derived from Hoerner and others.

  2. Karl –

    The geometry of the gear leg intersection fairings is informed by both Hoerner and Arnold. I’ve got all of Arnold’s videos, and Hoerner’s book as well. The important points are to not bulge out the thickness of the intersection with regards to the front view, and not to go too crazy making the radius huge. The general thinking on the wheel pants was derived by the same method – namely going through the same process that Arnold does, but with a different section, and of course in 3D.


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